A fiber optic sensor for noncontact measurement of shaft speed, torque and power

NASA Technical Reports Server (NTRS)

Madzsar, George C.

1990-01-01

A fiber optic sensor which enables noncontact measurement of the speed, torque and power of a rotating shaft was fabricated and tested. The sensor provides a direct measurement of shaft rotational speed and shaft angular twist, from which torque and power can be determined. Angles of twist between 0.005 and 10 degrees were measured. Sensor resolution is limited by the sampling rate of the analog to digital converter, while accuracy is dependent on the spot size of the focused beam on the shaft. Increasing the sampling rate improves measurement resolution, and decreasing the focused spot size increases accuracy. Digital processing allows for enhancement of an electronically or optically degraded signal.

Improved Force-And-Torque Sensor Assembly

NASA Technical Reports Server (NTRS)

Bamford, Robert M.

1991-01-01

Improved sensor assembly measures forces and torques of interaction between supporting and supported object. Measures all three components of force and all three components of torque. Force measurements uncoupled from torque measurements. Price for improved measurement capability, complexity and flexibility, excessive in some applications.

Dynamic coordinated control during mode transition process for a compound power-split hybrid electric vehicle

NASA Astrophysics Data System (ADS)

Su, Yanzhao; Hu, Minghui; Su, Ling; Qin, Datong; Zhang, Tong; Fu, Chunyun

2018-07-01

The fuel economy of the hybrid electric vehicles (HEVs) can be effectively improved by the mode transition (MT). However, for a power-split powertrain whose power-split transmission is directly connected to the engine, the engine ripple torque (ERT), inconsistent dynamic characteristics (IDC) of engine and motors, model estimation inaccuracies (MEI), system parameter uncertainties (SPU) can cause jerk and vibration of transmission system during the MT process, which will reduce the driving comfort and the life of the drive parts. To tackle these problems, a dynamic coordinated control strategy (DCCS), including a staged engine torque feedforward and feedback estimation (ETFBC) and an active damping feedback compensation (ADBC) based on drive shaft torque estimation (DSTE), is proposed. And the effectiveness of this strategy is verified using a plant model. Firstly, the powertrain plant model is established, and the MT process and problems are analyzed. Secondly, considering the characteristics of the engine torque estimation (ETE) model before and after engine ignition, a motor torque compensation control based on the staged ERT estimation is developed. Then, considering the MEI, SPU and the load change, an ADBC based on a real-time nonlinear reduced-order robust observer of the DSTE is designed. Finally, the simulation results show that the proposed DCCS can effectively improve the driving comfort.

Nonlinear SVM-DTC for induction motor drive using input-output feedback linearization and high order sliding mode control.

PubMed

Ammar, Abdelkarim; Bourek, Amor; Benakcha, Abdelhamid

2017-03-01

This paper presents a nonlinear Direct Torque Control (DTC) strategy with Space Vector Modulation (SVM) for an induction motor. A nonlinear input-output feedback linearization (IOFL) is implemented to achieve a decoupled torque and flux control and the SVM is employed to reduce high torque and flux ripples. Furthermore, the control scheme performance is improved by inserting a super twisting speed controller in the outer loop and a load torque observer to enhance the speed regulation. The combining of dual nonlinear strategies ensures a good dynamic and robustness against parameters variation and disturbance. The system stability has been analyzed using Lyapunov stability theory. The effectiveness of the control algorithm is investigated by simulation and experimental validation using Matlab/Simulink software with real-time interface based on dSpace 1104. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Full-order observer for direct torque control of induction motor based on constant V/F control technique.

PubMed

Pimkumwong, Narongrit; Wang, Ming-Shyan

2018-02-01

This paper presents another control method for the three-phase induction motor that is direct torque control based on constant voltage per frequency control technique. This method uses the magnitude of stator flux and torque errors to generate the stator voltage and phase angle references for controlling the induction motor by using constant voltage per frequency control method. Instead of hysteresis comparators and optimum switching table, the PI controllers and space vector modulation technique are used to reduce torque and stator-flux ripples and achieve constant switching frequency. Moreover, the coordinate transformations are not required. To implement this control method, a full-order observer is used to estimate stator flux and overcome the problems from drift and saturation in using pure integrator. The feedback gains are designed by simple manner to improve the convergence of stator flux estimation, especially in low speed range. Furthermore, the necessary conditions to maintain the stability for feedback gain design are introduced. The simulation and experimental results show accurate and stable operation of the introduced estimator and good dynamic response of the proposed control method. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Postactivation Potentiation of the Plantar Flexors Does Not Directly Translate to Jump Performance in Female Elite Young Soccer Players.

PubMed

Prieske, Olaf; Maffiuletti, Nicola A; Granacher, Urs

2018-01-01

High-intensity muscle actions have the potential to temporarily improve muscle contractile properties (i.e., postactivation potentiation, PAP) thereby inducing acute performance enhancements. There is evidence that balance training can improve performance during strength exercises. Taking these findings together, the purpose of this study was to examine the acute effects of a combined balance and strength (B+S) exercise vs. a strength only (S) exercise on twitch contractile properties, maximum voluntary strength, and jump performance in young athletes. Female elite young soccer players ( N = 12) aged 14-15 years conducted three experimental conditions in randomized order: S included 3 sets of 8-10 dynamic leg extensions at 80% of the 1-repetition maximum, B+S consisted of 3 sets of 40 s double-leg stances on a balance board prior to leg extensions (same as S), and a resting control period. Before and 7 min after exercise, participants were tested for their electrically-evoked isometric twitches (i.e., twitch peak torque, twitch rate of torque development) and maximal voluntary contraction (MVC) torque of the plantar flexor muscles. Additionally, countermovement (CMJ) and drop jump (DJ) performances (i.e., CMJ/DJ height, DJ ground contact time) were assessed. Significant effects of condition on twitch contractile properties ( p < 0.05, d = 1.1) and jump performance outputs ( p < 0.05, 1.1 ≤ d ≤ 1.2) were found. Post-hoc tests revealed that S compared to control produced larger PAP for twitch peak torques by trend ( p = 0.07, d = 1.8, 33 vs. 21%) and significantly larger PAP for twitch rate of torque development ( p < 0.05, d = 2.4, 55 vs. 43%). Following B+S compared to control, significant improvements in CMJ height ( p < 0.01, d = 1.9, 3%) and DJ contact time were found ( p < 0.01, d = 2.0, 10%). This study revealed protocol-specific acute performance improvements. While S resulted in significant increases in twitch contractile properties, B+S produced significant enhancements in jump performance. It is concluded that PAP effects in the plantar flexors may not directly translate to improved jump performance in female elite young soccer players. Therefore, the observed gains in jump performance following B+S are most likely related to neuromuscular changes (e.g., intramuscular coordination) rather than improved contractile properties.

Postactivation Potentiation of the Plantar Flexors Does Not Directly Translate to Jump Performance in Female Elite Young Soccer Players

PubMed Central

Prieske, Olaf; Maffiuletti, Nicola A.; Granacher, Urs

2018-01-01

High-intensity muscle actions have the potential to temporarily improve muscle contractile properties (i.e., postactivation potentiation, PAP) thereby inducing acute performance enhancements. There is evidence that balance training can improve performance during strength exercises. Taking these findings together, the purpose of this study was to examine the acute effects of a combined balance and strength (B+S) exercise vs. a strength only (S) exercise on twitch contractile properties, maximum voluntary strength, and jump performance in young athletes. Female elite young soccer players (N = 12) aged 14–15 years conducted three experimental conditions in randomized order: S included 3 sets of 8–10 dynamic leg extensions at 80% of the 1-repetition maximum, B+S consisted of 3 sets of 40 s double-leg stances on a balance board prior to leg extensions (same as S), and a resting control period. Before and 7 min after exercise, participants were tested for their electrically-evoked isometric twitches (i.e., twitch peak torque, twitch rate of torque development) and maximal voluntary contraction (MVC) torque of the plantar flexor muscles. Additionally, countermovement (CMJ) and drop jump (DJ) performances (i.e., CMJ/DJ height, DJ ground contact time) were assessed. Significant effects of condition on twitch contractile properties (p < 0.05, d = 1.1) and jump performance outputs (p < 0.05, 1.1 ≤ d ≤ 1.2) were found. Post-hoc tests revealed that S compared to control produced larger PAP for twitch peak torques by trend (p = 0.07, d = 1.8, 33 vs. 21%) and significantly larger PAP for twitch rate of torque development (p < 0.05, d = 2.4, 55 vs. 43%). Following B+S compared to control, significant improvements in CMJ height (p < 0.01, d = 1.9, 3%) and DJ contact time were found (p < 0.01, d = 2.0, 10%). This study revealed protocol-specific acute performance improvements. While S resulted in significant increases in twitch contractile properties, B+S produced significant enhancements in jump performance. It is concluded that PAP effects in the plantar flexors may not directly translate to improved jump performance in female elite young soccer players. Therefore, the observed gains in jump performance following B+S are most likely related to neuromuscular changes (e.g., intramuscular coordination) rather than improved contractile properties. PMID:29628898

Mode transition coordinated control for a compound power-split hybrid car

NASA Astrophysics Data System (ADS)

Wang, Chen; Zhao, Zhiguo; Zhang, Tong; Li, Mengna

2017-03-01

With a compound power-split transmission directly connected to the engine in hybrid cars, dramatic fluctuations in engine output torque result in noticeable jerks when the car is in mode transition from electric drive mode to hybrid drive mode. This study designed a mode transition coordinated control strategy, and verified that strategy's effectiveness with both simulations and experiments. Firstly, the mode transition process was analyzed, and ride comfort issues during the mode transition process were demonstrated. Secondly, engine ripple torque was modeled using the measured cylinder pumping pressure when the engine was not in operation. The complete dynamic plant model of the power-split hybrid car was deduced, and its effectiveness was validated by a comparison of experimental and simulation results. Thirdly, a coordinated control strategy was designed to determine the desired engine torque, motor torque, and the moment of fuel injection. Active damping control with two degrees of freedom, based on reference output shaft speed estimation, was designed to mitigate driveline speed oscillations. Carrier torque estimation based on transmission kinematics and dynamics was used to suppress torque disturbance during engine cranking. The simulation and experimental results indicate that the proposed strategy effectively suppressed vehicle jerks and improved ride comfort during mode transition.

State feedback integral control for a rotary direct drive servo valve using a Lyapunov function approach.

PubMed

Yu, Jue; Zhuang, Jian; Yu, Dehong

2015-01-01

This paper concerns a state feedback integral control using a Lyapunov function approach for a rotary direct drive servo valve (RDDV) while considering parameter uncertainties. Modeling of this RDDV servovalve reveals that its mechanical performance is deeply influenced by friction torques and flow torques; however, these torques are uncertain and mutable due to the nature of fluid flow. To eliminate load resistance and to achieve satisfactory position responses, this paper develops a state feedback control that integrates an integral action and a Lyapunov function. The integral action is introduced to address the nonzero steady-state error; in particular, the Lyapunov function is employed to improve control robustness by adjusting the varying parameters within their value ranges. This new controller also has the advantages of simple structure and ease of implementation. Simulation and experimental results demonstrate that the proposed controller can achieve higher control accuracy and stronger robustness. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Bioactive ceramic coating of cancellous screws improves the osseointegration in the cancellous bone.

PubMed

Lee, Jae Hyup; Nam, Hwa; Ryu, Hyun-Seung; Seo, Jun-Hyuk; Chang, Bong-Soon; Lee, Choon-Ki

2011-05-01

A number of methods for coating implants with bioactive ceramics have been reported to improve osseointegration in bone, but the effects of bioactive ceramic coatings on the osseointegration of cancellous screws are not known. Accordingly, biomechanical and histomorphometric analyses of the bone-screw interface of uncoated cancellous screws and cancellous screws coated with four different bioactive ceramics were performed. After coating titanium alloy cancellous screws with calcium pyrophosphate (CPP), CaO-SiO(2)-B(2)O(3) glass-ceramics (CSG), apatite-wollastonite 1:3 glass-ceramics (W3G), and CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass-ceramics (BGS-7) using an enameling method, the coated and the uncoated screws were inserted into the proximal tibia and distal femur metaphysis of seven male mongrel dogs. The torque values of the screws were measured at the time of insertion and at removal after 8 weeks. The bone-screw contact ratio was analyzed by histomorphometry. There was no significant difference in the insertion torque between the uncoated and coated screws. The torque values of the CPP and BGS-7 groups measured at removal after 8 weeks were significantly higher than those of the uncoated group. Moreover, the values of the CPP and BGS-7 groups were significantly higher than the insertion torques. The fraction of bone-screw interface measured from the undecalcified histological slide showed that the CPP, W3G, and BGS-7 groups had significantly higher torque values in the cortical bone area than the uncoated group, and the CPP and BGS-7 groups had significantly higher torque values in the cancellous bone area than the uncoated group. In conclusion, a cancellous screw coated with CPP and BGS-7 ceramic bonds directly to cancellous bone to improve the bone-implant osseointegration. This may broaden the indications for cancellous screws by clarifying their contribution to improving osseointegration, even in the cancellous bone area.

Torque and Learning and Behavior Problems in Children.

ERIC Educational Resources Information Center

Zendel, Ivan H.; Pihl, R. O.

1980-01-01

Findings indicate minimal differences, on diagnostic tests, between children who exhibited torque and those who did not. Torque is defined as the circling of any X in a clockwise direction. Torque is not associated with learning problems in school. Diagnostic utility of torque should be carefully considered. (Author)

Reduction of Cogging Torque in Dual Rotor Permanent Magnet Generator for Direct Coupled Wind Energy Systems

PubMed Central

Paulsamy, Sivachandran

2014-01-01

In wind energy systems employing permanent magnet generator, there is an imperative need to reduce the cogging torque for smooth and reliable cut in operation. In a permanent magnet generator, cogging torque is produced due to interaction of the rotor magnets with slots and teeth of the stator. This paper is a result of an ongoing research work that deals with various methods to reduce cogging torque in dual rotor radial flux permanent magnet generator (DRFPMG) for direct coupled stand alone wind energy systems (SAWES). Three methods were applied to reduce the cogging torque in DRFPMG. The methods were changing slot opening width, changing magnet pole arc width and shifting of slot openings. A combination of these three methods was applied to reduce the cogging torque to a level suitable for direct coupled SAWES. Both determination and reduction of cogging torque were carried out by finite element analysis (FEA) using MagNet Software. The cogging torque of DRFPMG has been reduced without major change in induced emf. A prototype of 1 kW, 120 rpm DRFPMG was fabricated and tested to validate the simulation results. The test results have good agreement with the simulation predictions. PMID:25202746

Reduction of cogging torque in dual rotor permanent magnet generator for direct coupled wind energy systems.

PubMed

Paulsamy, Sivachandran

2014-01-01

In wind energy systems employing permanent magnet generator, there is an imperative need to reduce the cogging torque for smooth and reliable cut in operation. In a permanent magnet generator, cogging torque is produced due to interaction of the rotor magnets with slots and teeth of the stator. This paper is a result of an ongoing research work that deals with various methods to reduce cogging torque in dual rotor radial flux permanent magnet generator (DRFPMG) for direct coupled stand alone wind energy systems (SAWES). Three methods were applied to reduce the cogging torque in DRFPMG. The methods were changing slot opening width, changing magnet pole arc width and shifting of slot openings. A combination of these three methods was applied to reduce the cogging torque to a level suitable for direct coupled SAWES. Both determination and reduction of cogging torque were carried out by finite element analysis (FEA) using MagNet Software. The cogging torque of DRFPMG has been reduced without major change in induced emf. A prototype of 1 kW, 120 rpm DRFPMG was fabricated and tested to validate the simulation results. The test results have good agreement with the simulation predictions.

78 FR 40956 - Airworthiness Directives; Eurocopter Deutschland (Eurocopter) Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-09

... compressor pulley to the rotor brake disc lost torque and allowed the pulley to separate. After the... installed in a tightening direction, or if the pulley is loose, remove and inspect the pulley as described.... (ii) Install the pulley and torque each mount bolt to 90 inch- pounds. After torqueing, determine...

Super Turbocharging the Direct Injection Diesel engine

NASA Astrophysics Data System (ADS)

Boretti, Albert

2018-03-01

The steady operation of a turbocharged diesel direct injection (TDI) engine featuring a variable speed ratio mechanism linking the turbocharger shaft to the crankshaft is modelled in the present study. Key parameters of the variable speed ratio mechanism are range of speed ratios, efficiency and inertia, in addition to the ability to control relative speed and flow of power. The device receives energy from, or delivers energy to, the crankshaft or the turbocharger. In addition to the pistons of the internal combustion engine (ICE), also the turbocharger thus contributes to the total mechanical power output of the engine. The energy supply from the crankshaft is mostly needed during sharp accelerations to avoid turbo-lag, and to boost torque at low speeds. At low speeds, the maximum torque is drastically improved, radically expanding the load range. Additionally, moving closer to the points of operation of a balanced turbocharger, it is also possible to improve both the efficiency η, defined as the ratio of the piston crankshaft power to the fuel flow power, and the total efficiency η*, defined as the ratio of piston crankshaft power augmented of the power from the turbocharger shaft to the fuel flow power, even if of a minimal extent. The energy supply to the crankshaft is possible mostly at high speeds and high loads, where otherwise the turbine could have been waste gated, and during decelerations. The use of the energy at the turbine otherwise waste gated translates in improvements of the total fuel conversion efficiency η* more than the efficiency η. Much smaller improvements are obtained for the maximum torque, yet again moving closer to the points of operation of a balanced turbocharger. Adopting a much larger turbocharger (target displacement x speed 30% larger than a conventional turbocharger), better torque outputs and fuel conversion efficiencies η* and η are possible at every speed vs. the engine with a smaller, balanced turbocharger. This result motivates further studies of the mechanism that may considerably benefit traditional powertrains based on diesel engines.

Forces and moments generated by the human arm: Variability and control

PubMed Central

Xu, Y; Terekhov, AV; Latash, ML; Zatsiorsky, VM

2012-01-01

This is an exploratory study of the accurate endpoint force vector production by the human arm in isometric conditions. We formulated three common-sense hypotheses and falsified them in the experiment. The subjects (n=10) exerted static forces on the handle in eight directions in a horizontal plane for 25 seconds. The forces were of 4 magnitude levels (10 %, 20%, 30% and 40% of individual MVC). The torsion moment on the handle (grasp moment) was not specified in the instruction. The two force components and the grasp moment were recorded, and the shoulder, elbow, and wrist joint torques were computed. The following main facts were observed: (a) While the grasp moment was not prescribed by the instruction, it was always produced. The moment magnitude and direction depended on the instructed force magnitude and direction. (b) The within-trial angular variability of the exerted force vector (angular precision) did not depend on the target force magnitude (a small negative correlation was observed). (c) Across the target force directions, the variability of the exerted force magnitude and directional variability exhibited opposite trends: In the directions where the variability of force magnitude was maximal, the directional variability was minimal and vice versa. (d) The time profiles of joint torques in the trials were always positively correlated, even for the force directions where flexion torque was produced at one joint and extension torque was produced at the other joint. (e) The correlations between the grasp moment and the wrist torque were negative across the tasks and positive within the individual trials. (f) In static serial kinematic chains, the pattern of the joint torques distribution could not be explained by an optimization cost function additive with respect to the torques. Plans for several future experiments have been suggested. PMID:23080084

Plyometric Long Jump Training With Progressive Loading Improves Kinetic and Kinematic Swimming Start Parameters.

PubMed

Rebutini, Vanessa Z; Pereira, Gleber; Bohrer, Roberta C D; Ugrinowitsch, Carlos; Rodacki, André L F

2016-09-01

Rebutini, VZ, Pereira, G, Bohrer, RCD, Ugrinowitsch, C, and Rodacki, ALF. Plyometric long jump training with progressive loading improves kinetic and kinematic swimming start parameters. J Strength Cond Res 30(9): 2392-2398, 2016-This study was aimed to determine the effects of a plyometric long jump training program on torque around the lower limb joints and kinetic and kinematics parameters during the swimming jump start. Ten swimmers performed 3 identical assessment sessions, measuring hip and knee muscle extensors during maximal voluntary isometric contraction and kinetic and kinematics parameters during the swimming jump start, at 3 instants: INI (2 weeks before the training program, control period), PRE (2 weeks after INI measurements), and POST (24-48 hours after 9 weeks of training). There were no significant changes from INI to PRE measurements. However, the peak torque and rate of torque development increased significantly from PRE to POST measurements for both hip (47 and 108%) and knee (24 and 41%) joints. There were significant improvements to the horizontal force (7%), impulse (9%), and angle of resultant force (19%). In addition, there were significant improvements to the center of mass displacement (5%), horizontal takeoff velocity (16%), horizontal velocity at water entrance (22%), and peak angle velocity for the knee (15%) and hip joints (16%). Therefore, the plyometric long jump training protocol was effective to enhance torque around the lower limb joints and to control the resultant vector direction, to increase the swimming jump start performance. These findings suggest that coaches should use long jump training instead of vertical jump training to improve swimming start performance.

Effects of underestimating the kinematics of trunk rotation on simultaneous reaching movements: predictions of a biomechanical model

PubMed Central

2013-01-01

Background Rotation of the torso while reaching produces torques (e.g., Coriolis torque) that deviate the arm from its planned trajectory. To ensure an accurate reaching movement, the brain may take these perturbing torques into account during movement planning or, alternatively, it may correct hand trajectory during movement execution. Irrespective of the process selected, it is expected that an underestimation of trunk rotation would likely induce inaccurate shoulder and elbow torques, resulting in hand deviation. Nonetheless, it is still undetermined to what extent a small error in the perception of trunk rotations, translating into an inappropriate selection of motor commands, would affect reaching accuracy. Methods To investigate, we adapted a biomechanical model (J Neurophysiol 89: 276-289, 2003) to predict the consequences of underestimating trunk rotations on right hand reaching movements performed during either clockwise or counter clockwise torso rotations. Results The results revealed that regardless of the degree to which the torso rotation was underestimated, the amplitude of hand deviation was much larger for counter clockwise rotations than for clockwise rotations. This was attributed to the fact that the Coriolis and centripetal joint torques were acting in the same direction during counter clockwise rotation yet in opposite directions during clockwise rotations, effectively cancelling each other out. Conclusions These findings suggest that in order to anticipate and compensate for the interaction torques generated during torso rotation while reaching, the brain must have an accurate prediction of torso rotation kinematics. The present study proposes that when designing upper limb prostheses controllers, adding a sensor to monitor trunk kinematics may improve prostheses control and performance. PMID:23758968

A new instantaneous torque control of PM synchronous motor for high-performance direct-drive applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, S.K.; Kim, H.S.; Kim, C.G.

1998-05-01

a new instantaneous torque-control strategy is presented for high-performance control of a permanent magnet (PM) synchronous motor. In order to deal with the torque pulsating problem of a PM synchronous motor in a low-speed region, new torque estimation and control techniques are proposed. The linkage flux of a PM synchronous motor is estimated using a model reference adaptive system technique, and the developed torque is instantaneously controlled by the proposed torque controller combining a variable structure control (VSC) with a space-vector pulse-width modulation (PWM). The proposed control provides the advantage of reducing the torque pulsation caused by the nonsinusoidal fluxmore » distribution. This control strategy is applied to the high-torque PM synchronous motor drive system for direct-drive applications and implemented by using a software of the digital signal processor (DSP) TMS320C30. The simulations and experiments are carried out for this system, and the results well demonstrate the effectiveness of the proposed control.« less

Design and analysis of a direct-drive wind power generator with ultra-high torque density

NASA Astrophysics Data System (ADS)

Jian, Linni; Shi, Yujun; Wei, Jin; Zheng, Yanchong

2015-05-01

In order to get rid of the nuisances caused by mechanical gearboxes, generators with low rated speed, which can be directly connected to wind turbines, are attracting increasing attention. The purpose of this paper is to propose a new direct-drive wind power generator (DWPG), which can offer ultra-high torque density. First, magnetic gear (MG) is integrated to achieve non-contact torque transmission and speed variation. Second, armature windings are engaged to achieve electromechanical energy conversion. Interior permanent magnet (PM) design on the inner rotor is adopted to boost the torque transmission capability of the integrated MG. Nevertheless, due to lack of back iron on the stator, the proposed generator does not exhibit prominent salient feature, which usually exists in traditional interior PM (IPM) machines. This makes it with good controllability and high power factor as the surface-mounted permanent magnet machines. The performance is analyzed using finite element method. Investigation on the magnetic field harmonics demonstrates that the permanent-magnetic torque offered by the MG can work together with the electromagnetic torque offered by the armature windings to balance the driving torque captured by the wind turbine. This allows the proposed generator having the potential to offer even higher torque density than its integrated MG.

Flux-Based Deadbeat Control of Induction-Motor Torque

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Lorenz, Robert D.

2003-01-01

An improved method and prior methods of deadbeat direct torque control involve the use of pulse-width modulation (PWM) of applied voltages. The prior methods are based on the use of stator flux and stator current as state variables, leading to mathematical solutions of control equations in forms that do not lend themselves to clear visualization of solution spaces. In contrast, the use of rotor and stator fluxes as the state variables in the present improved method lends itself to graphical representations that aid in understanding possible solutions under various operating conditions. In addition, the present improved method incorporates the superposition of high-frequency carrier signals for use in a motor-self-sensing technique for estimating the rotor shaft angle at any speed (including low or even zero speed) without need for additional shaft-angle-measuring sensors.

Design Evaluation of Wind Turbine Spline Couplings Using an Analytical Model: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Y.; Keller, J.; Wallen, R.

2015-02-01

Articulated splines are commonly used in the planetary stage of wind turbine gearboxes for transmitting the driving torque and improving load sharing. Direct measurement of spline loads and performance is extremely challenging because of limited accessibility. This paper presents an analytical model for the analysis of articulated spline coupling designs. For a given torque and shaft misalignment, this analytical model quickly yields insights into relationships between the spline design parameters and resulting loads; bending, contact, and shear stresses; and safety factors considering various heat treatment methods. Comparisons of this analytical model against previously published computational approaches are also presented.

An Enhanced Three-Level Voltage Switching State Scheme for Direct Torque Controlled Open End Winding Induction Motor

NASA Astrophysics Data System (ADS)

Kunisetti, V. Praveen Kumar; Thippiripati, Vinay Kumar

2018-01-01

Open End Winding Induction Motors (OEWIM) are popular for electric vehicles, ship propulsion applications due to less DC link voltage. Electric vehicles, ship propulsions require ripple free torque. In this article, an enhanced three-level voltage switching state scheme for direct torque controlled OEWIM drive is implemented to reduce torque and flux ripples. The limitations of conventional Direct Torque Control (DTC) are: possible problems during low speeds and starting, it operates with variable switching frequency due to hysteresis controllers and produces higher torque and flux ripple. The proposed DTC scheme can abate the problems of conventional DTC with an enhanced voltage switching state scheme. The three-level inversion was obtained by operating inverters with equal DC-link voltages and it produces 18 voltage space vectors. These 18 vectors are divided into low and high frequencies of operation based on rotor speed. The hardware results prove the validity of proposed DTC scheme during steady-state and transients. From simulation and experimental results, proposed DTC scheme gives less torque and flux ripples on comparison to two-level DTC. The proposed DTC is implemented using dSPACE DS-1104 control board interface with MATLAB/SIMULINK-RTI model.

Development of an ankle torque measurement device for measuring ankle torque during walking.

PubMed

Tanino, Genichi; Tomita, Yutaka; Mizuno, Shiho; Maeda, Hirofumi; Miyasaka, Hiroyuki; Orand, Abbas; Takeda, Kotaro; Sonoda, Shigeru

2015-05-01

[Purpose] To develop a device for measuring the torque of an ankle joint during walking in order to quantify the characteristics of spasticity of the ankle and to verify the functionality of the device by testing it on the gait of an able-bodied individual and an equinovarus patient. [Subjects and Methods] An adjustable posterior strut (APS) ankle-foot orthosis (AFO) was used in which two torque sensors were mounted on the aluminum strut for measuring the anterior-posterior (AP) and medial-lateral (ML) directions. Two switches were also mounted at the heel and toe in order to detect the gait phase. An able-bodied individual and a left hemiplegic patient with equinovarus participated. They wore the device and walked on a treadmill to investigate the device's functionality. [Results] Linear relationships between the torques and the corresponding output of the torque sensors were observed. Upon the analyses of gait of an able-body subject and a hemiplegic patient, we observed toque matrices in both AP and ML directions during the gait of the both subjects. [Conclusion] We developed a device capable of measuring the torque in the AP and ML directions of ankle joints during gait.

An Enhanced Three-Level Voltage Switching State Scheme for Direct Torque Controlled Open End Winding Induction Motor

NASA Astrophysics Data System (ADS)

Kunisetti, V. Praveen Kumar; Thippiripati, Vinay Kumar

2018-06-01

Open End Winding Induction Motors (OEWIM) are popular for electric vehicles, ship propulsion applications due to less DC link voltage. Electric vehicles, ship propulsions require ripple free torque. In this article, an enhanced three-level voltage switching state scheme for direct torque controlled OEWIM drive is implemented to reduce torque and flux ripples. The limitations of conventional Direct Torque Control (DTC) are: possible problems during low speeds and starting, it operates with variable switching frequency due to hysteresis controllers and produces higher torque and flux ripple. The proposed DTC scheme can abate the problems of conventional DTC with an enhanced voltage switching state scheme. The three-level inversion was obtained by operating inverters with equal DC-link voltages and it produces 18 voltage space vectors. These 18 vectors are divided into low and high frequencies of operation based on rotor speed. The hardware results prove the validity of proposed DTC scheme during steady-state and transients. From simulation and experimental results, proposed DTC scheme gives less torque and flux ripples on comparison to two-level DTC. The proposed DTC is implemented using dSPACE DS-1104 control board interface with MATLAB/SIMULINK-RTI model.

Magnification of starting torques of dc motors by maximum power point trackers in photovoltaic systems

NASA Technical Reports Server (NTRS)

Appelbaum, Joseph; Singer, S.

1989-01-01

Direct current (dc) motors are used in terrestrial photovoltaic (PV) systems such as in water-pumping systems for irrigation and water supply. Direct current motors may also be used for space applications. Simple and low weight systems including dc motors may be of special interest in space where the motors are directly coupled to the solar cell array (with no storage). The system will operate only during times when sufficient insolation is available. An important performance characteristic of electric motors is the starting to rated torque ratio. Different types of dc motors have different starting torque ratios. These ratios are dictated by the size of solar cell array, and the developed motor torque may not be sufficient to overcome the load starting torque. By including a maximum power point tracker (MPPT) in the PV system, the starting to rated torque ratio will increase, the amount of which depends on the motor type. The starting torque ratio is calculated for the permanent magnet, series and shunt excited dc motors when powered by solar cell arrays for two cases: with and without MPPT's. Defining a motor torque magnification by the ratio of the motor torque with an MPPT to the motor torque without an MPPT, a magnification of 3 was obtained for the permanent magnet motor and a magnification of 7 for both the series and shunt motors. The effect of the variation of solar insolation on the motor starting torque was covered. All motor types are less sensitive to insolation variation in systems including MPPT's as compared to systems with MPPT's. The analysis of this paper will assist the PV system designed to determine whether or not to include an MPPT in the system for a specific motor type.

Cogging Torque Estimation of Permanent Magnet Motors Resulting from Magnetic Anisotropy of Non-oriented Electrical Steel Sheets

NASA Astrophysics Data System (ADS)

Daikoku, Akihiro; Yamaguchi, Shinichi; Toide, Yukari; Fujiwara, Koji; Takahashi, Norio

This paper examines the cogging torque of permanent magnet motors resulting from the magnetic anisotropy of non-oriented steel sheets used for magnetic core. The cogging torque due to the magnetic anisotropy is calculated by FEM using two modeling methods; one is the newly developed method which takes account of the two-dimensional magnetic properties in arbitrary directions, and the other is the conventional method which uses only two magnetization curves both in rolling and transverse directions. In the proposed method, the measured magnetic properties are treated in two different ways; in the first way the data are used directly, and in the second way the data are interpolated using Bèzier surface. As a result, all of three models show the cogging torque component resulting from the magnetic anisotropy, that has less pulsation numbers per rotation than that of isotropic model. The difference of the cogging torque amplitude between the three models is small in the region of low magnetic flux density, however, it gradually becomes large along with the increase in magnetic flux density. The measured results of cogging torque is proximate to the results calculated by two-dimensional magnetic property method using the magnetic property data directly. The error is approximately 4% at the point where the cogging torque component resulting from the magnetic anisotropy is maximum.

Torque Compensator for Mirror Mountings

NASA Technical Reports Server (NTRS)

Howe, S. D.

1983-01-01

Device nulls flexural distributions of pivotal torques. Magnetic compensator for flexing pivot torque consists of opposing fixed and movable magnet bars. Magnetic torque varies nonlinearly as function of angle of tilt of movable bar. Positions of fixed magnets changed to improve magnetic torque linearity.

Direction-Specific Impairments in Cervical Range of Motion in Women with Chronic Neck Pain: Influence of Head Posture and Gravitationally Induced Torque.

PubMed

Rudolfsson, Thomas; Björklund, Martin; Svedmark, Åsa; Srinivasan, Divya; Djupsjöbacka, Mats

2017-01-01

Cervical range of motion (ROM) is commonly assessed in clinical practice and research. In a previous study we decomposed active cervical sagittal ROM into contributions from lower and upper levels of the cervical spine and found level- and direction-specific impairments in women with chronic non-specific neck pain. The present study aimed to validate these results and investigate if the specific impairments can be explained by the neutral posture (defining zero flexion/extension) or a movement strategy to avoid large gravitationally induced torques on the cervical spine. Kinematics of the head and thorax was assessed in sitting during maximal sagittal cervical flexion/extension (high torque condition) and maximal protraction (low torque condition) in 120 women with chronic non-specific neck pain and 40 controls. We derived the lower and upper cervical angles, and the head centre of mass (HCM), from a 3-segment kinematic model. Neutral head posture was assessed using a standardized procedure. Previous findings of level- and direction-specific impairments in neck pain were confirmed. Neutral head posture was equal between groups and did not explain the direction-specific impairments. The relative magnitude of group difference in HCM migration did not differ between high and low torques conditions, lending no support for our hypothesis that impairments in sagittal ROM are due to torque avoidance behaviour. The direction- and level-specific impairments in cervical sagittal ROM can be generalised to the population of women with non-specific neck pain. Further research is necessary to clarify if torque avoidance behaviour can explain the impairments.

Nonlinear Control of the Doubly Fed Induction Motor with Copper Losses Minimization for Electrical Vehicle

NASA Astrophysics Data System (ADS)

Drid, S.; Nait-Said, M.-S.; Tadjine, M.; Makouf, A.

2008-06-01

There is an increasing interest in electric vehicles due to environmental concerns. Recent efforts are directed toward developing an improved propulsion system for electric vehicles applications with minimal power losses. This paper deals with the high efficient vector control for the reduction of copper losses of the doubly fed motor. Firstly, the feedback linearization control based on Lyapunov approach is employed to design the underlying controller achieving the double fluxes orientation. The fluxes controllers are designed independently of the speed. The speed controller is designed using the Lyapunov method especially employed to the unknown load torques. The global asymptotic stability of the overall system is theoretically proven. Secondly, a new Torque Copper Losses Factor is proposed to deal with the problem of the machine copper losses. Its main function is to optimize the torque in keeping the machine saturation at an acceptable level. This leads to a reduction in machine currents and therefore their accompanied copper losses guaranteeing improved machine efficiency. The simulation results in comparative presentation confirm largely the effectiveness of the proposed DFIM control with a very interesting energy saving contribution.

Design and control of one precise tracking simulation bed for Chinese 20/30 meter optic/infrared telescope

NASA Astrophysics Data System (ADS)

Ren, Changzhi; Li, Xiaoyan; Song, Xiaoli; Niu, Yong; Li, Aihua; Zhang, Zhenchao

2012-09-01

Direct drive technology is the key to solute future 30-m and larger telescope motion system to guarantee a very high tracking accuracy, in spite of unbalanced and sudden loads such as wind gusts and in spite of a structure that, because of its size, can not be infinitely stiff. However, this requires the design and realization of unusually large torque motor that the torque slew rate must be extremely steep too. A conventional torque motor design appears inadequate. This paper explores one redundant unit permanent magnet synchronous motor and its simulation bed for 30-m class telescope. Because its drive system is one high integrated electromechanical system, one complexly electromechanical design method is adopted to improve the efficiency, reliability and quality of the system during the design and manufacture circle. This paper discusses the design and control of the precise tracking simulation bed in detail.

Direction-Specific Impairments in Cervical Range of Motion in Women with Chronic Neck Pain: Influence of Head Posture and Gravitationally Induced Torque

PubMed Central

Björklund, Martin; Svedmark, Åsa; Srinivasan, Divya; Djupsjöbacka, Mats

2017-01-01

Background Cervical range of motion (ROM) is commonly assessed in clinical practice and research. In a previous study we decomposed active cervical sagittal ROM into contributions from lower and upper levels of the cervical spine and found level- and direction-specific impairments in women with chronic non-specific neck pain. The present study aimed to validate these results and investigate if the specific impairments can be explained by the neutral posture (defining zero flexion/extension) or a movement strategy to avoid large gravitationally induced torques on the cervical spine. Methods Kinematics of the head and thorax was assessed in sitting during maximal sagittal cervical flexion/extension (high torque condition) and maximal protraction (low torque condition) in 120 women with chronic non-specific neck pain and 40 controls. We derived the lower and upper cervical angles, and the head centre of mass (HCM), from a 3-segment kinematic model. Neutral head posture was assessed using a standardized procedure. Findings Previous findings of level- and direction-specific impairments in neck pain were confirmed. Neutral head posture was equal between groups and did not explain the direction-specific impairments. The relative magnitude of group difference in HCM migration did not differ between high and low torques conditions, lending no support for our hypothesis that impairments in sagittal ROM are due to torque avoidance behaviour. Interpretation The direction- and level-specific impairments in cervical sagittal ROM can be generalised to the population of women with non-specific neck pain. Further research is necessary to clarify if torque avoidance behaviour can explain the impairments. PMID:28099504

Gravitational and Dynamic Components of Muscle Torque Underlie Tonic and Phasic Muscle Activity during Goal-Directed Reaching.

PubMed

Olesh, Erienne V; Pollard, Bradley S; Gritsenko, Valeriya

2017-01-01

Human reaching movements require complex muscle activations to produce the forces necessary to move the limb in a controlled manner. How gravity and the complex kinetic properties of the limb contribute to the generation of the muscle activation pattern by the central nervous system (CNS) is a long-standing and controversial question in neuroscience. To tackle this issue, muscle activity is often subdivided into static and phasic components. The former corresponds to posture maintenance and transitions between postures. The latter corresponds to active movement production and the compensation for the kinetic properties of the limb. In the present study, we improved the methodology for this subdivision of muscle activity into static and phasic components by relating them to joint torques. Ten healthy subjects pointed in virtual reality to visual targets arranged to create a standard center-out reaching task in three dimensions. Muscle activity and motion capture data were synchronously collected during the movements. The motion capture data were used to calculate postural and dynamic components of active muscle torques using a dynamic model of the arm with 5 degrees of freedom. Principal Component Analysis (PCA) was then applied to muscle activity and the torque components, separately, to reduce the dimensionality of the data. Muscle activity was also reconstructed from gravitational and dynamic torque components. Results show that the postural and dynamic components of muscle torque represent a significant amount of variance in muscle activity. This method could be used to define static and phasic components of muscle activity using muscle torques.

Gravitational and Dynamic Components of Muscle Torque Underlie Tonic and Phasic Muscle Activity during Goal-Directed Reaching

PubMed Central

Olesh, Erienne V.; Pollard, Bradley S.; Gritsenko, Valeriya

2017-01-01

Human reaching movements require complex muscle activations to produce the forces necessary to move the limb in a controlled manner. How gravity and the complex kinetic properties of the limb contribute to the generation of the muscle activation pattern by the central nervous system (CNS) is a long-standing and controversial question in neuroscience. To tackle this issue, muscle activity is often subdivided into static and phasic components. The former corresponds to posture maintenance and transitions between postures. The latter corresponds to active movement production and the compensation for the kinetic properties of the limb. In the present study, we improved the methodology for this subdivision of muscle activity into static and phasic components by relating them to joint torques. Ten healthy subjects pointed in virtual reality to visual targets arranged to create a standard center-out reaching task in three dimensions. Muscle activity and motion capture data were synchronously collected during the movements. The motion capture data were used to calculate postural and dynamic components of active muscle torques using a dynamic model of the arm with 5 degrees of freedom. Principal Component Analysis (PCA) was then applied to muscle activity and the torque components, separately, to reduce the dimensionality of the data. Muscle activity was also reconstructed from gravitational and dynamic torque components. Results show that the postural and dynamic components of muscle torque represent a significant amount of variance in muscle activity. This method could be used to define static and phasic components of muscle activity using muscle torques. PMID:29018339

Spin-orbit torque in a thin film of the topological insulator Bi2Se3: Crossover from the ballistic to diffusive regime

NASA Astrophysics Data System (ADS)

Ren, Y. J.; Deng, W. Y.; Geng, H.; Shen, R.; Shao, L. B.; Sheng, L.; Xing, D. Y.

2017-12-01

The spin-orbit torque provides an efficient method for switching the direction of a magnetization by using an electric field. Owing to the spin-orbit coupling, when an electric field is applied, a nonequilibrium spin density is generated, which exerts a torque on the local magnetization. Here, we investigate the spin-orbit torque in a thin film of topological insulator \\text{Bi}2\\text{Se}3 based upon a Boltzmann equation, with proper boundary conditions, which is applicable from the ballistic regime to the diffusive regime. It is shown that due to the spin-momentum interlocking of the electron surface states, the magnitude of the field-like torque is simply in linear proportion to the longitudinal electrical current. For a fixed electric field, the spin-orbit torque is proportional to the sample length in the ballistic limit, and saturates to a constant in the diffusive limit. The dependence of the torque on the magnetization direction and exchange coupling strength is also studied. Our theory may offer useful guidance for experimental investigations of the spin-orbit torque in finite-size systems.

Leveraging Disturbance Observer Based Torque Control for Improved Impedance Rendering with Series Elastic Actuators

NASA Technical Reports Server (NTRS)

Mehling, Joshua S.; Holley, James; O'Malley, Marcia K.

2015-01-01

The fidelity with which series elastic actuators (SEAs) render desired impedances is important. Numerous approaches to SEA impedance control have been developed under the premise that high-precision actuator torque control is a prerequisite. Indeed, the design of an inner torque compensator has a significant impact on actuator impedance rendering. The disturbance observer (DOB) based torque control implemented in NASA's Valkyrie robot is considered here and a mathematical model of this torque control, cascaded with an outer impedance compensator, is constructed. While previous work has examined the impact a disturbance observer has on torque control performance, little has been done regarding DOBs and impedance rendering accuracy. Both simulation and a series of experiments are used to demonstrate the significant improvements possible in an SEA's ability to render desired dynamic behaviors when utilizing a DOB. Actuator transparency at low impedances is improved, closed loop hysteresis is reduced, and the actuator's dynamic response to both commands and interaction torques more faithfully matches that of the desired model. All of this is achieved by leveraging DOB based control rather than increasing compensator gains, thus making improved SEA impedance control easier to achieve in practice.

3-D sprag ratcheting tool

NASA Technical Reports Server (NTRS)

Wade, Michael O. (Inventor); Poland, Jr., James W. (Inventor)

2003-01-01

A ratcheting device comprising a driver head assembly which includes at least two 3-D sprag elements positioned within a first groove within the driver head assembly such that at least one of the 3-D sprag elements may lockingly engage the driver head assembly and a mating hub assembly to allow for rotation of the hub assembly in one direction with respect to the driver head assembly. This arrangement allows the ratcheting tool to impart torque in either the clockwise or counterclockwise direction without having to first rotate the ratcheting tool in the direction opposite the direction in which the torque is applied. This arrangement also allows the ratcheting tool to impart torque in either the clockwise or counterclockwise direction while in the neutral position.

Torque limited drive for manual valves

DOEpatents

Elliott, Philip G.; Underwood, Daniel E.

1989-01-01

The present invention is directed to a torque-limiting handwheel device for preventing manual valves from being damaged due to the application of excessive torque during the opening or closing operation of the valves. Torque can only be applied when ridges in the handwheel assembly engage in channels machined in the face of the baseplate. The amount of torque required for disengagement of the ridges from the channels is determined by the force exerted by various Bellville springs and the inclination of the side faces of the channels.

Torque limited drive for manual valves

DOEpatents

Elliott, Philip G.; Underwood, Daniel E.

1989-06-06

The present invention is directed to a torque-limiting handwheel device for preventing manual valves from being damaged due to the application of excessive torque during the opening or closing operation of the valves. Torque can only be applied when ridges in the handwheel assembly engage in channels machined in the face of the baseplate. The amount of torque required for disengagement of the ridges from the channels is determined by the force exerted by various Bellville springs and the inclination of the side faces of the channels.

Determining a Method of Enabling and Disabling the Integral Torque in the SDO Science and Inertial Mode Controllers

NASA Technical Reports Server (NTRS)

Vess, Melissa F.; Starin, Scott R.

2007-01-01

During design of the SDO Science and Inertial mode PID controllers, the decision was made to disable the integral torque whenever system stability was in question. Three different schemes were developed to determine when to disable or enable the integral torque, and a trade study was performed to determine which scheme to implement. The trade study compared complexity of the control logic, risk of not reenabling the integral gain in time to reject steady-state error, and the amount of integral torque space used. The first scheme calculated a simplified Routh criterion to determine when to disable the integral torque. The second scheme calculates the PD part of the torque and looked to see if that torque would cause actuator saturation. If so, only the PD torque is used. If not, the integral torque is added. Finally, the third scheme compares the attitude and rate errors to limits and disables the integral torque if either of the errors is greater than the limit. Based on the trade study results, the third scheme was selected. Once it was decided when to disable the integral torque, analysis was performed to determine how to disable the integral torque and whether or not to reset the integrator once the integral torque was reenabled. Three ways to disable the integral torque were investigated: zero the input into the integrator, which causes the integral part of the PID control torque to be held constant; zero the integral torque directly but allow the integrator to continue integrating; or zero the integral torque directly and reset the integrator on integral torque reactivation. The analysis looked at complexity of the control logic, slew time plus settling time between each calibration maneuver step, and ability to reject steady-state error. Based on the results of the analysis, the decision was made to zero the input into the integrator without resetting it. Throughout the analysis, a high fidelity simulation was used to test the various implementation methods.

Charge-induced spin torque in Weyl semimetals

NASA Astrophysics Data System (ADS)

Kurebayashi, Daichi; Nomura, Kentaro

In this work, we present phenomenological and microscopic derivations of spin torques in magnetically doped Weyl semimetals. As a result, we obtain the analytical expression of the spin torque generated, without a flowing current, when the chemical potential is modulated. We also find that this spin torque is a direct consequence of the chiral anomaly. Therefore, observing this spin torque in magnetic Weyl semimetals might be an experimental evidence of the chiral anomaly. This spin torque has also a great advantage in application. In contrast to conventional current-induced spin torques such as the spin-transfer torques, this spin torque does not accompany a constant current flow. Thus, devices using this operating principle is free from the Joule heating and possibly have higher efficiency than devices using conventional current-induced spin torques. This work was supported by JSPS KAKENHI Grant Number JP15H05854 and JP26400308.

Emergence of Huge Negative Spin-Transfer Torque in Atomically Thin Co layers

NASA Astrophysics Data System (ADS)

Je, Soong-Geun; Yoo, Sang-Cheol; Kim, Joo-Sung; Park, Yong-Keun; Park, Min-Ho; Moon, Joon; Min, Byoung-Chul; Choe, Sug-Bong

2017-04-01

Current-induced domain wall motion has drawn great attention in recent decades as the key operational principle of emerging magnetic memory devices. As the major driving force of the motion, the spin-orbit torque on chiral domain walls has been proposed and is currently extensively studied. However, we demonstrate here that there exists another driving force, which is larger than the spin-orbit torque in atomically thin Co films. Moreover, the direction of the present force is found to be the opposite of the prediction of the standard spin-transfer torque, resulting in the domain wall motion along the current direction. The symmetry of the force and its peculiar dependence on the domain wall structure suggest that the present force is, most likely, attributed to considerable enhancement of a negative nonadiabatic spin-transfer torque in ultranarrow domain walls. Careful measurements of the giant magnetoresistance manifest a negative spin polarization in the atomically thin Co films which might be responsible for the negative spin-transfer torque.

Electromagnetic torque tweezers: a versatile approach for measurement of single-molecule twist and torque.

PubMed

Janssen, Xander J A; Lipfert, Jan; Jager, Tessa; Daudey, Renier; Beekman, Jaap; Dekker, Nynke H

2012-07-11

The well-established single-molecule force-spectroscopy techniques have recently been complemented by methods that can measure torque and twist directly, notably magnetic torque tweezers and the optical torque wrench. A limitation of the current torque measurement schemes is the intrinsic coupling between the force and torque degrees of freedom. Here we present electromagnetic torque tweezers (eMTT) that combine permanent and electromagnets to enable independent control of the force and torsional trap stiffness for sensitive measurements of single molecule torque and twist. Using the eMTT, we demonstrate sensitive torque measurements on tethered DNA molecules from simple tracking of the beads' (x,y)-position, obviating the need for any angular tracking algorithms or markers. Employing the eMTT for high-resolution torque measurements, we experimentally confirm the theoretically predicted torque overshoot at the DNA buckling transition in high salt conditions. We envision that the flexibility and control afforded by the eMTT will enable a range of new torque and twist measurement schemes from single-molecules to living cells.

Joint torques in a freely walking insect reveal distinct functions of leg joints in propulsion and posture control

PubMed Central

2016-01-01

Determining the mechanical output of limb joints is critical for understanding the control of complex motor behaviours such as walking. In the case of insect walking, the neural infrastructure for single-joint control is well described. However, a detailed description of the motor output in form of time-varying joint torques is lacking. Here, we determine joint torques in the stick insect to identify leg joint function in the control of body height and propulsion. Torques were determined by measuring whole-body kinematics and ground reaction forces in freely walking animals. We demonstrate that despite strong differences in morphology and posture, stick insects show a functional division of joints similar to other insect model systems. Propulsion was generated by strong depression torques about the coxa–trochanter joint, not by retraction or flexion/extension torques. Torques about the respective thorax–coxa and femur–tibia joints were often directed opposite to fore–aft forces and joint movements. This suggests a posture-dependent mechanism that counteracts collapse of the leg under body load and directs the resultant force vector such that strong depression torques can control both body height and propulsion. Our findings parallel propulsive mechanisms described in other walking, jumping and flying insects, and challenge current control models of insect walking. PMID:26791608

Vehicle handling and stability control by the cooperative control of 4WS and DYC

NASA Astrophysics Data System (ADS)

Shen, Huan; Tan, Yun-Sheng

2017-07-01

This paper proposes an integrated control system that cooperates with the four-wheel steering (4WS) and direct yaw moment control (DYC) to improve the vehicle handling and stability. The design works of the four-wheel steering and DYC control are based on sliding mode control. The integration control system produces the suitable 4WS angle and corrective yaw moment so that the vehicle tracks the desired yaw rate and sideslip angle. Considering the change of the vehicle longitudinal velocity that means the comfort of driving conditions, both the driving torque and braking torque are used to generate the corrective yaw moment. Simulation results show the effectiveness of the proposed control algorithm.

76 FR 55785 - Airworthiness Directives; Bombardier, Inc. Model DHC-8-400 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-09

... the elevator torque tube rivets, and re-identifying the assemblies. You may obtain further information... with the autopilot engaged. Investigations revealed that loose rivets in the torque tube assemblies caused relative motion between the crank arms and torque tubes. Loose rivets could result in excessive...

77 FR 40828 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-11

... certain main landing gear (MLG) upper torque link bolts is reduced significantly due to incorrect fabrication. This proposed AD would require replacing certain MLG upper torque link bolts with a new or... safe life limit on certain MLG upper torque link bolts is reduced significantly due to incorrect...

Universal adaptive torque control for PM motors for field-weakening region operation

DOEpatents

Royak, Semyon [Beachwood, OH; Harbaugh, Mark M [Richfield, OH; Breitzmann, Robert J [South Russel, OH; Nondahl, Thomas A [Wauwatosa, WI; Schmidt, Peter B [Franklin, WI; Liu, Jingbo [Milwaukee, WI

2011-03-29

The invention includes a motor controller and method for controlling a permanent magnet motor. In accordance with one aspect of the present technique, a permanent magnet motor is controlled by, among other things, receiving a torque command, determining a normalized torque command by normalizing the torque command to a characteristic current of the motor, determining a normalized maximum available voltage, determining an inductance ratio of the motor, and determining a direct-axis current based upon the normalized torque command, the normalized maximum available voltage, and the inductance ratio of the motor.

Direct mechanical torque sensor for model wind turbines

NASA Astrophysics Data System (ADS)

Kang, Hyung Suk; Meneveau, Charles

2010-10-01

A torque sensor is developed to measure the mechanical power extracted by model wind turbines. The torque is measured by mounting the model generator (a small dc motor) through ball bearings to the hub and by preventing its rotation by the deflection of a strain-gauge-instrumented plate. By multiplying the measured torque and rotor angular velocity, a direct measurement of the fluid mechanical power extracted from the flow is obtained. Such a measurement is more advantageous compared to measuring the electrical power generated by the model generator (dc motor), since the electrical power is largely affected by internal frictional, electric and magnetic losses. Calibration experiments are performed, and during testing, the torque sensor is mounted on a model wind turbine in a 3 rows × 3 columns array of wind turbines in a wind tunnel experiment. The resulting electrical and mechanical powers are quantified and compared over a range of applied loads, for three different incoming wind velocities. Also, the power coefficients are obtained as a function of the tip speed ratio. Significant differences between the electrical and mechanical powers are observed, which highlights the importance of using the direct mechanical power measurement for fluid dynamically meaningful results. A direct calibration with the measured current is also explored. The new torque sensor is expected to contribute to more accurate model wind tunnel tests which should provide added flexibility in model studies of the power that can be harvested from wind turbines and wind-turbine farms.

Direct Torque Control of a Small Wind Turbine with a Sliding-Mode Speed Controller

NASA Astrophysics Data System (ADS)

Sri Lal Senanayaka, Jagath; Karimi, Hamid Reza; Robbersmyr, Kjell G.

2016-09-01

In this paper. the method of direct torque control in the presence of a sliding-mode speed controller is proposed for a small wind turbine being used in water heating applications. This concept and control system design can be expanded to grid connected or off-grid applications. Direct torque control of electrical machines has shown several advantages including very fast dynamics torque control over field-oriented control. Moreover. the torque and flux controllers in the direct torque control algorithms are based on hvsteretic controllers which are nonlinear. In the presence of a sliding-mode speed control. a nonlinear control system can be constructed which is matched for AC/DC conversion of the converter that gives fast responses with low overshoots. The main control objectives of the proposed small wind turbine can be maximum power point tracking and soft-stall power control. This small wind turbine consists of permanent magnet synchronous generator and external wind speed. and rotor speed measurements are not required for the system. However. a sensor is needed to detect the rated wind speed overpass events to activate proper speed references for the wind turbine. Based on the low-cost design requirement of small wind turbines. an available wind speed sensor can be modified. or a new sensor can be designed to get the required measurement. The simulation results will be provided to illustrate the excellent performance of the closed-loop control system in entire wind speed range (4-25 m/s).

Directional biases reveal utilization of arm's biomechanical properties for optimization of motor behavior.

PubMed

Goble, Jacob A; Zhang, Yanxin; Shimansky, Yury; Sharma, Siddharth; Dounskaia, Natalia V

2007-09-01

Strategies used by the CNS to optimize arm movements in terms of speed, accuracy, and resistance to fatigue remain largely unknown. A hypothesis is studied that the CNS exploits biomechanical properties of multijoint limbs to increase efficiency of movement control. To test this notion, a novel free-stroke drawing task was used that instructs subjects to make straight strokes in as many different directions as possible in the horizontal plane through rotations of the elbow and shoulder joints. Despite explicit instructions to distribute strokes uniformly, subjects showed biases to move in specific directions. These biases were associated with a tendency to perform movements that included active motion at one joint and largely passive motion at the other joint, revealing a tendency to minimize intervention of muscle torque for regulation of the effect of interaction torque. Other biomechanical factors, such as inertial resistance and kinematic manipulability, were unable to adequately account for these significant biases. Also, minimizations of jerk, muscle torque change, and sum of squared muscle torque were analyzed; however, these cost functions failed to explain the observed directional biases. Collectively, these results suggest that knowledge of biomechanical cost functions regarding interaction torque (IT) regulation is available to the control system. This knowledge may be used to evaluate potential movements and to select movement of "low cost." The preference to reduce active regulation of interaction torque suggests that, in addition to muscle energy, the criterion for movement cost may include neural activity required for movement control.

Spin transfer torque in antiferromagnetic spin valves: From clean to disordered regimes

NASA Astrophysics Data System (ADS)

Saidaoui, Hamed Ben Mohamed; Manchon, Aurelien; Waintal, Xavier

2014-05-01

Current-driven spin torques in metallic spin valves composed of antiferromagnets are theoretically studied using the nonequilibrium Green's function method implemented on a tight-binding model. We focus our attention on G-type and L-type antiferromagnets in both clean and disordered regimes. In such structures, spin torques can either rotate the magnetic order parameter coherently (coherent torque) or compete with the internal antiferromagnetic exchange (exchange torque). We show that, depending on the symmetry of the spin valve, the coherent and exchange torques can either be in the plane, ∝n×(q×n) or out of the plane ∝n×q, where q and n are the directions of the order parameter of the polarizer and the free antiferromagnetic layers, respectively. Although disorder conserves the symmetry of the torques, it strongly reduces the torque magnitude, pointing out the need for momentum conservation to ensure strong spin torque in antiferromagnetic spin valves.

Knudsen torque on heated micro beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Qi; Liang, Tengfei; Ye, Wenjing

Thermally induced mechanical loading has been shown to have significant effects on micro/nano objects immersed in a gas with a non-uniform temperature field. While the majority of existing studies and related applications focus on forces, we investigate the torque, and thus the rotational motion, produced by such a mechanism. Using the asymptotic analysis in the near continuum regime, the Knudsen torque acting on an asymmetrically located uniformly heated microbeam in a cold enclosure is investigated. The existence of a non-zero net torque is demonstrated. In addition, it has been found that by manipulating the system configuration, the rotational direction ofmore » the torque can be changed. Two types of rotational motion of the microbeam have been identified: the pendulum motion of a rectangular beam, and the unidirectional rotation of a cylindrical beam. A rotational frequency of 4 rpm can be achieved for the cylindrical beam with a diameter of 3μm at Kn = 0.005. Illustrated by the simulations using the direct simulation of Monte Carlo, the Knudsen torque can be much increased in the transition regime, demonstrating the potential of Knudsen torque serving as a rotation engine for micro/nano objects.« less

Efficacy of kinesio taping on isokinetic quadriceps torque in knee osteoarthritis: a double blinded randomized controlled study.

PubMed

Anandkumar, Sudarshan; Sudarshan, Shobhalakshmi; Nagpal, Pratima

2014-08-01

Double blind pre-test post-test control group design. To compare the isokinetic quadriceps torque, standardized stair-climbing task (SSCT) and pain during SSCT between subjects diagnosed with knee osteoarthritis pre and post kinesio tape (KT) application with and without tension. Strength of the quadriceps and torque producing capability is frequently found to be compromised in knee osteoarthritis. The efficacy of KT in improving isokinetic quadriceps torque in knee osteoarthritis is unknown, forming the basis for this study. Forty subjects were randomly allocated to either the experimental (therapeutic KT with tension) or control group (sham KT without tension) with the allocation being concealed. Pre and post test measurements of isokinetic quadriceps torque, SSCT and pain during SSCT were carried out by a blinded assessor. A large effect size with significant improvements in the peak quadriceps torque (concentric and eccentric at angular velocities of 90° per second and 120° per second), SSCT and pain were obtained in the experimental group when compared to the control group. Application of therapeutic KT is effective in improving isokinetic quadriceps torque, SSCT and reducing pain in knee osteoarthritis.

Displacement of Implant Abutments Following Initial and Repeated Torqueing.

PubMed

Yilmaz, Burak; Gilbert, Andy B; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2015-01-01

To measure and compare the three-dimensional (3D) position of nine different abutments manufactured by different manufacturers after repeated torqueing on an internal-hexagon implant. Nine tapered implants were placed into an acrylic resin block. Five specimens each of nine different abutments (n = 45) were placed into one of nine implants. The abutments were handtightened and then torqued to the manufacturer-recommended torque of 30 Ncm. After 10 minutes, 30 Ncm of torque was reapplied. Another 10 minutes elapsed before testing was completed. Images were recorded in 12-second intervals. The spatial relationship of the abutments to the resin block was determined using 3D digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the abutments were calculated in three dimensions and overall for both torque applications. Statistical comparisons were done with a t test and a step-down Bonferroni correction. The overall 3D displacement of the Atlantis Titanium abutment after the second applied torque was significantly greater than that of two of the eight other abutments. Displacement in all three dimensions for the Atlantis Titanium abutment changed direction between the first and second torque applications. All abutments moved further in the same direction except for the Atlantis Titanium abutment, which moved back toward its original hand-tightened position horizontally after the second torque application. Re-torqueing of abutments after a 10-minute interval leads to minor displacement of varying degrees between the abutment and a tapered implant. A potential effect of embedment relaxation and/or manufacturing errors should be taken into consideration when selecting an abutment for a cement-retained crown on a tapered implant. Accordingly, clinicians may benefit from adjusting cement-retained implant crowns after re-torqueing the abutments to prevent potential occlusal and interproximal contact problems.

Advanced Direct-Drive Generator for Improved Availability of Oscillating Wave Surge Converter Power Generation Systems Phase II 10hp 30rpm Radial-Flux Magnetically Geared Generator Test Data

DOE Data Explorer

Ouyang, Wen; Tchida, Colin

2017-05-02

Static torque, no load, constant speed, and sinusoidal oscillation test data for a 10hp, 300rpm magnetically-geared generator prototype using either an adjustable load bank for a fixed resistance or an output power converter.

An Analytical Calculation of Frictional and Bending Moments at the Head-Neck Interface of Hip Joint Implants during Different Physiological Activities.

PubMed

Farhoudi, Hamidreza; Oskouei, Reza H; Pasha Zanoosi, Ali A; Jones, Claire F; Taylor, Mark

2016-12-05

This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based on the kinematics of four patients and the implant characteristics of a metal-on-metal implant. Depending on the body weight and type of activity, the moments and torques had significant variations in both magnitude and direction over the activity cycles. For the nine investigated activities, the maximum magnitude of the frictional moment ranged from 2.6 to 7.1 Nm. The maximum magnitude of the torque acting on the head-neck interface ranged from 2.3 to 5.7 Nm. The bending moment acting on the head-neck interface varied from 7 to 21.6 Nm. One-leg-standing had the widest range of frictional torque on the head-neck interface (11 Nm) while normal walking had the smallest range (6.1 Nm). The widest range, together with the maximum magnitude of torque, bending moment, and frictional moment, occurred during one-leg-standing of the lightest patient. Most of the simulated activities resulted in frictional torques that were near the previously reported oxide layer depassivation threshold torque. The predicted bending moments were also found at a level believed to contribute to the oxide layer depassivation. The calculated magnitudes and directions of the moments, applied directly to the head-neck taper junction, provide realistic mechanical loading data for in vitro and computational studies on the mechanical behaviour and multi-axial fretting at the head-neck interface.

An Analytical Calculation of Frictional and Bending Moments at the Head-Neck Interface of Hip Joint Implants during Different Physiological Activities

PubMed Central

Farhoudi, Hamidreza; Oskouei, Reza H.; Pasha Zanoosi, Ali A.; Jones, Claire F.; Taylor, Mark

2016-01-01

This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based on the kinematics of four patients and the implant characteristics of a metal-on-metal implant. Depending on the body weight and type of activity, the moments and torques had significant variations in both magnitude and direction over the activity cycles. For the nine investigated activities, the maximum magnitude of the frictional moment ranged from 2.6 to 7.1 Nm. The maximum magnitude of the torque acting on the head-neck interface ranged from 2.3 to 5.7 Nm. The bending moment acting on the head-neck interface varied from 7 to 21.6 Nm. One-leg-standing had the widest range of frictional torque on the head-neck interface (11 Nm) while normal walking had the smallest range (6.1 Nm). The widest range, together with the maximum magnitude of torque, bending moment, and frictional moment, occurred during one-leg-standing of the lightest patient. Most of the simulated activities resulted in frictional torques that were near the previously reported oxide layer depassivation threshold torque. The predicted bending moments were also found at a level believed to contribute to the oxide layer depassivation. The calculated magnitudes and directions of the moments, applied directly to the head-neck taper junction, provide realistic mechanical loading data for in vitro and computational studies on the mechanical behaviour and multi-axial fretting at the head-neck interface. PMID:28774104

Ultrasound melted polymer sleeve for improved screw anchorage in trabecular bone--A novel screw augmentation technique.

PubMed

Schmoelz, W; Mayr, R; Schlottig, F; Ivanovic, N; Hörmann, R; Goldhahn, J

2016-03-01

Screw anchorage in osteoporotic bone is still limited and makes treatment of osteoporotic fractures challenging for surgeons. Conventional screws fail in poor bone quality due to loosening at the screw-bone interface. A new technology should help to improve this interface. In a novel constant amelioration process technique, a polymer sleeve is melted by ultrasound in the predrilled screw hole prior to screw insertion. The purpose of this study was to investigate in vitro the effect of the constant amelioration process platform technology on primary screw anchorage. Fresh frozen femoral heads (n=6) and vertebrae (n=6) were used to measure the maximum screw insertion torque of reference and constant amelioration process augmented screws. Specimens were cut in cranio-caudal direction, and the screws (reference and constant amelioration process) were implanted in predrilled holes in the trabecular structure on both sides of the cross section. This allowed the pairwise comparison of insertion torque for constant amelioration process and reference screws (femoral heads n=18, vertebrae n=12). Prior to screw insertion, a micro-CT scan was made to ensure comparable bone quality at the screw placement location. The mean insertion torque for the constant amelioration process augmented screws in both, the femoral heads (44.2 Ncm, SD 14.7) and the vertebral bodies (13.5 Ncm, SD 6.3) was significantly higher than for the reference screws of the femoral heads (31.7 Ncm, SD 9.6, p<0.001) and the vertebral bodies (7.1 Ncm, SD 4.5, p<0.001). The interconnection of the melted polymer sleeve with the surrounding trabecular bone in the constant amelioration process technique resulted in a higher screw insertion torque and can improve screw anchorage in osteoporotic trabecular bone. Copyright © 2016 Elsevier Ltd. All rights reserved.

78 FR 70205 - Airworthiness Directives; Eurocopter France Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-25

... 332 L2 and Model EC 225 LP helicopters. According to EASA, analysis of tightening torques revealed some cases of tightening torque loss, which can lead to the formation of a crack at the MGB bar... rear of the MGB bar attaching fittings for tightening torque loss and, if the loss is equal to or...

77 FR 36137 - Airworthiness Directives; AGUSTA S.p.A. Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-18

... the upper end of collective control rod C2 to torque tube C3 is properly installed. This AD is... prevent separation of the collective control rod from the torque tube, loss of control of the collective... helicopters because the production quality control procedures did not require recording the applied torque on...

Strength deficits of the shoulder complex during isokinetic testing in people with chronic stroke

PubMed Central

Nascimento, Lucas R.; Teixeira-Salmela, Luci F.; Polese, Janaine C.; Ada, Louise; Faria, Christina D. C. M.; Laurentino, Glória E. C.

2014-01-01

OBJECTIVES: To examine the strength deficits of the shoulder complex after stroke and to characterize the pattern of weakness according to type of movement and type of isokinetic parameter. METHOD: Twelve chronic stroke survivors and 12 age-matched healthy controls had their shoulder strength measured using a Biodex isokinetic dynamometer. Concentric measures of peak torque and work during shoulder movements were obtained in random order at speeds of 60°/s for both groups and sides. Type of movement was defined as scapulothoracic (protraction and retraction), glenohumeral (shoulder internal and external rotation) or combined (shoulder flexion and extension). Type of isokinetic parameter was defined as maximum (peak torque) or sustained (work). Strength deficits were calculated using the control group as reference. RESULTS: The average strength deficit for the paretic upper limb was 52% for peak torque and 56% for work. Decreases observed in the non-paretic shoulder were 21% and 22%, respectively. Strength deficit of the scapulothoracic muscles was similar to the glenohumeral muscles, with a mean difference of 6% (95% CI -5 to 17). Ability to sustain torque throughout a given range of motion was decreased as much as the peak torque, with a mean difference of 4% (95% CI -2 to 10). CONCLUSIONS: The findings suggest that people after stroke might benefit from strengthening exercises directed at the paretic scapulothoracic muscles in addition to exercises of arm elevation. Clinicians should also prescribe different exercises to improve the ability to generate force and the ability to sustain the torque during a specific range of motion. PMID:25003280

Role of magnetic exchange interaction due to magnetic anisotropy on inverse spin Hall voltage at FeSi3%/Pt thin film bilayer interface

NASA Astrophysics Data System (ADS)

Shah, Jyoti; Ahmad, Saood; Chaujar, Rishu; Puri, Nitin K.; Negi, P. S.; Kotnala, R. K.

2017-12-01

In our recent studies inverse spin Hall voltage (ISHE) was investigated by ferromagnetic resonance (FMR) using bilayer FeSi3%/Pt thin film prepared by pulsed laser deposition (PLD) technique. In ISHE measurement microwave signal was applied on FeSi3% film along with DC magnetic field. Higher magnetization value along the film-plane was measured by magnetic hysteresis (M-H) loop. Presence of magnetic anisotropy has been obtained by M-H loop which showed easy direction of magnetization when applied magnetic field is parallel to the film plane. The main result of this study is that FMR induced inverse spin Hall voltage 12.6 μV at 1.0 GHz was obtained across Pt layer. Magnetic exchange field at bilayer interface responsible for field torque was measured 6 × 1014 Ω-1 m-2 by spin Hall magnetoresistance. The damping torque and spin Hall angle have been evaluated as 0.084 and 0.071 respectively. Presence of Si atom in FeSi3% inhomogenize the magnetic exchange field among accumulated spins at bilayer interface and feebly influenced by spin torque of FeSi3% layer. Weak field torque suppresses the spin pumping to Pt layer thus low value of inverse spin Hall voltage is obtained. This study provides an excellent opportunity to investigate spin transfer torque effect, thus motivating a more intensive experimental effort for its utilization at maximum potential. The improvement in spin transfer torque may be useful in spin valve, spin battery and spin transistor application.

Design and Simulation of a MEMS Control Moment Gyroscope for the Sub-Kilogram Spacecraft

PubMed Central

Chang, Honglong; Jiao, Wenlong; Fu, Qianyan; Xie, Jianbing; Yuan, Weizheng

2010-01-01

A novel design of a microelectromechanical systems (MEMS) control moment gyroscope (MCMG) was proposed in this paper in order to generate a torque output with a magnitude of 10−6 N·m. The MCMG consists of two orthogonal angular vibration systems, i.e., the rotor and gimbal; the coupling between which is based on the Coriolis effect and will cause a torque output in the direction perpendicular to the two vibrations. The angular rotor vibration was excited by the in-plane electrostatic rotary comb actuators, while the angular gimbal vibration was driven by an out-of-plane electrostatic parallel plate actuator. A possible process flow to fabricate the structure was proposed and discussed step by step. Furthermore, an array configuration using four MCMGs as an effective element, in which the torque was generated with a phase difference of 90 degrees between every two MCMGs, was proposed to smooth the inherent fluctuation of the torque output for a vibrational MCMG. The parasitic torque was cancelled by two opposite MCMGs with a phase difference of 180 degrees. The designed MCMG was about 1.1 cm × 1.1 cm × 0.04 cm in size and 0.1 g in weight. The simulation results showed that the maximum torque output of a MCMG, the resonant frequency of which was approximately 1,000 Hz, was about 2.5 × 10−8 N·m. The element with four MCMGs could generate a torque of 5 × 10−8 N·m. The torque output could reach a magnitude of 10−6 N·m when the frequency was improved from 1,000 Hz to 10,000 Hz. Using arrays of 4 × 4 effective elements on a 1 kg spacecraft with a standard form factor of 10 cm × 10 cm × 10 cm, a 10 degrees attitude change could be achieved in 26.96 s. PMID:22319346

Design and simulation of a MEMS control moment gyroscope for the sub-kilogram spacecraft.

PubMed

Chang, Honglong; Jiao, Wenlong; Fu, Qianyan; Xie, Jianbing; Yuan, Weizheng

2010-01-01

A novel design of a microelectromechanical systems (MEMS) control moment gyroscope (MCMG) was proposed in this paper in order to generate a torque output with a magnitude of 10(-6) N·m. The MCMG consists of two orthogonal angular vibration systems, i.e., the rotor and gimbal; the coupling between which is based on the Coriolis effect and will cause a torque output in the direction perpendicular to the two vibrations. The angular rotor vibration was excited by the in-plane electrostatic rotary comb actuators, while the angular gimbal vibration was driven by an out-of-plane electrostatic parallel plate actuator. A possible process flow to fabricate the structure was proposed and discussed step by step. Furthermore, an array configuration using four MCMGs as an effective element, in which the torque was generated with a phase difference of 90 degrees between every two MCMGs, was proposed to smooth the inherent fluctuation of the torque output for a vibrational MCMG. The parasitic torque was cancelled by two opposite MCMGs with a phase difference of 180 degrees. The designed MCMG was about 1.1 cm×1.1 cm×0.04 cm in size and 0.1 g in weight. The simulation results showed that the maximum torque output of a MCMG, the resonant frequency of which was approximately 1,000 Hz, was about 2.5×10(-8) N·m. The element with four MCMGs could generate a torque of 5×10(-8) N·m. The torque output could reach a magnitude of 10(-6) N·m when the frequency was improved from 1,000 Hz to 10,000 Hz. Using arrays of 4×4 effective elements on a 1 kg spacecraft with a standard form factor of 10 cm×10 cm×10 cm, a 10 degrees attitude change could be achieved in 26.96 s.

Modelling grain alignment by radiative torques and hydrogen formation torques in reflection nebula

NASA Astrophysics Data System (ADS)

Hoang, Thiem; Lazarian, A.; Andersson, B.-G.

2015-04-01

Reflection nebulae - dense cores - illuminated by surrounding stars offer a unique opportunity to directly test our quantitative model of grain alignment based on radiative torques (RATs) and to explore new effects arising from additional torques. In this paper, we first perform detailed modelling of grain alignment by RATs for the IC 63 reflection nebula illuminated both by a nearby γ Cas star and the diffuse interstellar radiation field. We calculate linear polarization pλ of background stars by radiatively aligned grains and explore the variation of fractional polarization (pλ/AV) with visual extinction AV across the cloud. Our results show that the variation of pV/AV versus AV from the dayside of IC 63 to its centre can be represented by a power law (p_V/A_V∝ A_V^{η }) with different slopes depending on AV. We find a shallow slope η ˜ -0.1 for AV < 3 and a very steep slope η ˜ -2 for AV > 4. We then consider the effects of additional torques due to H2 formation and model grain alignment by joint action of RATs and H2 torques. We find that pV/AV tends to increase with an increasing magnitude of H2 torques. In particular, the theoretical predictions obtained for pV/AV and peak wavelength λmax in this case show an improved agreement with the observational data. Our results reinforce the predictive power of the RAT alignment mechanism in a broad range of environmental conditions and show the effect of pinwheel torques in environments with efficient H2 formation. Physical parameters involved in H2 formation may be constrained using detailed modelling of grain alignment combined with observational data. In addition, we discuss implications of our modelling for interpreting latest observational data by Planck and other ground-based instruments.

Speed And Power Control Of An Engine By Modulation Of The Load Torque

DOEpatents

Ziph, Benjamin; Strodtman, Scott; Rose, Thomas K

1999-01-26

A system and method of speed and power control for an engine in which speed and power of the engine is controlled by modulation of the load torque. The load torque is manipulated in order to cause engine speed, and hence power to be changed. To accomplish such control, the load torque undergoes a temporary excursion in the opposite direction of the desired speed and power change. The engine and the driven equipment will accelerate or decelerate accordingly as the load torque is decreased or increased, relative to the essentially fixed or constant engine torque. As the engine accelerates or decelerates, its power increases or decreases in proportion.

Role of external torque in the formation of ion thermal internal transport barriers

NASA Astrophysics Data System (ADS)

Jhang, Hogun; Kim, S. S.; Diamond, P. H.

2012-04-01

We present an analytic study of the impact of external torque on the formation of ion internal transport barriers (ITBs). A simple analytic relation representing the effect of low external torque on transport bifurcations is derived based on a two field transport model of pressure and toroidal momentum density. It is found that the application of an external torque can either facilitate or hamper bifurcation in heat flux driven plasmas depending on its sign relative to the direction of intrinsic torque. The ratio between radially integrated momentum (i.e., external torque) density to power input is shown to be a key macroscopic control parameter governing the characteristics of bifurcation.

Lunar and Solar Torques on the Oceanic Tides

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Bills, Bruce G.; Chao, Benjamin F.

1998-01-01

Brosche and Seiler recently suggested that direct lunar and solar tidal torques on the oceanic tides play a significant role in the earth's short-period angular momentum balance ("short-period" here meaning daily and sub-daily). We reexamine that suggestion here, concentrating on axial torques and hence on variations in rotation rate. Only those spherical harmonic components of the ocean tide having the same degree and order as the tidal potential induce nonzero torques. Prograde components (those moving in the same direction as the tide-generating body) produce the familiar secular braking of the earth's rotation. Retrograde components, however, produce rapid variations in UTI at twice the tidal frequency. There also exist interaction torques between tidal constituents, e.g. solar torques on lunar tides. They generate UTI variations at frequencies equal to the sums and differences of the original tidal frequencies. We give estimates of the torques and angular momentum variations for each of the important regimes, secular to quarter-diurnal. For the M(sub 2) potential acting on the M(sub 2) ocean tide, we find an associated angular momentum variation of amplitude 3 x 10(exp 19) N m. This is 5 to 6 orders of magnitude smaller than the angular momentum variations associated with tidal currents. We conclude that these torques do not play a significant role in the short-period angular momentum balance.

An Experimental Study on the Darrieus-Savonius Turbine for the Tidal Current Power Generation

NASA Astrophysics Data System (ADS)

Kyozuka, Yusaku

The Darrieus turbine is popular for tidal current power generation in Japan. It is simple in structure with straight wings rotating around a vertical axis, so that it has no directionality against the motion of tidal flow which changes its direction twice a day. However, there is one defect in the Darrieus turbine; its small starting torque. Once it stops, a Darrieus turbine is hard to re-start until a fairly fast current is exerted on it. To improve the starting torque of the Darrieus turbine used for tidal power generation, a hybrid turbine, composed of a Darrieus turbine and a Savonius rotor is proposed. Hydrodynamic characteristics of a semi-circular section used for the Savonius bucket were measured in a wind tunnel. The torque of a two bucket Savonius rotor was measured in a circulating water channel, where four different configurations of the bucket were compared. A combined Darrieus and Savonius turbine was tested in the circulating water channel, where the effect of the attaching angle between Darrieus wing and Savonius rotor was studied. Finally, power generation experiments using a 48 pole electric generator were conducted in a towing tank and the power coefficients were compared with the results of experiments obtained in the circulating water channel.

A self-calibrating multicomponent force/torque measuring system

NASA Astrophysics Data System (ADS)

Marangoni, Rafael R.; Schleichert, Jan; Rahneberg, Ilko; Hilbrunner, Falko; Fröhlich, Thomas

2018-07-01

A multicomponent self-calibrating force and torque sensor is presented. In this system, the principle of a Kibble balance is adapted for the traceable force and torque measurement in three orthogonal directions. The system has two operating modes: the velocity mode and the force/torque sensing mode. In the velocity mode, the calibration of the sensor is performed, while in the force/torque sensing mode, forces and torques are measured by using the principle of the electromagnetic force compensation. Details about the system are provided, with the main components of the sensor and a description of the operational procedure. A prototype of the system is currently being implemented for measuring forces and torques in a range of  ±2 N and  ±0.1 N · m respectively. A maximal relative expanded measurement uncertainty (k  =  2) of 1 · 10‑4 is expected for the force and torque measurements.

Forces and torques on rigid inclusions in an elastic environment: Resulting matrix-mediated interactions, displacements, and rotations

NASA Astrophysics Data System (ADS)

Puljiz, Mate; Menzel, Andreas M.

2017-05-01

Embedding rigid inclusions into elastic matrix materials is a procedure of high practical relevance, for instance, for the fabrication of elastic composite materials. We theoretically analyze the following situation. Rigid spherical inclusions are enclosed by a homogeneous elastic medium under stick boundary conditions. Forces and torques are directly imposed from outside onto the inclusions or are externally induced between them. The inclusions respond to these forces and torques by translations and rotations against the surrounding elastic matrix. This leads to elastic matrix deformations, and in turn results in mutual long-ranged matrix-mediated interactions between the inclusions. Adapting a well-known approach from low-Reynolds-number hydrodynamics, we explicitly calculate the displacements and rotations of the inclusions from the externally imposed or induced forces and torques. Analytical expressions are presented as a function of the inclusion configuration in terms of displaceability and rotateability matrices. The role of the elastic environment is implicitly included in these relations. That is, the resulting expressions allow a calculation of the induced displacements and rotations directly from the inclusion configuration, without having to explicitly determine the deformations of the elastic environment. In contrast to the hydrodynamic case, compressibility of the surrounding medium is readily taken into account. We present the complete derivation based on the underlying equations of linear elasticity theory. In the future, the method will, for example, be helpful to characterize the behavior of externally tunable elastic composite materials, to accelerate numerical approaches, as well as to improve the quantitative interpretation of microrheological results.

75 FR 38058 - Airworthiness Directives; BAE Systems (Operations) Limited Model BAe 146 and Avro 146-RJ Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-01

... torque spanner to the specifications in the torque figures shown in Table 2. of the Accomplishment... torque check of the tension bolts. Related investigative actions include: Inspecting the condition of the... of the nut being tightened to the end of the thread. Examining the wear pattern on the seating...

75 FR 63045 - Airworthiness Directives; BAE SYSTEMS (OPERATIONS) LIMITED Model BAe 146 and Avro 146-RJ Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-14

... the fitting and wing structure. Checking the nuts with a suitable torque spanner to the specifications in the torque figures shown in Table 2. of the Accomplishment Instructions of BAE SYSTEMS (OPERATIONS... installed, and Doing either an ultrasonic inspection for damaged bolts or torque check of the tension bolts...

Influence of second-order bracket-archwire misalignments on loads generated during third-order archwire rotation in orthodontic treatment.

PubMed

Romanyk, Dan L; George, Andrew; Li, Yin; Heo, Giseon; Carey, Jason P; Major, Paul W

2016-05-01

To investigate the influence of a rotational second-order bracket-archwire misalignment on the loads generated during third-order torque procedures. Specifically, torque in the second- and third-order directions was considered. An orthodontic torque simulator (OTS) was used to simulate the third-order torque between Damon Q brackets and 0.019 × 0.025-inch stainless steel archwires. Second-order misalignments were introduced in 0.5° increments from a neutral position, 0.0°, up to 3.0° of misalignment. A sample size of 30 brackets was used for each misalignment. The archwire was then rotated in the OTS from its neutral position up to 30° in 3° increments and then unloaded in the same increments. At each position, all forces and torques were recorded. Repeated-measures analysis of variance was used to determine if the second-order misalignments significantly affected torque values in the second- and third-order directions. From statistical analysis of the experimental data, it was found that the only statistically significant differences in third-order torque between a misaligned state and the neutral position occurred for 2.5° and 3.0° of misalignment, with mean differences of 2.54 Nmm and 2.33 Nmm, respectively. In addition, in pairwise comparisons of second-order torque for each misalignment increment, statistical differences were observed in all comparisons except for 0.0° vs 0.5° and 1.5° vs 2.0°. The introduction of a second-order misalignment during third-order torque simulation resulted in statistically significant differences in both second- and third-order torque response; however, the former is arguably clinically insignificant.

Multi-objective decoupling algorithm for active distance control of intelligent hybrid electric vehicle

NASA Astrophysics Data System (ADS)

Luo, Yugong; Chen, Tao; Li, Keqiang

2015-12-01

The paper presents a novel active distance control strategy for intelligent hybrid electric vehicles (IHEV) with the purpose of guaranteeing an optimal performance in view of the driving functions, optimum safety, fuel economy and ride comfort. Considering the complexity of driving situations, the objects of safety and ride comfort are decoupled from that of fuel economy, and a hierarchical control architecture is adopted to improve the real-time performance and the adaptability. The hierarchical control structure consists of four layers: active distance control object determination, comprehensive driving and braking torque calculation, comprehensive torque distribution and torque coordination. The safety distance control and the emergency stop algorithms are designed to achieve the safety and ride comfort goals. The optimal rule-based energy management algorithm of the hybrid electric system is developed to improve the fuel economy. The torque coordination control strategy is proposed to regulate engine torque, motor torque and hydraulic braking torque to improve the ride comfort. This strategy is verified by simulation and experiment using a forward simulation platform and a prototype vehicle. The results show that the novel control strategy can achieve the integrated and coordinated control of its multiple subsystems, which guarantees top performance of the driving functions and optimum safety, fuel economy and ride comfort.

Evaluation Method for Fieldlike-Torque Efficiency by Modulation of the Resonance Field

NASA Astrophysics Data System (ADS)

Kim, Changsoo; Kim, Dongseuk; Chun, Byong Sun; Moon, Kyoung-Woong; Hwang, Chanyong

2018-05-01

The spin Hall effect has attracted a lot of interest in spintronics because it offers the possibility of a faster switching route with an electric current than with a spin-transfer-torque device. Recently, fieldlike spin-orbit torque has been shown to play an important role in the magnetization switching mechanism. However, there is no simple method for observing the fieldlike spin-orbit torque efficiency. We suggest a method for measuring fieldlike spin-orbit torque using a linear change in the resonance field in spectra of direct-current (dc)-tuned spin-torque ferromagnetic resonance. The fieldlike spin-orbit torque efficiency can be obtained in both a macrospin simulation and in experiments by simply subtracting the Oersted field from the shifted amount of resonance field. This method analyzes the effect of fieldlike torque using dc in a normal metal; therefore, only the dc resistivity and the dimensions of each layer are considered in estimating the fieldlike spin-torque efficiency. The evaluation of fieldlike-torque efficiency of a newly emerging material by modulation of the resonance field provides a shortcut in the development of an alternative magnetization switching device.

Calibration of the optical torque wrench.

PubMed

Pedaci, Francesco; Huang, Zhuangxiong; van Oene, Maarten; Dekker, Nynke H

2012-02-13

The optical torque wrench is a laser trapping technique that expands the capability of standard optical tweezers to torque manipulation and measurement, using the laser linear polarization to orient tailored microscopic birefringent particles. The ability to measure torque of the order of kBT (∼4 pN nm) is especially important in the study of biophysical systems at the molecular and cellular level. Quantitative torque measurements rely on an accurate calibration of the instrument. Here we describe and implement a set of calibration approaches for the optical torque wrench, including methods that have direct analogs in linear optical tweezers as well as introducing others that are specifically developed for the angular variables. We compare the different methods, analyze their differences, and make recommendations regarding their implementations.

Measurement of the Differential and Total Thrust and Torque of Six Full-Scale Adjustable-Pitch Propellers

NASA Technical Reports Server (NTRS)

Stickle, George W

1933-01-01

Force measurements giving total thrust and torque, and propeller slip stream surveys giving differential thrust and torque were simultaneously made on each of six full-scale propellers in the 20-foot propeller-research tunnel of the National Advisory Committee for Aeronautics. They were adjustable-pitch metal propellers 9.5 feet in diameter; three had modified Clark Y blade sections and three had modified RAF-6 blade sections. This report gives the differential thrust and torque and the variation caused by changing the propeller tip speed and the pitch setting. The total thrust and torque obtained from integration of the thrust and torque distribution curves are compared with those obtained by direct force measurements.

Force, Torque and Stiffness: Interactions in Perceptual Discrimination

PubMed Central

Wu, Bing; Klatzky, Roberta L.; Hollis, Ralph L.

2011-01-01

Three experiments investigated whether force and torque cues interact in haptic discrimination of force, torque and stiffness, and if so, how. The statistical relation between force and torque was manipulated across four experimental conditions: Either one type of cue varied while the other was constant, or both varied so as to be positively correlated, negatively correlated, or uncorrelated. Experiment 1 showed that the subjects’ ability to discriminate force was improved by positively correlated torque but impaired with uncorrelated torque, as compared to the constant torque condition. Corresponding effects were found in Experiment 2 for the influence of force on torque discrimination. These findings indicate that force and torque are integrated in perception, rather than being processed as separate dimensions. A further experiment demonstrated facilitation of stiffness discrimination by correlated force and torque, whether the correlation was positive or negative. The findings suggest new means of augmenting haptic feedback to facilitate perception of the properties of soft objects. PMID:21359137

The role of vision, speed, and attention in overcoming directional biases during arm movements.

PubMed

Dounskaia, Natalia; Goble, Jacob A

2011-03-01

Previous research has revealed directional biases (preferences to select movements in specific directions) during horizontal arm movements with the use of a free-stroke drawing task. The biases were interpreted as a result of a tendency to generate motion at either the shoulder or elbow (leading joint) and move the other (subordinate) joint predominantly passively to avoid neural effort for control of interaction torque. Here, we examined influence of vision, movement speed, and attention on the directional biases. Participants performed the free-stroke drawing task, producing center-out strokes in randomly selected directions. Movements were performed with and without vision and at comfortable and fast pace. A secondary, cognitive task was used to distract attention. Preferred directions remained the same in all conditions. Bias strength mildly increased without vision, especially during fast movements. Striking increases in bias strength were caused by the secondary task, pointing to additional cognitive load associated with selection of movements in the non-preferred directions. Further analyses demonstrated that the tendency to minimize active interference with interaction torque at the subordinate joint matched directional biases in all conditions. This match supports the explanation of directional biases as a result of a tendency to minimize neural effort for interaction torque control. The cognitive load may enhance this tendency in two ways, directly, by reducing neural capacity for interaction torque control, and indirectly, by decreasing capacity of working memory that stores visited directions. The obtained results suggest strong directional biases during daily activities because natural arm movements usually subserve cognitive tasks.

Torque resistance of impression copings after direct implant impression: An in vitro evaluation of impression materials with and without adhesive.

PubMed

Auroy, Pascal; Nicolas, Emanuel; Bedouin, Yvan

2017-01-01

No data are available on the ability of an impression coping to resist the manual placement of an abutment replica (implant analog) during prosthodontic laboratory procedures after a direct (pick-up) impression. The purpose of this in vitro study was to evaluate the torque resistance of impression copings after a direct impression, that is, the amount of rotational torque sufficient to induce irreversible displacement of impression copings in the impression material bulk once the impression has been made. A reference model with 5 abutment replicas was constructed. Five impression copings were screwed onto the abutment replicas, and standardized impressions were made. A controlled twisting force was applied to each impression coping. A torque tester recorded the torque variation. Three elastomeric impression materials were tested. ANOVA and the Tukey test (α=.05) were performed using an average of 30 measurements per impression material, with and without adhesive. ANOVA and the Tukey test results showed that the adhesive, cohesive, and mechanical bonds between the impression coping and the impression material depended greatly on the type of material and that the average rupture threshold of these bonds was statistically significantly different in pairwise comparisons (P<.05). The curve analysis showed that when the impression materials are used with adhesives, the deformation of the interface is irreversible beyond 5 Ncm of torque. The polyether impression material is the direct impression material that showed the highest breakdown threshold for adhesive bonding when used without an adhesive. The use of an adhesive on impression copings leads to irreversible deformation of the interface at torque stresses well below the adhesive bond threshold of the same materials used without an adhesive. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

75 FR 3418 - Airworthiness Directives; British Aerospace Regional Aircraft Model HP.137 Jetstream Mk.1...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-21

... tightening torque are contained in APPH SB 32-76 Revision 1. As a result, pistons which were previously... formula for calculating the piston safe life. This calculation and a revised end fitting tightening torque... piston rod adjacent to the eye-end. This was caused by excessive torque which had been applied to the eye...

77 FR 12450 - Airworthiness Directives; BRP-Powertrain GmbH & Co KG Rotax Reciprocating Engines

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-01

... have been tightened to the correct torque value, i.e. not in accordance with the specification. This... AD requires performing a one-time inspection of the oil system for leaks and a torque check of the... performing a one-time inspection of the oil system for leaks and a torque check of the oil pump attachment...

76 FR 53312 - Airworthiness Directives; Agusta S.p.A. Model A109A and A109AII Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-26

... disassembling the tail rotor hub and blades assembly and inspecting for damage. If the tightening torque value..., and no further action is required. If the tightening torque value is greater than 700 kgcm, the hub plug must be replaced with an airworthy part. Torque the new hub plug to the specified tightening...

76 FR 9513 - Airworthiness Directives; BURKHART GROB LUFT-UND Model G 103 C Twin III SL Gliders

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-18

... plate) and tighten it, applying the torque following page 6.12 of the G 103 C TWIN III SL Maintenance...: The torque values and tolerances of the upper pulley wheel grooved nut have been standardized in the..., before further flight, readjust the torque of the upper pulley wheel grooved nut using the updated...

75 FR 39811 - Airworthiness Directives; The Boeing Company Model 777 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-13

... Service Bulletin 777-57A0064, dated March 26, 2009, it is not necessary to perform the torque check on the... instructions in Boeing Alert Service Bulletin 777-57A0064, dated March 26, 2009, a torque check is redundant... are less than those for the torque check. Boeing notes that it plans to issue a new revision to this...

Hydrodynamic Torques and Rotations of Superparamagnetic Bead Dimers

NASA Astrophysics Data System (ADS)

Pease, Christopher; Etheridge, J.; Wijesinghe, H. S.; Pierce, C. J.; Prikockis, M. V.; Sooryakumar, R.

Chains of micro-magnetic particles are often rotated with external magnetic fields for many lab-on-a-chip technologies such as transporting beads or mixing fluids. These applications benefit from faster responses of the actuated particles. In a rotating magnetic field, the magnetization of superparamagnetic beads, created from embedded magnetic nano-particles within a polymer matrix, is largely characterized by induced dipoles mip along the direction of the field. In addition there is often a weak dipole mop that orients out-of-phase with the external rotating field. On a two-bead dimer, the simplest chain of beads, mop contributes a torque Γm in addition to the torque from mip. For dimers with beads unbound to each other, mop rotates individual beads which generate an additional hydrodynamic torque on the dimer. Whereas, mop directly torques bound dimers. Our results show that Γm significantly alters the average frequency-dependent dimer rotation rate for both bound and unbound monomers and, when mop exceeds a critical value, increases the maximum dimer rotation frequency. Models that include magnetic and hydrodynamics torques provide good agreement with the experimental findings over a range of field frequencies.

Electromagnetic Torque in Tokamaks with Toroidal Asymmetries

NASA Astrophysics Data System (ADS)

Logan, Nikolas Christopher

Toroidal rotation and rotation shear strongly influences stability and confinement in tokamaks. Breaking of the toroidal symmetry by fields orders of magnitude smaller than the axisymmetric field can, however, produce electromagnetic torques that significantly affect the plasma rotation, stability and confinement. These electromagnetic torques are the study of this thesis. There are two typical types of electromagnetic torques in tokamaks: 1) "resonant torques" for which a plasma current defined by a single toroidal and single poloidal harmonic interact with external currents and 2) "nonresonant torques" for which the global plasma response to nonaxisymmetric fields is phase shifted by kinetic effects that drive the rotation towards a neoclassical offset. This work describes the diagnostics and analysis necessary to evaluate the torque by measuring the rate of momentum transfer per unit area in the vacuum region between the plasma and external currents using localized magnetic sensors to measure the Maxwell stress. These measurements provide model independent quantification of both the resonant and nonresonant electromagnetic torques, enabling direct verification of theoretical models. Measured values of the nonresonant torque are shown to agree well with the perturbed equilibrium nonambipolar transport (PENT) code calculation of torque from cross field transport in nonaxisymmetric equilibria. A combined neoclassical toroidal viscosity (NTV) theory, valid across a wide range of kinetic regimes, is fully implemented for the first time in general aspect ratio and shaped plasmas. The code captures pitch angle resonances, reproducing previously inaccessible collisionality limits in the model. The complete treatment of the model enables benchmarking to the hybrid kinetic MHD stability codes MARS-K and MISK, confirming the energy-torque equivalency principle in perturbed equilibria. Experimental validations of PENT results confirm the torque applied by nonaxisymmetric coils is often proportional to the energy put into the dominant ideal MHD kink mode. This reduces the control of nonresonant torque to a single mode model, enabling efficient feed forward optimization of applied fields. Initial results including the anisotropic kinetic pressure tensor directly in the plasma eigenmode calculations are presented here, and may eventually provide accurate metrics for multimodal coupling similar to the established single mode metrics.

Starting characteristics of direct current motors powered by solar cells

NASA Technical Reports Server (NTRS)

Singer, S.; Appelbaum, J.

1989-01-01

Direct current motors are used in photovoltaic systems. Important characteristics of electric motors are the starting to rated current and torque ratios. These ratios are dictated by the size of the solar cell array and are different for the various dc motor types. Discussed here is the calculation of the starting to rated current ratio and starting to rated torque ratio of the permanent magnet, and series and shunt excited motors when powered by solar cells for two cases: with and without a maximum-power-point-tracker (MPPT) included in the system. Comparing these two cases, one gets a torque magnification of about 3 for the permanent magnet motor and about 7 for other motor types. The calculation of the torques may assist the PV system designer to determine whether or not to include an MPPT in the system.

Magnetic torque anomaly in the quantum limit of Weyl semimetals

PubMed Central

Moll, Philip J. W.; Potter, Andrew C.; Nair, Nityan L.; Ramshaw, B. J.; Modic, K. A.; Riggs, Scott; Zeng, Bin; Ghimire, Nirmal J.; Bauer, Eric D.; Kealhofer, Robert; Ronning, Filip; Analytis, James G.

2016-01-01

Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to the topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems. PMID:27545105

Magnetic torque anomaly in the quantum limit of Weyl semimetals

DOE PAGES

Moll, Philip J. W.; Potter, Andrew C.; Nair, Nityan L.; ...

2016-08-22

Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to themore » topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems.« less

Modulation of motor control in saccadic behaviors by TMS over the posterior parietal cortex.

PubMed

Liang, Wei-Kuang; Juan, Chi-Hung

2012-08-01

The right posterior parietal cortex (rPPC) has been found to be critical in shaping visual selection and distractor-induced saccade curvature in the context of predictive as well as nonpredictive visual cues by means of transcranial magnetic stimulation (TMS) interference. However, the dynamic details of how distractor-induced saccade curvatures are affected by rPPC TMS have not yet been investigated. This study aimed to elucidate the key dynamic properties that cause saccades to curve away from distractors with different degrees of curvature in various TMS and target predictability conditions. Stochastic optimal feedback control theory was used to model the dynamics of the TMS saccade data. This allowed estimation of torques, which was used to identify the critical dynamic mechanisms producing saccade curvature. The critical mechanisms of distractor-induced saccade curvatures were found to be the motor commands and torques in the transverse direction. When an unpredictable saccade target occurred with rPPC TMS, there was an initial period of greater distractor-induced torque toward the side opposite the distractor in the transverse direction, immediately followed by a relatively long period of recovery torque that brought the deviated trace back toward the target. The results imply that the mechanisms of distractor-induced saccade curvature may be comprised of two mechanisms: the first causing the initial deviation and the second bringing the deviated trace back toward the target. The pattern of the initial torque in the transverse direction revealed the former mechanism. Conversely, the later mechanism could be well explained as a consequence of the control policy in this model. To summarize, rPPC TMS increased the initial torque away from the distractor as well as the recovery torque toward the target.

Microgrid Restraining Strategy Based on Improved DC Grid Connected DFIG Torque Ripple

NASA Astrophysics Data System (ADS)

Fei, Xia; Yang, Zhixiong; Zongze, Xia

2017-05-01

Aiming to the voltage of the stator side is generated by the modulation of the SSC in the improved topology, especially under the circumstance with the asymmTeric fault of stator side, DFIG’s electromagnTeic torque, amplifies ripple of grid-connected power for the grid side. The novel control mTehod suitable to stator side converter and rotor side converter based on reduced-order resonant controller (RORC) is proposed in this thesis, DFIG’s torque and output power performance are improved. Under the RORC control conditions the transfer functions of stator current and torque control system are established, the amplitude characteristic and the system stability of RORC control are analysed. The simulation results in Matlab/Simulink verify the correctness and validity of the proposed mTehod.

Directed flux motor

NASA Technical Reports Server (NTRS)

Wilson, Andrew (Inventor); Punnoose, Andrew (Inventor); Strausser, Katherine (Inventor); Parikh, Neil (Inventor)

2011-01-01

A directed flux motor described utilizes the directed magnetic flux of at least one magnet through ferrous material to drive different planetary gear sets to achieve capabilities in six actuated shafts that are grouped three to a side of the motor. The flux motor also utilizes an interwoven magnet configuration which reduces the overall size of the motor. The motor allows for simple changes to modify the torque to speed ratio of the gearing contained within the motor as well as simple configurations for any number of output shafts up to six. The changes allow for improved manufacturability and reliability within the design.

Propeller torque load and propeller shaft torque response correlation during ice-propeller interaction

NASA Astrophysics Data System (ADS)

Polić, Dražen; Ehlers, Sören; Æsøy, Vilmar

2017-03-01

Ships use propulsion machinery systems to create directional thrust. Sailing in ice-covered waters involves the breaking of ice pieces and their submergence as the ship hull advances. Sometimes, submerged ice pieces interact with the propeller and cause irregular fluctuations of the torque load. As a result, the propeller and engine dynamics become imbalanced, and energy propagates through the propulsion machinery system until equilibrium is reached. In such imbalanced situations, the measured propeller shaft torque response is not equal to the propeller torque. Therefore, in this work, the overall system response is simulated under the ice-related torque load using the Bond graph model. The energy difference between the propeller and propeller shaft is estimated and related to their corresponding mechanical energy. Additionally, the mechanical energy is distributed among modes. Based on the distribution, kinetic and potential energy are important for the correlation between propeller torque and propeller shaft response.

Angular dependence of spin-orbit spin-transfer torques

NASA Astrophysics Data System (ADS)

Lee, Ki-Seung; Go, Dongwook; Manchon, Aurélien; Haney, Paul M.; Stiles, M. D.; Lee, Hyun-Woo; Lee, Kyung-Jin

2015-04-01

In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.

Barbell deadlift training increases the rate of torque development and vertical jump performance in novices.

PubMed

Thompson, Brennan J; Stock, Matt S; Shields, JoCarol E; Luera, Micheal J; Munayer, Ibrahim K; Mota, Jacob A; Carrillo, Elias C; Olinghouse, Kendra D

2015-01-01

The primary purpose of this study was to examine the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors. A secondary aim was to analyze the relationships between training-induced changes in rapid torque and vertical jump performance. Fifty-four subjects (age, mean ± SD = 23 ± 3 years) were randomly assigned to a control (n = 20) or training group (n = 34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and after the intervention. Torque-time curves were used to calculate rate of torque development (RTD) values at peak and at 50 and 200 milliseconds from torque onset. Barbell deadlift training induced significant pre- to post-increases of 18.8-49.0% for all rapid torque variables (p < 0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm (7.4%; p < 0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r = 0.30-0.37, p < 0.01-0.03). These findings showed that a 10-week barbell deadlift training program was effective at enhancing rapid torque capacities in both the knee extensors and flexors. Changes in rapid torque were associated with improvements in vertical jump height, suggesting a transfer of adaptations from deadlift training to an explosive, performance-based task. Professionals may use these findings when attempting to design effective, time-efficient resistance training programs to improve explosive strength capacities in novices.

Detecting Casimir torque with an optically levitated nanorod

NASA Astrophysics Data System (ADS)

Xu, Zhujing; Li, Tongcang

2017-09-01

The linear momentum and angular momentum of virtual photons of quantum vacuum fluctuations can induce the Casimir force and the Casimir torque, respectively. While the Casimir force has been measured extensively, the Casimir torque has not been observed experimentally though it was predicted over 40 years ago. Here we propose to detect the Casimir torque with an optically levitated nanorod near a birefringent plate in vacuum. The axis of the nanorod tends to align with the polarization direction of the linearly polarized optical tweezer. When its axis is not parallel or perpendicular to the optical axis of the birefringent crystal, it will experience a Casimir torque that shifts its orientation slightly. We calculate the Casimir torque and Casimir force acting on a levitated nanorod near a birefringent crystal. We also investigate the effects of thermal noise and photon recoils on the torque and force detection. We prove that a levitated nanorod in vacuum will be capable of detecting the Casimir torque under realistic conditions, and will be an important tool in precision measurements.

Stresses in Implant-Supported Fixed Complete Dentures with Different Screw-Tightening Sequences and Torque Application Modes.

PubMed

Barcellos, Leonardo H; Palmeiro, Marina Lobato; Naconecy, Marcos M; Geremia, Tomás; Cervieri, André; Shinkai, Rosemary S

2018-05-17

To compare the effects of different screw-tightening sequences and torque applications on stresses in implant-supported fixed complete dentures supported by five abutments. Strain gauges fixed to the abutments were used to test the sequences 2-4-3-1-5; 1-2-3-4-5; 3-2-4-1-5; and 2-5-4-1-3 with direct 10-Ncm torque or progressive torque (5 + 10 Ncm). Data were analyzed using analysis of variance and standardized effect size. No effects of tightening sequence or torque application were found except for the sequence 3-2-4-1-5 and some small to moderate effect sizes. Screw-tightening sequences and torque application modes have only a marginal effect on residual stresses.

The stability of steady motion of magnetic domain wall: Role of higher-order spin-orbit torques

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Peng-Bin, E-mail: hepengbin@hnu.edu.cn; Yan, Han; Cai, Meng-Qiu

The steady motion of magnetic domain wall driven by spin-orbit torques is investigated analytically in the heavy/ferromagnetic metal nanowires for three cases with a current transverse to the in-plane and perpendicular easy axis, and along the in-plane easy axis. By the stability analysis of Walker wall profile, we find that if including the higher-order spin-orbit torques, the Walker breakdown can be avoided in some parameter regions of spin-orbit torques with a current transverse to or along the in-plane easy axis. However, in the case of perpendicular anisotropy, even considering the higher-order spin-orbit torques, the velocity of domain wall cannot bemore » efficiently enhanced by the current. Furthermore, the direction of wall motion is dependent on the configuration and chirality of domain wall with a current along the in-plane easy axis or transverse to the perpendicular one. Especially, the direction of motion can be controlled by the initial chirality of domain wall. So, if only involving the spin-orbit mechanism, it is preferable to adopt the scheme of a current along the in-plane easy axis for enhancing the velocity and controlling the direction of domain wall.« less

Spin-Orbit Torques and Anisotropic Magnetization Damping in Skyrmion Crystals

NASA Astrophysics Data System (ADS)

Hals, Kjetil; Brataas, Arne

2014-03-01

We theoretically study the effects of reactive and dissipative homogeneous spin-orbit torques and anisotropic damping on the current-driven skyrmion dynamics in cubic chiral magnets. Our results demonstrate that spin-orbit torques play a significant role in the current-induced skyrmion velocity. The dissipative spin-orbit torque generates a relativistic Magnus force on the skyrmions, whereas the reactive spin-orbit torque yields a correction to both the drift velocity along the current direction and the transverse velocity associated with the Magnus force. The spin-orbit torque corrections to the velocity scale linearly with the skyrmion size, which is inversely proportional to the spin-orbit coupling. Consequently, the reactive spin-orbit torque correction can be the same order of magnitude as the non-relativistic contribution. More importantly, the dissipative spin-orbit torque can be the dominant force that causes a deflected motion of the skyrmions if the torque exhibits a linear or quadratic relationship with the spin-orbit coupling. In addition, we demonstrate that the skyrmion velocity is determined by anisotropic magnetization damping parameters governed by the skyrmion size.

Helicopter transmission arrangements with split-torque gear trains

NASA Technical Reports Server (NTRS)

White, G.

1983-01-01

As an alternative to component development, the case for improved drive-train configuration is argued. In particular, the use of torque-splitting gear trains is proposed as a practicable means of improving the effectiveness of helicopter main gearboxes.

75 FR 35619 - Airworthiness Directives; Piper Aircraft, Inc. Models PA-32R-301T and PA-46-350P Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-23

... tighten to an July 28, 2010 (the initial torque of effective date of 40 in. lbs. Tap the this AD... installation than by a change in clamp design. Their experience shows proper installation, torque techniques, and pre-torque alignments of components go a long way in preventing clamp failures down the road. We...

Effects of solar radiation pressure torque on the rotational motion of an artificial satellite

NASA Technical Reports Server (NTRS)

Zanardi, Maria Cecilia F. P. S.; Vilhenademoraes, Rodolpho

1992-01-01

The motion of an artificial satellite about its center of mass is studied considering torques due to the gravity gradient and direct solar radiation pressure. A model for direct solar radiation torque is derived for a circular cylindrical satellite. An analytical solution is obtained by the method of variation of the parameters. This solution shows that the angular variables have secular variation but that the modulus of the rotational angular momentum, the projection of rotational angular momentum on the z axis of the moment of inertia and inertial axis z, suffer only periodic variations. Considering a hypothetical artificial satellite, a numerical application is demonstrated.

76 FR 62649 - Airworthiness Directives; The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-11

.../fire seals of the blocker doors on the thrust reverser torque boxes on the engines, and replacing affected aero/fire seals with new, improved aero/fire seals. That second supplemental NPRM was prompted by a report that the top 3 inches of the aero/fire seals of the blocker doors on the thrust reverser...

Bidirectional helical motility of cytoplasmic dynein around microtubules

PubMed Central

Can, Sinan; Dewitt, Mark A; Yildiz, Ahmet

2014-01-01

Cytoplasmic dynein is a molecular motor responsible for minus-end-directed cargo transport along microtubules (MTs). Dynein motility has previously been studied on surface-immobilized MTs in vitro, which constrains the motors to move in two dimensions. In this study, we explored dynein motility in three dimensions using an MT bridge assay. We found that dynein moves in a helical trajectory around the MT, demonstrating that it generates torque during cargo transport. Unlike other cytoskeletal motors that produce torque in a specific direction, dynein generates torque in either direction, resulting in bidirectional helical motility. Dynein has a net preference to move along a right-handed helical path, suggesting that the heads tend to bind to the closest tubulin binding site in the forward direction when taking sideways steps. This bidirectional helical motility may allow dynein to avoid roadblocks in dense cytoplasmic environments during cargo transport. DOI: http://dx.doi.org/10.7554/eLife.03205.001 PMID:25069614

Dirac spin-orbit torques and charge pumping at the surface of topological insulators

NASA Astrophysics Data System (ADS)

Ndiaye, Papa B.; Akosa, C. A.; Fischer, M. H.; Vaezi, A.; Kim, E.-A.; Manchon, A.

2017-07-01

We address the nature of spin-orbit torques at the magnetic surfaces of topological insulators using the linear-response theory. We find that the so-called Dirac torques in such systems possess a different symmetry compared to their Rashba counterpart, as well as a high anisotropy as a function of the magnetization direction. In particular, the damping torque vanishes when the magnetization lies in the plane of the topological-insulator surface. We also show that the Onsager reciprocal of the spin-orbit torque, the charge pumping, induces an enhanced anisotropic damping. Via a macrospin model, we numerically demonstrate that these features have important consequences in terms of magnetization switching.

Current induced domain wall dynamics in the presence of spin orbit torques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boulle, O., E-mail: Olivier.boulle@cea.fr; Buda-Prejbeanu, L. D.; Jué, E.

2014-05-07

Current induced domain wall (DW) motion in perpendicularly magnetized nanostripes in the presence of spin orbit torques is studied. We show using micromagnetic simulations that the direction of the current induced DW motion and the associated DW velocity depend on the relative values of the field like torque (FLT) and the Slonczewski like torques (SLT). The results are well explained by a collective coordinate model which is used to draw a phase diagram of the DW dynamics as a function of the FLT and the SLT. We show that a large increase in the DW velocity can be reached bymore » a proper tuning of both torques.« less

Use of Mixer Torque Rheometer to Clarify the Relationship between the Kneading States of Wet Mass and the Dissolution of Final Product in High Shear Granulation.

PubMed

Otsuka, Tomoko; Kuroiwa, Yosuke; Sato, Kazunari; Yamashita, Kazunari; Hakomori, Tadashi; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

2018-01-01

The properties of wet mass, which indicate the progress of high shear granulation processes, usually have an effect on final product properties, such as tablet dissolution. The mixer torque rheometer (MTR) is a useful tool for quantitatively measuring the 'kneading state' of wet mass and detecting differences in granules. However, there have been no studies of the relationship between the MTR torque and the final product properties to date. In this study, we measured the MTR torque of wet granules at different kneading states, which were prepared by changing the granulation conditions. We then evaluated the relationship between the MTR torque and the dissolution rate of the final product properties. The amperage of the high shear granulator is usually monitored during granulation, but we could not detect a difference in the kneading state through the amperage. However, using MTR torque we were able to quantify the difference of the wet mass. Moreover, MTR torque showed a high correlation with dissolution, compared with the correlations with other intermediate properties, such as granules particle size and tablet hardness. These other properties are affected by following processes and are not properties that directly relate to the kneading state. Thus, MTR torque is a property of wet mass after granulation, and it can be used to directly evaluate differences of the kneading state, and as a result, dissolution. These results indicate the importance of controlling the kneading state, i.e., the progress of granulation, and the utility of MTR for detecting differences in wet mass.

Wind tunnel testing of 5-bladed H-rotor wind turbine with the integration of the omni-direction-guide-vane

NASA Astrophysics Data System (ADS)

Fazlizan, A.; Chong, W. T.; Omar, W. Z. W.; Mansor, S.; Zain, Z. M.; Pan, K. C.; Oon, C. S.

2012-06-01

A novel omni-direction-guide-vane (ODGV) that surrounds a vertical axis wind turbine (VAWT) is designed to improve the wind turbine performance by increasing the oncoming wind speed and guiding the wind-stream through optimum flow angles before impinging onto the turbine blades. Wind tunnel testing was performed to measure the performance of a 5-bladed H-rotor wind turbine with Wortmann FX63-137 airfoil blades, with and without the integration of the ODGV. The test was conducted using a scaled model turbine which was constructed to simulate the VAWT enclosed by the ODGV on a building. The diameter and height of the ODGV are 2 times larger than the VAWT's. Torque, rotational speed and power measurements were performed by using torque transducer with hysteresis brake applied to the rotor shaft. The VAWT shows an improvement on its self-starting behavior where the cut-in speed reduced to 4 m/s with the ODGV (7.35 m/s without the ODGV). Since the VAWT is able to self-start at lower wind speed, the working hour of the wind turbine would increase. At the wind speed of 6 m/s and free-running condition (only rotor inertia and bearing friction were applied), the ODGV helps to increase the rotor RPM by 182%. At the same wind speed (6 m/s), the ODGV helps to increase the power output by 3.48 times at peak torque. With this innovative design, the size of VAWT can be reduced for a given power output and should generate interest in the market, even for regions with weaker winds.

The flagellar motor of Caulobacter crescentus generates more torque when a cell swims backward

PubMed Central

Lele, Pushkar P.; Roland, Thibault; Shrivastava, Abhishek; Chen, Yihao; Berg, Howard C.

2016-01-01

Caulobacter crescentus, a monotrichous bacterium, swims by rotating a single right-handed helical filament. CW motor rotation thrusts the cell forward 1, a mode of motility known as the pusher mode; CCW motor rotation pulls the cell backward, a mode of motility referred to as the puller mode 2. The situation is opposite in E. coli, a peritrichous bacterium, where CCW rotation of multiple left-handed filaments drives the cell forward. The flagellar motor in E. coli generates more torque in the CCW direction than the CW direction in swimming cells 3,4. However, monotrichous bacteria including C. crescentus swim forward and backward at similar speeds, prompting the assumption that motor torques in the two modes are the same 5,6. Here, we present evidence that motors in C. crescentus develop higher torques in the puller mode than in the pusher mode, and suggest that the anisotropy in torque-generation is similar in two species, despite the differences in filament handedness and motor bias (probability of CW rotation). PMID:27499800

Development of Face Gear Technology for Industrial and Aerospace Power Transmission

NASA Technical Reports Server (NTRS)

Heath, Gregory F.; Filler, Robert R.; Tan, Jie

2002-01-01

Tests of a 250 horsepower proof-of-concept (POC) split torque face gear transmission were completed by The Boeing Company in Mesa, Arizona, while working under a Defense Advanced Research Projects Agency (DARPA) Technology Reinvestment Program (TRP) This report provides a summary of these cooperative tests, which were jointly funded by Boeing and DARPA Design, manufacture and testing of the scaled-power TRP split torque gearbox followed preliminary evaluations of the concept performed early in the program The testing demonstrated the theory of operation for the concentric, tapered face gear assembly The results showed that the use of floating pinions in a concentric face gear arrangement produces a nearly even torque split The POC split torque tests determined that, with some improvements, face gears can be applied effectively in a split torque configuration which yields significant weight, cost and reliability improvements over conventional designs.

Magnetic torque on a rotating superconducting sphere

NASA Technical Reports Server (NTRS)

Holdeman, L. B.

1975-01-01

The London theory of superconductivity is used to calculate the torque on a superconducting sphere rotating in a uniform applied magnetic field. The London theory is combined with classical electrodynamics for a calculation of the direct effect of excess charge on a rotating superconducting sphere. Classical electrodynamics, with the assumption of a perfect Meissner effect, is used to calculate the torque on a superconducting sphere rotating in an arbitrary magnetic induction; this macroscopic approach yields results which are correct to first order. Using the same approach, the torque due to a current loop encircling the rotating sphere is calculated.

Controller for a High-Power, Brushless dc Motor

NASA Technical Reports Server (NTRS)

Fleming, David J.; Makdad, Terence A.

1987-01-01

Driving and braking torques controllable. Control circuit operates 7-kW, 45-lb-ft (61-N-m), three-phase, brushless dc motor in both motor and generator modes. In motor modes, energy from power source is pulse-width modulated to motor through modified "H-bridge" circuit, in generator mode, energy from motor is pulse-width modulated into bank of load resistors to provide variable braking torques. Circuit provides high-resolution torque control in both directions over wide range of speeds and torques. Tested successfully at bus voltages up to 200 Vdc and currents up to 45 A.

Measurement of the torque on a single stretched and twisted DNA using magnetic tweezers.

PubMed

Mosconi, Francesco; Allemand, Jean François; Bensimon, David; Croquette, Vincent

2009-02-20

We deduced the torque applied on a single stretched and twisted DNA by integrating the change in the molecule's extension with respect to force as it is coiled. While consistent with previous direct measurements of the torque at high forces (F>1 pN), this method, which is simple and does not require a sophisticated setup, allows for lower force estimates. We used this approach to deduce the effective torsional modulus of DNA, which decreases with force, and to estimate the buckling torque of DNA as a function of force in various salt conditions.

Remote control canard missile with a free-rolling tail brake torque system

NASA Technical Reports Server (NTRS)

Blair, A. B., Jr.

1981-01-01

An experimental wind-tunnel investigation has been conducted at supersonic Mach numbers to determine the static aerodynamic characteristics of a cruciform canard-controlled missile with fixed and free-rolling tail-fin afterbodies. Mechanical coupling effects of the free-rolling tail afterbody were investigated using an electronic/electromagnetic brake system that provides arbitrary tail-fin brake torques with continuous measurements of tail-to-mainframe torque and tail-roll rate. Results are summarized to show the effects of fixed and free-rolling tail-fin afterbodies that include simulated measured bearing friction torques on the longitudinal and lateral-directional aerodynamic characteristics.

Variation of Electric Properties Between Surface Permanent Magnet and Interior Permanent Magnet Motor

NASA Astrophysics Data System (ADS)

Woo, Byung-Chul; Hong, Do-Kwan; Lee, Ji-Young

The most distinctive advantage of transverse flux motor(TFM) is high torque density which has prompted many researches into studying various design variants. TFM is well suited for low speed direct drive applications due to its high torque density. This paper deals with simulation based comparisons between a surface permanent magnet transverse flux motor(SPM-TFM) and an interior permanent magnet transverse flux motor(IPM-TFM). A commercial finite element analysis(FEA) software Maxwell 3D is used for electromagnetic field computation to fully analyze complex geometry of the TFMs. General characteristics, such as cogging torque, rated torque and torque ripple characteristics of the two TFMs are analyzed and compared by extensive 3D FEA.

The influence of aging on the isometric torque sharing patterns among the plantar flexor muscles.

PubMed

Oliveira, Liliam F; Verneque, Debora; Menegaldo, Luciano L

2017-01-01

Physiological cross-sectional area (PCSA) reduction of the triceps surae (TS) muscles during aging suggests a proportional loss of torque among its components: soleus, medial and lateral gastrocnemii. However, direct measurements of muscle forces in vivo are not feasible. The purpose of this paper was to compare, between older and young women, isometric ankle joint torque sharing patterns among TS muscles and tibialis anterior (TA). An EMG-driven model was used for estimating individual muscle torque contributions to the total plantar flexor torque, during sustained contractions of 10% and 40% of maximum voluntary contraction (MVC). Relative individual muscle contributions to the total plantar flexion torque were similar between older and young women groups, for both intensities, increasing from LG, MG to SOL. Muscle strength (muscle torque/body mass) was significantly greater for all TS components in 40% MVC contractions. Increased TA activation was observed in 10% of MVC for older people. Despite the reduced maximum isometric torque and muscle strength, the results suggest small variations of ankle muscle synergies during the aging process.

A Practical Torque Estimation Method for Interior Permanent Magnet Synchronous Machine in Electric Vehicles.

PubMed

Wu, Zhihong; Lu, Ke; Zhu, Yuan

2015-01-01

The torque output accuracy of the IPMSM in electric vehicles using a state of the art MTPA strategy highly depends on the accuracy of machine parameters, thus, a torque estimation method is necessary for the safety of the vehicle. In this paper, a torque estimation method based on flux estimator with a modified low pass filter is presented. Moreover, by taking into account the non-ideal characteristic of the inverter, the torque estimation accuracy is improved significantly. The effectiveness of the proposed method is demonstrated through MATLAB/Simulink simulation and experiment.

A Practical Torque Estimation Method for Interior Permanent Magnet Synchronous Machine in Electric Vehicles

PubMed Central

Zhu, Yuan

2015-01-01

The torque output accuracy of the IPMSM in electric vehicles using a state of the art MTPA strategy highly depends on the accuracy of machine parameters, thus, a torque estimation method is necessary for the safety of the vehicle. In this paper, a torque estimation method based on flux estimator with a modified low pass filter is presented. Moreover, by taking into account the non-ideal characteristic of the inverter, the torque estimation accuracy is improved significantly. The effectiveness of the proposed method is demonstrated through MATLAB/Simulink simulation and experiment. PMID:26114557

Alterations of the In Vivo Torque-Velocity Relationship of Human Skeletal Muscle Following 30 Days Exposure to Simulated Microgravity

NASA Technical Reports Server (NTRS)

Dudley, Gary A.; Duvoisin, Marc R.; Convertino, Victor A.; Buchanan, Paul

1989-01-01

The purpose of this study was to examine the effect of 30 d of 6 deg headdown bedrest (BR) on the in vivo strength of skeletal muscle. Peak angle specific (0.78 rad below horizontal) torque of the knee extensor (KE) and flexor (KF) muscle groups of both limbs was assessed during unilateral efforts at four speeds (0.52, 1.74, 2.97 and 4.19 rad/s) during concentric and at three speeds (0.52, 1.74 and 2.97 rad/s) during eccentric actions. The average decrease (P less than 0.05) of peak angle specific torque directly post-BR for the KE across speeds of concentric and eccentric actions was about 19% (n = 7). Recovery for 30 d following BR markedly improved strength to about 92% (P greater than 0.05) of 'normal'. Strength of the KF was not altered (P greater than 0.05) by BR (about a 6% decrease independent of speed and type of muscle action). Changes of strength were not affected by the type or speed of muscle action. The results indicate that strength of ex-tensor more than of flexor muscle groups of the lower limb is decreased by 30 d of bedrest and that this response does not alter the nature of the in vivo torque-velocity relation.

Spin-orbit torques and anisotropic magnetization damping in skyrmion crystals

NASA Astrophysics Data System (ADS)

Hals, Kjetil M. D.; Brataas, Arne

2014-02-01

The length scale of the magnetization gradients in chiral magnets is determined by the relativistic Dzyaloshinskii-Moriya interaction. Thus, even conventional spin-transfer torques are controlled by the relativistic spin-orbit coupling in these systems, and additional relativistic corrections to the current-induced torques and magnetization damping become important for a complete understanding of the current-driven magnetization dynamics. We theoretically study the effects of reactive and dissipative homogeneous spin-orbit torques and anisotropic damping on the current-driven skyrmion dynamics in cubic chiral magnets. Our results demonstrate that spin-orbit torques play a significant role in the current-induced skyrmion velocity. The dissipative spin-orbit torque generates a relativistic Magnus force on the skyrmions, whereas the reactive spin-orbit torque yields a correction to both the drift velocity along the current direction and the transverse velocity associated with the Magnus force. The spin-orbit torque corrections to the velocity scale linearly with the skyrmion size, which is inversely proportional to the spin-orbit coupling. Consequently, the reactive spin-orbit torque correction can be the same order of magnitude as the nonrelativistic contribution. More importantly, the dissipative spin-orbit torque can be the dominant force that causes a deflected motion of the skyrmions if the torque exhibits a linear or quadratic relationship with the spin-orbit coupling. In addition, we demonstrate that the skyrmion velocity is determined by anisotropic magnetization damping parameters governed by the skyrmion size.

Design and simulation of the direct drive servo system

NASA Astrophysics Data System (ADS)

Ren, Changzhi; Liu, Zhao; Song, Libin; Yi, Qiang; Chen, Ken; Zhang, Zhenchao

2010-07-01

As direct drive technology is finding their way into telescope drive designs for its many advantages, it would push to more reliable and cheaper solutions for future telescope complex motion system. However, the telescope drive system based on the direct drive technology is one high integrated electromechanical system, which one complex electromechanical design method is adopted to improve the efficiency, reliability and quality of the system during the design and manufacture circle. The telescope is one ultra-exact, ultra-speed, high precision and huge inertial instrument, which the direct torque motor adopted by the telescope drive system is different from traditional motor. This paper explores the design process and some simulation results are discussed.

Biomechanical design of escalading lower limb exoskeleton with novel linkage joints.

PubMed

Zhang, Guoan; Liu, Gangfeng; Ma, Sun; Wang, Tianshuo; Zhao, Jie; Zhu, Yanhe

2017-07-20

In this paper, an obstacle-surmounting-enabled lower limb exoskeleton with novel linkage joints that perfectly mimicked human motions was proposed. Currently, most lower exoskeletons that use linear actuators have a direct connection between the wearer and the controlled part. Compared to the existing joints, the novel linkage joint not only fitted better into compact chasis, but also provided greater torque when the joint was at a large bend angle. As a result, it extended the angle range of joint peak torque output. With any given power, torque was prioritized over rotational speed, because instead of rotational speed, sufficiency of torque is the premise for most joint actions. With insufficient torque, the exoskeleton will be a burden instead of enhancement to its wearer. With optimized distribution of torque among the joints, the novel linkage method may contribute to easier exoskeleton movements.

Torque measurement at the single-molecule level.

PubMed

Forth, Scott; Sheinin, Maxim Y; Inman, James; Wang, Michelle D

2013-01-01

Methods for exerting and measuring forces on single molecules have revolutionized the study of the physics of biology. However, it is often the case that biological processes involve rotation or torque generation, and these parameters have been more difficult to access experimentally. Recent advances in the single-molecule field have led to the development of techniques that add the capability of torque measurement. By combining force, displacement, torque, and rotational data, a more comprehensive description of the mechanics of a biomolecule can be achieved. In this review, we highlight a number of biological processes for which torque plays a key mechanical role. We describe the various techniques that have been developed to directly probe the torque experienced by a single molecule, and detail a variety of measurements made to date using these new technologies. We conclude by discussing a number of open questions and propose systems of study that would be well suited for analysis with torsional measurement techniques.

Thermally induced magnonic spin current, thermomagnonic torques, and domain-wall dynamics in the presence of Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Wang, X.-G.; Chotorlishvili, L.; Guo, G.-H.; Sukhov, A.; Dugaev, V.; Barnaś, J.; Berakdar, J.

2016-09-01

Thermally activated domain-wall (DW) motion in magnetic insulators has been considered theoretically, with a particular focus on the role of Dzyaloshinskii-Moriya interaction (DMI) and thermomagnonic torques. The thermally assisted DW motion is a consequence of the magnonic spin current due to the applied thermal bias. In addition to the exchange magnonic spin current and the exchange adiabatic and the entropic spin transfer torques, we also consider the DMI-induced magnonic spin current, thermomagnonic DMI fieldlike torque, and the DMI entropic torque. Analytical estimations are supported by numerical calculations. We found that the DMI has a substantial influence on the size and the geometry of DWs, and that the DWs become oriented parallel to the long axis of the nanostrip. Increasing the temperature smoothes the DWs. Moreover, the thermally induced magnonic current generates a torque on the DWs, which is responsible for their motion. From our analysis it follows that for a large enough DMI the influence of DMI-induced fieldlike torque is much stronger than that of the DMI and the exchange entropic torques. By manipulating the strength of the DMI constant, one can control the speed of the DW motion, and the direction of the DW motion can be switched, as well. We also found that DMI not only contributes to the total magnonic current, but also it modifies the exchange magnonic spin current, and this modification depends on the orientation of the steady-state magnetization. The observed phenomenon can be utilized in spin caloritronics devices, for example in the DMI based thermal diodes. By switching the magnetization direction, one can rectify the total magnonic spin current.

Membrane-based torque magnetometer: Enhanced sensitivity by optical readout of the membrane displacement

NASA Astrophysics Data System (ADS)

Blankenhorn, M.; Heintze, E.; Slota, M.; van Slageren, J.; Moores, B. A.; Degen, C. L.; Bogani, L.; Dressel, M.

2017-09-01

The design and realization of a torque magnetometer is reported that reads the deflection of a membrane by optical interferometry. The compact instrument allows for low-temperature measurements of tiny crystals less than a microgram with a significant improvement in sensitivity, signal-to-noise ratio as well as data acquisition time compared with conventional magnetometry and offers an enormous potential for further improvements and future applications in different fields. Magnetic measurements on single-molecule magnets demonstrate the applicability of the membrane-based torque magnetometer.

Membrane-based torque magnetometer: Enhanced sensitivity by optical readout of the membrane displacement.

PubMed

Blankenhorn, M; Heintze, E; Slota, M; van Slageren, J; Moores, B A; Degen, C L; Bogani, L; Dressel, M

2017-09-01

The design and realization of a torque magnetometer is reported that reads the deflection of a membrane by optical interferometry. The compact instrument allows for low-temperature measurements of tiny crystals less than a microgram with a significant improvement in sensitivity, signal-to-noise ratio as well as data acquisition time compared with conventional magnetometry and offers an enormous potential for further improvements and future applications in different fields. Magnetic measurements on single-molecule magnets demonstrate the applicability of the membrane-based torque magnetometer.

Special-Purpose High-Torque Permanent-Magnet Motors

NASA Technical Reports Server (NTRS)

Doane, George B., III

1995-01-01

Permanent-magnet brushless motors that must provide high commanded torques and satisfy unusual heat-removal requirement are developed. Intended for use as thrust-vector-control actuators in large rocket engines. Techniques and concepts used to design improved motors for special terrestrial applications. Conceptual motor design calls for use of rotor containing latest high-energy-product rare-earth permanent magnets so that motor produces required torque while drawing smallest possible currents from power supply. Torque generated by electromagnetic interaction between stator and permanent magnets in rotor when associated electronic circuits applied appropriately temporally and spatially phased currents to stator windings. Phase relationships needed to produce commanded torque computed in response to torque command and to electronically sensed angular position of rotor relative to stator.

An investigation into the torque density capabilities of flux-focusing magnetic gearboxes

NASA Astrophysics Data System (ADS)

Uppalapati, Krishna Kiran

Wind and many rotary based ocean energy conversion devices rely on a mechanical gearbox to increase their speed so as to match the requirements of the electromagnetic generator. However, mechanical gearboxes have a number of disadvantages such as the need for gear lubrication, no overload protection and the creation of acoustic noise. Frequently direct-drive generators are employed to overcome these issues, wherein the gearbox is removed and the shaft of the turbine is directly connected to the synchronous generator, either with an electrically excited or permanent magnet rotor. If the input speed to the generator is very low the torque must be very high in order to generate the necessary power. However, as the electrical loading of a synchronous generator is thermally limited, the size of the generator will become excessively large at high power levels. An alternative to these technologies is to consider replacing the mechanical gearbox with a magnetic gear. A magnetic gear can create speed change without any physical contact. It has inherent overload protection, and its non-contact operation offers the potential for high reliability. Despite significant progress, existing magnetic gear designs do not achieve torque densities that are competitive with mechanical gearboxes. This research has focused on designing a coaxial magnetic gear that can operate at a volumetric torque density that is comparable to a mechanical gearbox. A flux-focusing rotor topology also called spoke-type rotor magnet arrangement was adopted to improve the air-gap magnetic flux density which in turn improves the torque transferred between the rotors. Finite element analysis was utilized to conduct a parameter sweep analysis of the different geometric parameters of the magnetic gear. A sub-scale magnetic gear with a diameter of 110 mm and a scaled-up magnetic gear with a diameter of 228 mm was designed, constructed and experimentally evaluated. The torque and torque density of sub-scale design was measured to be 115 Nm and 151.2 Nm/L respectively and that of the scaled-up model was measured to be 731 Nm and 239 Nm/L respectively. An iterative magnetomechanical analysis technique was developed to study the deflection of the magnetic gear steel rotor bars due to the magnetic forces coming from the inner and outer rotor permanent magnets. The accuracy of the technique was validated by using an experimental test-stand. It was shown that the deflection is an important issue to consider especially if the air-gaps are small. A 2-D analytical based model was derived for the flux-focusing coaxial magnetic gear by using the separation of variables method to solve the Laplace and Poisson equation in each region. After applying the applicable Dirchlet and Neumann boundary conditions a set of 16 equations with 16 unknown Fourier coefficients was obtained. The 16 unknowns were solved numerically by putting the equations in a matrix form. It was shown that the analytical based model immensely reduced the torque and field computational time when compared to using finite element analysis. However, the analytical model does not take into consideration the non-linear properties of the steel. The benefits of using the analytical model was demonstrated by conducting a radial scaling and gear-ratio analysis.

Aeroservoelastic DAP missile fin development. [directionally attached piezoelectric actuator

NASA Technical Reports Server (NTRS)

Barrett, Ron

1993-01-01

The development of an active aeroservoelastic missile fin using directionally attached piezoelectric (DAP) actuator elements is detailed. Several different types of actuator elements are examined, including piezoelectric polymers, piezoelectric fiber composites, and conventionally attached piezoelectric (CAP) and DAP elements. These actuator elements are bonded to the substrate of a torque plate. The root of the torque plate is attached to a fuselage hard point or folding pivot. The tip of the plate is bonded to an aerodynamic shell which undergoes a pitch change as the plate twists. The design procedures used on the plate are discussed. A comparison of the various actuator element shows that DAP elements provide the highest deflections with the highest torsional stiffness. A torque plate was constructed from 0.2032 mm thick DAP elements bonded to a 0.127 mm thick AISI 1010 steel substrate. The torque plate produced static twist deflections in excess of +/- 3 deg. An aerodynamic shell with a modified NACA 0012 profile was added to the torque plate. This fin was tested in a wind tunnel at speeds up to 50 ms/sec. The static deflection of the fin was predicted to within 6 percent of the experimental data.

Advanced Direct-Drive Generator for Improved Availability of Oscillating Wave Surge Converter Power Generation Systems Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Englebretson, Steven; Ouyang, Wen; Tschida, Colin

This report summarizes the activities conducted under the DOE-EERE funded project DE-EE0006400, where ABB Inc. (ABB), in collaboration with Texas A&M’s Advanced Electric Machines & Power Electronics (EMPE) Lab and Resolute Marine Energy (RME) designed, derisked, developed, and demonstrated a novel magnetically geared electrical generator for direct-drive, low-speed, high torque MHK applications The project objective was to investigate a novel and compact direct-drive electric generator and its system aspects that would enable elimination of hydraulic components in the Power Take-Off (PTO) of a Marine and Hydrokinetic (MHK) system with an oscillating wave surge converter (OWSC), thereby improving the availability ofmore » the MHK system. The scope of this project was limited to the development and dry lab demonstration of a low speed generator to enable future direct drive MHK systems.« less

Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

DOEpatents

Konrad, C.E.; Boothe, R.W.

1994-02-15

A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figures.

Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

DOEpatents

Konrad, C.E.; Boothe, R.W.

1996-01-23

A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figs.

Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

DOEpatents

Konrad, Charles E.; Boothe, Richard W.

1996-01-01

A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

DOEpatents

Konrad, Charles E.; Boothe, Richard W.

1994-01-01

A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

On the stability of motion of several types of heavy symmetric gyroscopes with damping torques

NASA Astrophysics Data System (ADS)

Ge, Z.-M.; Wu, M.-H.

Sufficient conditions for the stability of motion of several gyroscopes are obtained using Liapunov's direct method. The stability of a 'temporarily' sleeping top with damping torque is considered for the cases of the support being fixed, being in vertical harmonic motion, and being in vertical periodic motion. Sufficient conditions are also obtained for the stability of a heavy symmetric gyroscope with damping torque and motor torque for the cases of regular precession, vertical axis permanent rotation with and without the axis of the outer gimbal being inclined, and the gyroscope being in a Newtonian central gravitational field.

Torque measurements reveal sequence-specific cooperative transitions in supercoiled DNA

PubMed Central

Oberstrass, Florian C.; Fernandes, Louis E.; Bryant, Zev

2012-01-01

B-DNA becomes unstable under superhelical stress and is able to adopt a wide range of alternative conformations including strand-separated DNA and Z-DNA. Localized sequence-dependent structural transitions are important for the regulation of biological processes such as DNA replication and transcription. To directly probe the effect of sequence on structural transitions driven by torque, we have measured the torsional response of a panel of DNA sequences using single molecule assays that employ nanosphere rotational probes to achieve high torque resolution. The responses of Z-forming d(pGpC)n sequences match our predictions based on a theoretical treatment of cooperative transitions in helical polymers. “Bubble” templates containing 50–100 bp mismatch regions show cooperative structural transitions similar to B-DNA, although less torque is required to disrupt strand–strand interactions. Our mechanical measurements, including direct characterization of the torsional rigidity of strand-separated DNA, establish a framework for quantitative predictions of the complex torsional response of arbitrary sequences in their biological context. PMID:22474350

Twin-enhanced magnetic torque

NASA Astrophysics Data System (ADS)

Hobza, Anthony; García-Cervera, Carlos J.; Müllner, Peter

2018-07-01

Magnetic shape memory alloys experience magnetic-field-induced torque due to magnetocrystalline anisotropy and shape anisotropy. In a homogeneous magnetic field, torque results in bending of long samples. This study investigates the torque on a single crystal of Ni-Mn-Ga magnetic shape memory alloy constrained with respect to bending in an external magnetic field. The dependence of the torque on external magnetic field magnitude, strain, and twin boundary structure was studied experimentally and with computer simulations. With increasing magnetic field, the torque increased until it reached a maximum near 700 mT. Above 200 mT, the torque was not symmetric about the equilibrium orientation for a sample with one twin boundary. The torque on two specimen with equal strain but different twin boundary structures varied systematically with the spatial arrangement of crystallographic twins. Numerical simulations show that twin boundaries suppress the formation of 180° domains if the direction of easy magnetization between two twin boundaries is parallel to a free surface and the magnetic field is perpendicular to that surface. For a particular twin microstructure, the torque decreases with increasing strain by a factor of six due to the mutual compensation of magnetocrystalline and shape anisotropy. When free rotation is suppressed such as in transducers of magneto-mechanical actuators, magnetic-field-induced torque creates strong bending forces, which may cause friction and failure under cyclic loading.

Validity of trunk extensor and flexor torque measurements using isokinetic dynamometry.

PubMed

Guilhem, Gaël; Giroux, Caroline; Couturier, Antoine; Maffiuletti, Nicola A

2014-12-01

This study aimed to evaluate the validity and test-retest reliability of trunk muscle strength testing performed with a latest-generation isokinetic dynamometer. Eccentric, isometric, and concentric peak torque of the trunk flexor and extensor muscles was measured in 15 healthy subjects. Muscle cross sectional area (CSA) and surface electromyographic (EMG) activity were respectively correlated to peak torque and submaximal isometric torque for erector spinae and rectus abdominis muscles. Reliability of peak torque measurements was determined during test and retest sessions. Significant correlations were consistently observed between muscle CSA and peak torque for all contraction types (r=0.74-0.85; P<0.001) and between EMG activity and submaximal isometric torque (r ⩾ 0.99; P<0.05), for both extensor and flexor muscles. Intraclass correlation coefficients were comprised between 0.87 and 0.95, and standard errors of measurement were lower than 9% for all contraction modes. The mean difference in peak torque between test and retest ranged from -3.7% to 3.7% with no significant mean directional bias. Overall, our findings establish the validity of torque measurements using the tested trunk module. Also considering the excellent test-retest reliability of peak torque measurements, we conclude that this latest-generation isokinetic dynamometer could be used with confidence to evaluate trunk muscle function for clinical or athletic purposes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Type-2 fuzzy logic control based MRAS speed estimator for speed sensorless direct torque and flux control of an induction motor drive.

PubMed

Ramesh, Tejavathu; Kumar Panda, Anup; Shiva Kumar, S

2015-07-01

In this research study, a model reference adaptive system (MRAS) speed estimator for speed sensorless direct torque and flux control (DTFC) of an induction motor drive (IMD) using two adaptation mechanism schemes are proposed to replace the conventional proportional integral controller (PIC). The first adaptation mechanism scheme is based on Type-1 fuzzy logic controller (T1FLC), which is used to achieve high performance sensorless drive in both transient as well as steady state conditions. However, the Type-1 fuzzy sets are certain and unable to work effectively when higher degree of uncertainties presents in the system which can be caused by sudden change in speed or different load disturbances, process noise etc. Therefore, a new Type-2 fuzzy logic controller (T2FLC) based adaptation mechanism scheme is proposed to better handle the higher degree of uncertainties and improves the performance and also robust to various load torque and sudden change in speed conditions, respectively. The detailed performances of various adaptation mechanism schemes are carried out in a MATLAB/Simulink environment with a speed sensor and speed sensorless modes of operation when an IMD is operating under different operating conditions, such as, no-load, load and sudden change in speed, respectively. To validate the different control approaches, the system also implemented on real-time system and adequate results are reported for its validation. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Immediate effects of whole body vibration on patellar tendon properties and knee extension torque.

PubMed

Rieder, F; Wiesinger, H-P; Kösters, A; Müller, E; Seynnes, O R

2016-03-01

Reports about the immediate effects of whole body vibration (WBV) exposure upon torque production capacity are inconsistent. However, the changes in the torque-angle relationship observed by some authors after WBV may hinder the measurement of torque changes at a given angle. Acute changes in tendon mechanical properties do occur after certain types of exercise but this hypothesis has never been tested after a bout of WBV. The purpose of the present study was to investigate whether tendon compliance is altered immediately after WBV, effectively shifting the optimal angle of peak torque towards longer muscle length. Twenty-eight subjects were randomly assigned to either a WBV (n = 14) or a squatting control group (n = 14). Patellar tendon CSA, stiffness and Young's modulus and knee extension torque-angle relationship were measured using ultrasonography and dynamometry 1 day before and directly after the intervention. Tendon CSA was additionally measured 24 h after the intervention to check for possible delayed onset of swelling. The vibration intervention had no effects on patellar tendon CSA, stiffness and Young's modulus or the torque-angle relationship. Peak torque was produced at ~70° knee angle in both groups at pre- and post-test. Additionally, the knee extension torque globally remained unaffected with the exception of a small (-6%) reduction in isometric torque at a joint angle of 60°. The present results indicate that a single bout of vibration exposure does not substantially alter patellar tendon properties or the torque-angle relationship of knee extensors.

Relationship between magnitude of applied torque in pre-swing phase and gait change for prevention of trip in elderly people.

PubMed

Miyake, Tamon; Tsukune, Mariko; Kobayashi, Yo; Sugano, Shigeki; Fujie, Masakatsu G

2016-08-01

Elderly people are at risk of tripping because of their narrow range of articular motion. To avoid tripping, gait training that improves their range of articular motion would be beneficial. In this study we propose a gait-training robot that applies a torque during the pre-swing phase to achieve this goal. We investigated the relationship between magnitude of applied torque and change in the range of knee-articular motion while walking before and after the application of this torque. We developed a wearable robot and carried out an experiment on human participants in which a motor pulls a string embedded on the robotic frame, applying torque in the pre-swing phase for a period of 20 [s]. Before and after applying torque the participant walked normally for 15 [s] without interference from the robot. We found that knee flexion angle increased after applying the torque if the torque was within the range of approximately 6-8 [Nm]. Therefore, we were able to verify that a new range of knee articular motion can be learned through application of torque.

Optimization of chiral structures for microscale propulsion.

PubMed

Keaveny, Eric E; Walker, Shawn W; Shelley, Michael J

2013-02-13

Recent advances in micro- and nanoscale fabrication techniques allow for the construction of rigid, helically shaped microswimmers that can be actuated using applied magnetic fields. These swimmers represent the first steps toward the development of microrobots for targeted drug delivery and minimally invasive surgical procedures. To assess the performance of these devices and improve on their design, we perform shape optimization computations to determine swimmer geometries that maximize speed in the direction of a given applied magnetic torque. We directly assess aspects of swimmer shapes that have been developed in previous experimental studies, including helical propellers with elongated cross sections and attached payloads. From these optimizations, we identify key improvements to existing designs that result in swimming speeds that are 70-470% of their original values.

Observation of plasma rotation driven by static nonaxisymmetric magnetic fields in a tokamak.

PubMed

Garofalo, A M; Burrell, K H; DeBoo, J C; deGrassie, J S; Jackson, G L; Lanctot, M; Reimerdes, H; Schaffer, M J; Solomon, W M; Strait, E J

2008-11-07

We present the first evidence for the existence of a neoclassical toroidal rotation driven in a direction counter to the plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, the nonresonant field torque slows down the plasma toward the neoclassical "offset" rotation rate. With small injected neutral beam momentum, the toroidal rotation is accelerated toward the offset rotation, with resulting improvement in the global energy confinement time. The observed magnitude, direction, and radial profile of the offset rotation are consistent with neoclassical theory predictions.

Cortical bone strains around straight and angulated immediate orthodontic microimplants: a pilot study.

PubMed

Cehreli, Secil; Yilmaz, Alev; Arman-Ozcirpici, Ayca

2013-04-01

To measure strains around orthodontic implants upon torque tightening and loading and to assess correlations between factors influencing primary stability. Self-drilling implants were placed into bovine iliac crest blocks after CT assessments. Upon bonding of strain gauges on bone adjacent to the implants, strain measurements were performed using a data acquisition system during torque tightening and 250 g orthodontic force application by elastic chains. The torque required to place straight implants (12.16 N.cm) was higher than 30- to 40-degree angulated implants (9.31 N.cm) (P < 0.05). Cortical bone strain amplitudes of both implant placements were comparable (P > 0.05). Strains during torque tightening of straight (196 με) and tilted (114 με) implants were higher than those obtained during orthodontic loading (20-30 με). Despite the positive and direct relationship found between torque and torque strain output, strong correlations between other parameters could not be detected. Vertically aligned and 30- to 40-degree angulated immediate orthodontic microimplants are associated with low amplitude strains upon torque tightening and orthodontic loading.

A dual-channel flux-switching permanent magnet motor for hybrid electric vehicles

NASA Astrophysics Data System (ADS)

Hua, Wei; Wu, Zhongze; Cheng, Ming; Wang, Baoan; Zhang, Jianzhong; Zhou, Shigui

2012-04-01

The flux-switching permanent magnet (FSPM) motor is a relatively novel brushless machine having both magnets and concentrated windings in the stator, which exhibits inherently sinusoidal PM flux-linkage, back-EMF waveforms, and high torque capability. However, in the application of hybrid electric vehicles, it is essential to prevent magnets and armature windings moving in radial direction due to the possible vibration during operation, and to ensure fault-tolerant capability. Hence, in this paper based on an original FSPM motor, a dual-channel FSPM (DC-FSPM) motor with modified structure to fix both armature windings and magnets and improved reliability is proposed for a practical 10 kW integral starter/generator (ISG) in hybrid electric vehicles. The influences of different solutions and the end-effect on the static characteristics, are evaluated based on the 2D and 3D finite element analysis, respectively. Finally, both the predicted and experimental results, compared with a prototype DC-FSPM motor and an interior PM motor used in Honda Civic, confirm that the more sinusoidal back-EMF waveform and lower torque ripple can be achieved in the DC-FSPM motor, whereas the torque is smaller under the same coil current.

Spin-orbit torques in magnetic bilayers

NASA Astrophysics Data System (ADS)

Haney, Paul

2015-03-01

Spintronics aims to utilize the coupling between charge transport and magnetic dynamics to develop improved and novel memory and logic devices. Future progress in spintronics may be enabled by exploiting the spin-orbit coupling present at the interface between thin film ferromagnets and heavy metals. In these systems, applying an in-plane electrical current can induce magnetic dynamics in single domain ferromagnets, or can induce rapid motion of domain wall magnetic textures. There are multiple effects responsible for these dynamics. They include spin-orbit torques and a chiral exchange interaction (the Dzyaloshinskii-Moriya interaction) in the ferromagnet. Both effects arise from the combination of ferromagnetism and spin-orbit coupling present at the interface. There is additionally a torque from the spin current flux impinging on the ferromagnet, arising from the spin hall effect in the heavy metal. Using a combination of approaches, from drift-diffusion to Boltzmann transport to first principles methods, we explore the relative contributions to the dynamics from these different effects. We additionally propose that the transverse spin current is locally enhanced over its bulk value in the vicinity of an interface which is oriented normal to the charge current direction.

A Physics Experiment Concerning the Measurement of the Torque of a Rotating Body Using a Magnetoelectrical Technique

ERIC Educational Resources Information Center

Sakon, Takuo; Nakagawa, Keisuke

2016-01-01

A physical experiment concerning the moment of inertia of a rigid disk is described. Basic physical quantities such as the moment of inertia and torque are very important in elementary physics courses. This experiment was designed to improve students' understanding of the relation between the rigid moment of inertia and torque. The moment of…

Torque Measurement at the Single Molecule Level

PubMed Central

Forth, Scott; Sheinin, Maxim Y.; Inman, James; Wang, Michelle D.

2017-01-01

Methods for exerting and measuring forces on single molecules have revolutionized the study of the physics of biology. However, it is often the case that biological processes involve rotation or torque generation, and these parameters have been more difficult to access experimentally. Recent advances in the single molecule field have led to the development of techniques which add the capability of torque measurement. By combining force, displacement, torque, and rotational data, a more comprehensive description of the mechanics of a biomolecule can be achieved. In this review, we highlight a number of biological processes for which torque plays a key mechanical role. We describe the various techniques that have been developed to directly probe the torque experienced by a single molecule, and detail a variety of measurements made to date using these new technologies. We conclude by discussing a number of open questions and propose systems of study which would be well suited for analysis with torsional measurement techniques. PMID:23541162

Measurements of the toroidal torque balance of error field penetration locked modes

DOE PAGES

Shiraki, Daisuke; Paz-Soldan, Carlos; Hanson, Jeremy M.; ...

2015-01-05

Here, detailed measurements from the DIII-D tokamak of the toroidal dynamics of error field penetration locked modes under the influence of slowly evolving external fields, enable study of the toroidal torques on the mode, including interaction with the intrinsic error field. The error field in these low density Ohmic discharges is well known based on the mode penetration threshold, allowing resonant and non-resonant torque effects to be distinguished. These m/n = 2/1 locked modes are found to be well described by a toroidal torque balance between the resonant interaction with n = 1 error fields, and a viscous torque inmore » the electron diamagnetic drift direction which is observed to scale as the square of the perturbed field due to the island. Fitting to this empirical torque balance allows a time-resolved measurement of the intrinsic error field of the device, providing evidence for a time-dependent error field in DIII-D due to ramping of the Ohmic coil current.« less

75 FR 26883 - Airworthiness Directives; Empresa Brasileira de Aeronautica S.A. (EMBRAER) Model ERJ 170 and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-13

... slat actuator structural failure (rupture) and its adjacent actuator torque limiter failing high... outboard slat actuator structural failure (rupture) and its adjacent actuator torque limiter failing high... requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in...

78 FR 3363 - Airworthiness Directives; the Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-16

...-mechanical brake flex shaft (short flexshaft) of the thrust reverser actuation system (TRAS). This proposed... the electro-mechanical brake and center drive unit (CDU) cone brake to verify the holding torque, and... describes a functional test of the electro-mechanical brake and CDU cone brake to verify the holding torque...

78 FR 34288 - Airworthiness Directives; Eurocopter France Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-07

... attaching fittings. If more than a 20 percent tightening torque load loss is discovered, the ASBs require... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA-2013... detect the torque loss of the bolts that secure the MGB bar attaching fittings and to prevent cracks that...

78 FR 25664 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-02

... lead to loss of transmission of THSA torque loads from the ballscrew to the tie-bar and consequent THSA... rupture, may lead to loss of transmission of THSA torque loads from the ballscrew to the tie-bar and... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 39 [Docket No. FAA-2013...

Torque vectoring for improving stability of small electric vehicles

NASA Astrophysics Data System (ADS)

Grzegożek, W.; Weigel-Milleret, K.

2016-09-01

The electric vehicles solutions based on the individually controlled electric motors propel a single wheel allow to improve the dynamic properties of the vehicle by varying the distribution of the driving torque. Most of the literature refer to the vehicles with a track typical for passenger cars. This paper examines whether the narrow vehicle (with a very small track) torque vectoring bring a noticeable change of the understeer characteristics and whether torque vectoring is possible to use in securing a narrow vehicle from roll over (roll mitigation). The paper contains road tests of the steering characteristics (steady state understeer characteristic quasi-static acceleration with a fixed steering wheel (SH = const) and on the constant radius track (R = const)) of the narrow vehicle. The vehicle understeer characteristic as a function of a power distribution is presented.

Analysis of Vibration and Acoustic Noise in Permanent Magnet Motors.

NASA Astrophysics Data System (ADS)

Hwang, Sangmoon

The drive motor is a frequent source of vibration and acoustic noise in many precision spindle motors. One of the electromagnetic sources of vibration in permanent magnet motors is the torque ripple, consisting of the reluctance torque and electromagnetic torque fluctuation. This type of vibration is becoming more serious with the advent of new high-grade magnets with increased flux density. Acoustic noise of electromagnetic origin is difficult to predict and its exact mechanism is unclear. The mechanism of noise generation should be revealed to design a quieter motor which is the modern customer's demand. For motor operation at low speeds and loads, torque ripple due to the reluctance torque is often a source of vibration and control difficulty. The reluctance torque in a motor was calculated from the flux density by a finite element method and the Maxwell stress method. Effects of design parameters, such as stator slot width, permanent slot width, airgap length and magnetization direction, were investigated. Magnet pole shaping, by gradually decreasing the magnet thickness toward edges, yields a sinusoidal shape of the reluctance torque with reduced harmonics, thus reducing the vibration. This dissertation also presents two motor design techniques: stator tooth notching and rotor pole skewing with magnet pole shaping, and the effect of each method on the output torque. The analysis shows that the reluctance torque can be nearly eliminated by the suggested designs, with minimal sacrifice of the output torque. In permanent magnet DC motors, the most popular design type is the trapezoidal back electro-motive force (BEMF), for switched DC controllers. It is demonstrated that the output torque profile of one phase energized is qualitatively equivalent to the BEMF profile for motors with reduced reluctance torque. It implies that design of BEMF profile is possible by magnetic modeling of a motor, without expensive and time-consuming experiments for different designs. The effect of various design parameters on the output torque and torque ripple are discussed. Design parameters include winding patterns, magnetization direction, magnet arc length, number of segments in poles and magnet pole shaping. New designs of trapezoidal BEMF motors are proposed to reduce the electromagnetic torque ripple. Magnet stepping and magnet edge shaping with reduced arc length, significantly reduce torque ripple, with minimal sacrifice of the maximum output torque. Acoustic noise of electromagnetic origin is investigated using a magnetic frame which emulates a DC motor. The driving electromagnetic force is calculated using finite element analysis and the resulting vibration and acoustic noise is measured. Acoustic noise of purely electromagnetic origin was also tested with a DC brushless motor to confirm the results of the magnetic frame. The mechanism of noise generation in a DC motor is a quasi-static response of a stator not only at the fundamental frequency but also at higher harmonic frequencies of alternating switched DC, which is a current characteristic of a DC motor. Noise generation is significantly aggravated when some of those harmonics are close to the resonant frequencies of the stator. Therefore, acoustic noise is highly dependent upon the excitation current shape, as higher harmonics may match with resonant frequencies of the stator.

Improving socket design to prevent difficult removal of locking screws.

PubMed

Lin, Chen-Huei; Chao, Ching-Kong; Tang, Yi-Hsuan; Lin, Jinn

2018-03-01

Reports of driver slippage leading to difficult locking screw removals have increased since the adoption of titanium for screw fabrication; the use of titanium is known to cause cross-threading and cold welding. Such problems occur most frequently in screws with hex sockets, and may cause serious surgical complications. This study aimed to improve screw socket design to prevent slippage and difficult screw removal. Three types of small sockets (hex, Torx, and cruciate) and six types of large sockets (hex, Torx, Octatorx, Torx+ I, Torx+ II, and Torx+ III) with screw head diameters of 5.5 mm were manufactured from titanium, and corresponding screwdrivers were manufactured from stainless steel. The screw heads and drivers were mounted on a material testing machine, and torsional tests were conducted to simulate screw usage in clinical settings at two insertion depths: 1 and 2 mm. Ten specimens were tested from each design, and the maximum torque and failure patterns were recorded and compared. For small sockets in 2 mm conditions, the hex with the largest driver core had the highest torque, followed by Torx and cruciate. In these tests, the drivers were twisted off in all specimens. However, under the 1 mm condition, the hex slipped and the torque decreased markedly. Overall, torque was higher for large sockets than for small sockets. The Octatorx, with a large core and simultaneous deformation of the driver and socket lobes, had the highest torque at almost twice that of the small hex. The hex had the lowest torque, a result of slippage in both the 1 and 2 mm conditions. Torx plus designs, with more designed degrees of freedom, were able to maintain a higher driving angle and larger core for higher torque. The hex design showed slipping tendencies with a marked decrease in torque, especially under conditions with inadequate driver engagement. Large sockets allowed for substantial increases in torque. The Torx, Octatorx, and Torx plus designs displayed better performance than the hexes. Improvements to the socket design could effectively prevent slippage and solve difficult screw removal problems. Copyright © 2018. Published by Elsevier Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moll, Philip J. W.; Potter, Andrew C.; Nair, Nityan L.

Electrons in materials with linear dispersion behave as massless Weyl- or Dirac-quasiparticles, and continue to intrigue due to their close resemblance to elusive ultra-relativistic particles as well as their potential for future electronics. Yet the experimental signatures of Weyl-fermions are often subtle and indirect, in particular if they coexist with conventional, massive quasiparticles. Here we show a pronounced anomaly in the magnetic torque of the Weyl semimetal NbAs upon entering the quantum limit state in high magnetic fields. The torque changes sign in the quantum limit, signalling a reversal of the magnetic anisotropy that can be directly attributed to themore » topological nature of the Weyl electrons. Our results establish that anomalous quantum limit torque measurements provide a direct experimental method to identify and distinguish Weyl and Dirac systems.« less

EMG-Torque Dynamics Change With Contraction Bandwidth.

PubMed

Golkar, Mahsa A; Jalaleddini, Kian; Kearney, Robert E

2018-04-01

An accurate model for ElectroMyoGram (EMG)-torque dynamics has many uses. One of its applications which has gained high attention among researchers is its use, in estimating the muscle contraction level for the efficient control of prosthesis. In this paper, the dynamic relationship between the surface EMG and torque during isometric contractions at the human ankle was studied using system identification techniques. Subjects voluntarily modulated their ankle torque in dorsiflexion direction, by activating their tibialis anterior muscle, while tracking a pseudo-random binary sequence in a torque matching task. The effects of contraction bandwidth, described by torque spectrum, on EMG-torque dynamics were evaluated by varying the visual command switching time. Nonparametric impulse response functions (IRF) were estimated between the processed surface EMG and torque. It was demonstrated that: 1) at low contraction bandwidths, the identified IRFs had unphysiological anticipatory (i.e., non-causal) components, whose amplitude decreased as the contraction bandwidth increased. We hypothesized that this non-causal behavior arose, because the EMG input contained a component due to feedback from the output torque, i.e., it was recorded from within a closed-loop. Vision was not the feedback source since the non-causal behavior persisted when visual feedback was removed. Repeating the identification using a nonparametric closed-loop identification algorithm yielded causal IRFs at all bandwidths, supporting this hypothesis. 2) EMG-torque dynamics became faster and the bandwidth of system increased as contraction modulation rate increased. Thus, accurate prediction of torque from EMG signals must take into account the contraction bandwidth sensitivity of this system.

Effect of Off-Axis Screw Insertion, Insertion Torque, and Plate Contouring on Locked Screw Strength

PubMed Central

Gallagher, Bethany; Silva, Matthew J.; Ricci, William M.

2015-01-01

Objectives This study quantifies the effects of insertion torque, off-axis screw angulation, and plate contouring on the strength of locking plate constructs. Methods Groups of locking screws (n = 6–11 screws) were inserted at 50%, 100%, 150%, and 200% of the manufacturer-recommended torque (3.2 Nm) into locking compression plates at various angles: orthogonal (control), 5-degree angle off-axis, and 10-degree angle off-axis. Screws were loaded to failure by a transverse force (parallel to the plate) either in the same (“+”) or opposite direction (“−”) of the initial screw angulation. Separately, locking plates were bent to 5 and 10-degree angles, with the bend apex at a screw hole. Locking screws inserted orthogonally into the apex hole at 100% torque were loaded to failure. Results Orthogonal insertion resulted in the highest average load to failure, 2577 ± 141 N (range, 2413–2778 N), whereas any off-axis insertion significantly weakened constructs (165–1285 N, at 100% torque) (P < 0.05). For “+” loading, torque beyond 100% did not increase strength, but 50% torque reduced screw strength (P < 0.05). Loading in the “−” direction consistently resulted in higher strengths than “+” loading (P < 0.05). Plate contouring of 5-degree angle did not significantly change screw strength compared with straight plates but contouring of 10-degree angle significantly reduced load to failure (P < 0.05). Conclusions To maximize the screw plate interface strength, locking screws should be inserted without cross-threading. The mechanical stability of locked screws is significantly compromised by loose insertion, off-axis insertion, or severe distortion of the locking mechanism. PMID:24343255

Inner Core Tilt and Polar Motion: Probing the Dynamics Deep Inside the Earth

NASA Astrophysics Data System (ADS)

Dumberry, M.; Bloxham, J.

2003-12-01

A tilted inner core permits exchange of angular momentum between the core and the mantle through gravitational and pressure torques and, as a result, changes in the direction of Earth's axis of rotation with respect to the mantle. Some of the observed variations in the direction of Earth's rotation could then be caused by equatorial torques on the inner core which tilt the latter out of its alignment with the mantle. In this work, we investigate whether such a scenario could explain the decade polar motion known as the Markowitz wobble. We show that a decade polar motion of the same amplitude as the observed Markowitz wobble requires a torque of 1020 N m which tilts the inner core by 0.07 degrees. This result critically depends on the viscosity of the inner core; for a viscosity less than 5 x 1017 Pa s, larger torques are required. A torque of 1020 N m with decadal periodicity can perhaps be produced by electromagnetic coupling between the inner core and a component of the flow in the outer core known as torsional oscillations, provided that the radial magnetic field at the inner core boundary is on the order of 3 to 4 mT and satisfies certain geometrical constraints. The resulting polar motion thus produced is eccentric and polarized, in agreement with the observations. Our model suggests that equatorial torques at the inner core boundary might also excite the Chandler wobble, provided shorter wavelength torsional oscillations with higher natural frequencies have enough power or provided there exists another physical mechanism that can generate a large torque at a 14 month period.

Mechanical effects of third-order movement in self-ligated brackets by the measurement of torque expression.

PubMed

Major, Thomas W; Carey, Jason P; Nobes, David S; Heo, Giseon; Major, Paul W

2011-01-01

Axial rotation of orthodontic wire produces buccal or lingual root movement and is often referred to as third-order movement or "torque expression." The objective of this study was to quantify torque expression in 3 self-ligation bracket systems (Damon Q, Ormco, Orange, Calif; In-Ovation R, GAC, Bohemia, NY; and Speed, Strite Industries, Cambridge, Ontario, Canada) during loading and unloading. A stepper motor was used to rotate a wire in a fixed bracket slot from -15° to 63° in 3° increments, and then back to -15°. The bracket was mounted on top of a load cell that measured forces and moments in all directions. Damon's and In-Ovation's maximum average torque values at 63° were 105 and 113 Nmm, respectively. Many Speed brackets experienced premature loss of torque between 48° and 63°, and the average maximum was 82 Nmm at 54°. The torque plays for Damon, In-Ovation, and Speed were 11.3°, 11.9°, and 10.8°, respectively. Generally, In-Ovation expressed the most torque at a given angle of twist, followed by Damon and then Speed. However, there was no significant difference between brackets below 34 Nmm of torque. From a clinical perspective, the torque plays between brackets were virtually indistinguishable. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia].

PubMed

Placzek, R; Deuretzbacher, G; Meiss, A L

2002-12-01

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

Knudsen torque: A rotational mechanism driven by thermal force

NASA Astrophysics Data System (ADS)

Li, Qi; Liang, Tengfei; Ye, Wenjing

2014-09-01

Thermally induced mechanical loading has been shown to have significant effects on micro- and nano-objects immersed in a gas with a nonuniform temperature field. While the majority of existing studies and related applications focus on forces, we investigate the torque, and thus the rotational motion, produced by such a mechanism. Our study has found that a torque can be induced if the configuration of the system is asymmetric. In addition, both the magnitude and the direction of the torque depend highly on the system configuration, indicating the possibility of manipulating the rotational motion via geometrical design. Based on this feature, two types of rotational micromotor that are of practical importance, namely pendulum motor and unidirectional motor, are designed. The magnitude of the torque at Kn =0.5 can reach to around 2nN×μm for a rectangular microbeam with a length of 100μm.

Design and characterization of a torque-controllable actuator for knee assistance during sit-to-stand.

PubMed

Shepherd, Max K; Rouse, Elliott J

2016-08-01

Individuals with post-stroke hemiparesis often have difficulty standing out of a chair. One way to potentially improve sit-to-stand is to provide knee extension assistance using a powered knee exoskeleton. An exoskeleton providing unilateral, partial assistance during sit-to-stand would need to be torque-controllable. There are no knee exoskeletons on the market suitable for conducting experiments assisting stroke patients with sit-to-stand, so to enable such experiments a research device was developed. The purpose of this report is to present the design of a novel knee exoskeleton actuator that uses a fiberglass leaf spring in series to improve torque-controllability, and present a characterization of the actuator performance. The actuator is capable of the required torque and speed for sit-to-stand, has high bandwidth (25 Hz), low output impedance at low frequencies (<;0.5 Nm), and excellent torque tracking. An orthotic brace built upon this actuator will enable an in-depth study on the biomechanical effects of providing stroke subjects with knee extension assistance during sit-to-stand.

The incidence of isolated penile torsion in North India: A study of 5,018 male neonates.

PubMed

Bhat, Amilal; Bhat, Mahakshit; Kumar, Vinay; Goyal, Suresh; Bhat, Akshita; Patni, Madhu

2017-10-01

Congenital penile torsion is a three-dimensional deformity with helical rotation of the distal corporal bodies with the penile crurae remaining fixed to the pubic rami. The first case of congenital penile torsion (hypospadias) was described in 1857. Isolated penile torsion is an under-reported anomaly. The reported incidence of isolated penile torsion is 1.7-27% and severe torsion is 0.7%. There are no studies available from Indian subcontinent on the incidence of isolated penile torque. The objective of this study was to determine the overall incidence of isolated penile torque in a north Indian population. A prospective study of deliveries of male children was conducted at our institute between April 2014 and June 2015. Penile torsion was measured using a small protractor either by the deviation of the median raphae or the direction of the meatus. Data were collected on the incidence of congenital isolated penile torsion, including the degree and direction (left or right) of torsion. Torsion was classified as mild (<450), moderate (450-900), and severe (>900). Statistical analysis was done using the chi-square test with variables of age and parity of the mother and weight of the child. There were 99 cases of isolated penile torque among 5018 male neonates assessed for penile torque. The incidence of isolated penile torque was 19.7 per 1000 births. The degree of torsion varied from 30 to 110° (average 51.46°). Seventy-nine percent (79%) of them had left side and 21% had right side torque (4:1). The degree of torsion was mild in 30%, with 20% having left side torque and 10% having right side torque (2:1). A moderate degree of torsion was seen in 69%: 84% of them had left torque and only 16% had right sided torque (5:1). Only one patient had severe left torque. The incidence of isolated congenital penile torsion was highest in the maternal age group of >30 years followed by the 26-30-year age group, and was lowest in 21-25 year age group. In multiparous women, the incidence of isolated congenital penile torsion was highest (2.54%), and it was lowest in primiparous women (1.36%). The incidence of isolated penile torsion was 1.97% and the left-to-right ratio was 3:1, but for moderate torque it was 5:1. There was a strong association between incidence of penile torque with the age of the mother (p = 0.012) and parity (p = 0.008) but not with the weight of the baby (p = 0.415). Copyright © 2017 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

A novel flux-switching permanent magnet machine with v-shaped magnets

NASA Astrophysics Data System (ADS)

Zhao, Guishu; Hua, Wei

2017-05-01

In this paper, firstly a novel 6-stator-coil/17-rotor-pole (6/17) flux-switching permanent magnet (FSPM) machine with V-shaped magnets, deduced from conventional 12/17 FSPM machines is proposed to achieve more symmetrical phase back-electromotive force (back-EMF), and smaller torque ripple by comparing with an existing 6/10 V-shaped FSPM machine. Then, to obtain larger electromagnetic torque, less torque ripple, and easier mechanical processing, two improved variants based on the original 6/17 V-shaped topology are proposed. For the first variant, the separate stator-core segments located on the stator yoke are connected into a united stator yoke, while for the second variant the stator core is a whole entity by adding magnetic bridges at the ends of permanent magnets (PMs). Consequently, the performances of the three 6/17 V-shaped FSPM machines, namely, the original one and the two variants, are conducted by finite element analysis (FEA). The results reveal that the first variant exhibits significantly larger torque and considerably improved torque per magnet volume, i.e., the magnet utilization ratio than the original one, and the second variant exhibits the smallest torque ripple, least total harmonic distribution (THD) of phase back-EMF, and easiest mechanical processing for manufacturing.

78 FR 56601 - Airworthiness Directives; Fokker Services B.V. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-13

... torque values of nuts on circuit breakers, contactors, and terminal blocks of the EPC and battery relay... blocks of the EPC and battery relay panel, as applicable; and do all applicable adjustments of the torque... contacts and nuts on circuit breakers, contactors, and terminal blocks of the EPC and battery relay panel...

76 FR 27617 - Airworthiness Directives; Bombardier, Inc. Model DHC-8-400 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-12

.... Investigations revealed that loose rivets in the torque tube assemblies caused relative motion between the crank arms and torque tubes. Loose rivets could result in excessive wear and subsequent significant backlash... June 27, 2011. ADDRESSES: You may send comments by any of the following methods: Federal eRulemaking...

76 FR 66618 - Airworthiness Directives; Eurocopter France (Eurocopter) Model EC225LP Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-27

... tightening torque of the screws which secure the assembly. Since then, Eurocopter has developed a.... EASB 05A005 specifies checking the dome fairing support for a crack and readjusting the tightening torque of the dome fairing-to-dome fairing support attachment screws. If a crack is found, the EASB...

75 FR 17887 - Airworthiness Directives; The Boeing Company Model 767 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-08

... torque to the nut and bolt of the main track downstop assembly. The corrective actions include: Installing a bolt and spacer with a new nut (including applying torque to make sure that it has been.... Tightening the existing nut. Boeing Special Attention Service Bulletin 767-57-0118, dated October 8, 2009...

Role of spin diffusion in current-induced domain wall motion for disordered ferromagnets

NASA Astrophysics Data System (ADS)

Akosa, Collins Ashu; Kim, Won-Seok; Bisig, André; Kläui, Mathias; Lee, Kyung-Jin; Manchon, Aurélien

2015-03-01

Current-induced spin transfer torque and magnetization dynamics in the presence of spin diffusion in disordered magnetic textures is studied theoretically. We demonstrate using tight-binding calculations that weak, spin-conserving impurity scattering dramatically enhances the nonadiabaticity. To further explore this mechanism, a phenomenological drift-diffusion model for incoherent spin transport is investigated. We show that incoherent spin diffusion indeed produces an additional spatially dependent torque of the form ˜∇2[m ×(u .∇ ) m ] +ξ ∇2[(u .∇ ) m ] , where m is the local magnetization direction, u is the direction of injected current, and ξ is a parameter characterizing the spin dynamics (precession, dephasing, and spin-flip). This torque, which scales as the inverse square of the domain wall width, only weakly enhances the longitudinal velocity of a transverse domain wall but significantly enhances the transverse velocity of vortex walls. The spatial-dependent spin transfer torque uncovered in this study is expected to have significant impact on the current-driven motion of abrupt two-dimensional textures such as vortices, skyrmions, and merons.

Comparison study between wind turbine and power kite wakes

NASA Astrophysics Data System (ADS)

Haas, T.; Meyers, J.

2017-05-01

Airborne Wind Energy (AWE) is an emerging technology in the field of renewable energy that uses kites to harvest wind energy. However, unlike for conventional wind turbines, the wind environment in AWE systems has not yet been studied in much detail. We propose a simulation framework using Large Eddy Simulation to model the wakes of such kite systems and offer a comparison with turbine-like wakes. In order to model the kite effects on the flow, a lifting line technique is used. We investigate different wake configurations related to the operation modes of wind turbines and airborne systems in drag mode. In the turbine mode, the aerodynamic torque of the blades is directly added to the flow. In the kite drag mode, the aerodynamic torque of the wings is directly balanced by an opposite torque induced by on-board generators; this results in a total torque on the flow that is zero. We present the main differences in wake characteristics, especially flow induction and vorticity fields, for the depicted operation modes both with laminar and turbulent inflows.

Characterization of the non axial thrust generated by large solid propellant rocket motors in three axis stabilized ascent

NASA Technical Reports Server (NTRS)

Kosmann, W. J.; Dionne, E. R.; Klemetson, R. W.

1978-01-01

Nonaxial thrusts produced by solid rocket motors during three-axis stabilized attitude control have been determined from ascent experience on twenty three Burner II, Burner IIA and Block 5D-1 upper stage vehicles. A data base representing four different rocket motor designs (three spherical and one extended spherical) totaling twenty five three-axis stabilized firings is generated. Solid rocket motor time-varying resultant and lateral side force vector magnitudes, directions and total impulses, and roll torque couple magnitudes, directions, and total impulses are tabulated in the appendix. Population means and three sigma deviations are plotted. Existing applicable ground test side force and roll torque magnitudes and total impulses are evaluated and compared to the above experience data base. Within the spherical motor population, the selected AEDC ground test data consistently underestimated experienced motor side forces, roll torques and total impulses. Within the extended spherical motor population, the selected AEDC test data predicted experienced motor side forces, roll torques, and total impulses, with surprising accuracy considering the very small size of the test and experience populations.

Self-consistent perturbed equilibrium with neoclassical toroidal torque in tokamaks

DOE PAGES

Park, Jong-Kyu; Logan, Nikolas C.

2017-03-01

Toroidal torque is one of the most important consequences of non-axisymmetric fields in tokamaks. The well-known neoclassical toroidal viscosity (NTV) is due to the second-order toroidal force from anisotropic pressure tensor in the presence of these asymmetries. This work shows that the first-order toroidal force originating from the same anisotropic pressure tensor, despite having no flux surface average, can significantly modify the local perturbed force balance and thus must be included in perturbed equilibrium self-consistent with NTV. The force operator with an anisotropic pressure tensor is not self-adjoint when the NTV torque is finite and thus is solved directly formore » each component. This approach yields a modified, non-self-adjoint Euler-Lagrange equation that can be solved using a variety of common drift-kinetic models in generalized tokamak geometry. The resulting energy and torque integral provides a unique way to construct a torque response matrix, which contains all the information of self-consistent NTV torque profiles obtainable by applying non-axisymmetric fields to the plasma. This torque response matrix can then be used to systematically optimize non-axisymmetric field distributions for desired NTV profiles. Published by AIP Publishing.« less

A torque estimator for a traveling wave ultrasonic motor--application to an active claw.

PubMed

Giraud, Frédéric; Semail, Betty

2006-08-01

Depending on its electrical-to-mechanical energy conversion process, the torque on a traveling wave ultrasonic motor (TWUM)'s shaft is not directly proportional to a measurable electrical variable, such as current or voltage. But it is derived from a complicated process at the stator/rotor interface. The load torque is thus quite unknown, and this can be a disadvantage in applications in which a torque limitation is required or a torque measurement is needed. The aim of this article is to come up with a straightforward torque estimator on a TWUM. For that purpose, the motor is modeled; this modeling leads to different estimator strategies. More specifically, we chose a strategy for which a speed sensor is useless, relying only on the stator's resonant behavior. The parameters of the motor needed for the estimator are measured afterward, and some nonlinearities are identified and taken into account. Several experimental trials then are carried out to check the performance of the estimator. A claw actuated by a TWUM is presented because this is a typical application in which the knowledge of the torque helps guarantee the safety of the device.

Current control of PMSM based on maximum torque control reference frame

NASA Astrophysics Data System (ADS)

Ohnuma, Takumi

2017-07-01

This study presents a new method of current controls of PMSMs (Permanent Magnet Synchronous Motors) based on a maximum torque control reference frame, which is suitable for high-performance controls of the PMSMs. As the issues of environment and energy increase seriously, PMSMs, one of the AC motors, are becoming popular because of their high-efficiency and high-torque density in various applications, such as electric vehicles, trains, industrial machines, and home appliances. To use the PMSMs efficiently, a proper current control of the PMSMs is necessary. In general, a rotational coordinate system synchronizing with the rotor is used for the current control of PMSMs. In the rotating reference frame, the current control is easier because the currents on the rotating reference frame can be expressed as a direct current in the controller. On the other hand, the torque characteristics of PMSMs are non-linear and complex; the PMSMs are efficient and high-density though. Therefore, a complicated control system is required to involve the relation between the torque and the current, even though the rotating reference frame is adopted. The maximum torque control reference frame provides a simpler way to control efficiently the currents taking the torque characteristics of the PMSMs into consideration.

Predicting cancellous bone failure during screw insertion.

PubMed

Reynolds, Karen J; Cleek, Tammy M; Mohtar, Aaron A; Hearn, Trevor C

2013-04-05

Internal fixation of fractures often requires the tightening of bone screws to stabilise fragments. Inadequate application of torque can leave the fracture unstable, while over-tightening results in the stripping of the thread and loss of fixation. The optimal amount of screw torque is specific to each application and in practice is difficult to attain due to the wide variability in bone properties including bone density. The aim of the research presented in this paper is to investigate the relationships between motor torque and screw compression during powered screw insertion, and to evaluate whether the torque during insertion can be used to predict the ultimate failure torque of the bone. A custom test rig was designed and built for bone screw experiments. By inserting cancellous bone screws into synthetic, ovine and human bone specimens, it was established that variations related to bone density could be automatically detected through the effects of the bone on the rotational characteristics of the screw. The torque measured during screw insertion was found to be directly related to bone density and can be used, on its own, as a good predictor of ultimate failure torque of the bone. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Advances in the analysis and design of constant-torque springs

NASA Technical Reports Server (NTRS)

McGuire, John R.; Yura, Joseph A.

1996-01-01

In order to improve the design procedure of constant-torque springs used in aerospace applications, several new analysis techniques have been developed. These techniques make it possible to accurately construct a torque-rotation curve for any general constant-torque spring configuration. These new techniques allow for friction in the system to be included in the analysis, an area of analysis that has heretofore been unexplored. The new analysis techniques also include solutions for the deflected shape of the spring as well as solutions for drum and roller support reaction forces. A design procedure incorporating these new capabilities is presented.

Drag Reduction and Performance Improvement of Hydraulic Torque Converters with Multiple Biological Characteristics.

PubMed

Chunbao, Liu; Li, Li; Yulong, Lei; Changsuo, Liu; Yubo, Zhang

2016-01-01

Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved. The mechanism accounting for drag reduction of three factors was also investigated. After bionic design, the torque ratio and the highest efficiencies of YJSW335 were both advanced, which were very difficult to achieve through traditional design method. Moreover, the highest efficiency of the low speed area and high speed area is 85.65% and 86.32%, respectively. By economic matching analysis of the original and bionic powertrains, the latter can significantly reduce the fuel consumption and improve the operating economy of the loader.

Drag Reduction and Performance Improvement of Hydraulic Torque Converters with Multiple Biological Characteristics

PubMed Central

Chunbao, Liu; Changsuo, Liu; Yubo, Zhang

2016-01-01

Fish-like, dolphin-like, and bionic nonsmooth surfaces were employed in a hydraulic torque converter to achieve drag reduction and performance improvement, which were aimed at reducing profile loss, impacting loss and friction loss, respectively. YJSW335, a twin turbine torque converter, was bionically designed delicately. The biological characteristics consisted of fish-like blades in all four wheels, dolphin-like structure in the first turbine and the stator, and nonsmooth surfaces in the pump. The prediction performance of bionic YJSW335, obtained by computational fluid dynamics simulation, was improved compared with that of the original model, and then it could be proved that drag reduction had been achieved. The mechanism accounting for drag reduction of three factors was also investigated. After bionic design, the torque ratio and the highest efficiencies of YJSW335 were both advanced, which were very difficult to achieve through traditional design method. Moreover, the highest efficiency of the low speed area and high speed area is 85.65% and 86.32%, respectively. By economic matching analysis of the original and bionic powertrains, the latter can significantly reduce the fuel consumption and improve the operating economy of the loader. PMID:27752220

Thermomagnetic torques in polyatomic gases

NASA Technical Reports Server (NTRS)

Hildebrandt, A. F.; Wood, C. T.

1972-01-01

The application of the Scott effect to the dynamics of galactic and stellar rotation is investigated. Efforts were also made to improve the sensitivity and stability of torque measurements and understand the microscopic mechanism that causes the Scott effect.

Winding Schemes for Wide Constant Power Range of Double Stator Transverse Flux Machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Husain, Tausif; Hassan, Iftekhar; Sozer, Yilmaz

2015-05-01

Different ring winding schemes for double sided transverse flux machines are investigated in this paper for wide speed operation. The windings under investigation are based on two inverters used in parallel. At higher power applications this arrangement improves the drive efficiency. The new winding structure through manipulation of the end connection splits individual sets into two and connects the partitioned turns from individual stator sets in series. This configuration offers the flexibility of torque profiling and a greater flux weakening region. At low speeds and low torque only one winding set is capable of providing the required torque thus providingmore » greater fault tolerance. At higher speeds one set is dedicated to torque production and the other for flux control. The proposed method improves the machine efficiency and allows better flux weakening which is desirable for traction applications.« less

A model predictive current control of flux-switching permanent magnet machines for torque ripple minimization

NASA Astrophysics Data System (ADS)

Huang, Wentao; Hua, Wei; Yu, Feng

2017-05-01

Due to high airgap flux density generated by magnets and the special double salient structure, the cogging torque of the flux-switching permanent magnet (FSPM) machine is considerable, which limits the further applications. Based on the model predictive current control (MPCC) and the compensation control theory, a compensating-current MPCC (CC-MPCC) scheme is proposed and implemented to counteract the dominated components in cogging torque of an existing three-phase 12/10 FSPM prototyped machine, and thus to alleviate the influence of the cogging torque and improve the smoothness of electromagnetic torque as well as speed, where a comprehensive cost function is designed to evaluate the switching states. The simulated results indicate that the proposed CC-MPCC scheme can suppress the torque ripple significantly and offer satisfactory dynamic performances by comparisons with the conventional MPCC strategy. Finally, experimental results validate both the theoretical and simulated predictions.

Effect of q-profile structure on intrinsic torque reversals

NASA Astrophysics Data System (ADS)

Lu, Zhixin

2014-10-01

Intrinsic toroidal rotation plays an important role in mitigating macroinstability and regulating turbulent transport in ITER, where neutral beams are not sufficient to provide the requisite torque. Recent experiments on C-Mod with LHCD observed rotation reversal related to a change in the q profile. In this work, we focus on understanding the physics of intrinsic rotation reversals in LHCD plasmas, using nonlinear, global gyro-kinetic simulations and analysis of mode structure and spectrum symmetry breaking. The sensitive dependence of turbulent residual stress on magnetic shear is identified and characterized. The basic residual stress is non-vanishing when the k-parallel spectrum symmetry is broken, e.g., by E × B shear induced radial shift, non-uniformity in turbulence intensity, etc.. It is found that at low magnetic shear, the poloidal harmonics can shift strongly in the radial direction, as a feature of non-local effects, due to radial propagation and amplitude variation of the mode. This new symmetry breaking mechanism leads to a change in the sign of spectrum averaged parallel wave vector and thus the direction of intrinsic torque. Theoretical study shows that the competition between magnetic drift and ion kinetic effects determines the non-local effects and the structure of the asymmetry. Specifically, it is found that the direction of the intrinsic torque changes from counter- to co-current in the core, when magnetic shear decreases through a critical value. A critical shear ŝR = 0 . 2 ~ 0 . 5 for reversal of CTEM-induced intrinsic torque found by simulation is consistent with that from the LHCD C-Mod reversal experiments. In addition, simulations indicate ŝR = 1 ~ 2 for the reversal of ITG-induced torque, a prediction which can be tested by experiments. This work is supported by CER and CMTFO, UCSD and U.S. DOE-PPPL Contract DE-AC02-09CH11466.

Dynamic Torque and Vertical Force Analysis during Nickel-titanium Rotary Root Canal Preparation with Different Modes of Reciprocal Rotation.

PubMed

Tokita, Daisuke; Ebihara, Arata; Nishijo, Miki; Miyara, Kana; Okiji, Takashi

2017-10-01

The purpose of the present study was to compare 2 modes of reciprocal movement (torque-sensitive and time-dependent reciprocal rotation) with continuous rotation in terms of torque and apical force generation during nickel-titanium rotary root canal instrumentation. A custom-made automated root canal instrumentation and torque/force analyzing device was used to prepare simulated canals in resin blocks and monitor the torque and apical force generated in the blocks during preparation. Experimental groups (n = 7, each) consisted of (1) torque-sensitive reciprocal rotation with torque-sensitive vertical movement (group TqR), (2) time-dependent reciprocal rotation with time-dependent vertical movement (group TmR), and (3) continuous rotation with time-dependent vertical movement (group CR). The canals were instrumented with TF Adaptive SM1 and SM2 rotary files (SybronEndo, Orange, CA), and the torque and apical force were measured during instrumentation with SM2. The mean and maximum torque and apical force values were statistically analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The recordings showed intermittent increases of upward apical force and clockwise torque, indicating the generation and release of screw-in forces. The maximum upward apical force values in group TmR were significantly smaller than those in group CR (P < .05). The maximum torque values in clockwise and counterclockwise directions in groups TqR and TmR were significantly smaller than those in group CR (P < .05). Under the present experimental conditions using TF Adaptive instruments, both torque-sensitive and time-dependent reciprocal rotation generated significantly lower maximum torque and may have advantages in reducing stress generation caused by screw-in forces when compared with continuous rotation. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Comparison of different passive knee extension torque-angle assessments.

PubMed

Freitas, Sandro R; Vaz, João R; Bruno, Paula M; Valamatos, Maria J; Mil-Homens, Pedro

2013-11-01

Previous studies have used isokinetic dynamometry to assess joint torques and angles during passive extension of the knee, often without reporting upon methodological errors and reliability outcomes. In addition, the reliability of the techniques used to measure passive knee extension torque-angle and the extent to which reliability may be affected by the position of the subjects is also unclear. Therefore, we conducted an analysis of the intra- and inter-session reliability of two methods of assessing passive knee extension: (A) a 2D kinematic analysis coupled to a custom-made device that enabled the direct measurement of resistance to stretch and (B) an isokinetic dynamometer used in two testing positions (with the non-tested thigh either flexed at 45° or in the neutral position). The intra-class correlation coefficients (ICCs) of torque, the slope of the torque-angle curve, and the parameters of the mathematical model that were fit to the torque-angle data for the above conditions were measured in sixteen healthy male subjects (age: 21.4 ± 2.1 yr; BMI: 22.6 ± 3.3 kg m(-2); tibial length: 37.4 ± 3.4 cm). The results found were: (1) methods A and B led to distinctly different torque-angle responses; (2) passive torque-angle relationship and stretch tolerance were influenced by the position of the non-tested thigh; and (3) ICCs obtained for torque were higher than for the slope and for the mathematical parameters that were fit to the torque-angle curve. In conclusion, the measurement method that is used and the positioning of subjects can influence the passive knee extension torque-angle outcome.

Operationality Improvement Control of Electric Power Assisted Wheelchair by Fuzzy Algorithm Considering Posture Angle

NASA Astrophysics Data System (ADS)

Murakami, Hiroki; Seki, Hirokazu; Minakata, Hideaki; Tadakuma, Susumu

This paper describes a novel operationality improvement control for electric power assisted wheelchairs. “Electric power assisted wheelchair” which assists the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people, however, the performance of the straight and circular road driving must be further improved because the two wheels drive independently. This paper proposes a novel operationality improvement control by fuzzy algorithm to realize the stable driving on straight and circular roads. The suitable assisted torque of the right and left wheels is determined by fuzzy algorithm based on the posture angular velocity, the posture angle of the wheelchair, the human input torque proportion and the total human torque of the right and left wheels. Some experiments on the practical roads show the effectiveness of the proposed control system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jong-Kyu; Logan, Nikolas C.

Toroidal torque is one of the most important consequences of non-axisymmetric fields in tokamaks. The well-known neoclassical toroidal viscosity (NTV) is due to the second-order toroidal force from anisotropic pressure tensor in the presence of these asymmetries. This work shows that the first-order toroidal force originating from the same anisotropic pressure tensor, despite having no flux surface average, can significantly modify the local perturbed force balance and thus must be included in perturbed equilibrium self-consistent with NTV. The force operator with an anisotropic pressure tensor is not self-adjoint when the NTV torque is finite and thus is solved directly formore » each component. This approach yields a modified, non-self-adjoint Euler-Lagrange equation that can be solved using a variety of common drift-kinetic models in generalized tokamak geometry. The resulting energy and torque integral provides a unique way to construct a torque response matrix, which contains all the information of self-consistent NTV torque profiles obtainable by applying non-axisymmetric fields to the plasma. This torque response matrix can then be used to systematically optimize non-axisymmetric field distributions for desired NTV profiles. Published by AIP Publishing.« less

Torque Production in a Halbach Machine

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.; Vrnak, Daniel R.

2006-01-01

The NASA John H. Glenn Research Center initiated the investigation of torque production in a Halbach machine for the Levitated Ducted Fan (LDF) Project to obtain empirical data in determining the feasibility of using a Halbach motor for the project. LDF is a breakthrough technology for "Electric Flight" with the development of a clean, quiet, electric propulsor system. Benefits include zero emissions, decreased dependence on fossil fuels, increased efficiency, increased reliability, reduced maintenance, and decreased operating noise levels. A commercial permanent magnet brushless motor rotor was tested with a custom stator. An innovative rotor utilizing a Halbach array was designed and developed to fit directly into the same stator. The magnets are oriented at 90deg to the adjacent magnet, which cancels the magnetic field on the inside of the rotor and strengthens the field on the outside of the rotor. A direct comparison of the commercial rotor and the Halbach rotor was made. In addition, various test models were designed and developed to validate the basic principles described, and the theoretical work that was performed. The report concludes that a Halbach array based motor can provide significant improvements in electric motor performance and reliability.

75 FR 7407 - Airworthiness Directives; Piper Aircraft, Inc. Models PA-32R-301T and PA-46-350P Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-19

... the next 25 tighten to an NH1009399-10 or Lycoming P/ hours time-in- initial torque of N 40D23255-340M... torque and re- safety wire the V- band coupling. (2) Do not install any Eaton/ As of the effective Not...

Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

PubMed Central

Santamaría-Arrieta, Gorka; Brizuela-Velasco, Aritza; Fernández-González, Felipe J.; Chávarri-Prado, David; Chento-Valiente, Yelko; Solaberrieta, Eneko; Diéguez-Pereira, Markel; Yurrebaso-Asúa, Jaime

2016-01-01

Background This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]). Results The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p<0.05). However, no statistically significant differences were obtained between ISQ values at 10 or 12 mm drilling depths (p>0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p >0.05). Conclusions Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values. Key words:Implant stability quotient, overdrilling, primary stability, resonance frequency analysis, torque. PMID:27398182

Cogging Torque Reduction in a Permanent Magnet Wind Turbine Generator: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, E.; Green, J.

2002-01-01

In this paper, we investigate three design options to minimize cogging torque: uniformity of air gap, pole width, and skewing. Although the design improvement is intended for small wind turbines, it is also applicable to larger wind turbines.

Electric vehicle drive train with rollback detection and compensation

DOEpatents

Konrad, C.E.

1994-12-27

An electric vehicle drive train includes a controller for detecting and compensating for vehicle rollback, as when the vehicle is started upward on an incline. The vehicle includes an electric motor rotatable in opposite directions corresponding to opposite directions of vehicle movement. A gear selector permits the driver to select an intended or desired direction of vehicle movement. If a speed and rotational sensor associated with the motor indicates vehicle movement opposite to the intended direction of vehicle movement, the motor is driven to a torque output magnitude as a nonconstant function of the rollback speed to counteract the vehicle rollback. The torque function may be either a linear function of speed or a function of the speed squared. 6 figures.

Electric vehicle drive train with rollback detection and compensation

DOEpatents

Konrad, Charles E.

1994-01-01

An electric vehicle drive train includes a controller for detecting and compensating for vehicle rollback, as when the vehicle is started upward on an incline. The vehicle includes an electric motor rotatable in opposite directions corresponding to opposite directions of vehicle movement. A gear selector permits the driver to select an intended or desired direction of vehicle movement. If a speed and rotational sensor associated with the motor indicates vehicle movement opposite to the intended direction of vehicle movement, the motor is driven to a torque output magnitude as a nonconstant function of the rollback speed to counteract the vehicle rollback. The torque function may be either a linear function of speed or a function of the speed squared.

Prehension Synergies in Three Dimensions

PubMed Central

Shim, Jae Kun; Latash, Mark L.; Zatsiorsky, Vladimir M.

2010-01-01

The goal of this study was to investigate the conjoint changes of digit forces/moments in 3 dimensions during static prehension under external torques acting on the object in one plane. The experimental paradigm was similar to holding a book vertically in the air where the center of mass of the book is located farther from the hand than the points of digit contacts. Three force and 3 moment components from each digit were recorded during static prehension of a customized handle. Subjects produced forces and moments in all 3 directions, although the external torques were exerted on the handheld object about only the Z-axis. The 3-dimensional response to a 2-dimensional task was explained by the cause– effect chain effects prompted by the noncollinearity of the normal forces of the thumb and the 4 fingers (represented by the “virtual finger”). Because the forces are not collinear (not along the same line), they generate moments of force about X- and Y-axes that are negated by the finger forces along the Y- and X-directions. The magnitudes of forces produced by lateral fingers (index and little) with longer moment arms were larger compared with the central fingers (middle and ring). At the virtual finger (an imaginary digit whose mechanical action is equivalent to the summed action of the 4 fingers) level, the relative contribution of different fractions of the resistive moment produced by subjects did not depend on the torque magnitude. We conclude that the CNS 1) solves a planar prehension task by producing forces and moments in all 3 directions, 2) uses mechanical advantage of fingers, and 3) shares the total torque among finger forces and moments in a particular way disregarding the torque magnitude. PMID:15456799

A Highly Backdrivable, Lightweight Knee Actuator for Investigating Gait in Stroke

PubMed Central

Sulzer, James S.; Roiz, Ronald A.; Peshkin, Michael A.; Patton, James L.

2012-01-01

Many of those who survive a stroke develop a gait disability known as stiff-knee gait (SKG). Characterized by reduced knee flexion angle during swing, people with SKG walk with poor energy efficiency and asymmetry due to the compensatory mechanisms required to clear the foot. Previous modeling studies have shown that knee flexion activity directly before the foot leaves the ground, and this should result in improved knee flexion angle during swing. The goal of this research is to physically test this hypothesis using robotic intervention. We developed a device that is capable of assisting knee flexion torque before swing but feels imperceptible (transparent) for the rest of the gait cycle. This device uses sheathed Bowden cable to control the deflection of a compliant torsional spring in a configuration known as a Series Elastic Remote Knee Actuator (SERKA). In this investigation, we describe the design and evaluation of SERKA, which includes a pilot experiment on stroke subjects. SERKA could supply a substantial torque (12 N· m) in less than 20 ms, with a maximum torque of 41 N·m. The device resisted knee flexion imperceptibly when desired, at less than 1 N·m rms torque during normal gait. With the remote location of the actuator, the user experiences a mass of only 1.2 kg on the knee. We found that the device was capable of increasing both peak knee flexion angle and velocity during gait in stroke subjects. Thus, the SERKA is a valid experimental device that selectively alters knee kinetics and kinematics in gait after stroke. PMID:22563305

Displacement comparison of CAD-CAM titanium and zirconia abutments to implants with different conical connections.

PubMed

Yilmaz, Burak; Hashemzadeh, Shervin; Seidt, Jeremy D; Clelland, Nancy L

2018-04-01

To compare the displacements of CAD-CAM zirconia and titanium abutments into different internal connection systems after torquing. OsseoSpeed EV and OsseoSpeed TX implants (n=10) were placed in resin blocks. Zirconia and titanium abutments (n=5) were first hand tightened and then tightened to the recommended torque (20Ncm for TX and 25Ncm for EV). Displacements of abutments between screw tightening by hand and torque driver was measured using three-dimensional digital image correlation (3D DIC) technique. Displacements were measured in U (front/back), V (into/outward), W (right/left) directions and 3-dimensionally (3D). ANOVA with restricted maximum likelihood estimation method was used to analyze the data. Bonferroni-corrected t tests was used to determine the statistical differences (α=0.05). 3D displacement of zirconia and titanium abutments was significantly greater in OsseoSpeed EV implant (P<0.001). Displacement of zirconia and titanium abutments was not significantly different within implant systems, 3D (P≥0.386) and in each direction (P≥0.382). In U and V directions, zirconia and titanium abutments displaced significantly more towards negative in OsseoSpeed EV implant (P<0.019). Within the OsseoSpeed TX system, abutments displaced significantly more in V direction compared to the U and W (P≤0.005), and within the Osseospeed EV system, abutment displacements were significantly different amongst directions and displacements in V were the greatest (P<0.001). Abutments displaced more in the implant that required higher torque values to tighten the abutment. The amount of displacement in both systems was clinically small. Abutment material did not affect the magnitude of displacement. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

FMR and torque studies of highly stressed magnetostrictive polycrystalline CoPd alloy films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubowik, J.; Szymanski, B.

1994-03-01

Ferromagnetic resonance (FMR) and torque curves have been measured in electrodeposited CoPd alloy films with composition ranged from Co{sub 13}Pd{sub 83} to Co{sub 45}Pd{sub 55}. The authors show that the origin of the multimode structure of FMR spectra in these strongly magnetostrictive polycrystalline films can be satisfactory explained on the basis of the independent-grain-approach for a textured microstructure. The fourfold periodicity of the torque curves for the compositional range of 30--35 at% is assumed to be oriented by inhomogeneous distribution of the magnetization direction.

Tooth shape optimization of brushless permanent magnet motors for reducing torque ripples

NASA Astrophysics Data System (ADS)

Hsu, Liang-Yi; Tsai, Mi-Ching

2004-11-01

This paper presents a tooth shape optimization method based on a generic algorithm to reduce the torque ripple of brushless permanent magnet motors under two different magnetization directions. The analysis of this design method mainly focuses on magnetic saturation and cogging torque and the computation of the optimization process is based on an equivalent magnetic network circuit. The simulation results, obtained from the finite element analysis, are used to confirm the accuracy and performance. Finite element analysis results from different tooth shapes are compared to show the effectiveness of the proposed method.

Tool for Torquing Circular Electrical-Connector Collars

NASA Technical Reports Server (NTRS)

Gaulke, Kathryn; Werneth, Russell; Grunsfeld, John; O'Neill, Patrick; Snyder, Russ

2006-01-01

An improved tool has been devised for applying torque to lock and unlock knurled collars on circular electrical connectors. The tool was originally designed for, and used by, astronauts working in outer space on the Hubble Space Telescope (HST). The tool is readily adaptable to terrestrial use in installing and removing the same or similar circular electrical connectors as well as a wide variety of other cylindrical objects, the tightening and loosening of which entail considerable amounts of torque.

Effect of Real-Time Feedback on Screw Placement Into Synthetic Cancellous Bone.

PubMed

Gustafson, Peter A; Geeslin, Andrew G; Prior, David M; Chess, Joseph L

2016-08-01

The objective of this study is to evaluate whether real-time torque feedback may reduce the occurrence of stripping when inserting nonlocking screws through fracture plates into synthetic cancellous bone. Five attending orthopaedic surgeons and 5 senior level orthopaedic residents inserted 8 screws in each phase. In phase I, screws were inserted without feedback simulating conventional techniques. In phase II, screws were driven with visual torque feedback. In phase III, screws were again inserted with conventional techniques. Comparison of these 3 phases with respect to screw insertion torque, surgeon rank, and perception of stripping was used to establish the effects of feedback. Seventy-three of 239 screws resulted in stripping. During the first phase, no feedback was provided and the overall strip rate was 41.8%; this decreased to 15% with visual feedback (P < 0.001) and returned to 35% when repeated without feedback. With feedback, a lower average torque was applied over a narrower torque distribution. Residents stripped 40.8% of screws compared with 20.2% for attending surgeons. Surgeons were poor at perceiving whether they stripped. Prevention and identification of stripping is influenced by surgeon perception of tactile sensation. This is significantly improved with utilization of real-time visual feedback of a torque versus roll curve. This concept of real-time feedback seems beneficial toward performance in synthetic cancellous bone and may lead to improved fixation in cancellous bone in a surgical setting.

Do peak torque angles of muscles change following anterior cruciate ligament reconstruction using hamstring or patellar tendon graft?

PubMed

Yosmaoğlu, Hayri Baran; Baltacı, Gül; Sönmezer, Emel; Özer, Hamza; Doğan, Deha

2017-12-01

This study aims to compare the effects of anterior cruciate ligament (ACL) reconstruction using autogenous hamstring or patellar tendon graft on the peak torque angle. The study included 132 patients (103 males, 29 females; mean age 29±9 year) who were performed ACL reconstruction with autogenous hamstring or patellar tendon graft. The peak torque angles in the quadriceps and hamstring muscles were recorded using an isokinetic dynamometer. Angle of peak knee flexion torque occurred significantly earlier within the range of motion on the operated side than nonoperated side at 180°/second in the hamstring tendon group. Angle of peak knee extension torque occurred significantly earlier within the range of motion on the operated side than nonoperated side at 180°/second in the patellar tendon group. There were no statistically significant differences in the flexion and extension peak torque angles between the operated and nonoperated knees at 60°/second in both groups. The angle of peak torque at relatively high angular velocities is affected after ACL reconstruction in patients with hamstring or patellar tendon grafts. The graft donor site directly influences this parameter. This finding may be important for clinicians in terms of preventing re-injury.

A Computational Model of Torque Generation: Neural, Contractile, Metabolic and Musculoskeletal Components

PubMed Central

Callahan, Damien M.; Umberger, Brian R.; Kent-Braun, Jane A.

2013-01-01

The pathway of voluntary joint torque production includes motor neuron recruitment and rate-coding, sarcolemmal depolarization and calcium release by the sarcoplasmic reticulum, force generation by motor proteins within skeletal muscle, and force transmission by tendon across the joint. The direct source of energetic support for this process is ATP hydrolysis. It is possible to examine portions of this physiologic pathway using various in vivo and in vitro techniques, but an integrated view of the multiple processes that ultimately impact joint torque remains elusive. To address this gap, we present a comprehensive computational model of the combined neuromuscular and musculoskeletal systems that includes novel components related to intracellular bioenergetics function. Components representing excitatory drive, muscle activation, force generation, metabolic perturbations, and torque production during voluntary human ankle dorsiflexion were constructed, using a combination of experimentally-derived data and literature values. Simulation results were validated by comparison with torque and metabolic data obtained in vivo. The model successfully predicted peak and submaximal voluntary and electrically-elicited torque output, and accurately simulated the metabolic perturbations associated with voluntary contractions. This novel, comprehensive model could be used to better understand impact of global effectors such as age and disease on various components of the neuromuscular system, and ultimately, voluntary torque output. PMID:23405245

Interface-Enhanced Spin-Orbit Torques and Current-Induced Magnetization Switching of Pd /Co /AlOx Layers

NASA Astrophysics Data System (ADS)

Ghosh, Abhijit; Garello, Kevin; Avci, Can Onur; Gabureac, Mihai; Gambardella, Pietro

2017-01-01

Magnetic heterostructures that combine large spin-orbit torque efficiency, perpendicular magnetic anisotropy, and low resistivity are key to developing electrically controlled memory and logic devices. Here, we report on vector measurements of the current-induced spin-orbit torques and magnetization switching in perpendicularly magnetized Pd /Co /AlOx layers as a function of Pd thickness. We find sizable dampinglike (DL) and fieldlike (FL) torques, on the order of 1 mT per 107 A /cm2 , which have different thicknesses and magnetization angle dependencies. The analysis of the DL torque efficiency per unit current density and the electric field using drift-diffusion theory leads to an effective spin Hall angle and spin-diffusion length of Pd larger than 0.03 and 7 nm, respectively. The FL spin-orbit torque includes a significant interface contribution, is larger than estimated using drift-diffusion parameters, and, furthermore, is strongly enhanced upon rotation of the magnetization from the out-of-plane to the in-plane direction. Finally, taking advantage of the large spin-orbit torques in this system, we demonstrate bipolar magnetization switching of Pd /Co /AlOx layers with a similar current density to that used for Pt /Co layers with a comparable perpendicular magnetic anisotropy.

Knobology in use: an experimental evaluation of ergonomics recommendations.

PubMed

Overgård, Kjell Ivar; Fostervold, Knut Inge; Bjelland, Hans Vanhauwaert; Hoff, Thomas

2007-05-01

The scientific basis for ergonomics recommendations for controls has usually not been related to active goal-directed use. The present experiment tests how different knob sizes and torques affect operator performance. The task employed is to control a pointer by the use of a control knob, and is as such an experimentally defined goal-directed task relevant to machine systems in general. Duration of use, error associated with use (overshooting of the goal area) and movement reproduction were used as performance measures. Significant differences between knob sizes were found for movement reproduction. High torques led to less overshooting as opposed to low torques. The results from duration of use showed a tendency that the differences between knob sizes were reduced from the first iteration to the second iteration. The present results indicate that the ergonomically recommended ranges of knob sizes might differently affect operator performance.

Design and experimental validation for direct-drive fault-tolerant permanent-magnet vernier machines.

PubMed

Liu, Guohai; Yang, Junqin; Chen, Ming; Chen, Qian

2014-01-01

A fault-tolerant permanent-magnet vernier (FT-PMV) machine is designed for direct-drive applications, incorporating the merits of high torque density and high reliability. Based on the so-called magnetic gearing effect, PMV machines have the ability of high torque density by introducing the flux-modulation poles (FMPs). This paper investigates the fault-tolerant characteristic of PMV machines and provides a design method, which is able to not only meet the fault-tolerant requirements but also keep the ability of high torque density. The operation principle of the proposed machine has been analyzed. The design process and optimization are presented specifically, such as the combination of slots and poles, the winding distribution, and the dimensions of PMs and teeth. By using the time-stepping finite element method (TS-FEM), the machine performances are evaluated. Finally, the FT-PMV machine is manufactured, and the experimental results are presented to validate the theoretical analysis.

Direct Observation of Zhang-Li Torque Expansion of Magnetic Droplet Solitons

NASA Astrophysics Data System (ADS)

Chung, Sunjae; Le, Q. Tuan; Ahlberg, Martina; Awad, Ahmad A.; Weigand, Markus; Bykova, Iuliia; Khymyn, Roman; Dvornik, Mykola; Mazraati, Hamid; Houshang, Afshin; Jiang, Sheng; Nguyen, T. N. Anh; Goering, Eberhard; Schütz, Gisela; Gräfe, Joachim; Åkerman, Johan

2018-05-01

Magnetic droplets are nontopological dynamical solitons that can be nucleated in nanocontact based spin torque nano-oscillators (STNOs) with perpendicular magnetic anisotropy free layers. While theory predicts that the droplet should be of the same size as the nanocontact, its inherent drift instability has thwarted attempts at observing it directly using microscopy techniques. Here, we demonstrate highly stable magnetic droplets in all-perpendicular STNOs and present the first detailed droplet images using scanning transmission X-ray microscopy. In contrast to theoretical predictions, we find that the droplet diameter is about twice as large as the nanocontact. By extending the original droplet theory to properly account for the lateral current spread underneath the nanocontact, we show that the large discrepancy primarily arises from current-in-plane Zhang-Li torque adding an outward pressure on the droplet perimeter. Electrical measurements on droplets nucleated using a reversed current in the antiparallel state corroborate this picture.

The effect of different torque wrenches on rotational stiffness in compressive femoral nails: a biomechanical study.

PubMed

Karaarslan, A A; Acar, N

2018-02-01

Rotation instability and locking screws failure are common problems. We aimed to determine optimal torque wrench offering maximum rotational stiffness without locking screw failure. We used 10 conventional compression nails, 10 novel compression nails and 10 interlocking nails with 30 composite femurs. We examined rotation stiffness and fracture site compression value by load cell with 3, 6 and 8 Nm torque wrenches using torsion apparatus with a maximum torque moment of 5 Nm in both directions. Rotational stiffness of composite femur-nail constructs was calculated. Rotational stiffness of composite femur-compression nail constructs compressed by 6 Nm torque wrench was 3.27 ± 1.81 Nm/angle (fracture site compression: 1588 N) and 60% more than that compressed with 3 Nm torque wrench (advised previously) with 2.04 ± 0.81 Nm/angle (inter fragmentary compression: 818 N) (P = 0.000). Rotational stiffness of composite-femur-compression nail constructs compressed by 3 Nm torque wrench was 2.04 ± 0.81 Nm/angle (fracture site compression: 818 N) and 277% more than that of interlocking nail with 0.54 ± 0.08 Nm/angle (fracture site compression: 0 N) (P = 0.000). Rotational stiffness and fracture site compression value produced by 3 Nm torque wrench was not satisfactory. To obtain maximum rotational stiffness and fracture site compression value without locking screw failure, 6 Nm torque wrench in compression nails and 8 Nm torque wrench in novel compression nails should be used.

Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects

PubMed Central

DiZio, Paul; Lackner, James R.

2013-01-01

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241–258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm. PMID:23803330

Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects.

PubMed

Pigeon, Pascale; Dizio, Paul; Lackner, James R

2013-09-01

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241-258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm.

Disturbance torque rejection properties of the NASA/JPL 70-meter antenna axis servos

NASA Technical Reports Server (NTRS)

Hill, R. E.

1989-01-01

Analytic methods for evaluating pointing errors caused by external disturbance torques are developed and applied to determine the effects of representative values of wind and friction torque. The expressions relating pointing errors to disturbance torques are shown to be strongly dependent upon the state estimator parameters, as well as upon the state feedback gain and the flow versus pressure characteristics of the hydraulic system. Under certain conditions, when control is derived from an uncorrected estimate of integral position error, the desired type 2 servo properties are not realized and finite steady-state position errors result. Methods for reducing these errors to negligible proportions through the proper selection of control gain and estimator correction parameters are demonstrated. The steady-state error produced by a disturbance torque is found to be directly proportional to the hydraulic internal leakage. This property can be exploited to provide a convenient method of determining system leakage from field measurements of estimator error, axis rate, and hydraulic differential pressure.

Nanoscale imaging of magnetization reversal driven by spin-orbit torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, Ian; Chen, P. J.; Gopman, Daniel B.

We use scanning electron microscopy with polarization analysis to image deterministic, spin-orbit torque-driven magnetization reversal of in-plane magnetized CoFeB rectangles in zero applied magnetic field. The spin-orbit torque is generated by running a current through heavy metal microstrips, either Pt or Ta, upon which the CoFeB rectangles are deposited. We image the CoFeB magnetization before and after a current pulse to see the effect of spin-orbit torque on the magnetic nanostructure. The observed changes in magnetic structure can be complex, deviating significantly from a simple macrospin approximation, especially in larger elements. Overall, however, the directions of the magnetization reversal inmore » the Pt and Ta devices are opposite, consistent with the opposite signs of the spin Hall angles of these materials. Lastly, our results elucidate the effects of current density, geometry, and magnetic domain structure on magnetization switching driven by spin-orbit torque.« less

Nanoscale imaging of magnetization reversal driven by spin-orbit torque

DOE PAGES

Gilbert, Ian; Chen, P. J.; Gopman, Daniel B.; ...

2016-09-23

We use scanning electron microscopy with polarization analysis to image deterministic, spin-orbit torque-driven magnetization reversal of in-plane magnetized CoFeB rectangles in zero applied magnetic field. The spin-orbit torque is generated by running a current through heavy metal microstrips, either Pt or Ta, upon which the CoFeB rectangles are deposited. We image the CoFeB magnetization before and after a current pulse to see the effect of spin-orbit torque on the magnetic nanostructure. The observed changes in magnetic structure can be complex, deviating significantly from a simple macrospin approximation, especially in larger elements. Overall, however, the directions of the magnetization reversal inmore » the Pt and Ta devices are opposite, consistent with the opposite signs of the spin Hall angles of these materials. Lastly, our results elucidate the effects of current density, geometry, and magnetic domain structure on magnetization switching driven by spin-orbit torque.« less

Design, analysis and modeling of a novel hybrid powertrain system based on hybridized automated manual transmission

NASA Astrophysics Data System (ADS)

Wu, Guang; Dong, Zuomin

2017-09-01

Hybrid electric vehicles are widely accepted as a promising short to mid-term technical solution due to noticeably improved efficiency and lower emissions at competitive costs. In recent years, various hybrid powertrain systems were proposed and implemented based on different types of conventional transmission. Power-split system, including Toyota Hybrid System and Ford Hybrid System, are well-known examples. However, their relatively low torque capacity, and the drive of alternative and more advanced designs encouraged other innovative hybrid system designs. In this work, a new type of hybrid powertrain system based hybridized automated manual transmission (HAMT) is proposed. By using the concept of torque gap filler (TGF), this new hybrid powertrain type has the potential to overcome issue of torque gap during gearshift. The HAMT design (patent pending) is described in details, from gear layout and design of gear ratios (EV mode and HEV mode) to torque paths at different gears. As an analytical tool, mutli-body model of vehicle equipped with this HAMT was built to analyze powertrain dynamics at various steady and transient modes. A gearshift was decomposed and analyzed based basic modes. Furthermore, a Simulink-SimDriveline hybrid vehicle model was built for the new transmission, driveline and vehicle modular. Control strategy has also been built to harmonically coordinate different powertrain components to realize TGF function. A vehicle launch simulation test has been completed under 30% of accelerator pedal position to reveal details during gearshift. Simulation results showed that this HAMT can eliminate most torque gap that has been persistent issue of traditional AMT, improving both drivability and performance. This work demonstrated a new type of transmission that features high torque capacity, high efficiency and improved drivability.

The influence of abutment screw tightening on screw joint configuration.

PubMed

Lang, Lisa A; Wang, Rui-Feng; May, Kenneth B

2002-01-01

Limiting abutment-to-implant hexagonal discrepancies and rotational movement of the abutment around the implant to less than 5 degrees would result in a more stable screw joint. However, the exact relationship after abutment screw tightening is unknown, as is the effect of a counter-torque device in limiting abutment movement during screw tightening. This study examined the orientation of the abutment hexagon to the implant hexagon after tightening of the abutment screw for several abutment systems with and without the use of a counter-torque device. Thirty conical self-tapping implants (3.75 x 10.0 mm) and 10 wide-platform Brånemark System implants (5.0 x 10.0 mm), along with 10 abutment specimens from the CeraOne, Estheticone, Procera, and AuraAdapt systems, were selected for this investigation. The implants were placed in a holding device prior to tightening of the abutments. When the tightening torque recommended for each abutment system was reached with the use of a torque controller, each implant abutment specimen was removed from the holding device and embedded in a hard resin medium. The specimens were sectioned in a horizontal direction at the level of the hexagons and cleansed of debris prior to examination. The hexagon orientations were assessed as the degree and direction of rotation of the abutment hexagon around the implant hexagon. The range of the maximum degrees of rotation for all 4 abutment groups tightened with or without the counter-torque device was slightly more than 3.53 degrees. The absolute degrees of rotation for all 4 abutment groups were less than 1.50 degrees with or without the use of the counter-torque device. The hexagon-to-hexagon orientation measured as rotational fit on all abutment systems was below the 5 degrees suggested as optimal for screw joint stability. The absolute degrees of rotation for all 4 abutment groups were less than 1.50 degrees regardless of whether the counter-torque device was used.

Methodology for Determining Limit Torques for Threaded Fasteners

NASA Technical Reports Server (NTRS)

Hissam, Andy

2011-01-01

In aerospace design, where minimizing weight is always a priority, achieving the full capacity from fasteners is essential. To do so, the initial bolt preload must be maximized. The benefits of high preload are well documented and include improved fatigue resistance, a stiffer joint, and resistance to loosening. But many factors like elastic interactions and embedment tend to lower the initial preload placed on the bolt. These factors provide additional motivation to maximize the initial preload. But, to maximize bolt preload, you must determine what torque to apply. Determining this torque is greatly complicated by the large preload scatter generally seen with torque control. This paper presents a detailed methodology for generating limit torques for threaded fasteners. This methodology accounts for the large scatter in preload found with torque control, and therefore, addresses the statistical nature of the problem. It also addresses prevailing torque, a feature common in aerospace fasteners. Although prevailing torque provides a desired locking feature, it can also increase preload scatter. In addition, it can limit the amount of preload that can be generated due to the torsion it creates in the bolt. This paper discusses the complications of prevailing torque and how best to handle it. A wide range of torque-tension bolt testing was conducted in support of this research. The results from this research will benefit the design engineer as well as analyst involved in the design of bolted joints, leading to better, more optimized structural designs.

Design and analysis of a flux intensifying permanent magnet embedded salient pole wind generator

NASA Astrophysics Data System (ADS)

Guo, Yujing; Jin, Ping; Lin, Heyun; Yang, Hui; Lyu, Shukang

2018-05-01

This paper presents an improved flux intensifying permanent magnet embedded salient pole wind generator (FI-PMESPWG) with mirror symmetrical magnetizing directions permanent magnet (PM) for improving generator's performances. The air-gap flux densities, the output voltage, the cogging torque and the d- and q-axis inductances of FI-PMESPWG are all calculated and analyzed by using the finite element method (FEM). To highlight the advantages of the proposed FI-PMESPWG, an original permanent magnet embedded salient pole wind generator (PMESPWG) model is adopted for comparison under the same operating conditions. The calculating results show that the air-gap flux densities of FI-PMESPWG are intensified with the same magnet amounts because the PMs are set in a form of V shape in each pole. The difference between d-axis inductance and q-axis inductance of the proposed FI-PMESPWG is reduced. Thus, the output power of the proposed FI-PMESPWG reaches a higher value than that of the original PMESPWG at the same current phase angle. The cogging torque is diminished because the flux path is changed. All the analysis results indicate that the electromagnetic characteristics of the proposed FI-PMESPWG are significantly better than that of the original PMESPWG.

What Strains the Anterior Cruciate Ligament During a Pivot Landing?

PubMed Central

Oh, Youkeun K.; Lipps, David B.; Ashton-Miller, James A.; Wojtys, Edward M.

2015-01-01

Background The relative contributions of an axial tibial torque and frontal plane moment to anterior cruciate ligament (ACL) strain during pivot landings are unknown. Hypothesis The peak normalized relative strain in the anteromedial (AM) bundle of the ACL is affected by the direction of the axial tibial torque but not by the direction of the frontal plane moment applied concurrently during a simulated jump landing. Study Design Controlled and descriptive laboratory studies. Methods Fifteen adult male knees with pretensioned knee muscle-tendon unit forces were loaded under a simulated pivot landing test. Compression, flexion moment, internal or external tibial torque, and knee varus or valgus moment were simultaneously applied to the distal tibia while recording the 3D knee loads and tibiofemoral kinematics. The AM-ACL relative strain was measured using a 3-mm differential variable reluctance transducer. The results were analyzed using nonparametric Wilcoxon signed–rank tests. A 3D dynamic biomechanical knee model was developed using ADAMS and validated to help interpret the experimental results. Results The mean (SD) peak AM-ACL relative strain was 192% greater (P <.001) under the internal tibial torque combined with a knee varus or valgus moment (7.0% [3.9%] and 7.0% [4.1%], respectively) than under external tibial torque with the same moments (2.4% [2.5%] and 2.4% [3.2%], respectively). The knee valgus moment augmented the AM-ACL strain due to the slope of the tibial plateau inducing mechanical coupling (ie, internal tibial rotation and knee valgus moment); this augmentation occurred before medial knee joint space opening. Conclusion An internal tibial torque combined with a knee valgus moment is the worst-case ACL loading condition. However, it is the internal tibial torque that primarily causes large ACL strain. Clinical Relevance Limiting the maximum coefficient of friction between the shoe and playing surface should limit the peak internal tibial torque that can be applied to the knee during jump landings, thereby reducing peak ACL strain and the risk for noncontact injury. PMID:22223717

Final report on the torque key komparison CCM.T-K1.2 measurand torque: 0 N.m, 500 N.m, 1000 N.m

NASA Astrophysics Data System (ADS)

Röske, Dirk

2015-01-01

The purpose of the CIPM subsequent bilateral comparison CCM.T-K1.2 was to link another participant, namely the National Institute of Metrology (Thailand), in short NIMT, to the CCM.T-K1 torque key comparison. The measuring capabilities up to 1000 N.m of dead-weight torque standard machines with supported lever were investigated. The pilot laboratory was the same in both comparisons—it was the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany). The same two very stable torque transducers with well-known properties were used as travelling standards. The measurements at the participating laboratory were carried out between November 2007 and February 2008. According to the technical protocol, torque steps of 500 N.m and 1000 N.m had to be measured both in clockwise and anticlockwise directions. Corrections had to be applied to the results reported by the participants taking into account the use of different amplifiers, the creep (due to different loading times of the machines) and the environmental conditions in the laboratories (temperature and relative humidity of the ambient air). The results of the pilot laboratory in this bilateral comparison are in very good agreement with the same results obtained in the CCM.T-K1 comparison. For each of the transducers, the two torque steps and both senses of direction of the torque vector, the key comparison reference value of the CCM.T-K1 was taken, and the results of participant NIMT were calculated with respect to these values. The agreement between the results is very good. The smallest expanded (k = 2) relative uncertainty of the machine stated by the participant is 1 × 10-4. The results of the comparison support this uncertainty statement. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

75 FR 39185 - Airworthiness Directives; The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-08

... and torque checks of the hanger fittings and strut forward bulkhead of the forward engine mount and... requires repetitive inspections and torque checks of the hanger fittings and strut forward bulkhead of the... corrective actions are replacing the fasteners; removing loose fasteners; tightening all Group A [[Page 39187...

Precessional switching of antiferromagnets by electric field induced Dzyaloshinskii-Moriya torque

NASA Astrophysics Data System (ADS)

Kim, T. H.; Grünberg, P.; Han, S. H.; Cho, B. K.

2018-05-01

Antiferromagnetic insulators (AFIs) have attracted much interest from many researchers as promising candidates for use in ultrafast, ultralow-dissipation spintronic devices. As a fast method of reversing magnetization, precessional switching is realized when antiferromagnetic Néel orders l =(s1+s2 )/2 surmount the magnetic anisotropy or potential barrier in a given magnetic system, which is described well by the antiferromagnetic plane pendulum (APP) model. Here, we report that, as an alternative switching scenario, the direct coupling of an electric field with Dzyaloshinskii-Moriya (DM) interaction, which stems from spin-orbit coupling, is exploited for optimal switching. We derive the pendulum equation of motion of antiferromagnets, where DM torque is induced by a pulsed electric field. The temporal DM interaction is found to not only be in the form of magnetic torques (e.g., spin-orbit torque or magnetic field) but also modifies the magnetic potential that limits l 's activity; as a result, appropriate controls (e.g., direction, magnitude, and pulse shape) of the induced DM vector realize deterministic reversal in APP. The results present an approach for the control of a magnetic storage device by means of an electric field.

Correlation and prediction of dynamic human isolated joint strength from lean body mass

NASA Technical Reports Server (NTRS)

Pandya, Abhilash K.; Hasson, Scott M.; Aldridge, Ann M.; Maida, James C.; Woolford, Barbara J.

1992-01-01

A relationship between a person's lean body mass and the amount of maximum torque that can be produced with each isolated joint of the upper extremity was investigated. The maximum dynamic isolated joint torque (upper extremity) on 14 subjects was collected using a dynamometer multi-joint testing unit. These data were reduced to a table of coefficients of second degree polynomials, computed using a least squares regression method. All the coefficients were then organized into look-up tables, a compact and convenient storage/retrieval mechanism for the data set. Data from each joint, direction and velocity, were normalized with respect to that joint's average and merged into files (one for each curve for a particular joint). Regression was performed on each one of these files to derive a table of normalized population curve coefficients for each joint axis, direction, and velocity. In addition, a regression table which included all upper extremity joints was built which related average torque to lean body mass for an individual. These two tables are the basis of the regression model which allows the prediction of dynamic isolated joint torques from an individual's lean body mass.

Musculotendinous Stiffness of Triceps Surae, Maximal Rate of Force Development, and Vertical Jump Performance

PubMed Central

Driss, Tarak; Rouis, Majdi; Jaafar, Hamdi; Vandewalle, Henry

2015-01-01

The relationships between ankle plantar flexor musculotendinous stiffness (MTS) and performance in a countermovement vertical jump (CMJ) and maximal rate of torque development (MRTD) were studied in 27 active men. MTS was studied by means of quick releases at 20 (S 0.2), 40 (S 0.4), 60 (S 0.6), and 80% (S 0.8) of maximal voluntary torque (T MVC). CMJ was not correlated with strength indices but was positively correlated with MRTD/BM, S 0.4/BM. The slope α 2 and intercept β 2 of the torque-stiffness relationships from 40 to 80% T MVC were correlated negatively (α 2) and positively (β 2) with CMJ. The different stiffness indices were not correlated with MRTD. The prediction of CMJ was improved by the introduction of MRTD in multiple regressions between CMJ and stiffness. CMJ was also negatively correlated with indices of curvature of the torque-stiffness relationship. The subjects were subdivided in 3 groups in function of CMJ (groups H, M, and L for high, medium, and low performers, resp.). There was a downward curvature of the torque-stiffness relationship at high torques in group H or M and the torque-stiffness regression was linear in group L only. These results suggested that torque-stiffness relationships with a plateau at high torques are more frequent in the best jumpers. PMID:25710026

Improved rolling element bearings provide low torque and small temperature rise in ultrahigh vacuum environment

NASA Technical Reports Server (NTRS)

Glenn, D. C.

1966-01-01

Rolling element bearing with stainless steel races and rolling elements and a porous bronze cage successfully operates in ultrahigh vacuum environments at a low torque and with small temperature rise. All components are burnished in molybdenum disulfide.

A predictive control framework for torque-based steering assistance to improve safety in highway driving

NASA Astrophysics Data System (ADS)

Ercan, Ziya; Carvalho, Ashwin; Tseng, H. Eric; Gökaşan, Metin; Borrelli, Francesco

2018-05-01

Haptic shared control framework opens up new perspectives on the design and implementation of the driver steering assistance systems which provide torque feedback to the driver in order to improve safety. While designing such a system, it is important to account for the human-machine interactions since the driver feels the feedback torque through the hand wheel. The controller should consider the driver's impact on the steering dynamics to achieve a better performance in terms of driver's acceptance and comfort. In this paper we present a predictive control framework which uses a model of driver-in-the-loop steering dynamics to optimise the torque intervention with respect to the driver's neuromuscular response. We first validate the system in simulations to compare the performance of the controller in nominal and model mismatch cases. Then we implement the controller in a test vehicle and perform experiments with a human driver. The results show the effectiveness of the proposed system in avoiding hazardous situations under different driver behaviours.

Librations and Interior Structure of the Galilean Satellites

NASA Astrophysics Data System (ADS)

van Hoolst, T.; Baland, R.; Karatekin, O.; Rambaux, N.

2009-12-01

We investigate the influence of the interior structure of the Galilean satellites on their rotation variations (or librations). Since the Galilean satellites are significantly aspherical due to rotation and static tides, Jupiter exerts a gravitational torque on them. In a circular orbit, the long axis of a satellite would always point towards Jupiter and the gravitational torque would be zero. However, the eccentric orbits of the Galilean satellites lead to misalignment of the long axis with the direction to Jupiter and result in non-zero gravitational torques that tend to modify the rotation of the satellites. Since the torque varies with the orbital phase, the main libration period is equal to the orbital period. In a first-order approximation, the libration amplitude is usually calculated by assuming that the satellite reacts rigidly to the gravitational torque. The corresponding amplitudes, expressed as a shift at the surface of the orientation of the long axis with respect to that for the mean rotation rate, decrease with increasing distance from Jupiter from a few hundred meters for Io to about ten meter for Callisto. Internal liquid layers, such as a subsurface ocean, can lead to differential rotation of the solid and liquid layers and to differences of the libration of surface with respect to that for a rigid libration. Here, we present a method to determine the influence of gravitational and pressure interactions between internal layers on the libration of the Galilean satellites. For Io, we show that the liquid core has only a small effect on the surface librations. For Europa, Ganymede and Callisto, the presence of a subsurface ocean can significantly increase the libration amplitude. We also study the effect of the possible existence of two liquid layers in Ganymede and Europa: a subsurface ocean and a liquid core. We quantify the sensitivity of the libration amplitude to the internal structure and assess expected improvements in the interior structure of the Galilean satellites from future libration observations with the joint NASA/ESA Europa Jupiter System Mission.

Numerical and experimental study on vorticity measurement in liquid metal using local Lorentz force velocimetry

NASA Astrophysics Data System (ADS)

Hernández, Daniel; Marangoni, Rafael; Schleichert, Jan; Karcher, Christian; Fröhlich, Thomas; Wondrak, Thomas

2018-03-01

Local Lorentz force velocimetry (local LFV) is a contactless velocity measurement technique for liquid metals. Due to the relative movement between an electrically conductive fluid and a static applied magnetic field, eddy currents and a flow-braking Lorentz force are generated inside the metal melt. This force is proportional to the flow rate or to the local velocity, depending on the volume subset of the flow spanned by the magnetic field. By using small-size magnets, a localized magnetic field distribution is achieved allowing a local velocity assessment in the region adjacent to the wall. In the present study, we describe a numerical model of our experiments at a continuous caster model where the working fluid is GaInSn in eutectic composition. Our main goal is to demonstrate that this electromagnetic technique can be applied to measure vorticity distributions, i.e. to resolve velocity gradients as well. Our results show that by using a cross-shaped magnet system, the magnitude of the torque perpendicular to the surface of the mold significantly increases improving its measurement in a liquid metal flow. According to our numerical model, this torque correlates with the vorticity of the velocity in this direction. Before validating our numerical predictions, an electromagnetic dry calibration of the measurement system composed of a multicomponent force and torque sensor and a cross-shaped magnet was done using a rotating disk made of aluminum. The sensor is able to measure simultaneously all three components of force and torque, respectively. This calibration step cannot be avoided and it is used for an accurate definition of the center of the magnet with respect to the sensor’s coordinate system for torque measurements. Finally, we present the results of the experiments at the mini-LIMMCAST facility showing a good agreement with the numerical model.

Effects of inactivation of the anterior interpositus nucleus on the kinematic and dynamic control of multijoint movement.

PubMed

Cooper, S E; Martin, J H; Ghez, C

2000-10-01

We previously showed that inactivating the anterior interpositus nucleus in cats disrupts prehension; paw paths, normally straight and accurate, become curved, hypometric, and more variable. In the present study, we determined the joint kinematic and dynamic origins of this impairment. Animals were restrained in a hammock and trained to reach and grasp a cube of meat from a narrow food well at varied heights; movements were monitored using the MacReflex analysis system. The anterior interpositus nucleus was inactivated by microinjection of the GABA agonist muscimol (0.25-0.5 microgram in 0.5 microliter saline). For each joint, we computed the torque due to gravity, inertial resistance (termed self torque), interjoint interactions (termed interaction torque), and the combined effects of active muscle contraction and passive soft tissue stretch (termed generalized muscle torque). Inactivation produced significant reductions in the amplitude, velocity, and acceleration of elbow flexion. However, these movements continued to scale normally with target height. Shoulder extension was reduced by inactivation but wrist angular displacement and velocity were not. Inactivation also produced changes in the temporal coordination between elbow, shoulder, and wrist kinematics. Dynamic analysis showed that elbow flexion both before and during inactivation was produced by the combined action of muscle and interaction torque, but that the timing depended on muscle torque. Elbow interaction and muscle torques were scaled to target height both before and during inactivation. Inactivation produced significant reductions in elbow flexor interaction and muscle torques. The duration of elbow flexor muscle torque was prolonged to compensate for the reduction in flexor interaction torque. Shoulder extension was produced by extensor interaction and muscle torques both before and during inactivation. Inactivation produced a reduction in shoulder extension, primarily by reduced interaction torque, but without compensation. Wrist plantarflexion, which occurred during elbow flexion, was driven by plantarflexor interaction and gravitational torques both before and during inactivation. Muscle torque acted in the opposite direction with a phase lead to restrain the plantarflexor interaction torque. During inactivation, there was a reduction in plantarflexor interaction torque and a loss of the phase lead of the muscle torque. Our findings implicate the C1/C3 anterior interpositus zone of the cerebellum in the anticipatory control of intersegmental dynamics during reaching, which zone is required for coordinating the motions of the shoulder and wrist with those of the elbow. In contrast, this cerebellar zone does not play a role in scaling the movement to match a target.

Relationship Between Insertion Torque and Resonance Frequency Measurements, Performed by Resonance Frequency Analysis, in Micromobility of Dental Implants: An In Vitro Study.

PubMed

Brizuela-Velasco, Aritza; Álvarez-Arenal, Ángel; Gil-Mur, Francisco Javier; Herrero-Climent, Mariano; Chávarri-Prado, David; Chento-Valiente, Yelko; Dieguez-Pereira, Markel

2015-10-01

To evaluate the micromobility of dental implants under occlusal loading in relation to stability measurements of resonance frequency analysis and insertion torque. The sample comprised of 24 implants inserted in 12 fresh cow ribs. Insertion torque and Osstell implant stability quotient (ISQ) measurements were recorded. An "ad hoc" acrylic premolar was made on a temporary abutment and screwed to each implant, and a force of 100 N was subsequently applied at an angle of 6 degrees. Implant micromotion was measured using a Questar microscope with a resolution of 2 μm and an image analysis program. Data show a statistically significant inverse correlation between the ISQ values and implant micromotion under a load of 100 N (R = 0.86, P < 0.0001). The same relationship is found between insertion torque and implant micromotion, although the relationship is linear up to 34 N·cm and becomes exponential for higher values (R = 0.78, P < 0.0001). A direct correlation is established between insertion torque and ISQ values. There is an inverse relationship between both ISQ and insertion torque values and implant micromotion under a load of 100 N.

Maximum voluntary joint torque as a function of joint angle and angular velocity: model development and application to the lower limb.

PubMed

Anderson, Dennis E; Madigan, Michael L; Nussbaum, Maury A

2007-01-01

Measurements of human strength can be important during analyses of physical activities. Such measurements have often taken the form of the maximum voluntary torque at a single joint angle and angular velocity. However, the available strength varies substantially with joint position and velocity. When examining dynamic activities, strength measurements should account for these variations. A model is presented of maximum voluntary joint torque as a function of joint angle and angular velocity. The model is based on well-known physiological relationships between muscle force and length and between muscle force and velocity and was tested by fitting it to maximum voluntary joint torque data from six different exertions in the lower limb. Isometric, concentric and eccentric maximum voluntary contractions were collected during hip extension, hip flexion, knee extension, knee flexion, ankle plantar flexion and dorsiflexion. Model parameters are reported for each of these exertion directions by gender and age group. This model provides an efficient method by which strength variations with joint angle and angular velocity may be incorporated into comparisons between joint torques calculated by inverse dynamics and the maximum available joint torques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Z. X.; Wang, W. X.; Diamond, P. H.

We report that intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. Here we focus on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (sˆ) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak sˆ . Basedmore » on realistic profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak sˆ discharges and that the value of sˆ crit is consistent with the experimental results sˆ exp crit [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. In conclusion, the consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive sˆ .« less

A pressure-based force and torque prediction technique for the study of fish-like swimming

PubMed Central

Dabiri, John O.; Lauder, George V.

2017-01-01

Many outstanding questions about the evolution and function of fish morphology are linked to swimming dynamics, and a detailed knowledge of time-varying forces and torques along the animal’s body is a key component in answering many of these questions. Yet, quantifying these forces and torques experimentally represents a major challenge that to date prevents a full understanding of fish-like swimming. Here, we develop a method for obtaining these force and torque data non-invasively using standard 2D digital particle image velocimetry in conjunction with a pressure field algorithm. We use a mechanical flapping foil apparatus to model fish-like swimming and measure forces and torques directly with a load cell, and compare these measured values to those estimated simultaneously using our pressure-based approach. We demonstrate that, when out-of-plane flows are relatively small compared to the planar flow, and when pressure effects sufficiently dominate shear effects, this technique is able to accurately reproduce the shape, magnitude, and timing of locomotor forces and torques experienced by a fish-like swimmer. We conclude by exploring of the limits of this approach and its feasibility in the study of freely-swimming fishes. PMID:29216264

Mechanics of torque generation in the bacterial flagellar motor.

PubMed

Mandadapu, Kranthi K; Nirody, Jasmine A; Berry, Richard M; Oster, George

2015-08-11

The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual "power stroke." Specifically, we propose that ion-induced conformational changes about a proline "hinge" residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque-speed and speed-ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator.

Ironless armature torque motor

NASA Technical Reports Server (NTRS)

Fisher, R. L.

1972-01-01

Four iron-less armature torque motors, four Hall device position sensor assemblies, and two test fixtures were fabricated. The design approach utilized samarium cobalt permanent magnets, a large airgap, and a three-phase winding in a stationary ironless armature. Hall devices were employed to sense rotor position. An ironless armature torque motor having an outer diameter of 4.25 inches was developed to produce a torque constant of 65 ounce-inches per ampere with a resistance of 20.5 ohms. The total weight, including structural elements, was 1.58 pounds. Test results indicated that all specifications were met except for generated voltage waveform. It is recommended that investigations be made concerning the generated voltage waveform to determine if it may be improved.

A method for reduction of cogging torque in brushless DC motor considering the distribution of magnetization by 3DEMCN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hur, J.; Hyun, D.S.; Hong, J.P.

1998-09-01

The method of reducing cogging torque and improving average torque has been studied by changing the dead zone angle of trapezoidal magnetization distribution of ring type rotor magnet in brushless DC motor (BLDCM). Because BLDCM has 3-D shape of overhang, 3-D analysis should be used for exact computation of its magnetic field. 3-D equivalent magnetic circuit network method (3-D EMCN) which can analyze an accurate 3-D magnetic field has been introduced. The analysis results of cogging torque using 3-D EMCN are compared with ones of 3-D finite element method (3-D FEM) and experimental data.

A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

PubMed Central

SALIBA, Felipe Miguel; CARDOSO, Mayra; TORRES, Marcelo Ferreira; TEIXEIRA, Alexandre Carvalho; LOURENÇO, Eduardo José Veras; TELLES, Daniel de Moraes

2011-01-01

Objectives Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. Material and methods Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. Results There was a significant difference between the means of Group 1 (38.62±6.43 Ncm) and Group 2 (48.47±5.04 Ncm), with p=0.001. Conclusion This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws. PMID:21437472

Coating dental implant abutment screws with diamondlike carbon doped with diamond nanoparticles: the effect on maintaining torque after mechanical cycling.

PubMed

Lepesqueur, Laura Soares; de Figueiredo, Viviane Maria Gonçalves; Ferreira, Leandro Lameirão; Sobrinho, Argemiro Soares da Silva; Massi, Marcos; Bottino, Marco Antônio; Nogueira Junior, Lafayette

2015-01-01

To determine the effect of maintaining torque after mechanical cycling of abutment screws that are coated with diamondlike carbon and coated with diamondlike carbon doped with diamond nanoparticles, with external and internal hex connections. Sixty implants were divided into six groups according to the type of connection (external or internal hex) and the type of abutment screw (uncoated, coated with diamondlike carbon, and coated with diamondlike carbon doped with diamond nanoparticles). The implants were inserted into polyurethane resin and crowns of nickel chrome were cemented on the implants. The crowns had a hole for access to the screw. The initial torque and the torque after mechanical cycling were measured. The torque values maintained (in percentages) were evaluated. Statistical analysis was performed using one-way analysis of variance and the Tukey test, with a significance level of 5%. The largest torque value was maintained in uncoated screws with external hex connections, a finding that was statistically significant (P = .0001). No statistically significant differences were seen between the groups with and without coating in maintaining torque for screws with internal hex connections (P = .5476). After mechanical cycling, the diamondlike carbon with and without diamond doping on the abutment screws showed no improvement in maintaining torque in external and internal hex connections.

MULTIPLE DIFFERENTIAL ROTARY MECHANICAL DRIVE

DOEpatents

Smits, R.G.

1964-01-28

This patent relates to a mechanism suitable for such applications as driving two spaced-apart spools which carry a roll film strip under conditions where the film movement must be rapidly started, stopped, and reversed while maintaining a constant tension on the film. The basic drive is provided by a variable speed, reversible rnotor coupled to both spools through a first differential mechanism and driving both spools in the same direction. A second motor, providing a constant torque, is connected to the two spools through a second differential mechanism and is coupled to impart torque to one spool in a first direction anid to the other spool in the reverse direction thus applying a constant tension to the film passing over the two spools irrespective of the speed or direction of rotation thereof. (AEC)

In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique.

PubMed

Matsukawa, Keitaro; Yato, Yoshiyuki; Kato, Takashi; Imabayashi, Hideaki; Asazuma, Takashi; Nemoto, Koichi

2014-02-15

The insertional torque of pedicle screws using the cortical bone trajectory (CBT) was measured in vivo. To investigate the effectiveness of the CBT technique by measurement of the insertional torque. The CBT follows a mediolateral and caudocephalad directed path, engaging with cortical bone maximally from the pedicle to the vertebral body. Some biomechanical studies have demonstrated favorable characteristics of the CBT technique in cadaveric lumbar spine. However, no in vivo study has been reported on the mechanical behavior of this new trajectory. The insertional torque of pedicle screws using CBT and traditional techniques were measured intraoperatively in 48 consecutive patients. A total of 162 screws using the CBT technique and 36 screws using the traditional technique were compared. In 8 of 48 patients, the side-by-side comparison of 2 different insertional techniques for each vertebra were performed, which formed the H group. In addition, the insertional torque was correlated with bone mineral density. The mean maximum insertional torque of CBT screws and traditional screws were 2.49 ± 0.99 Nm and 1.24 ± 0.54 Nm, respectively. The CBT screws showed 2.01 times higher torque and the difference was significant between the 2 techniques (P < 0.01). In the H group, the insertional torque were 2.71 ± 1.36 Nm in the CBT screws and 1.58 ± 0.44 Nm in the traditional screws. The CBT screws demonstrated 1.71 times higher torque and statistical significance was achieved (P < 0.01). Positive linear correlations between maximum insertional torque and bone mineral density were found in both technique, the correlation coefficient of traditional screws (r = 0.63, P < 0.01) was higher than that of the CBT screws (r = 0.59, P < 0.01). The insertional torque using the CBT technique is about 1.7 times higher than the traditional technique. 2.

Asymmetry in the clockwise and counterclockwise rotation of the bacterial flagellar motor

PubMed Central

Yuan, Junhua; Fahrner, Karen A.; Turner, Linda; Berg, Howard C.

2010-01-01

Cells of Escherichia coli are able to swim up gradients of chemical attractants by modulating the direction of rotation of their flagellar motors, which spin alternately clockwise (CW) and counterclockwise (CCW). Rotation in either direction has been thought to be symmetric and exhibit the same torques and speeds. The relationship between torque and speed is one of the most important measurable characteristics of the motor, used to distinguish specific mechanisms of motor rotation. Previous measurements of the torque–speed relationship have been made with cells lacking the response regulator CheY that spin their motors exclusively CCW. In this case, the torque declines slightly up to an intermediate speed called the “knee speed” after which it falls rapidly to zero. This result is consistent with a “power-stroke” mechanism for torque generation. Here, we measure the torque–speed relationship for cells that express large amounts of CheY and only spin their motors CW. We find that the torque decreases linearly with speed, a result remarkably different from that for CCW rotation. We obtain similar results for wild-type cells by reexamining data collected in previous work. We speculate that CCW rotation might be optimized for runs, with higher speeds increasing the ability of cells to sense spatial gradients, whereas CW rotation might be optimized for tumbles, where the object is to change cell trajectories. But why a linear torque–speed relationship might be optimum for the latter purpose we do not know. PMID:20615986

Receding horizon online optimization for torque control of gasoline engines.

PubMed

Kang, Mingxin; Shen, Tielong

2016-11-01

This paper proposes a model-based nonlinear receding horizon optimal control scheme for the engine torque tracking problem. The controller design directly employs the nonlinear model exploited based on mean-value modeling principle of engine systems without any linearizing reformation, and the online optimization is achieved by applying the Continuation/GMRES (generalized minimum residual) approach. Several receding horizon control schemes are designed to investigate the effects of the integral action and integral gain selection. Simulation analyses and experimental validations are implemented to demonstrate the real-time optimization performance and control effects of the proposed torque tracking controllers. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Torque Splitting by a Concentric Face Gear Transmission

NASA Technical Reports Server (NTRS)

Filler, Robert R.; Heath, Gregory F.; Slaughter, Stephen C.; Lewicki, David G.

2002-01-01

Tests of a 167 Kilowatt (224 Horsepower) split torque face gearbox were performed by the Boeing Company in Mesa, Arizona, while working under a Defense Advanced Research Projects Agency (DARPA) Technology Reinvestment Program (TRP). This paper provides a summary of these cooperative tests, which were jointly funded by Boeing and DARPA. Design, manufacture and testing of the scaled-power TRP proof-of-concept (POC) split torque gearbox followed preliminary evaluations of the concept performed early in the program. The split torque tests were run using 200 N-m (1767 in-lbs) torque input to each side of the transmission. During tests, two input pinions were slow rolled while in mesh with the two face gears. Two idler gears were also used in the configuration to recombine torque near the output. Resistance was applied at the output face gear to create the required loading conditions in the gear teeth. A system of weights, pulleys and cables were used in the test rig to provide both the input and output loading. Strain gages applied in the tooth root fillets provided strain indication used to determine torque splitting conditions at the input pinions. The final two pinion-two idler tests indicated 52% to 48% average torque split capabilities for the two pinions. During the same tests, a 57% to 43% average distribution of the torque being recombined to the upper face gear from the lower face gear was measured between the two idlers. The POC split torque tests demonstrated that face gears can be applied effectively in split torque rotorcraft transmissions, yielding good potential for significant weight, cost and reliability improvements over existing equipment using spiral bevel gearing.

Optimal filtering and Bayesian detection for friction-based diagnostics in machines.

PubMed

Ray, L R; Townsend, J R; Ramasubramanian, A

2001-01-01

Non-model-based diagnostic methods typically rely on measured signals that must be empirically related to process behavior or incipient faults. The difficulty in interpreting a signal that is indirectly related to the fundamental process behavior is significant. This paper presents an integrated non-model and model-based approach to detecting when process behavior varies from a proposed model. The method, which is based on nonlinear filtering combined with maximum likelihood hypothesis testing, is applicable to dynamic systems whose constitutive model is well known, and whose process inputs are poorly known. Here, the method is applied to friction estimation and diagnosis during motion control in a rotating machine. A nonlinear observer estimates friction torque in a machine from shaft angular position measurements and the known input voltage to the motor. The resulting friction torque estimate can be analyzed directly for statistical abnormalities, or it can be directly compared to friction torque outputs of an applicable friction process model in order to diagnose faults or model variations. Nonlinear estimation of friction torque provides a variable on which to apply diagnostic methods that is directly related to model variations or faults. The method is evaluated experimentally by its ability to detect normal load variations in a closed-loop controlled motor driven inertia with bearing friction and an artificially-induced external line contact. Results show an ability to detect statistically significant changes in friction characteristics induced by normal load variations over a wide range of underlying friction behaviors.

Design, simulation and modelling of auxiliary exoskeleton to improve human gait cycle.

PubMed

Ashkani, O; Maleki, A; Jamshidi, N

2017-03-01

Exoskeleton is a walking assistance device that improves human gait cycle through providing auxiliary force and transferring physical load to the stronger muscles. This device takes the natural state of organ and follows its natural movement. Exoskeleton functions as an auxiliary device to help those with disabilities in hip and knee such as devotees, elderly farmers and agricultural machinery operators who suffer from knee complications. In this research, an exoskeleton designed with two screw jacks at knee and hip joints. To simulate extension and flexion movements of the leg joints, bearings were used at the end of hip and knee joints. The generated torque and motion angles of these joints obtained as well as the displacement curves of screw jacks in the gait cycle. Then, the human gait cycle was simulated in stance and swing phases and the obtained torque curves were compared. The results indicated that they followed the natural circle of the generated torque in joints with a little difference from each other. The maximum displacement obtained 4 and 6 cm in hip and knee joints jack respectively. The maximum torques in hip and knee joints were generated in foot contact phase. Also the minimum torques in hip and knee joints were generated in toe off and heel off phases respectively.

Multibody dynamics simulation of an all-wheel-drive motorcycle for handling and energy efficiency investigations

NASA Astrophysics Data System (ADS)

Griffin, J. W.; Popov, A. A.

2018-07-01

It is now possible, through electrical, hydraulic or mechanical means, to power the front wheel of a motorcycle. The aim of this is often to improve performance in limit-handling scenarios including off-road low-traction conditions and on-road high-speed cornering. Following on from research into active torque distribution in 4-wheeled vehicles, the possibility exists for efficiency improvements to be realised by reducing the total amount of energy dissipated as slip at the wheel-road contact. This paper presents the results of an investigation into the effect that varying the torque distribution ratio has on the energy consumption of the two-wheeled vehicle. A 13-degree of freedom multibody model was created, which includes the effects of suspension, aerodynamics and gyroscopic bodies. SimMechanics, from the MathWorks?, is used for automatic generation of equations of motion and time-domain simulation, in conjunction with MATLAB and Simulink. A simple driver model is used to control the speed and yaw rate of the motorcycle. The handling characteristics of the motorcycle are quantitatively analysed, and the impact of torque distribution on energy consumption is considered during straight line and cornering situations. The investigation has shown that only a small improvement in efficiency can be made by transferring a portion of the drive torque to the front wheel. Tyre longevity could be improved by reduced slip energy dissipation.

Effects of bearing cleaning and lube environment on bearing performance

NASA Technical Reports Server (NTRS)

Ward, Peter C.

1995-01-01

Running torque data of SR6 ball bearings are presented for different temperatures and speeds. The data are discussed in contrast to generally used torque prediction models and point out the need to obtain empirical data in critical applications. Also, the effects of changing bearing washing techniques from old, universally used CFC-based systems to CFC-free aqueous/alkaline solutions are discussed. Data on wettability, torque and lubricant life using SR3 ball bearings are presented. In general, performance is improved using the new aqueous washing techniques.

Computations of Torque-Balanced Coaxial Rotor Flows

NASA Technical Reports Server (NTRS)

Yoon, Seokkwan; Chan, William M.; Pulliam, Thomas H.

2017-01-01

Interactional aerodynamics has been studied for counter-rotating coaxial rotors in hover. The effects of torque balancing on the performance of coaxial-rotor systems have been investigated. The three-dimensional unsteady Navier-Stokes equations are solved on overset grids using high-order accurate schemes, dual-time stepping, and a hybrid turbulence model. Computational results for an experimental model are compared to available data. The results for a coaxial quadcopter vehicle with and without torque balancing are discussed. Understanding interactions in coaxial-rotor flows would help improve the design of next-generation autonomous drones.

Magnetization reversal in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jia, E-mail: lijia@wipm.ac.cn

2014-10-07

We theoretically investigate the dynamics of magnetization in ferromagnetic thin films induced by spin-orbit interaction with Slonczewski-like spin transfer torque. We reproduce the experimental results of perpendicular magnetic anisotropy films by micromagnetic simulation. Due to the spin-orbit interaction, the magnetization can be switched by changing the direction of the current with the assistant of magnetic field. By increasing the current amplitude, wider range of switching events can be achieved. Time evolution of magnetization has provided us a clear view of the process, and explained the role of minimum external field. Slonczewski-like spin transfer torque modifies the magnetization when current ismore » present. The magnitude of the minimum external field is determined by the strength of the Slonczewski-like spin transfer torque. The investigations may provide potential applications in magnetic memories.« less

In-line drivetrain and four wheel drive work machine using same

DOEpatents

Hoff, Brian

2008-08-05

A four wheel drive articulated mine loader is powered by a fuel cell and propelled by a single electric motor. The drivetrain has the first axle, second axle, and motor arranged in series on the work machine chassis. Torque is carried from the electric motor to the back differential via a pinion meshed with the ring gear of the back differential. A second pinion oriented in an opposite direction away from the ring gear is coupled to a drive shaft to transfer torque from the ring gear to the differential of the front axle. Thus, the ring gear of the back differential acts both to receive torque from the motor and to transfer torque to the forward axle. The in-line drive configuration includes a single electric motor and a single reduction gear to power the four wheel drive mine loader.

Hyperstaticity for ergonomie design of a wrist exoskeleton.

PubMed

Esmaeili, Mohammad; Jarrassé, Nathanaël; Dailey, Wayne; Burdet, Etienne; Campolo, Domenico

2013-06-01

Increasing the level of transparency in rehabilitation devices has been one of the main goals in robot-aided neurorehabilitation for the past two decades. This issue is particularly important to robotic structures that mimic the human counterpart's morphology and attach directly to the limb. Problems arise for complex joints such as the human wrist, which cannot be accurately matched with a traditional mechanical joint. In such cases, mechanical differences between human and robotic joint cause hyperstaticity (i.e. overconstraint) which, coupled with kinematic misalignments, leads to uncontrolled force/torque at the joint. This paper focuses on the prono-supination (PS) degree of freedom of the forearm. The overall force and torque in the wrist PS rotation is quantified by means of a wrist robot. A practical solution to avoid hyperstaticity and reduce the level of undesired force/torque in the wrist is presented, which is shown to reduce 75% of the force and 68% of the torque.

Improvement of the limit torque for the torque limiter with magnetic rheological fluid

NASA Astrophysics Data System (ADS)

Umehara, Noritsugu; Kita, Shizuo

Robots are coming to support and help our life. The robots that work together with human need to avoid sever hitting and holding that force is more than the adequate and comfortable range. In order to keep the force to the safe level in the robot arms, t he limit torque should be controlled on the basis of the case the robot used. Magnetic rheological fluids were tried to be used for the clutch that transmission torque can be controlled continuously because MR fluids can be controlled its viscosity by magnetic field. However those clutch devices were too heavy and large to use for the robot arms. Therefore we tried to increase the sensitivity of magnetic field to viscosity of MR fluids. By applying rough surface for the mating surface, sensitivity of the magnetic field to the shearing torque increase drastically in the case of co-axial torque meter. On the other hand, the changing of the size of the orifice is effective to increase the sensitivity of the magnetic field on the flow resistance in the case of the orifice type equipment.

Magnetic Fluctuation-Driven Intrinsic Flow in a Toroidal Plasma

NASA Astrophysics Data System (ADS)

Brower, D. L.; Ding, W. X.; Lin, L.; Almagri, A. F.; den Hartog, D. J.; Sarff, J. S.

2012-10-01

Magnetic fluctuations have been long observed in various magnetic confinement configurations. These perturbations may arise naturally from plasma instabilities such as tearing modes and energetic particle driven modes, but they can also be externally imposed by error fields or external magnetic coils. It is commonly observed that large MHD modes lead to plasma locking (no rotation) due to torque produced by eddy currents on the wall, and it is predicted that stochastic field induces flow damping where the radial electric field is reduced. Flow generation is of great importance to fusion plasma research, especially low-torque devices like ITER, as it can act to improve performance. Here we describe new measurements in the MST reversed field pinch (RFP) showing that the coherent interaction of magnetic and particle density fluctuations can produce a turbulent fluctuation-induced kinetic force, which acts to drive intrinsic plasma rotation. Key observations include; (1) the average kinetic force resulting from density fluctuations, ˜ 0.5 N/m^3, is comparable to the intrinsic flow acceleration, and (2) between sawtooth crashes, the spatial distribution of the kinetic force is directed to create a sheared parallel flow profile that is consistent with the measured flow profile in direction and amplitude, suggesting the kinetic force is responsible for intrinsic plasma rotation.

A ring-type multi-DOF ultrasonic motor with four feet driving consistently.

PubMed

Shi, Shengjun; Xiong, Huaiyin; Liu, Yingxiang; Chen, Weishan; Liu, Junkao

2017-04-01

A new type of multiple-degree-of-freedom (multi-DOF) ultrasonic motor was developed aiming at high output torque and compact structure. To reach this purpose, a ring type composite stator was proposed with four driving feet uniformly arranged in the inner circumference of the ring stator. The stator employs two orthogonal axial bending modes and a radial bending mode, by exciting two of them simultaneously, to generate elliptic trajectories on driving feet tips and to push sphere rotor around x, y and z axis respectively. Based on the deduced criteria, a specific combination of the A(0,5) axial bending modes and R(0,2) radial bending mode were chosen to realize that the rotating directions of the elliptical driving trajectories on four feet tips can push the sphere rotor to spin in the same direction consistently, thus the efficiency and output performance will be improved by decreasing the slip between feet and rotor. FEM was used to design the motor including selecting key parameters to tune the resonant frequencies by sensitivity analysis, and a prototype was fabricated and tested. The experiment results showed that the maximum output torque of the motor is 0.118Nm and the maximum speed is 55r/min. Copyright © 2017 Elsevier B.V. All rights reserved.

Computing the motor torque of Escherichia coli.

PubMed

Das, Debasish; Lauga, Eric

2018-06-13

The rotary motor of bacteria is a natural nano-technological marvel that enables cell locomotion by powering the rotation of semi-rigid helical flagellar filaments in fluid environments. It is well known that the motor operates essentially at constant torque in counter-clockwise direction but past work have reported a large range of values of this torque. Focusing on Escherichia coli cells that are swimming and cells that are stuck on a glass surface for which all geometrical and environmental parameters are known (N. C. Darnton et al., J. Bacteriol., 2007, 189, 1756-1764), we use two validated numerical methods to compute the value of the motor torque consistent with experiments. Specifically, we use (and compare) a numerical method based on the boundary integral representation of Stokes flow and also develop a hybrid method combining boundary element and slender body theory to model the cell body and flagellar filament, respectively. Using measured rotation speed of the motor, our computations predict a value of the motor torque in the range 440 pN nm to 829 pN nm, depending critically on the distance between the flagellar filaments and the nearby surface.

Expanding torque possibilities: A skeletally anchored torqued cantilever for uprighting "kissing molars".

PubMed

Barros, Sérgio Estelita; Janson, Guilherme; Chiqueto, Kelly; Ferreira, Eduardo; Rösing, Cassiano

2018-04-01

Several uprighting mechanics and devices have been used for repositioning tipped molars. "Kissing molars" (KMs) are an uncommon tooth impaction involving 2 severely tipped mandibular molars with their occlusal surfaces positioned crown to crown, with the roots pointing in opposite directions. Orthodontic uprighting of KMs has not been a usual treatment protocol, and it can be a challenging task due to the severe tipping and double impaction, requiring efficient and well-controlled uprighting mechanics. An innovative skeletally anchored cantilever, which uses the torque principle for uprighting tipped molars, is suggested. This torqued cantilever is easy to manufacture, install, and activate; it is a well-known torque that is effective for producing root movement. A successful treatment of symptomatic KMs, involving the first and second molars, was achieved with this cantilever. Thus, clinicians should consider the suggested uprighting mechanics and orthodontic device as a more conservative alternative to extraction of KMs, depending on the patient's age, involved teeth in KMs, tipping severity, and impaction positions. Copyright © 2018 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Unsteady loading of a vertical-axis turbine in the interaction with an upstream deflector

NASA Astrophysics Data System (ADS)

Kim, Daegyoum; Gharib, Morteza

2014-01-01

Torque generation and flow distribution of a lift-based vertical-axis turbine with an upstream deflecting plate are investigated in water tunnel experiments. The deployment of a deflector in front of a lift-based turbine is a promising approach to increase local flow velocity and enhance energy conversion efficiency without consideration for complicated control. For the turbine with the deflector, the phase during which the blade passes near the front end of the turbine has a major contribution to torque increase from the case without the deflector. Meanwhile, the deflector can have a negative effect in torque generation at the phase when the blade moves upstream against free stream if the turbine is placed close to the deflector in a crosswise direction. The change of nearby flow distribution by the deflector is also examined to find its correlation with torque generation. When the blade rotates through the near-wake region of the deflector, the blade can collides with the vortical structure shed from the deflector. This interaction causes significant torque fluctuation.

Magnetic attitude control torque generation of a gravity gradient stabilized satellite

NASA Astrophysics Data System (ADS)

Suhadis, N. M.; Salleh, M. B.; Rajendran, P.

2018-05-01

Magnetic torquer is used to generate a magnetic dipole moment onboard satellites whereby a control torque for attitude control purposes is generated when it couples with the geomagnetic field. This technique has been considered very attractive for satellites operated in Low Earth Orbit (LEO) as the strength of the geomagnetic field is relatively high below the altitude of 1000 km. This paper presents the algorithm used to generate required magnetic dipole moment by 3 magnetic torquers mounted onboard a gravity gradient stabilized satellite operated at an altitude of 540 km with nadir pointing mission. As the geomagnetic field cannot be altered and its magnitude and direction vary with respect to the orbit altitude and inclination, a comparison study of attitude control torque generation performance with various orbit inclination is performed where the structured control algorithm is simulated for 13°, 33° and 53° orbit inclinations to see how the variation of the satellite orbit affects the satellite's attitude control torque generation. Results from simulation show that the higher orbit inclination generates optimum magnetic attitude control torque for accurate nadir pointing mission.

Mathematical models for principles of gyroscope theory

NASA Astrophysics Data System (ADS)

Usubamatov, Ryspek

2017-01-01

Gyroscope devices are primary units for navigation and control systems that have wide application in engineering. The main property of the gyroscope device is maintaining the axis of a spinning rotor. This gyroscope peculiarity is represented in terms of gyroscope effects in which known mathematical models have been formulated on the law of kinetic energy conservation and the change in the angular momentum. The gyroscope theory is represented by numerous publications, which mathematical models do not match the actual torques and motions in these devices.. The nature of gyroscope effects is more complex than represented in known publications. Recent investigations in this area have demonstrated that on a gyroscope can act until eleven internal torques simultaneously and interdependently around two axes. These gyroscope torques are generated by spinning rotor's mass-elements and by the gyroscope center-mass based on action of several inertial forces. The change in the angular momentum does not play first role for gyroscope motions. The external load generates several internal torques which directions may be distinguished. This situation leads changing of the angular velocities of gyroscope motions around two axes. Formulated mathematical models of gyroscope internal torques are representing the fundamental principle of gyroscope theory. In detail, the gyroscope is experienced the resistance torque generated by the centrifugal and Coriolis forces of the spinning rotor and the precession torque generated by the common inertial forces and the change in the angular momentum. The new mathematical models for the torques and motions of the gyroscope confirmed for most unsolvable problems. The mathematical models practically tested and the results are validated the theoretical approach.

Inner core tilt and polar motion

NASA Astrophysics Data System (ADS)

Dumberry, Mathieu; Bloxham, Jeremy

2002-11-01

A tilted inner core permits exchange of angular momentum between the core and the mantle through gravitational and pressure torques and, as a result, changes in the direction of Earth's axis of rotation with respect to the mantle. We have developed a model to calculate the amplitude of the polar motion that results from an equatorial torque at the inner core boundary which tilts the inner core out of alignment with the mantle. We specifically address the issue of the role of the inner core tilt in the decade polar motion known as the Markowitz wobble. We show that a decade polar motion of the same amplitude as the observed Markowitz wobble requires a torque of 1020 N m which tilts the inner core by 0.07 degrees. This result critically depends on the viscosity of the inner core; for a viscosity less than 5 × 1017 Pa s, larger torques are required. We investigate the possibility that a torque of 1020 N m with decadal periodicity can be produced by electromagnetic coupling between the inner core and torsional oscillations of the flow in the outer core. We demonstrate that a radial magnetic field at the inner core boundary of 3 to 4 mT is required to obtain a torque of such amplitude. The resulting polar motion is eccentric and polarized, in agreement with the observations. Our model suggests that equatorial torques at the inner core boundary might also excite the Chandler wobble, provided there exists a physical mechanism that can generate a large torque at a 14 month period.

Control of spin-orbit torques through crystal symmetry in WTe2/ferromagnet bilayers

NASA Astrophysics Data System (ADS)

MacNeill, D.; Stiehl, G. M.; Guimaraes, M. H. D.; Buhrman, R. A.; Park, J.; Ralph, D. C.

2017-03-01

Recent discoveries regarding current-induced spin-orbit torques produced by heavy-metal/ferromagnet and topological-insulator/ferromagnet bilayers provide the potential for dramatically improved efficiency in the manipulation of magnetic devices. However, in experiments performed to date, spin-orbit torques have an important limitation--the component of torque that can compensate magnetic damping is required by symmetry to lie within the device plane. This means that spin-orbit torques can drive the most current-efficient type of magnetic reversal (antidamping switching) only for magnetic devices with in-plane anisotropy, not the devices with perpendicular magnetic anisotropy that are needed for high-density applications. Here we show experimentally that this state of affairs is not fundamental, but rather one can change the allowed symmetries of spin-orbit torques in spin-source/ferromagnet bilayer devices by using a spin-source material with low crystalline symmetry. We use WTe2, a transition-metal dichalcogenide whose surface crystal structure has only one mirror plane and no two-fold rotational invariance. Consistent with these symmetries, we generate an out-of-plane antidamping torque when current is applied along a low-symmetry axis of WTe2/Permalloy bilayers, but not when current is applied along a high-symmetry axis. Controlling spin-orbit torques by crystal symmetries in multilayer samples provides a new strategy for optimizing future magnetic technologies.

Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue.

PubMed

Matthews, Martyn J; Heron, Kate; Todd, Stefanie; Tomlinson, Andrew; Jones, Paul; Delextrat, Anne; Cohen, Daniel D

2017-05-01

To investigate the effect of two hamstring training protocols on eccentric peak torque before and after soccer specific fatigue. Twenty-two university male soccer players. Isokinetic strength tests were performed at 60°/s pre and post fatigue, before and after 2 different training interventions. A 45-min soccer specific fatigue modified BEAST protocol (M-BEAST) was used to induce fatigue. Players were randomly assigned to a 4 week hamstrings conditioning intervention with either a maximum strength (STR) or a muscle endurance (END) emphasis. The following parameters were evaluated: Eccentric peak torque (EccPT), angle of peak torque (APT), and angle specific torques at knee joint angles of 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and 90°. There was a significant effect of the M-BEAST on the Eccentric torque angle profile before training as well as significant improvements in post-fatigue torque angle profile following the effects of both strength and muscle endurance interventions. Forty-five minutes of simulated soccer activity leads to reduced eccentric hamstring torque at longer muscle lengths. Short-term conditioning programs (4-weeks) with either a maximum strength or a muscular endurance emphasis can equally reduce fatigue induced loss of strength over this time period. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of 4 Weeks of Explosive-type Strength Training for the Plantar Flexors on the Rate of Torque Development and Postural Stability in Elderly Individuals.

PubMed

Kobayashi, Y; Ueyasu, Y; Yamashita, Y; Akagi, R

2016-06-01

This study aimed to investigate the effect of a 4-week explosive-type strength training program for the plantar flexors on the rate of torque development and postural stability. The participants were 56 elderly men and women divided into training (17 men and 15 women) and control (14 men and 10 women) groups. The participants in the training group underwent explosive-type strength training of the plantar flexors 2 days per week for 4 weeks. Training consisted of 3 sets of 10 repetitions of explosive plantar flexion lasting less than 1 s. The following parameters were determined: muscle volume of the plantar flexors estimated by the muscle thickness and lower leg length, maximal voluntary contraction torque and rate of torque development of plantar flexion, and one-leg standing ability. The training increased the maximal voluntary contraction torque and rate of torque development, but corresponding increases in muscle volume and one-leg standing ability were not found. These results suggest that, for elderly individuals, the 4-week explosive-type strength training of the plantar flexors is effective for increasing the maximal voluntary contraction torque and rate of torque development of plantar flexion but is not effective for improving postural stability. © Georg Thieme Verlag KG Stuttgart · New York.

The effect of different screw-rod design on the anti-rotational torque: a biomechanical comparison of three conventional screw-rod constructs.

PubMed

Huang, Zifang; Wang, Chongwen; Fan, Hengwei; Sui, Wenyuan; Li, Xueshi; Wang, Qifei; Yang, Junlin

2017-07-28

Screw-rod constructs have been widely used to correct spinal deformities, but the effects of different screw-rod systems on anti-rotational torque have not been determined. This study aimed to analyze the biomechanical effect of different rod-screw constructs on anti-rotational torque. Three conventional spinal screw-rod systems (Legacy, RF-F-10 and USSII) were used to test the anti-rotational torque in the material test machine. ANOVA was performed to evaluate the anti-rotational capacity of different pedicle screws-rod constructs. The anti-rotational torque of Legacy group, RF-F-10 group and USSII group were 12.3 ± 1.9 Nm, 6.8 ± 0.4 Nm, and 3.9 ± 0.8 Nm, with a P value lower than 0.05. This results indicated that the Legacy screws-rod construct could provide a highest anti-rotation capacity, which is 68% and 210% greater than RF-F-10 screw-rod construct and USSII screw-rod respectively. The anti-rotational torque may be mainly affected by screw cap and groove design. Our result showed the anti-rotational torque are: Legacy system > RF-F-10 system > USSII system, suggesting that appropriate rod-screw constructs selection in surgery may be vital for anti-rotational torque improvement and preventing derotation correction loss.

Relationships Between Knee Extension Moments During Weighted and Unweighted Gait and Strength Measures That Predict Knee Moments After ACL Reconstruction.

PubMed

Hartigan, Erin; Aucoin, Jennifer; Carlson, Rita; Klieber-Kusak, Melanie; Murray, Thomas; Shaw, Bernadette; Lawrence, Michael

Weighted gait increases internal knee extension moment impulses (KEMI) in the anterior cruciate ligament-reconstructed (ACLR) limb; however, limb differences persist. (1) KEMI during normal gait will influence KEMI during weighted gait and (2) peak knee extension (PKE) torque and time to reach PKE torque will predict KEMI during gait tasks. Descriptive laboratory study. Twenty-four women and 14 men completed 3 gait tasks (unweighted, vest, sled) and strength testing after discharge from rehabilitation and clearance to return to sports. KEMI were calculated during the first 25% of stance. PKE torque and time to reach PKE torque were obtained using a dynamometer. Data on the ACLR limb and symmetry indices (SIs) were analyzed for each sex. Women presented with asymmetrical PKE torques and KEMI across tasks. There were three correlations noted for KEMI: between the walk and vest, walk and sled, and vest and sled tasks. Slower time to PKE torque predicted limb asymmetries across tasks and KEMI in the ACLR limb during the sled task. Men presented with asymmetrical PKE torques and KEMI during the sled task. There was a correlation noted for KEMI between walk and vest tasks only. During the sled task, ACLR limb time to PKE torque predicted KEMI in the ACLR limb and PKE torque SI predicted KEMI SI. Women use asymmetrical KEMI profiles during all gait tasks, and those with worse KEMI during walking have worse KEMI during weighted gait. Men have asymmetrical KEMI when sled towing, and these KEMIs do not correlate with KEMI during walking or vest tasks. PKE torque deficits persist when attempting to return to sports. Only men use gains in PKE torque to improve KEMI profiles. Although quicker PKE torque generation will increase KEMI in women, normalization of KEMI profiles will not occur by increasing rate of force development only. Gait retraining is recommended to correct asymmetrical KEMI profiles used across gait tasks in women.

75 FR 9809 - Airworthiness Directives; Airbus Model A330-243, -341, -342, and -343 Airplanes; and Model A340...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-04

..., as a consequence of the over-torque, fail and move away, it would lead to loss of the vertical load pins, which could result in loss of the primary and/or secondary load path of the forward and/or aft..., as a consequence of the over-torque, fail and move away, it would lead to loss of the vertical load...

Angular velocity affects trunk muscle strength and EMG activation during isokinetic axial rotation.

PubMed

Fan, Jian-Zhong; Liu, Xia; Ni, Guo-Xin

2014-01-01

To evaluate trunk muscle strength and EMG activation during isokinetic axial rotation at different angular velocities. Twenty-four healthy young men performed isokinetic axial rotation in right and left directions at 30, 60, and 120 degrees per second angular velocity. Simultaneously, surface EMG was recorded on external oblique (EO), internal oblique (IO), and latissimus dorsi (LD) bilaterally. In each direction, with the increase of angular velocity, peak torque decreased, whereas peak power increased. During isokinetic axial rotation, contralateral EO as well as ipsilateral IO and LD acted as primary agonists, whereas, ipsilateral EO as well as contralateral IO and LD acted as primary antagonistic muscles. For each primary agonist, the root mean square values decreased with the increase of angular velocity. Antagonist coactiviation was observed at each velocity; however, it appears to be higher with the increase of angular velocity. Our results suggest that velocity of rotation has great impact on the axial rotation torque and EMG activity. An inverse relationship of angular velocity was suggested with the axial rotation torque as well as root mean square value of individual trunk muscle. In addition, higher velocity is associated with higher coactivation of antagonist, leading to a decrease in torque with the increase of velocity.

Prediction of the body rotation-induced torques on the arm during reaching movements: evidence from a proprioceptively deafferented subject.

PubMed

Guillaud, Etienne; Simoneau, Martin; Blouin, Jean

2011-06-01

Reaching for a target while rotating the trunk generates substantial Coriolis and centrifugal torques that push the arm in the opposite direction of the rotations. These torques rarely perturb movement accuracy, suggesting that they are compensated for during the movement. Here we tested whether signals generated during body motion (e.g., vestibular) can be used to predict the torques induced by the body rotation and to modify the motor commands accordingly. We asked a deafferented subject to reach for a memorized visual target in darkness. At the onset of the reaching, the patient was rotated 25° or 40° in the clockwise or the counterclockwise directions. During the rotation, the patient's head remained either fixed in space (Head-Fixed condition) or fixed on the trunk (Head Rotation condition). At the rotation onset, the deafferented patient's hand largely deviated from the mid-sagittal plane in both conditions. The hand deviations were compensated for in the Head Rotation condition only. These results highlight the computational faculty of the brain and show that body rotation-related information can be processed for predicting the consequence of the rotation dynamics on the reaching arm movements. Copyright © 2011 Elsevier Ltd. All rights reserved.

Implementation of Temperature Sequential Controller on Variable Speed Drive

NASA Astrophysics Data System (ADS)

Cheong, Z. X.; Barsoum, N. N.

2008-10-01

There are many pump and motor installations with quite extensive speed variation, such as Sago conveyor, heating, ventilation and air conditioning (HVAC) and water pumping system. A common solution for these applications is to run several fixed speed motors in parallel, with flow control accomplish by turning the motors on and off. This type of control method causes high in-rush current, and adds a risk of damage caused by pressure transients. This paper explains the design and implementation of a temperature speed control system for use in industrial and commercial sectors. Advanced temperature speed control can be achieved by using ABB ACS800 variable speed drive-direct torque sequential control macro, programmable logic controller and temperature transmitter. The principle of direct torque sequential control macro (DTC-SC) is based on the control of torque and flux utilizing the stator flux field orientation over seven preset constant speed. As a result of continuous comparison of ambient temperature to the references temperatures; electromagnetic torque response is particularly fast to the motor state and it is able maintain constant speeds. Experimental tests have been carried out by using ABB ACS800-U1-0003-2, to validate the effectiveness and dynamic respond of ABB ACS800 against temperature variation, loads, and mechanical shocks.

Cerebellar ataxia: abnormal control of interaction torques across multiple joints.

PubMed

Bastian, A J; Martin, T A; Keating, J G; Thach, W T

1996-07-01

1. We studied seven subjects with cerebellar lesions and seven control subjects as they made reaching movements in the sagittal plane to a target directly in front of them. Reaches were made under three different conditions: 1) "slow-accurate," 2) "fast-accurate," and 3) "fast as possible." All subjects were videotaped moving in a sagittal plane with markers on the index finger, wrist, elbow, and shoulder. Marker positions were digitized and then used to calculate joint angles. For each of the shoulder, elbow and wrist joints, inverse dynamics equations based on a three-segment limb model were used to estimate the net torque (sum of components) and each of the component torques. The component torques consisted of the torque due to gravity, the dynamic interaction torques induced passively by the movement of the adjacent joint, and the torque produced by the muscles and passive tissue elements (sometimes called "residual" torque). 2. A kinematic analysis of the movement trajectory and the change in joint angles showed that the reaches of subjects with cerebellar lesions were abnormal compared with reaches of control subjects. In both the slow-accurate and fast-accurate conditions the cerebellar subjects made abnormally curved wrist paths; the curvature was greater in the slow-accurate condition. During the slow-accurate condition, cerebellar subjects showed target undershoot and tended to move one joint at a time (decomposition). During the fast-accurate reaches, the cerebellar subjects showed target overshoot. Additionally, in the fast-accurate condition, cerebellar subjects moved the joints at abnormal rates relative to one another, but the movements were less decomposed. Only three subjects were tested in the fast as possible condition; this condition was analyzed only to determine maximal reaching speeds of subjects with cerebellar lesions. Cerebellar subjects moved more slowly than controls in all three conditions. 3. A kinetic analysis of torques generated at each joint during the slow-accurate reaches and the fast-accurate reaches revealed that subjects with cerebellar lesions produced very different torque profiles compared with control subjects. In the slow-accurate condition, the cerebellar subjects produced abnormal elbow muscle torques that prevented the normal elbow extension early in the reach. In the fast-accurate condition, the cerebellar subjects produced inappropriate levels of shoulder muscle torque and also produced elbow muscle torques that did not very appropriately with the dynamic interaction torques that occurred at the elbow. Lack of appropriate muscle torque resulted in excessive contributions of the dynamic interaction torque during the fast-accurate reaches. 4. The inability to produce muscle torques that predict, accommodate, and compensate for the dynamic interaction torques appears to be an important cause of the classic kinematic deficits shown by cerebellar subjects during attempted reaching. These kinematic deficits include incoordination of the shoulder and the elbow joints, a curved trajectory, and overshoot. In the fast-accurate condition, cerebellar subjects often made inappropriate muscle torques relative to the dynamic interaction torques. Because of this, interaction torques often determined the pattern of incoordination of the elbow and shoulder that produced the curved trajectory and target overshoot. In the slow-accurate condition, we reason that the cerebellar subjects may use a decomposition strategy so as to simplify the movement and not have to control both joints simultaneously. From these results, we suggest that a major role of the cerebellum is in generating muscle torques at a joint that will predict the interaction torques being generated by other moving joints and compensate for them as they occur.

Design and Experimental Validation for Direct-Drive Fault-Tolerant Permanent-Magnet Vernier Machines

PubMed Central

Liu, Guohai; Yang, Junqin; Chen, Ming; Chen, Qian

2014-01-01

A fault-tolerant permanent-magnet vernier (FT-PMV) machine is designed for direct-drive applications, incorporating the merits of high torque density and high reliability. Based on the so-called magnetic gearing effect, PMV machines have the ability of high torque density by introducing the flux-modulation poles (FMPs). This paper investigates the fault-tolerant characteristic of PMV machines and provides a design method, which is able to not only meet the fault-tolerant requirements but also keep the ability of high torque density. The operation principle of the proposed machine has been analyzed. The design process and optimization are presented specifically, such as the combination of slots and poles, the winding distribution, and the dimensions of PMs and teeth. By using the time-stepping finite element method (TS-FEM), the machine performances are evaluated. Finally, the FT-PMV machine is manufactured, and the experimental results are presented to validate the theoretical analysis. PMID:25045729

Electromagnetic induced voltage signal to magnetic variation through torquing textured Fe81Ga19 alloy

NASA Astrophysics Data System (ADS)

Li, Mingming; Li, Jiheng; Bao, Xiaoqian; Mu, Xing; Gao, Xuexu

2017-07-01

The results of a study on the suitability of Fe-Ga alloys for torque sensor applications are presented. A Fe81Ga19 rod with a ⟨100⟩ preferred orientation along the length direction is prepared for the torque shaft and as the electromagnetic induction sensitive element, which is wound with three coils for signal excitation, signal pickup, and applied bias magnetic field, respectively. An apparent decrease in the induced voltage signal (peak voltage) of 3.88 mV is observed as the torque loading is 50 N m in the presence of a sine excitation signal (10 V, 1 kHz) and a bias current of 0.5 A. Meanwhile, a good repeatability and stress sensitivity are obtained, especially in the low torque range. These behaviors stem from the stress induced decrease in the magnetic permeability and the rotation of the arranged magnetic moment. Here, we use the Fe81Ga19 alloy as the shaft material; nevertheless, in practical use, the same effect can be achieved by forming a Fe-Ga layer with large magnetostriction on the surface of the torsion shaft. This work shows the prospect of Fe-Ga alloys for non-contact torque sensing, for the large magnetostriction and high sensitivity of magnetization to stress.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Z. X.; Tynan, G.; Center for Momentum Transport and Flow Organization and Center for Astrophysics and Space Science, University of California, San Diego, California 92093

Intrinsic torque, which can be generated by turbulent stresses, can induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals in intrinsic torque have been inferred from the observation of toroidal velocity changes in recent lower hybrid current drive (LHCD) experiments. This work focuses on understanding the cause of LHCD-induced intrinsic torque reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for the intrinsic torque reversal linked to magnetic shear (s{sup ^}) effects on the turbulence spectrum is identified. This reversal is a consequence of the ballooning structure at weak s{sup ^}. Based on realisticmore » profiles from the Alcator C-Mod LHCD experiments, simulations demonstrate that the intrinsic torque reverses for weak s{sup ^} discharges and that the value of s{sup ^}{sub crit} is consistent with the experimental results s{sup ^}{sub crit}{sup exp}≈0.2∼0.3 [Rice et al., Phys. Rev. Lett. 111, 125003 (2013)]. The consideration of this intrinsic torque feature in our work is important for the understanding of rotation profile generation at weak s{sup ^} and its consequent impact on macro-instability stabilization and micro-turbulence reduction, which is crucial for ITER. It is also relevant to internal transport barrier formation at negative or weakly positive s{sup ^}.« less

Adaptive control schemes for improving dynamic performance of efficiency-optimized induction motor drives.

PubMed

Kumar, Navneet; Raj Chelliah, Thanga; Srivastava, S P

2015-07-01

Model Based Control (MBC) is one of the energy optimal controllers used in vector-controlled Induction Motor (IM) for controlling the excitation of motor in accordance with torque and speed. MBC offers energy conservation especially at part-load operation, but it creates ripples in torque and speed during load transition, leading to poor dynamic performance of the drive. This study investigates the opportunity for improving dynamic performance of a three-phase IM operating with MBC and proposes three control schemes: (i) MBC with a low pass filter (ii) torque producing current (iqs) injection in the output of speed controller (iii) Variable Structure Speed Controller (VSSC). The pre and post operation of MBC during load transition is also analyzed. The dynamic performance of a 1-hp, three-phase squirrel-cage IM with mine-hoist load diagram is tested. Test results are provided for the conventional field-oriented (constant flux) control and MBC (adjustable excitation) with proposed schemes. The effectiveness of proposed schemes is also illustrated for parametric variations. The test results and subsequent analysis confer that the motor dynamics improves significantly with all three proposed schemes in terms of overshoot/undershoot peak amplitude of torque and DC link power in addition to energy saving during load transitions. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Existing machine propulsion is transformed by state-of-the-art gearbox apparatus saves at least 50% energy

NASA Astrophysics Data System (ADS)

Abramov, V.

2013-12-01

This innovation on www.repowermachine.com is finalist at Clean-tech and Energy of 2012 Minnesota's TEKNE AWARDS. Vehicles are pushed by force of friction between their wheels and land, propellers and water or air according to Third Newton's law of physics of moving. Force of friction is dependent to vehicle weight as highest torque of wheel or propeller for vehicle moving from stop. Friction force DOES NOT dependent to motor power. Why existing SUV of 2,000 lb uses 550 hp motor when first vehicle has 0.75 hp motor (Carl Benz';s patent #37435, January 29, 1886 in Germany)? Gas or magnet field reaches needed torque of wheels too slowly because requires huge motor power for acceleration SUV from 0 to 100 mph for 5 second. The acceleration system by gas or magnet field uses additional energy for increasing motor shaft idle speed and reduces its highest torque of physical volume because necessary to increase motor power that equal/exceed motor power according to vehicle weight. Therefore, any transmission torque DOES NOT NEED and it is use as second brake. Ship, locomotives, helicopters, CNC machine tools, etc motor(s) directly turn wheels, propellers, spindles or ignore to use gear -transmission designs. How do you follow to Creator's physics law of LEVER for saving energy? Existing machine propulsion is transformed by one comprising least numbers of gears and maybe shafts from above state-of-the-art 1,000 gearbox apparatus designs. It is installed or replaced transmission in existing propulsion that is transformed to non-accelerated propulsion. It cuts about 80% mechanical energy that acceleration system wastes in motor heat form, cuts time of movement by reaching each speed for 1-2 seconds. It produces all needed speeds and uses only idle speed of cheapest motor with reduced power and cost that have replaced existing motor too. There is opportunity to eliminate vehicle/machine roads traffics in cities that creates additional unknown GHG emissions Revolutionary methods capability to create 144 forward/72 reverse torque/overdrive speeds by one gear less than heavy-duty truck gearbox of 18 forward/2 reverse torque plus 10 compound gearboxes for vehicle maneuverability improvement. It capability to reduce size of motor up to 5x5x5x5x5x5=15,625 times by 7 shafts !!! Therefore, SUV non-accelerated propulsion comprising GAEES of 24 overdrive speeds that uses 20 hp motor idle speed only or torque that will be sufficient to move this SUV from stop. HEAVY-DUTY TRUCK: Chosen GAEEF of 36 torques/overdrive and 18 reverse speeds by 20 gears/5 shafts (in comparison to its 18 torques/2 reverse by 29 gears/4 shafts) reduces heavy-duty truck motor power from 400 hp to 50 hp. It increases energy economy in 400/50=8 times!!! PABLIC TRANSPORTATION: Existing cruise ship/locomotive with chosen GAEES of 64 torques/overdrive speeds and 32 reverse speeds by 22 gears/7 shafts that provide to reduce from 3000 hp to 200 hp for energy economy in 3000/200=15 times!!!

Biomechanical loading on the upper extremity increases from single key tapping to directional tapping.

PubMed

Qin, Jin; Trudeau, Matthieu; Katz, Jeffrey N; Buchholz, Bryan; Dennerlein, Jack T

2011-08-01

Musculoskeletal disorders associated with computer use span the joints of the upper extremity. Computing typically involves tapping in multiple directions. Thus, we sought to describe the loading on the finger, wrist, elbow and shoulder joints in terms of kinematic and kinetic difference across single key switch tapping to directional tapping on multiple keys. An experiment with repeated measures design was conducted. Six subjects tapped with their right index finger on a stand-alone number keypad placed horizontally in three conditions: (1) on single key switch (the number key 5); (2) left and right on number key 4 and 6; (3) top and bottom on number key 8 and 2. A force-torque transducer underneath the keypad measured the fingertip force. An active-marker infrared motion analysis system measured the kinematics of the fingertip, hand, forearm, upper arm and torso. Joint moments for the metacarpophalangeal, wrist, elbow, and shoulder joints were estimated using inverse dynamics. Tapping in the top-bottom orientation introduced the largest biomechanical loading on the upper extremity especially for the proximal joint, followed by tapping in the left-right orientation, and the lowest loading was observed during single key switch tapping. Directional tapping on average increased the fingertip force, joint excursion, and peak-to-peak joint torque by 45%, 190% and 55%, respectively. Identifying the biomechanical loading patterns associated with these fundamental movements of keying improves the understanding of the risks of upper extremity musculoskeletal disorders for computer keyboard users. Copyright © 2010 Elsevier Ltd. All rights reserved.

Direct current modulation of spin-Hall-induced spin torque ferromagnetic resonance in platinum/permalloy bilayer thin films

NASA Astrophysics Data System (ADS)

Hirayama, Shigeyuki; Mitani, Seiji; Otani, YoshiChika; Kasai, Shinya

2018-06-01

We examined the spin-Hall-induced spin torque ferromagnetic resonance (ST-FMR) in platinum/permalloy bilayer thin films under bias direct current (DC). The bias DC modulated the symmetric components of the ST-FMR spectra, while no dominant modulation was found in the antisymmetric components. A detailed analysis in combination with simple model calculations clarified that the major origin of the modulation can be attributed to the DC resistance change under the precessional motion of magnetization. This effect is the second order contribution for the precession angle, even though the contribution can be comparable to the rectification voltage under some specific conditions.

Direct measurement of torque and twist generated by a dye binding to DNA

NASA Astrophysics Data System (ADS)

Gore, Jeff; Bryant, Zev; Bustamante, Carlos

2004-03-01

Many biologically important chemicals and proteins change the twist of DNA upon binding. We have used magnetic tweezers to directly measure the torque and twist generated when ethidium bromide binds and unbinds to DNA. One end of the DNA is bound specifically to a glass coverslip and the opposite end is held away from the surface by a paramagnetic bead. Attached to the middle of the DNA is a second fluorescent bead whose position can be tracked with high angular and temporal resolution. On one side of the fluorescent bead binding site we have engineered a single strand nick that acts like a free swivel. Addition of ethidium bromide then powered rotation of the central fluorescent bead. After the ethidium bromide was bound we used magnesium to compete out the intercalated ethidium bromide, thus inducing a rotation in the opposite direction. We studied the torque generation, energetics, and kinetics associated with ethidium bromide binding and unbinding by tracking the rotation of the fluorescent bead. This system is a demonstration of a reversible chemically powered DNA-based rotary motor. We also expect that this technique will be useful in studying proteins that bind to or rotate DNA, including recA, polymerases, and topoisomerases.

Dual-rotor, radial-flux, toroidally-wound, permanent-magnet machine

DOEpatents

Qu, Ronghai; Lipo, Thomas A.

2005-08-02

The present invention provides a novel dual-rotor, radial-flux, toroidally-wound, permanent-magnet machine. The present invention improves electrical machine torque density and efficiency. At least one concentric surface-mounted permanent magnet dual-rotor is located inside and outside of a torus-shaped stator with back-to-back windings, respectively. The machine substantially improves machine efficiency by reducing the end windings and boosts the torque density by at least doubling the air gap and optimizing the machine aspect ratio.

Posterior Tibial Slope Angle Correlates With Peak Sagittal and Frontal Plane Knee Joint Loading During Robotic Simulations of Athletic Tasks.

PubMed

Bates, Nathaniel A; Nesbitt, Rebecca J; Shearn, Jason T; Myer, Gregory D; Hewett, Timothy E

2016-07-01

Tibial slope angle is a nonmodifiable risk factor for anterior cruciate ligament (ACL) injury. However, the mechanical role of varying tibial slopes during athletic tasks has yet to be clinically quantified. To examine the influence of posterior tibial slope on knee joint loading during controlled, in vitro simulation of the knee joint articulations during athletic tasks. Descriptive laboratory study. A 6 degree of freedom robotic manipulator positionally maneuvered cadaveric knee joints from 12 unique specimens with varying tibial slopes (range, -7.7° to 7.7°) through drop vertical jump and sidestep cutting tasks that were derived from 3-dimensional in vivo motion recordings. Internal knee joint torques and forces were recorded throughout simulation and were linearly correlated with tibial slope. The mean (±SD) posterior tibial slope angle was 2.2° ± 4.3° in the lateral compartment and 2.3° ± 3.3° in the medial compartment. For simulated drop vertical jumps, lateral compartment tibial slope angle expressed moderate, direct correlations with peak internally generated knee adduction (r = 0.60-0.65), flexion (r = 0.64-0.66), lateral (r = 0.57-0.69), and external rotation torques (r = 0.47-0.72) as well as inverse correlations with peak abduction (r = -0.42 to -0.61) and internal rotation torques (r = -0.39 to -0.79). Only frontal plane torques were correlated during sidestep cutting simulations. For simulated drop vertical jumps, medial compartment tibial slope angle expressed moderate, direct correlations with peak internally generated knee flexion torque (r = 0.64-0.69) and lateral knee force (r = 0.55-0.74) as well as inverse correlations with peak external torque (r = -0.34 to -0.67) and medial knee force (r = -0.58 to -0.59). These moderate correlations were also present during simulated sidestep cutting. The investigation supported the theory that increased posterior tibial slope would lead to greater magnitude knee joint moments, specifically, internally generated knee adduction and flexion torques. The knee torques that positively correlated with increased tibial slope angle in this investigation are associated with heightened risk of ACL injury. Therefore, the present data indicated that a higher posterior tibial slope is correlated to increased knee loads that are associated with heightened risk of ACL injury. © 2016 The Author(s).

A High Performance Torque Sensor for Milling Based on a Piezoresistive MEMS Strain Gauge

PubMed Central

Qin, Yafei; Zhao, Yulong; Li, Yingxue; Zhao, You; Wang, Peng

2016-01-01

In high speed and high precision machining applications, it is important to monitor the machining process in order to ensure high product quality. For this purpose, it is essential to develop a dynamometer with high sensitivity and high natural frequency which is suited to these conditions. This paper describes the design, calibration and performance of a milling torque sensor based on piezoresistive MEMS strain. A detailed design study is carried out to optimize the two mutually-contradictory indicators sensitivity and natural frequency. The developed torque sensor principally consists of a thin-walled cylinder, and a piezoresistive MEMS strain gauge bonded on the surface of the sensing element where the shear strain is maximum. The strain gauge includes eight piezoresistances and four are connected in a full Wheatstone circuit bridge, which is used to measure the applied torque force during machining procedures. Experimental static calibration results show that the sensitivity of torque sensor has been improved to 0.13 mv/Nm. A modal impact test indicates that the natural frequency of torque sensor reaches 1216 Hz, which is suitable for high speed machining processes. The dynamic test results indicate that the developed torque sensor is stable and practical for monitoring the milling process. PMID:27070620

Mechanical torque measurement predicts load to implant cut-out: a biomechanical study investigating DHS anchorage in femoral heads.

PubMed

Suhm, Norbert; Hengg, Clemens; Schwyn, Ronald; Windolf, Markus; Quarz, Volker; Hänni, Markus

2007-08-01

Bone strength plays an important role in implant anchorage. Bone mineral density (BMD) is used as surrogate parameter to quantify bone strength and to predict implant anchorage. BMD can be measured by means of quantitative computer tomography (QCT) or dual energy X-ray absorptiometry (DXA). These noninvasive methods for BMD measurement are not available pre- or intra-operatively. Instead, the surgeon could determine bone strength by direct mechanical measurement. We have evaluated mechanical torque measurement for (A) its capability to quantify local bone strength and (B) its predictive value towards load at implant cut-out. Our experimental study was performed using sixteen paired human cadaver proximal femurs. BMD was determined for all specimens by QCT. The torque to breakaway of the cancellous bone structure (peak torque) was measured by means of a mechanical probe at the exact position of subsequent DHS placement. The fixation strength of the DHS achieved was assessed by cyclic loading in a stepwise protocol beginning with 1,500 N increasing 500 N every 5,000 cycles until 4,000 N. A highly significant correlation of peak torque with BMD (QCT) was found (r = 0.902, r (2) = 0.814, P < 0.001). Peak torque correlated highly significant with the load at implant cut-out (r = 0.795, P < 0.001). All specimens with a measured peak torque below 6.79 Nm failed at the first load level of 1,500 N. The specimens with a peak torque above 8.63 Nm survived until the last load level of 4,000 N. Mechanical peak torque measurement is able to quantify bone strength. In an experimental setup, peak torque identifies those specimens that are likely to fail at low load. In clinical routine, implant migration and cut-out depend on several parameters, which are difficult to control, such as fracture type, fracture reduction achieved, and implant position. The predictive value of peak torque towards cut-out in a clinical set-up therefore has to be carefully validated.

Development of a Scientific Basis for Analysis of Aircraft Seating Systems

DTIC Science & Technology

1975-01-01

JOINT MOVEMENTS IN NORMAL MALE HUMAN ADULTS, Human Biology , Vol. 9, pp. 197-211, 1937. 10. Brinkley, J. W., DEVELOPMENT OF AEROSPACE ESCAPE SYSTEMS...Resisting Torque 21 8 Human Joint Resisting Torques: (a) Displacement- Limiting Moment; (b) Muscular Resistance 22 9 Fxternal Forces of Cushions, Floor...head strike on rigid cockpit structure. Also, the relatively low tolerance of the human b.ody to accelerations in a direction parallel to the spine

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening.

PubMed

Rebeeah, Hanadi A; Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin; Clelland, Nancy; Brantley, William

2018-01-01

Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of the crown to the model. The crowns were tightened according to the manufacturers' specifications using a torque driver, and the cameras recorded their relative position again. Three-dimensional image correlation was used to measure and compare crown positions, first hand tightened and then torque driven. The displacement test was repeated 3 times for each crown. Commercial image correlation software was used to extract the data and compare the amount of displacement vertically, mesiodistally, and buccolingually. Repeated-measures ANOVA calculated the relative displacements for all 5 specimens for each implant for both crown screw hand tightening and after applied torque. A Student t test with Bonferroni correction was used for pairwise comparison of interest to determine statistical differences between the 2 implants (α=.05). The mean vertical displacements were statistically higher than the mean displacements in the mesiodistal and buccolingual directions for both implants (P<.001). Mean displacements in all directions were statistically significant between iterations for both implants (P<.001). No statistically significant differences were found for displacements between implants at different directions and at different iterations (P>.05). Within the limitations of this in vitro study, screw-retained zirconia crowns tended to displace in all 3 directions, with the highest mean displacement in the vertical direction at iteration 1. However, the amount of displacement of crowns between the 2 different implants was statistically insignificant for all directions and iterations. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Experimental investigations of forces and torque in conventional and ultrasonically-assisted drilling of cortical bone.

PubMed

Alam, K; Mitrofanov, A V; Silberschmidt, V V

2011-03-01

Bone drilling is widely used in orthopaedics and surgery; it is a technically demanding surgical procedure. Recent technological improvements in this area are focused on efforts to reduce forces in bone drilling. This study focuses on forces and a torque required for conventional and ultrasonically-assisted tool penetration into fresh bovine cortical bone. Drilling tests were performed with two drilling techniques, and the influence of drilling speed, feed rate and parameters of ultrasonic vibration on the forces and torque was studied. Ultrasonically-assisted drilling (UAD) was found to reduce a drilling thrust force and torque compared to conventional drilling (CD). The mechanism behind lower levels of forces and torque was explored, using high-speed filming of a drill-bone interaction zone, and was linked to the chip shape and character of its formation. It is expected that UAD will produce holes with minimal effort and avoid unnecessary damage and accompanying pain during the incision. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Cloud-based shaft torque estimation for electric vehicle equipped with integrated motor-transmission system

NASA Astrophysics Data System (ADS)

Zhu, Xiaoyuan; Zhang, Hui; Yang, Bo; Zhang, Guichen

2018-01-01

In order to improve oscillation damping control performance as well as gear shift quality of electric vehicle equipped with integrated motor-transmission system, a cloud-based shaft torque estimation scheme is proposed in this paper by using measurable motor and wheel speed signals transmitted by wireless network. It can help reduce computational burden of onboard controllers and also relief network bandwidth requirement of individual vehicle. Considering possible delays during signal wireless transmission, delay-dependent full-order observer design is proposed to estimate the shaft torque in cloud server. With these random delays modeled by using homogenous Markov chain, robust H∞ performance is adopted to minimize the effect of wireless network-induced delays, signal measurement noise as well as system modeling uncertainties on shaft torque estimation error. Observer parameters are derived by solving linear matrix inequalities, and simulation results using acceleration test and tip-in, tip-out test demonstrate the effectiveness of proposed shaft torque observer design.

Direct Measurement of Helical Cell Motion of the Spirochete Leptospira

PubMed Central

Nakamura, Shuichi; Leshansky, Alexander; Magariyama, Yukio; Namba, Keiichi; Kudo, Seishi

2014-01-01

Leptospira are spirochete bacteria distinguished by a short-pitch coiled body and intracellular flagella. Leptospira cells swim in liquid with an asymmetric morphology of the cell body; the anterior end has a long-pitch spiral shape (S-end) and the posterior end is hook-shaped (H-end). Although the S-end and the coiled cell body called the protoplasmic cylinder are thought to be responsible for propulsion together, most observations on the motion mechanism have remained qualitative. In this study, we analyzed the swimming speed and rotation rate of the S-end, protoplasmic cylinder, and H-end of individual Leptospira cells by one-sided dark-field microscopy. At various viscosities of media containing different concentrations of Ficoll, the rotation rate of the S-end and protoplasmic cylinder showed a clear correlation with the swimming speed, suggesting that these two helical parts play a central role in the motion of Leptospira. In contrast, the H-end rotation rate was unstable and showed much less correlation with the swimming speed. Forces produced by the rotation of the S-end and protoplasmic cylinder showed that these two helical parts contribute to propulsion at nearly equal magnitude. Torque generated by each part, also obtained from experimental motion parameters, indicated that the flagellar motor can generate torque >4000 pN nm, twice as large as that of Escherichia coli. Furthermore, the S-end torque was found to show a markedly larger fluctuation than the protoplasmic cylinder torque, suggesting that the unstable H-end rotation might be mechanically related to changes in the S-end rotation rate for torque balance of the entire cell. Variations in torque at the anterior and posterior ends of the Leptospira cell body could be transmitted from one end to the other through the cell body to coordinate the morphological transformations of the two ends for a rapid change in the swimming direction. PMID:24411236

Direct measurement of helical cell motion of the spirochete leptospira.

PubMed

Nakamura, Shuichi; Leshansky, Alexander; Magariyama, Yukio; Namba, Keiichi; Kudo, Seishi

2014-01-07

Leptospira are spirochete bacteria distinguished by a short-pitch coiled body and intracellular flagella. Leptospira cells swim in liquid with an asymmetric morphology of the cell body; the anterior end has a long-pitch spiral shape (S-end) and the posterior end is hook-shaped (H-end). Although the S-end and the coiled cell body called the protoplasmic cylinder are thought to be responsible for propulsion together, most observations on the motion mechanism have remained qualitative. In this study, we analyzed the swimming speed and rotation rate of the S-end, protoplasmic cylinder, and H-end of individual Leptospira cells by one-sided dark-field microscopy. At various viscosities of media containing different concentrations of Ficoll, the rotation rate of the S-end and protoplasmic cylinder showed a clear correlation with the swimming speed, suggesting that these two helical parts play a central role in the motion of Leptospira. In contrast, the H-end rotation rate was unstable and showed much less correlation with the swimming speed. Forces produced by the rotation of the S-end and protoplasmic cylinder showed that these two helical parts contribute to propulsion at nearly equal magnitude. Torque generated by each part, also obtained from experimental motion parameters, indicated that the flagellar motor can generate torque >4000 pN nm, twice as large as that of Escherichia coli. Furthermore, the S-end torque was found to show a markedly larger fluctuation than the protoplasmic cylinder torque, suggesting that the unstable H-end rotation might be mechanically related to changes in the S-end rotation rate for torque balance of the entire cell. Variations in torque at the anterior and posterior ends of the Leptospira cell body could be transmitted from one end to the other through the cell body to coordinate the morphological transformations of the two ends for a rapid change in the swimming direction. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Improved lower extremity pedaling mechanics in individuals with stroke under maximal workloads.

PubMed

Linder, Susan M; Rosenfeldt, Anson B; Bazyk, Andrew S; Koop, Mandy Miller; Ozinga, Sarah; Alberts, Jay L

2018-05-01

Background Individuals with stroke present with motor control deficits resulting in the abnormal activation and timing of agonist and antagonist muscles and inefficient movement patterns. The analysis of pedaling biomechanics provides a window into understanding motor control deficits, which vary as a function of workload. Understanding the relationship between workload and motor control is critical when considering exercise prescription during stroke rehabilitation. Objectives To characterize pedaling kinematics and motor control processes under conditions in which workload was systematically increased to an eventual patient-specific maximum. Methods A cohort study was conducted in which 18 individuals with chronic stroke underwent a maximal exertion cardiopulmonary exercise test on a stationary cycle ergometer, during which pedaling torque was continuously recorded. Measures of force production, pedaling symmetry, and pedaling smoothness were obtained. Results Mean Torque increased significantly (p < 0.05) for both legs from initial to terminal workloads. Mean torque Symmetry Index, calculated for down and upstroke portions of the pedaling action, improved from 0.37(0.29) to 0.29(0.35) during downstroke (p = 0.007), and worsened during the upstroke: -0.37(0.38) to -0.62(0.46) (p < 0.001) from initial to terminal workloads. Low Torque Duration improved from initial to terminal workloads, decreasing from 121.1(52.9) to 58.1(39.6) degrees (p < 0.001), respectively. Smoothness of pedaling improved significantly from initial to terminal workloads (p < 0.001). Conclusions Improved pedaling kinematics at terminal workloads indicate that individuals with stroke demonstrate improved motor control with respect to the timing, sequencing, and activation of hemiparetic lower extremity musculature compared to lower workloads. Therapeutic prescription involving higher resistance may be necessary to sufficiently engage and activate the paretic lower extremity.

Improving the transparency of a rehabilitation robot by exploiting the cyclic behaviour of walking.

PubMed

van Dijk, W; van der Kooij, H; Koopman, B; van Asseldonk, E H F; van der Kooij, H

2013-06-01

To promote active participation of neurological patients during robotic gait training, controllers, such as "assist as needed" or "cooperative control", are suggested. Apart from providing support, these controllers also require that the robot should be capable of resembling natural, unsupported, walking. This means that they should have a transparent mode, where the interaction forces between the human and the robot are minimal. Traditional feedback-control algorithms do not exploit the cyclic nature of walking to improve the transparency of the robot. The purpose of this study was to improve the transparent mode of robotic devices, by developing two controllers that use the rhythmic behavior of gait. Both controllers use adaptive frequency oscillators and kernel-based non-linear filters. Kernelbased non-linear filters can be used to estimate signals and their time derivatives, as a function of the gait phase. The first controller learns the motor angle, associated with a certain joint angle pattern, and acts as a feed-forward controller to improve the torque tracking (including the zero-torque mode). The second controller learns the state of the mechanical system and compensates for the dynamical effects (e.g. the acceleration of robot masses). Both controllers have been tested separately and in combination on a small subject population. Using the feedforward controller resulted in an improved torque tracking of at least 52 percent at the hip joint, and 61 percent at the knee joint. When both controllers were active simultaneously, the interaction power between the robot and the human leg was reduced by at least 40 percent at the thigh, and 43 percent at the shank. These results indicate that: if a robotic task is cyclic, the torque tracking and transparency can be improved by exploiting the predictions of adaptive frequency oscillator and kernel-based nonlinear filters.

Transcutaneous electrical nerve stimulation combined with task-related training improves lower limb functions in subjects with chronic stroke.

PubMed

Ng, Shamay S M; Hui-Chan, Christina W Y

2007-11-01

Previous studies have shown that repeated sensory inputs could enhance brain plasticity and cortical motor output. The purpose of this study was to investigate whether combining electrically induced sensory inputs through transcutaneous electrical nerve stimulation (TENS) with task-related training (TRT) in a home-based program would augment voluntary motor output in chronic stroke survivors better than either treatment alone or no treatment. Eighty-eight patients with stroke were assigned randomly to receive a home-based program of (1) TENS, (2) TENS+TRT, (3) placebo TENS+TRT, or (4) no treatment (control) 5 days a week for 4 weeks. Outcome measurements included Composite Spasticity Scale, peak torques generated during maximum isometric voluntary contraction of ankle dorsiflexors and plantarflexors, and gait velocity recorded at baseline, after 2 and 4 weeks of treatment, and 4 weeks after treatment ended. When compared with TENS, the combined TENS+TRT group showed significantly greater improvement in ankle dorsiflexion torque at follow-up and in ankle plantarflexion torque at week 2 and follow-up (P<0.01). When compared with placebo+TRT, the TENS+TRT group produced earlier and greater reduction of plantarflexor spasticity and improvement in ankle dorsiflexion torque at week 2 (P<0.01). When compared with all 3 groups, the TENS+TRT group showed significantly greater improvement in gait velocity (P<0.01). In patients with chronic stroke, 20 sessions of a combined TENS+TRT home-based program decreased plantarflexor spasticity, improved dorsiflexor and plantarflexor strength, and increased gait velocity significantly more than TENS alone, placebo+TRT, or no treatment. Such improvements can even be maintained 4 weeks after treatment ended.

40 CFR 1039.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Code of Federal Regulations, 2013 CFR

2013-07-01

.... You may extend the sampling time to improve measurement accuracy of PM emissions, using good..., you may omit speed, torque, and power points from the duty-cycle regression statistics if the... mapped. (2) For variable-speed engines without low-speed governors, you may omit torque and power points...

40 CFR 1039.505 - How do I test engines using steady-state duty cycles, including ramped-modal testing?

Code of Federal Regulations, 2012 CFR

2012-07-01

.... You may extend the sampling time to improve measurement accuracy of PM emissions, using good..., you may omit speed, torque, and power points from the duty-cycle regression statistics if the... mapped. (2) For variable-speed engines without low-speed governors, you may omit torque and power points...

Locking design affects the jamming of screws in locking plates.

PubMed

Sandriesser, Sabrina; Rupp, Markus; Greinwald, Markus; Heiss, Christian; Augat, Peter; Alt, Volker

2018-06-01

The seizing of locking screws is a frequently encountered clinical problem during implant removal of locking compression plates (LCP) after completion of fracture healing. The aim of this study was to investigate the effect of two different locking mechanisms on the seizing of locking screws. Specifically, the removal torques before and after cyclic dynamic loading were assessed for screws inserted at the manufacturer-recommended torque or at an increased insertion torque. The seizing of 3.5-mm angular stable screws was assessed as a function of insertion torque for two different locking mechanisms (Thread & Conus and Thread Only). Locking screws (n=10 for each configuration) were inserted either according to the manufacturer-recommended torque or at an increased torque of 150% to simulate an over-insertion of the screw. Half of the screws were removed directly after insertion and the remaining half was removed after a dynamic load protocol of 100,000 cycles. The removal torques of locking screws exceeded the insertion torques for all tested conditions confirming the adequacy of the test setup in mimicking screw seizing in locked plating. Screw seizing was more pronounced for Thread Only design (+37%) compared to Thread & Conus design (+14%; P<0.0001). Cyclic loading of the locking construct consistently resulted in an increased seizing of the locking screws (P<0.0001). Clinical observations from patients treated with the Thread & Conus locking design confirm the biomechanical findings of reduction in seizing effect by using a Thread & Conus design. In conclusion, both over-tightening and cyclic loading are potential causes for screw seizing in locking plate implants. Both effects were found to be less pronounced in the Thread & Conus design as compared to the traditional Thread Only design. © 2018 Elsevier Ltd. All rights reserved.

EFFECT OF AXIAL TIBIAL TORQUE DIRECTION ON ACL RELATIVE STRAIN AND STRAIN RATE IN AN IN VITRO SIMULATED PIVOT LANDING

PubMed Central

Oh, Youkeun K.; Kreinbrink, Jennifer L.; Wojtys, Edward M.; Ashton-Miller, James A.

2011-01-01

Anterior cruciate ligament (ACL) injuries most frequently occur under the large loads associated with a unipedal jump landing involving a cutting or pivoting maneuver. We tested the hypotheses that internal tibial torque would increase the anteromedial (AM) bundle ACL relative strain and strain rate more than would the corresponding external tibial torque under the large impulsive loads associated with such landing maneuvers. Twelve cadaveric female knees [mean (SD) age: 65.0 (10.5) years] were tested. Pretensioned quadriceps, hamstring and gastrocnemius muscle-tendon unit forces maintained an initial knee flexion angle of 15°. A compound impulsive test load (compression, flexion moment and internal or external tibial torque) was applied to the distal tibia while recording the 3-D knee loads and tibofemoral kinematics. AM-ACL relative strain was measured using a 3mm DVRT. In this repeated measures experiment, the Wilcoxon Signed-Rank test was used to test the null hypotheses with p<0.05 considered significant. The mean (± SD) peak AM-ACL relative strains were 5.4±3.7 % and 3.1±2.8 % under internal and external tibial torque, respectively. The corresponding mean (± SD) peak AM-ACL strain rates reached 254.4±160.1 %/sec and 179.4±109.9 %/sec, respectively. The hypotheses were supported in that the normalized mean peak AM-ACL relative strain and strain rate were 70% and 42% greater under internal than external tibial torque, respectively (p=0.023, p=0.041). We conclude that internal tibial torque is a potent stressor of the ACL because it induces a considerably (70%) larger peak strain in the AM-ACL than does a corresponding external tibial torque. PMID:22025178

An optimized BP neural network based on genetic algorithm for static decoupling of a six-axis force/torque sensor

NASA Astrophysics Data System (ADS)

Fu, Liyue; Song, Aiguo

2018-02-01

In order to improve the measurement precision of 6-axis force/torque sensor for robot, BP decoupling algorithm optimized by GA (GA-BP algorithm) is proposed in this paper. The weights and thresholds of a BP neural network with 6-10-6 topology are optimized by GA to develop decouple a six-axis force/torque sensor. By comparison with other traditional decoupling algorithm, calculating the pseudo-inverse matrix of calibration and classical BP algorithm, the decoupling results validate the good decoupling performance of GA-BP algorithm and the coupling errors are reduced.

A Comprehensive Review of Permanent Magnet Transverse Flux Machines for Direct Drive Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Husain, Tausif; Hasan, Iftekhar

The use of direct drive machines in renewable and industrial applications are increasing at a rapid rate. Transverse flux machines (TFM) are ideally suited for direct drive applications due to their high torque density. In this paper, a comprehensive review of the permanent magnet (PM) TFMs for direct drive applications is presented. The paper introduces TFMs and their operating principle and then reviews the different type of TFMs proposed in the literature. The TFMs are categorized according to the number of stator sides, types of stator cores and magnet arrangement in the rotor. The review covers different design topologies, materialsmore » used for manufacturing, structural and thermal analysis, modeling and design optimization and cogging torque minimization in TFMs. The paper also reviews various applications and comparisons for TFMs that have been presented in the literature.« less

Evoked EMG-based torque prediction under muscle fatigue in implanted neural stimulation

NASA Astrophysics Data System (ADS)

Hayashibe, Mitsuhiro; Zhang, Qin; Guiraud, David; Fattal, Charles

2011-10-01

In patients with complete spinal cord injury, fatigue occurs rapidly and there is no proprioceptive feedback regarding the current muscle condition. Therefore, it is essential to monitor the muscle state and assess the expected muscle response to improve the current FES system toward adaptive force/torque control in the presence of muscle fatigue. Our team implanted neural and epimysial electrodes in a complete paraplegic patient in 1999. We carried out a case study, in the specific case of implanted stimulation, in order to verify the corresponding torque prediction based on stimulus evoked EMG (eEMG) when muscle fatigue is occurring during electrical stimulation. Indeed, in implanted stimulation, the relationship between stimulation parameters and output torques is more stable than external stimulation in which the electrode location strongly affects the quality of the recruitment. Thus, the assumption that changes in the stimulation-torque relationship would be mainly due to muscle fatigue can be made reasonably. The eEMG was proved to be correlated to the generated torque during the continuous stimulation while the frequency of eEMG also decreased during fatigue. The median frequency showed a similar variation trend to the mean absolute value of eEMG. Torque prediction during fatigue-inducing tests was performed based on eEMG in model cross-validation where the model was identified using recruitment test data. The torque prediction, apart from the potentiation period, showed acceptable tracking performances that would enable us to perform adaptive closed-loop control through implanted neural stimulation in the future.

Acceleration and torque feedback for robotic control - Experimental results

NASA Technical Reports Server (NTRS)

Mclnroy, John E.; Saridis, George N.

1990-01-01

Gross motion control of robotic manipulators typically requires significant on-line computations to compensate for nonlinear dynamics due to gravity, Coriolis, centripetal, and friction nonlinearities. One controller proposed by Luo and Saridis avoids these computations by feeding back joint acceleration and torque. This study implements the controller on a Puma 600 robotic manipulator. Joint acceleration measurement is obtained by measuring linear accelerations of each joint, and deriving a computationally efficient transformation from the linear measurements to the angular accelerations. Torque feedback is obtained by using the previous torque sent to the joints. The implementation has stability problems on the Puma 600 due to the extremely high gains inherent in the feedback structure. Since these high gains excite frequency modes in the Puma 600, the algorithm is modified to decrease the gain inherent in the feedback structure. The resulting compensator is stable and insensitive to high frequency unmodeled dynamics. Moreover, a second compensator is proposed which uses acceleration and torque feedback, but still allows nonlinear terms to be fed forward. Thus, by feeding the increment in the easily calculated gravity terms forward, improved responses are obtained. Both proposed compensators are implemented, and the real time results are compared to those obtained with the computed torque algorithm.

Mechanics of torque generation in the bacterial flagellar motor

PubMed Central

Mandadapu, Kranthi K.; Nirody, Jasmine A.; Berry, Richard M.; Oster, George

2015-01-01

The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual “power stroke.” Specifically, we propose that ion-induced conformational changes about a proline “hinge” residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque–speed and speed–ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator. PMID:26216959

Ultrasonic resonant piezoelectric actuator with intrinsic torque measurement.

PubMed

Pott, Peter P; Matich, Sebastian; Schlaak, Helmut F

2012-11-01

Piezoelectric ultrasonic actuators are widely used in small-scale actuation systems, in which a closed-loop position control is usually utilized. To save an additional torque sensor, the intrinsic measurement capabilities of the piezoelectric material can be employed. To prove feasibility, a motor setup with clearly separated actuation for the friction and driving forces is chosen. The motor concept is based on resonant ultrasonic vibrations. To assess the effects of the direct piezoelectric effect, a capacitance bridge-type circuit has been selected. Signal processing is done by a measurement card with an integrated field-programmable gate array. The motor is used to drive a winch, and different torques are applied by means of weights to be lifted. Assessing the bridge voltage, a good proportionality to the applied torque of 1.47 mV/mN·m is shown. A hysteresis of 1% has been determined. The chosen motor concept is useful for intrinsic torque measurement. However, it provides drawbacks in terms of limited mechanical performance, wear, and thermal losses because of the soft piezoelectric material. Future work will comprise the application of the method to commercially available piezoelectric actuators as well as the implementation of the measurement circuit in an embedded system.

Apparatus and method for non-invasive diagnosis and control of motor operated valve condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyon, R.H.; Chai, J.; Lang, J.H.

1997-01-14

An apparatus compares the torque from an MOV motor with the valve displacement, and from the comparison assesses MOV operating condition. A transducer measures the vibration of the housing of an MOV. The vibrations are due to the motions of the rotating elements within the housing, which motions are directly related to the motion of the valve relative to its seat. Signal processing apparatus analyzes the vibrations to recover the rotations of the rotating elements and thus the motion of the valve plug. Lost motion can also be determined (if a lost motion connection exists) by demodulating the vibration signalmore » and thus taking into account also the lost motion. Simultaneously, the forces applied to the valve are estimated by estimating the torque between the stator and the rotor of the motor. Such torque can be estimated from measuring the input current and voltage alone, using a forgetting factor and a correction for the forgetting factor. A signature derived from relating the torque to the valve position can be used to assess the condition of the MOV, by comparing the signature to signatures for MOVs of known conditions. The vibration analysis components generate signals that relate to the position of elements in the operator. Similarly, the torque estimator estimates the torque output by any type of electric motor, whether or not part of an MOV analysis unit. 28 figs.« less

Apparatus and method for non-invasive diagnosis and control of motor operated valve condition

DOEpatents

Lyon, R.H.; Chai, J.; Lang, J.H.; Hagman, W.H.; Umans, S.D.; Saarela, O.J.

1997-01-14

An apparatus compares the torque from an MOV motor with the valve displacement, and from the comparison assesses MOV operating condition. A transducer measures the vibration of the housing of an MOV. The vibrations are due to the motions of the rotating elements within the housing, which motions are directly related to the motion of the valve relative to its seat. Signal processing apparatus analyzes the vibrations to recover the rotations of the rotating elements and thus the motion of the valve plug. Lost motion can also be determined (if a lost motion connection exists) by demodulating the vibration signal and thus taking into account also the lost motion. Simultaneously, the forces applied to the valve are estimated by estimating the torque between the stator and the rotor of the motor. Such torque can be estimated from measuring the input current and voltage alone, using a forgetting factor and a correction for the forgetting factor. A signature derived from relating the torque to the valve position can be used to assess the condition of the MOV, by comparing the signature to signatures for MOVs of known conditions. The vibration analysis components generate signals that relate to the position of elements in the operator. Similarly, the torque estimator estimates the torque output by any type of electric motor, whether or not part of an MOV analysis unit. 28 figs.

Apparatus and method for non-invasive diagnosis and control of motor operated valve condition

DOEpatents

Lyon, Richard H.; Chai, Jangbom; Lang, Jeffrey H.; Hagman, Wayne H.; Umans, Stephen D.; Saarela, Olli J.

1997-01-01

An apparatus compares the torque from an MOV motor with the valve displacement, and from the comparison assesses MOV operating condition. A transducer measures the vibration of the housing of an MOV. The vibrations are due to the motions of the rotating elements within the housing, which motions are directly related to the motion of the valve relative to its seat. Signal processing apparatus analyzes the vibrations to recover the rotations of the rotating elements and thus the motion of the valve plug. Lost motion can also be determined (if a lost motion connection exists) by demodulating the vibration signal and thus taking into account also the lost motion. Simultaneously, the forces applied to the valve are estimated by estimating the torque between the stator and the rotor of the motor. Such torque can be estimated from measuring the input current and voltage alone, using a forgetting factor and a correction for the forgetting factor. A signature derived from relating the torque to the valve position can be used to assess the condition of the MOV, by comparing the signature to signatures for MOVs of known conditions. The vibration analysis components generate signals that relate to the position of elements in the operator. Similarly, the torque estimator estimates the torque output by any type of electric motor, whether or not part of an MOV analysis unit.

Measurement of plastic and elastic deformation due to third-order torque in self-ligated orthodontic brackets.

PubMed

Major, Thomas W; Carey, Jason P; Nobes, David S; Heo, Giseon; Major, Paul W

2011-09-01

Control of root torque is often achieved by introducing a twist in a rectangular archwire. The purpose of this study was to investigate third-order torque on different types of self-ligated brackets by analyzing the bracket's elastic and plastic deformations in conjunction with the expressed torque at varying angles of twist. An orthodontic bracket was mounted to a load cell that measured forces and moments in all directions. The wire was twisted in the bracket via a stepper motor, controlled by custom software. Overhead images were taken by a camera through a microscope and processed by using optical correlation to measure deformation. At the maximum torquing angle of 63° with 0.019 × 0.025-in stainless steel wire, the total elastic and plastic deformation values were 0.063, 0.033, and 0.137 mm for Damon Q (Ormco, Orange, Calif), In-Ovation R (GAC, Bohemia, NY), and Speed (Strite Industries, Cambridge, Ontario, Canada), respectively. The total plastic deformation values were 0.015, 0.006, and 0.086 mm, respectively, measured at 0° of unloading. In-Ovation R had the least deformation due to torquing of the 3 investigated bracket types. Damon Q and Speed on average had approximately 2.5 and 14 times greater maximum plastic deformation, respectively, than did In-Ovation R. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Role of the DELSEED Loop in Torque Transmission of F1-ATPase

PubMed Central

Tanigawara, Mizue; Tabata, Kazuhito V.; Ito, Yuko; Ito, Jotaro; Watanabe, Rikiya; Ueno, Hiroshi; Ikeguchi, Mitsunori; Noji, Hiroyuki

2012-01-01

F1-ATPase is an ATP-driven rotary motor that generates torque at the interface between the catalytic β-subunits and the rotor γ-subunit. The β-subunit inwardly rotates the C-terminal domain upon nucleotide binding/dissociation; hence, the region of the C-terminal domain that is in direct contact with γ—termed the DELSEED loop—is thought to play a critical role in torque transmission. We substituted all the DELSEED loop residues with alanine to diminish specific DELSEED loop-γ interactions and with glycine to disrupt the loop structure. All the mutants rotated unidirectionally with kinetic parameters comparable to those of the wild-type F1, suggesting that the specific interactions between DELSEED loop and γ is not involved in cooperative interplays between the catalytic β-subunits. Glycine substitution mutants generated half the torque of the wild-type F1, whereas the alanine mutant generated comparable torque. Fluctuation analyses of the glycine/alanine mutants revealed that the γ-subunit was less tightly held in the α3β3-stator ring of the glycine mutant than in the wild-type F1 and the alanine mutant. Molecular dynamics simulation showed that the DELSEED loop was disordered by the glycine substitution, whereas it formed an α-helix in the alanine mutant. Our results emphasize the importance of loop rigidity for efficient torque transmissions. PMID:23009846

Anomalous modulation of spin torque-induced ferromagnetic resonance caused by direct currents in permalloy/platinum bilayer thin films

NASA Astrophysics Data System (ADS)

Hirayama, Shigeyuki; Mitani, Seiji; Otani, YoshiChika; Kasai, Shinya

2018-01-01

We systematically investigated the spin-torque ferromagnetic resonance (ST-FMR) in permalloy/Pt bilayer thin films under bias direct currents. According to the conventional ST-FMR theory, the half widths of the resonant peaks in the spectra can be modulated by bias currents, which give a reliable value of the spin injection efficiency of the spin Hall effect. On the other hand, the symmetric components of the spectra show an unexpected strong bias current dependence, while the asymmetric components are free from the modulation. These findings suggest that some contributions are missing in the ST-FMR analysis of the ferromagnetic/nonmagnetic metal bilayer thin films.

Analytical YORP torques model with an improved temperature distribution function

NASA Astrophysics Data System (ADS)

Breiter, S.; Vokrouhlický, D.; Nesvorný, D.

2010-01-01

Previous models of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect relied either on the zero thermal conductivity assumption, or on the solutions of the heat conduction equations assuming an infinite body size. We present the first YORP solution accounting for a finite size and non-radial direction of the surface normal vectors in the temperature distribution. The new thermal model implies the dependence of the YORP effect in rotation rate on asteroids conductivity. It is shown that the effect on small objects does not scale as the inverse square of diameter, but rather as the first power of the inverse.

Control techniques to improve Space Shuttle solid rocket booster separation

NASA Technical Reports Server (NTRS)

Tomlin, D. D.

1983-01-01

The present Space Shuttle's control system does not prevent the Orbiter's main engines from being in gimbal positions that are adverse to solid rocket booster separation. By eliminating the attitude error and attitude rate feedback just prior to solid rocket booster separation, the detrimental effects of the Orbiter's main engines can be reduced. In addition, if angular acceleration feedback is applied, the gimbal torques produced by the Orbiter's engines can reduce the detrimental effects of the aerodynamic torques. This paper develops these control techniques and compares the separation capability of the developed control systems. Currently with the worst case initial conditions and each Shuttle system dispersion aligned in the worst direction (which is more conservative than will be experienced in flight), the solid rocket booster has an interference with the Shuttle's external tank of 30 in. Elimination of the attitude error and attitude rate feedback reduces that interference to 19 in. Substitution of angular acceleration feedback reduces the interference to 6 in. The two latter interferences can be eliminated by atess conservative analysis techniques, that is, by using a root sum square of the system dispersions.

Constant Switching Frequency DTC for Matrix Converter Fed Speed Sensorless Induction Motor Drive

NASA Astrophysics Data System (ADS)

Mir, Tabish Nazir; Singh, Bhim; Bhat, Abdul Hamid

2018-05-01

The paper presents a constant switching frequency scheme for speed sensorless Direct Torque Control (DTC) of Matrix Converter fed Induction Motor Drive. The use of matrix converter facilitates improved power quality on input as well as motor side, along with Input Power Factor control, besides eliminating the need for heavy passive elements. Moreover, DTC through Space Vector Modulation helps in achieving a fast control over the torque and flux of the motor, with added benefit of constant switching frequency. A constant switching frequency aids in maintaining desired power quality of AC mains current even at low motor speeds, and simplifies input filter design of the matrix converter, as compared to conventional hysteresis based DTC. Further, stator voltage estimation from sensed input voltage, and subsequent stator (and rotor) flux estimation is done. For speed sensorless operation, a Model Reference Adaptive System is used, which emulates the speed dependent rotor flux equations of the induction motor. The error between conventionally estimated rotor flux (reference model) and the rotor flux estimated through the adaptive observer is processed through PI controller to generate the rotor speed estimate.

Enhanced spin-torque in double tunnel junctions using a nonmagnetic-metal spacer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, C. H.; Cheng, Y. H.; Ko, C. W.

2015-10-12

This study proposes an enhancement in the spin-transfer torque of a magnetic tunnel junction (MTJ) designed with double-barrier layer structure using a nonmagnetic metal spacer, as a replacement for the ferromagnetic material, which is traditionally used in these double-barrier stacks. Our calculation results show that the spin-transfer torque and charge current density of the proposed double-barrier MTJ can be as much as two orders of magnitude larger than the traditional double-barrier one. In other words, the proposed double-barrier MTJ has a spin-transfer torque that is three orders larger than that of the single-barrier stack. This improvement may be attributed tomore » the quantum-well states that are formed in the nonmagnetic metal spacer and the resonant tunneling mechanism that exists throughout the system.« less

Planar Rotary Piezoelectric Motor Using Ultrasonic Horns

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Bao, Xiaoqi; Badescu, Mircea; Bar-Cohen, Yoseph; Geiyer, Daniel; Ostlund, Patrick N.; Allen, Phillip

2011-01-01

A motor involves a simple design that can be embedded into a plate structure by incorporating ultrasonic horn actuators into the plate. The piezoelectric material that is integrated into the horns is pre-stressed with flexures. Piezoelectric actuators are attractive for their ability to generate precision high strokes, torques, and forces while operating under relatively harsh conditions (temperatures at single-digit K to as high as 1,273 K). Electromagnetic motors (EM) typically have high rotational speed and low torque. In order to produce a useful torque, these motors are geared down to reduce the speed and increase the torque. This gearing adds mass and reduces the efficiency of the EM. Piezoelectric motors can be designed with high torques and lower speeds directly without the need for gears. Designs were developed for producing rotary motion based on the Barth concept of an ultrasonic horn driving a rotor. This idea was extended to a linear motor design by having the horns drive a slider. The unique feature of these motors is that they can be designed in a monolithic planar structure. The design is a unidirectional motor, which is driven by eight horn actuators, that rotates in the clockwise direction. There are two sets of flexures. The flexures around the piezoelectric material are pre-stress flexures and they pre-load the piezoelectric disks to maintain their being operated under compression when electric field is applied. The other set of flexures is a mounting flexure that attaches to the horn at the nodal point and can be designed to generate a normal force between the horn tip and the rotor so that to first order it operates independently and compensates for the wear between the horn and the rotor.

IMPACT OF GRAVITY LOADING ON POST-STROKE REACHING AND ITS RELATIONSHIP TO WEAKNESS

PubMed Central

Beer, Randall F.; Ellis, Michael D.; Holubar, Bradley G.; Dewald, Julius P.A.

2010-01-01

The ability to extend the elbow following stroke depends on the magnitude and direction of torques acting at the shoulder. The mechanisms underlying this link remain unclear. The purpose of this study was to evaluate whether the effects of shoulder loading on elbow function were related to weakness or its distribution in the paretic limb. Ten subjects with longstanding hemiparesis performed movements with the arm either passively supported against gravity by an air bearing, or by activation of shoulder muscles. Isometric maximum voluntary torques at the elbow and shoulder were measured using a load cell. The speed and range of elbow extension movements were negatively impacted by actively supporting the paretic limb against gravity. However, the effects of gravity loading were not related to proximal weakness or abnormalities in the elbow flexor–extensor strength balance. The findings support the existence of abnormal descending motor commands that constrain the ability of stroke survivors to generate elbow extension torque in combination with abduction torque at the shoulder. PMID:17486581

Optimal control of motorsport differentials

NASA Astrophysics Data System (ADS)

Tremlett, A. J.; Massaro, M.; Purdy, D. J.; Velenis, E.; Assadian, F.; Moore, A. P.; Halley, M.

2015-12-01

Modern motorsport limited slip differentials (LSD) have evolved to become highly adjustable, allowing the torque bias that they generate to be tuned in the corner entry, apex and corner exit phases of typical on-track manoeuvres. The task of finding the optimal torque bias profile under such varied vehicle conditions is complex. This paper presents a nonlinear optimal control method which is used to find the minimum time optimal torque bias profile through a lane change manoeuvre. The results are compared to traditional open and fully locked differential strategies, in addition to considering related vehicle stability and agility metrics. An investigation into how the optimal torque bias profile changes with reduced track-tyre friction is also included in the analysis. The optimal LSD profile was shown to give a performance gain over its locked differential counterpart in key areas of the manoeuvre where a quick direction change is required. The methodology proposed can be used to find both optimal passive LSD characteristics and as the basis of a semi-active LSD control algorithm.

Impact of gravity loading on post-stroke reaching and its relationship to weakness.

PubMed

Beer, Randall F; Ellis, Michael D; Holubar, Bradley G; Dewald, Julius P A

2007-08-01

The ability to extend the elbow following stroke depends on the magnitude and direction of torques acting at the shoulder. The mechanisms underlying this link remain unclear. The purpose of this study was to evaluate whether the effects of shoulder loading on elbow function were related to weakness or its distribution in the paretic limb. Ten subjects with longstanding hemiparesis performed movements with the arm either passively supported against gravity by an air bearing, or by activation of shoulder muscles. Isometric maximum voluntary torques at the elbow and shoulder were measured using a load cell. The speed and range of elbow extension movements were negatively impacted by actively supporting the paretic limb against gravity. However, the effects of gravity loading were not related to proximal weakness or abnormalities in the elbow flexor-extensor strength balance. The findings support the existence of abnormal descending motor commands that constrain the ability of stroke survivors to generate elbow extension torque in combination with abduction torque at the shoulder.

Cyclic Parameter Refinement of 4S-10 Hybrid Flux-Switching Motor for Lightweight Electric Vehicle

NASA Astrophysics Data System (ADS)

Rani, J. Abd; Sulaiman, E.; Kumar, R.

2017-08-01

A great deal of attention has been given to the reduction of lighting the vehicle because the lighter the vehicle the energy consumption is comparatively low. Hence, the lightweight electric vehicle was introduced for lower carbon footprint and the sizing of the vehicle itself. One of the components to reduce the weight of the vehicle is the propulsion system which comprised of electric motor functioning as the source of torque to drive the propulsion system of the machine. This paper presents the refinement methodology for the optimized design of the 4S-10P E-Core hybrid excitation flux switching motor. The purpose of the refinement methodology is to improve the torque production of the optimized motor. The result of the successful improvement of the torque production is justifiable for a lightweight electric vehicle to drive the propulsion system.

Cryogenic Flange and Seal Evaluation

NASA Technical Reports Server (NTRS)

Ramirez, Adrian

2014-01-01

The assembly of flanges, seals, and pipes are used to carry cryogenic fluid from a storage tank to the vehicle at launch sites. However, after a certain amount of cycles these raised face flanges with glass-filled Teflon gaskets have been found to have torque relaxation and are as a result susceptible to cryogenic fluid leakage if not re-torqued. The intent of this project is to identify alternate combinations of flanges and seals which may improve thermal cycle performance and decrease re-torque requirements. The general approach is to design a test fixture to evaluate leak characteristics between spiral and concentric serrations and to test alternate flange and seal combinations. Due to insufficient time, it was not possible to evaluate these different types of combinations for the combination that improved thermal cycle performance the most. However, the necessary drawings for the test fixture were designed and assembled along with the collection of the necessary parts.

Secular Dynamical Anti-friction in Galactic Nuclei

NASA Astrophysics Data System (ADS)

Madigan, Ann-Marie; Levin, Yuri

2012-07-01

We identify a gravitational-dynamical process in near-Keplerian potentials of galactic nuclei that occurs when an intermediate-mass black hole (IMBH) is migrating on an eccentric orbit through the stellar cluster towards the central supermassive black hole. We find that, apart from conventional dynamical friction, the IMBH experiences an often much stronger systematic torque due to the secular (i.e., orbit-averaged) interactions with the cluster's stars. The force which results in this torque is applied, counterintuitively, in the same direction as the IMBH's precession and we refer to its action as "secular dynamical anti-friction" (SDAF). We argue that SDAF, and not the gravitational ejection of stars, is responsible for the IMBH's eccentricity increase seen in the initial stages of previous N-body simulations. Our numerical experiments, supported by qualitative arguments, demonstrate that (1) when the IMBH's precession direction is artificially reversed, the torque changes sign as well, which decreases the orbital eccentricity; (2) the rate of eccentricity growth is sensitive to the IMBH migration rate, with zero systematic eccentricity growth for an IMBH whose orbit is artificially prevented from inward migration; and (3) SDAF is the strongest when the central star cluster is rapidly rotating. This leads to eccentricity growth/decrease for the clusters rotating in the opposite/same direction relative to the IMBH's orbital motion.

Mechanical evidence of the orbital angular momentum to energy ratio of vortex beams.

PubMed

Demore, Christine E M; Yang, Zhengyi; Volovick, Alexander; Cochran, Sandy; MacDonald, Michael P; Spalding, Gabriel C

2012-05-11

We measure, in a single experiment, both the radiation pressure and the torque due to a wide variety of propagating acoustic vortex beams. The results validate, for the first time directly, the theoretically predicted ratio of the orbital angular momentum to linear momentum in a propagating beam. We experimentally determine this ratio using simultaneous measurements of both the levitation force and the torque on an acoustic absorber exerted by a broad range of helical ultrasonic beams produced by a 1000-element matrix transducer array. In general, beams with helical phase fronts have been shown to contain orbital angular momentum as the result of the azimuthal component of the Poynting vector around the propagation axis. Theory predicts that for both optical and acoustic helical beams the ratio of the angular momentum current of the beam to the power should be given by the ratio of the beam's topological charge to its angular frequency. This direct experimental observation that the ratio of the torque to power does convincingly match the expected value (given by the topological charge to angular frequency ratio of the beam) is a fundamental result.

Forearm Torque and Lifting Strength: Normative Data.

PubMed

Axelsson, Peter; Fredrikson, Per; Nilsson, Anders; Andersson, Jonny K; Kärrholm, Johan

2018-02-10

To establish reference values for new methods designed to quantitatively measure forearm torque and lifting strength and to compare these values with grip strength. A total of 499 volunteers, 262 males and 237 females, aged 15 to 85 (mean, 44) years, were tested for lifting strength and forearm torque with the Kern and Baseline dynamometers. These individuals were also tested for grip strength with a Jamar dynamometer. Standardized procedures were used and information about sex, height, weight, hand dominance, and whether their work involved high or low manual strain was collected. Men had approximately 70% higher forearm torque and lifting strength compared with females. Male subjects aged 26 to 35 years and female subjects aged 36 to 45 years showed highest strength values. In patients with dominant right side, 61% to 78% had a higher or equal strength on this side in the different tests performed. In patients with dominant left side, the corresponding proportions varied between 41% and 65%. There was a high correlation between grip strength and forearm torque and lifting strength. Sex, body height, body weight, and age showed a significant correlation to the strength measurements. In a multiple regression model sex, age (entered as linear and squared) could explain 51% to 63% of the total variances of forearm torque strength and 30% to 36% of lifting strength. Reference values for lifting strength and forearm torque to be used in clinical practice were acquired. Grip strength has a high correlation to forearm torque and lifting strength. Sex, age, and height can be used to predict forearm torque and lifting strength. Prediction equations using these variables were generated. Normative data of forearm torque and lifting strength might improve the quality of assessment of wrist and forearm disorders as well as their treatments. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Analysis of elbow-joints misalignment in upper-limb exoskeleton.

PubMed

Malosio, Matteo; Pedrocchi, Nicola; Vicentini, Federico; Tosatti, Lorenzo Molinari

2011-01-01

This paper presents advantages of introducing elbow-joints misalignments in an exoskeleton for upper limb rehabilitation. Typical exoskeletons are characterized by axes of the device as much as possible aligned to the rotational axes of human articulations. This approach leads to advantages in terms of movements and torques decoupling, but can lead to limitations nearby the elbow singular configuration. A proper elbow axes misalignment between the exoskeleton and the human can improve the quality of collaborative rehabilitation therapies, in which a correct torque transmission from human articulations to mechanical joints of the device is required to react to torques generated by the patient. © 2011 IEEE

Internal- and External-Rotation Peak Toque in Little League Baseball Players With Subacromial Impingement Syndrome: Improved by Closed Kinetic Chain Shoulder Training.

PubMed

Lee, Dong-Rour; Kim, Laurentius Jongsoon

2016-08-01

Many studies have explored closed kinetic chain (CKC) shoulder exercises (SEs) with a sling because they are safer and more effective than open-chain exercises, especially in early stages of treatment. However, the application of CKC SE in youth baseball players has rarely been attempted, although teenage baseball players also experience shoulder pain. To investigate the effects of CKC SE on the peak torque of shoulder internal rotation (IR) and external rotation (ER) in youth baseball players. Single-group pretest, posttest. Biomechanics laboratory. 23 Little League Baseball players with subacromial impingement syndrome. The CKC SE with a sling was CKC shoulder-flexion exercise, extension exercise, IR exercise, and ER exercise. This exercise regimen was conducted 2 or 3 times/wk for 8 wk. The peak torque of shoulder IR and ER was measured using an isokinetic dynamometer. Concentric shoulder rotation was performed, with 5 repetitions at an angular velocity of 60°/s and 15 at 180°/s. The IR and ER peak torque significantly increased at each angular velocity after the exercise program. In particular, the increase in IR and ER peak torque values was statistically significant at an angular velocity of 180°/s. CKC SE was effective in increasing shoulder IR and ER strength, demonstrating its potential benefits in the prevention and treatment of shoulder injury. In addition, increased IR peak torque appears to improve throwing velocity in baseball players.

Eddy current damper

NASA Technical Reports Server (NTRS)

Ellis, R. C.; Fink, R. A.; Rich, R. W.

1989-01-01

A high torque capacity eddy current damper used as a rate limiting device for a large solar array deployment mechanism is discussed. The eddy current damper eliminates the problems associated with the outgassing or leaking of damping fluids. It also provides performance advantages such as damping torque rates, which are truly linear with respect to input speed, continuous 360 degree operation in both directions of rotation, wide operating temperature range, and the capability of convenient adjustment of damping rates by the user without disassembly or special tools.

Application of intelligent soft start in asynchronous motor

NASA Astrophysics Data System (ADS)

Du, Xue; Ye, Ying; Wang, Yuelong; Peng, Lei; Zhang, Suying

2018-05-01

The starting way of three phase asynchronous motor has full voltage start and step-down start. Direct starting brings large current impact, causing excessive local temperature to the power grid and larger starting torque will also impact the motor equipment and affect the service life of the motor. Aim at the problem of large current and torque caused by start-up, an intelligent soft starter is proposed. Through the application of intelligent soft start on asynchronous motor, highlights its application advantage in motor control.

The VSPA Foot: A Quasi-Passive Ankle-Foot Prosthesis With Continuously Variable Stiffness.

PubMed

Shepherd, Max K; Rouse, Elliott J

2017-12-01

Most commercially available prosthetic feet do not exhibit a biomimetic torque-angle relationship, and are unable to modulate their mechanics to assist with other mobility tasks, such as stairs and ramps. In this paper, we present a quasi-passive ankle-foot prosthesis with a customizable torque-angle curve and an ability to quickly modulate ankle stiffness between tasks. The customizable torque-angle curve is obtained with a cam-based transmission and a fiberglass leaf spring. To achieve variable stiffness, the leaf spring's support conditions can be actively modulated by a small motor, shifting the torque-angle curve to be more or less stiff. We introduce the design, characterize the available torque-angle curves, and present kinematics from a transtibial amputee subject performing level-ground walking, stair ascent/descent, and ramp ascent/descent. The subject exhibited a more normative range of motion on stairs and ramps at lower stiffness levels, and preferred different stiffness levels for each task. Paired with an appropriate intent recognition system, our novel ankle prosthesis could improve gait biomechanics during walking and many other mobility tasks.

Single-Resonance Longitudinal and Torsional Vibrator Combination-Type Motor: Improvement of Motor Characteristics

NASA Astrophysics Data System (ADS)

Shimanuki, Masaharu; Aoyagi, Manabu; Tomikawa, Yoshiro

1994-05-01

The present paper deals with the single-resonance longitudinal and torsional vibrator combination-type motor, which is one of the ultrasonic motors with a relatively large torque. To improve the characteristics of this motor, the authors studied the calculation method of the resonance frequencies and designed the motor so that the resonance frequencies of the longitudinal and torsional vibrations were very close to the measured ones, because it was thought that the motor characteristics were largely affected by the degree of approximation of the resonance frequencies. Experimental results have proven that the prototype motor produced large torque with a maximum of 14.0 kgf·cm under a total electrical input power of 30 W; this value was 1.5 times as large as that reported previously. That is, it has been clarified that with sufficient degree of approximation of the resonance frequencies, as mentioned above, the output torque of the motor could be greatly improved; however, its efficiency (maximum of 13.1%) was maintained at almost the same value as before.

Assessment of System Frequency Support Effect of PMSG-WTG Using Torque-Limit-Based Inertial Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiao; Gao, Wenzhong; Wang, Jianhui

2017-02-16

To release the 'hidden inertia' of variable-speed wind turbines for temporary frequency support, a method of torque-limit based inertial control is proposed in this paper. This method aims to improve the frequency support capability considering the maximum torque restriction of a permanent magnet synchronous generator. The advantages of the proposed method are improved frequency nadir (FN) in the event of an under-frequency disturbance; and avoidance of over-deceleration and a second frequency dip during the inertial response. The system frequency response is different, with different slope values in the power-speed plane when the inertial response is performed. The proposed method ismore » evaluated in a modified three-machine, nine-bus system. The simulation results show that there is a trade-off between the recovery time and FN, such that a gradual slope tends to improve the FN and restrict the rate of change of frequency aggressively while causing an extension of the recovery time. These results provide insight into how to properly design such kinds of inertial control strategies for practical applications.« less

Biomechanical evaluation of macro and micro designed screw-type implants: an insertion torque and removal torque study in rabbits.

PubMed

Chowdhary, Ramesh; Jimbo, Ryo; Thomsen, Christian; Carlsson, Lennart; Wennerberg, Ann

2013-03-01

To investigate the combined effect of macro and pitch shortened threads on primary and secondary stability during healing, but before dynamic loading. Two sets of turned implants with different macro geometry were prepared. The test group possessed pitch shortened threads in between the large threads and the control group did not have thread alterations. The two implant groups were placed in both femur and tibiae of 10 lop-eared rabbits, and at the time of implant insertion, insertion torques were recorded. After 4 weeks, all implants were subjected to removal torque tests. The insertion torque values for the control and test groups for the tibia were 15.7 and 20.6 Ncm, respectively, and for the femur, 11.8, and 12.8 Ncm respectively. The removal torque values for the control and test groups in the tibia were 7.9 and 9.1 Ncm, respectively, and for the femur, 7.9 and 7.7 Ncm respectively. There was no statistically significant difference between the control and test groups. Under limited dynamic load, the addition of pitch shortened threads did not significantly improve either the primary or the secondary stability of the implants in bone. © 2011 John Wiley & Sons A/S.

An optical apparatus for rotation and trapping

PubMed Central

Gutiérrez-Medina, Braulio; Andreasson, Johan O. L.; Greenleaf, William J.; LaPorta, Arthur; Block, Steven M.

2010-01-01

We present details of the design, construction and testing of a single-beam optical tweezers apparatus capable of measuring and exerting torque, as well as force, on microfabricated, optically anisotropic particles (an ‘optical torque wrench’). The control of angular orientation is achieved by rotating the linear polarization of a trapping laser with an electro-optic modulator (EOM), which affords improved performance over previous designs. The torque imparted to the trapped particle is assessed by measuring the difference between left- and right-circular components of the transmitted light, and constant torque is maintained by feeding this difference signal back into a custom-designed electronic servo loop. The limited angular range of the EOM (±180°) is extended by rapidly reversing the polarization once a threshold angle is reached, enabling the torque clamp to function over unlimited, continuous rotations at high bandwidth. In addition, we developed particles suitable for rotation in this apparatus using microfabrication techniques. Altogether, the system allows for the simultaneous application of forces (~0.1–100 pN) and torques (~1–10,000 pN nm) in the study of biomolecules. As a proof of principle, we demonstrate how our instrument can be used to study the supercoiling of single DNA molecules. PMID:20627165

Effect of pole number and slot number on performance of dual rotor permanent magnet wind power generator using ferrite magnets

NASA Astrophysics Data System (ADS)

Xu, Peifeng; Shi, Kai; Sun, Yuxin; Zhua, Huangqiu

2017-05-01

Dual rotor permanent magnet (DRPM) wind power generator using ferrite magnets has the advantages of low cost, high efficiency, and high torque density. How to further improve the performance and reduce the cost of the machine by proper choice of pole number and slot number is an important problem to be solved when performing preliminarily design a DRPM wind generator. This paper presents a comprehensive performance comparison of a DRPM wind generator using ferrite magnets with different slot and pole number combinations. The main winding factors are calculated by means of the star of slots. Under the same machine volume and ferrite consumption, the flux linkage, back-electromotive force (EMF), cogging torque, output torque, torque pulsation, and losses are investigated and compared using finite element analysis (FEA). The results show that the slot and pole number combinations have an important impact on the generator properties.

Why do Cross-Flow Turbines Stall?

NASA Astrophysics Data System (ADS)

Cavagnaro, Robert; Strom, Benjamin; Polagye, Brian

2015-11-01

Hydrokinetic turbines are prone to instability and stall near their peak operating points under torque control. Understanding the physics of turbine stall may help to mitigate this undesirable occurrence and improve the robustness of torque controllers. A laboratory-scale two-bladed cross-flow turbine operating at a chord-based Reynolds number ~ 3 ×104 is shown to stall at a critical tip-speed ratio. Experiments are conducting bringing the turbine to this critical speed in a recirculating current flume by increasing resistive torque and allowing the rotor to rapidly decelerate while monitoring inflow velocity, torque, and drag. The turbine stalls probabilistically with a distribution generated from hundreds of such events. A machine learning algorithm identifies stall events and indicates the effectiveness of available measurements or combinations of measurements as predictors. Bubble flow visualization and PIV are utilized to observe fluid conditions during stall events including the formation, separation, and advection of leading-edge vortices involved in the stall process.

Amount of torque and duration of stretching affects correction of knee contracture in a rat model of spinal cord injury.

PubMed

Moriyama, Hideki; Tobimatsu, Yoshiko; Ozawa, Junya; Kito, Nobuhiro; Tanaka, Ryo

2013-11-01

Joint contractures are a common complication of many neurologic conditions, and stretching often is advocated to prevent and treat these contractures. However, the magnitude and duration of the stretching done in practice usually are guided by subjective clinical impressions. Using an established T8 spinal cord injury rat model of knee contracture, we sought to determine what combination of static or intermittent stretching, varied by magnitude (high or low) and duration (long or short), leads to the best (1) improvement in the limitation in ROM; (2) restoration of the muscular and articular factors leading to contractures; and (3) prevention and treatment of contracture-associated histologic alterations of joint capsule and articular cartilage. Using a rat animal model, the spinal cord was transected completely at the level of T8. The rats were randomly assigned to seven treatment groups (n = 4 per group), which were composed of static or intermittent stretching in combination with different amounts of applied torque magnitude and duration. We assessed the effect of stretching by measuring the ROM and evaluating the histologic alteration of the capsule and cartilage. Contractures improved in all treated groups except for the low-torque and short-duration static stretching conditions. High-torque stretching was effective against shortening of the synovial membrane and adhesions in the posterosuperior regions. Collagen Type II and VEGF in the cartilage were increased by stretching. High-torque and long-duration static stretching led to greater restoration of ROM than the other torque and duration treatment groups. Stretching was more effective in improving articular components of contractures compared with the muscular components. Stretching in this rat model prevented shortening and adhesion of the joint capsule, and affected biochemical composition, but did not change morphologic features of the cartilage. This animal study tends to support the ideas that static stretching can influence joint ROM and histologic qualities of joint tissues, and that the way stretching is performed influences its efficacy. However, further studies are warranted to determine if our findings are clinically applicable.

Actuation of a robotic fish caudal fin for low reaction torque

NASA Astrophysics Data System (ADS)

Yun, Dongwon; Kim, Kyung-Soo; Kim, Soohyun; Kyung, Jinho; Lee, Sunghee

2011-07-01

In this paper, a novel caudal fin for actuating a robotic fish is presented. The proposed caudal fin waves in a vertical direction with a specific spatial shape, which is determined by a so-called shape factor. For a specific shape factor, a traveling wave with a vertical phase difference is formed on a caudal fin during fin motion. It will be shown by the analysis that the maximum reaction torque at the joint of a caudal fin varies depending on the shape factors. Compared with a conventional plate type caudal fin, the proposed fin with a shape factor of 2π can eliminate the reaction torque perfectly, while keeping the propulsion force unchanged. The benefits of the proposed fin will be demonstrated by experiments.

Historical Variations in Inner Core Rotation and Polar Motion at Decade Timescales

NASA Astrophysics Data System (ADS)

Dumberry, M.

2005-12-01

Exchanges of angular momentum between the mantle, the fluid core and the solid inner core result in changes in the Earth's rotation. Torques in the axial direction produce changes in amplitude, or changes in length of day, while torques in the equatorial direction lead to changes in orientation of the rotation vector with respect to the mantle, or polar motion. In this work, we explore the possibility that a combination of electromagnetic and gravitational torques on the inner core can reproduce the observed decadal variations in polar motion known as the Markowitz wobble. Torsional oscillations, which involve azimuthal motions in the fluid core with typical periods of decades, entrain the inner core by electromagnetic traction. When the inner core is axially rotated, its surfaces of constant density are no longer aligned with the gravitational potential from mantle density heterogeneities, and this results in a gravitational torque between the two. The axial component of this torque has been previously described and is believed to be partly responsible for decadal changes in length of day. In this work, we show that it has also an equatorial component, which produces a tilt of the inner core and results in polar motion. The polar motion produced by this mechanism depends on the density structure in the mantle, the rheology of the inner core, and the time-history of the angle of axial misalignment between the inner core and the mantle. We reconstruct the latter using a model of torsional oscillations derived from geomagnetic secular variation. From this time-history, and by using published models of mantle density structure, we show that we can reproduce the salient characteristics of the Markowitz wobble: an eccentric decadal polar motion of 30-50 milliarcsecs oriented along a specific longitude. We discuss the implications of this result, noting that a match in both amplitude and phase of the observed Markowitz wobble allows the recovery of the historical rotational variations of the inner core, and also provides constraints on structure, rheology and dynamics of the Earth's deep interior that cannot be observed directly.

Torque and mechanomyogram relationships during electrically-evoked isometric quadriceps contractions in persons with spinal cord injury.

PubMed

Ibitoye, Morufu Olusola; Hamzaid, Nur Azah; Hasnan, Nazirah; Abdul Wahab, Ahmad Khairi; Islam, Md Anamul; Kean, Victor S P; Davis, Glen M

2016-08-01

The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Direct torque control method applied to the WECS based on the PMSG and controlled with backstepping approach

NASA Astrophysics Data System (ADS)

Errami, Youssef; Obbadi, Abdellatif; Sahnoun, Smail; Ouassaid, Mohammed; Maaroufi, Mohamed

2018-05-01

This paper proposes a Direct Torque Control (DTC) method for Wind Power System (WPS) based Permanent Magnet Synchronous Generator (PMSG) and Backstepping approach. In this work, generator side and grid-side converter with filter are used as the interface between the wind turbine and grid. Backstepping approach demonstrates great performance in complicated nonlinear systems control such as WPS. So, the control method combines the DTC to achieve Maximum Power Point Tracking (MPPT) and Backstepping approach to sustain the DC-bus voltage and to regulate the grid-side power factor. In addition, control strategy is developed in the sense of Lyapunov stability theorem for the WPS. Simulation results using MATLAB/Simulink validate the effectiveness of the proposed controllers.

Stator and Rotor Flux Based Deadbeat Direct Torque Control of Induction Machines

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Lorenz, Robert D.

2001-01-01

A new, deadbeat type of direct torque control is proposed, analyzed, and experimentally verified in this paper. The control is based on stator and rotor flux as state variables. This choice of state variables allows a graphical representation which is transparent and insightful. The graphical solution shows the effects of realistic considerations such as voltage and current limits. A position and speed sensorless implementation of the control, based on the self-sensing signal injection technique, is also demonstrated experimentally for low speed operation. The paper first develops the new, deadbeat DTC methodology and graphical representation of the new algorithm. It then evaluates feasibility via simulation and experimentally demonstrates performance of the new method with a laboratory prototype including the sensorless methods.

Stator and Rotor Flux Based Deadbeat Direct Torque Control of Induction Machines

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Lorenz, Robert D.

2003-01-01

A new, deadbeat type of direct torque control is proposed, analyzed and experimentally verified in this paper. The control is based on stator and rotor flux as state variables. This choice of state variables allows a graphical representation which is transparent and insightful. The graphical solution shows the effects of realistic considerations such as voltage and current limits. A position and speed sensorless implementation of the control, based on the self-sensing signal injection technique, is also demonstrated experimentally for low speed operation. The paper first develops the new, deadbeat DTC methodology and graphical representation of the new algorithm. It then evaluates feasibility via simulation and experimentally demonstrates performance of the new method with a laboratory prototype including the sensorless methods.

Stator and Rotor Flux Based Deadbeat Direct Torque Control of Induction Machines. Revision 1

NASA Technical Reports Server (NTRS)

Kenny, Barbara H.; Lorenz, Robert D.

2002-01-01

A new, deadbeat type of direct torque control is proposed, analyzed, and experimentally verified in this paper. The control is based on stator and rotor flux as state variables. This choice of state variables allows a graphical representation which is transparent and insightful. The graphical solution shows the effects of realistic considerations such as voltage and current limits. A position and speed sensorless implementation of the control, based on the self-sensing signal injection technique, is also demonstrated experimentally for low speed operation. The paper first develops the new, deadbeat DTC methodology and graphical representation of the new algorithm. It then evaluates feasibility via simulation and experimentally demonstrates performance of the new method with a laboratory prototype including the sensorless methods.

Design and analysis of an MR rotary brake for self-regulating braking torques.

PubMed

Yun, Dongwon; Koo, Jeong-Hoi

2017-05-01

This paper presents a novel Magneto-rheological (MR) brake system that can self-regulate the output braking torques. The proposed MR brake can generate a braking torque at a critical rotation speed without an external power source, sensors, or controllers, making it a simple and cost-effective device. The brake system consists of a rotary disk, permanent magnets, springs, and MR fluid. The permanent magnets are attached to the rotary disk via the springs, and they move outward through grooves with two different gap distances along the radial direction of the stator due to the centrifugal force. Thus, the position of the magnets is dependent on the spin speed, and it can determine the magnetic fields applied to MR fluids. Proper design of the stator geometry gives the system unique torque characteristics. To show the performance of an MR brake system, the electromagnetic characteristics of the system are analyzed, and the torques generated by the brake are calculated using the result of the electromagnetic analysis. Using a baseline model, a parametric study is conducted to investigate how the design parameters (geometric shapes and material selection) affect the performance of the brake system. After the simulation study, a prototype brake system is constructed and its performance is experimentally evaluated. The experimental results show that the prototype produced the maximum torque of 1.2 N m at the rotational speed of 100 rpm. The results demonstrate the feasibility of the proposed MR brake as a speed regulator in rotating systems.

The Enhancement of spin Hall torque efficiency and Reduction of Gilbert damping in spin Hall metal/normal metal/ferromagnetic trilayers

NASA Astrophysics Data System (ADS)

Nguyen, Minh-Hai; Pai, Chi-Feng; Ralph, Daniel C.; Buhrman, Robert A.

2015-03-01

The spin Hall effect (SHE) in ferromagnet/heavy metal bilayer structures has been demonstrated to be a powerful means for producing pure spin currents and for exerting spin-orbit damping-like and field-like torques on the ferromagnetic layer. Large spin Hall (SH) angles have been reported for Pt, beta-Ta and beta-W films and have been utilized to achieve magnetic switching of in-plane and out-of-plane magnetized nanomagnets, spin torque auto-oscillators, and the control of high velocity domain wall motion. For many of the proposed applications of the SHE it is also important to achieve an effective Gilbert damping parameter that is as low as possible. In general the spin orbit torques and the effective damping are predicted to depend directly on the spin-mixing conductance of the SH metal/ferromagnet interface. This opens up the possibility of tuning these properties with the insertion of a very thin layer of another metal between the SH metal and the ferromagnet. Here we will report on experiments with such trilayer structures in which we have observed both a large enhancement of the spin Hall torque efficiency and a significant reduction in the effective Gilbert damping. Our results indicate that there is considerable opportunity to optimize the effectiveness and energy efficiency of the damping-like torque through engineering of such trilayer structures. Supported in part by NSF and Samsung Electronics Corporation.

Electron Drift Speed And Current-Induced Drive Torques On A Domain Wall

NASA Astrophysics Data System (ADS)

Berger, Luc

2009-03-01

It has become fashionable to describe [1] current-induced torques on a DW in terms of an electron drift speed u = - P*j*muB/e*M where muB is the Bohr magneton and M the saturation magnetization. While appropriate for adiabatic torques, this quantity u is misleading and not the best choice in the case of non-adiabatic torques. For example, it leads [2] to beta not equal to alpha, where beta represents the intensity of the non-adiabatic torque, and alpha is the damping parameter. By writing equations of motion for conduction- electron spins in a moving frame where the electron gas is at rest, we find [3] a direct relation between damping and non- adiabatic torques. The correct electron drift speed turns out to be the speed of the frame, and is v = P*j/(n*q) where n and q are the carrier density and charge. It is related to the ordinary Hall constant R0 by v P*R0*j. After substituting v for u in the expression of the non-adiabatic torque, we find that beta = alpha holds now. Because v is larger than u in Permalloy, it can explain better the large current-induced DW speeds found [4] experimentally. In materials where R0> 0 and the carriers are dominantly hole-like, v and u have opposite signs, leading to different predictions for the sense of DW motion. We discuss examples of such materials. 1. G. Tatara and H. Kohno, Phys. Rev. Lett. 92, 086601 (2004). 2. H. Kohno et al., J. Phys. Soc. Japan, 75, 113706 (2006). 3. L. Berger, Phys. Rev. B 75, 174401 (2007). 4. M. Hayashi et al., Phys. Rev. Lett. 98, 037204 (2007).

Biomechanically determined hand force limits protecting the low back during occupational pushing and pulling tasks.

PubMed

Weston, Eric B; Aurand, Alexander; Dufour, Jonathan S; Knapik, Gregory G; Marras, William S

2018-06-01

Though biomechanically determined guidelines exist for lifting, existing recommendations for pushing and pulling were developed using a psychophysical approach. The current study aimed to establish objective hand force limits based on the results of a biomechanical assessment of the forces on the lumbar spine during occupational pushing and pulling activities. Sixty-two subjects performed pushing and pulling tasks in a laboratory setting. An electromyography-assisted biomechanical model estimated spinal loads, while hand force and turning torque were measured via hand transducers. Mixed modelling techniques correlated spinal load with hand force or torque throughout a wide range of exposures in order to develop biomechanically determined hand force and torque limits. Exertion type, exertion direction, handle height and their interactions significantly influenced dependent measures of spinal load, hand force and turning torque. The biomechanically determined guidelines presented herein are up to 30% lower than comparable psychophysically derived limits and particularly more protective for straight pushing. Practitioner Summary: This study utilises a biomechanical model to develop objective biomechanically determined push/pull risk limits assessed via hand forces and turning torque. These limits can be up to 30% lower than existing psychophysically determined pushing and pulling recommendations. Practitioners should consider implementing these guidelines in both risk assessment and workplace design moving forward.

Measurement of additional shear during sludge conditioning and dewatering.

PubMed

Ormeci, Banu; Ahmad, Ayaz

2009-07-01

Optimum polymer dose is influenced both by the polymer demand of the sludge and the shear applied during conditioning. Sludge exposed to additional shear following conditioning will experience a decrease in cake solids concentration for the same polymer dose. Therefore, it is necessary to measure or quantify the additional shear in order to optimize the conditioning and dewatering. There is currently no direct or indirect method to achieve this. The main objective of this study was to develop a method based on torque rheology to measure the amount of shear that a sludge network experiences during conditioning and dewatering. Anaerobically digested sludge samples were exposed to increasing levels of mixing intensities and times, and rheological characteristics of samples were measured using a torque rheometer. Several rheological parameters were evaluated including the peak torque and totalized torque (area under the rheograms). The results of this study show that at the optimum polymer dose, a linear relationship exists between the applied shear and the area under the rheograms, and this relationship can be used to estimate an unknown amount of shear that the sludge was exposed to. The method is useful as a research tool to study the effect of shear on dewatering but also as an optimization tool in a dewatering automation system based on torque rheology.

Kinetic analysis of the function of the upper body for elite race walkers during official men 20 km walking race.

PubMed

Hoga-Miura, Koji; Ae, Michiyoshi; Fujii, Norihisa; Yokozawa, Toshiharu

2016-10-01

This study investigated the function of the upper extremities of elite race walkers during official 20 km races, focusing on the angular momentum about the vertical axis and other parameters of the upper extremities. Sixteen walkers were analysed using the three-dimensional direct linear transformation method during three official men's 20 km walking races. The subjects, included participants at the Olympics and World Championships, who finished without disqualification and had not been disqualified during the two years prior to or following the races analysed in the present study. The angular momenta of the upper and lower body were counterbalanced as in running and normal walking. The momentum of the upper body was mainly generated by the upper extremities. The joint force moment of the right shoulder and the joint torque at the left shoulder just before right toe-off were significantly correlated with the walking speed. These were counterbalanced by other moments and torques to the torso torque, which worked to obtain a large mechanical energy flow from the recovery leg to the support leg in the final phase of the support phase. Therefore, a function of the shoulder torque was to counterbalance the torso torque to gain a fast walking speed with substantial mechanical energy flow.

Applying torque to the Escherichia coli flagellar motor using magnetic tweezers.

PubMed

van Oene, Maarten M; Dickinson, Laura E; Cross, Bronwen; Pedaci, Francesco; Lipfert, Jan; Dekker, Nynke H

2017-03-07

The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in principle allow the application and active control of a calibrated load torque, to study single flagellar motors in Escherichia coli. We manipulate the external load on the motor by adjusting the magnetic field experienced by a magnetic bead linked to the motor, and we probe the motor's response. A simple model describes the average motor speed over the entire range of applied fields. We extract the motor torque at stall and find it to be similar to the motor torque at drag-limited speed. In addition, use of the magnetic tweezers allows us to force motor rotation in both forward and backward directions. We monitor the motor's performance before and after periods of forced rotation and observe no destructive effects on the motor. Our experiments show how magnetic tweezers can provide active and fast control of the external load while also exposing remaining challenges in calibration. Through their non-invasive character and straightforward parallelization, magnetic tweezers provide an attractive platform to study nanoscale rotary motors at the single-motor level.

The Effects of Racket Inertia Tensor on Elbow Loadings and Racket Behavior for Central and Eccentric Impacts

PubMed Central

Nesbit, Steven M.; Elzinga, Michael; Herchenroder, Catherine; Serrano, Monika

2006-01-01

This paper discusses the inertia tensors of tennis rackets and their influence on the elbow swing torques in a forehand motion, the loadings transmitted to the elbow from central and eccentric impacts, and the racket acceleration responses from central and eccentric impacts. Inertia tensors of various rackets with similar mass and mass center location were determined by an inertia pendulum and were found to vary considerably in all three orthogonal directions. Tennis swing mechanics and impact analyses were performed using a computer model comprised of a full-body model of a human, a parametric model of the racket, and an impact function. The swing mechanics analysis of a forehand motion determined that inertia values had a moderate linear effect on the pronation-supination elbow torques required to twist the racket, and a minor effect on the flexion-extension and valgus-varus torques. The impact analysis found that mass center inertia values had a considerable effect on the transmitted torques for both longitudinal and latitudinal eccentric impacts and significantly affected all elbow torque components. Racket acceleration responses to central and eccentric impacts were measured experimentally and found to be notably sensitive to impact location and mass center inertia values. Key Points Tennis biomechanics. Racket inertia tensor. Impact analysis. Full-body computer model. PMID:24260004

Magnetic tweezers for the measurement of twist and torque.

PubMed

Lipfert, Jan; Lee, Mina; Ordu, Orkide; Kerssemakers, Jacob W J; Dekker, Nynke H

2014-05-19

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a "conventional" magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the "conventional" magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument.

Applying torque to the Escherichia coli flagellar motor using magnetic tweezers

PubMed Central

van Oene, Maarten M.; Dickinson, Laura E.; Cross, Bronwen; Pedaci, Francesco; Lipfert, Jan; Dekker, Nynke H.

2017-01-01

The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in principle allow the application and active control of a calibrated load torque, to study single flagellar motors in Escherichia coli. We manipulate the external load on the motor by adjusting the magnetic field experienced by a magnetic bead linked to the motor, and we probe the motor’s response. A simple model describes the average motor speed over the entire range of applied fields. We extract the motor torque at stall and find it to be similar to the motor torque at drag-limited speed. In addition, use of the magnetic tweezers allows us to force motor rotation in both forward and backward directions. We monitor the motor’s performance before and after periods of forced rotation and observe no destructive effects on the motor. Our experiments show how magnetic tweezers can provide active and fast control of the external load while also exposing remaining challenges in calibration. Through their non-invasive character and straightforward parallelization, magnetic tweezers provide an attractive platform to study nanoscale rotary motors at the single-motor level. PMID:28266562

Within- and between-session reliability of the maximal voluntary knee extension torque and activation.

PubMed

Park, Jihong; Hopkins, J Ty

2013-01-01

A ratio between the torque generated by maximal voluntary isometric contraction (MVIC) and exogenous electrical stimulus, central activation ratio (CAR), has been widely used to assess quadriceps function. To date, no data exist regarding between-session reliability of this measurement. Thirteen neurologically sound volunteers underwent three testing sessions (three trials per session) with 48 hours between-session. Subjects performed MVICs of the quadriceps with the knee locked at 90° flexion and the hip at 85°. Once the MVIC reached a plateau, an electrical stimulation from superimposed burst technique (SIB: 125 V with peak output current 450 mA) was manually delivered and transmitted directly to the quadriceps via stimulating electrodes. CAR was calculated by using the following equation: CAR = MVIC torque/MVIC + SIB torque. Intraclass correlation coefficients (ICC) were calculated within- (ICC((2,1))) and between-session (ICC((2,k))) for MVIC torques and CAR values. Our data show that quadriceps MVIC and CAR are very reliable both within- (ICC((2,1)) = 0.99 for MVIC; 0.94 for CAR) and between-measurement sessions (ICC((2,k)) = 0.92 for MVIC; 0.86 for CAR) in healthy young adults. For clinical research, more data of the patients with pathological conditions are required to ensure reproducibility of calculation of CAR.

Torque Limits for Fasteners in Composites

NASA Technical Reports Server (NTRS)

Zhao, Yi

2002-01-01

The two major classes of laminate joints are bonded and bolted. Often the two classes are combined as bonded-bolted joints. Several characteristics of fiber reinforced composite materials render them more susceptible to joint problems than conventional metals. These characteristics include weakness in in-plane shear, transverse tension/compression, interlaminar shear, and bearing strength relative to the strength and stiffness in the fiber direction. Studies on bolted joints of composite materials have been focused on joining assembly subject to in-plane loads. Modes of failure under these loading conditions are net-tension failure, cleavage tension failure, shear-out failure, bearing failure, etc. Although the studies of torque load can be found in literature, they mainly discussed the effect of the torque load on in-plane strength. Existing methods for calculating torque limit for a mechanical fastener do not consider connecting members. The concern that a composite member could be crushed by a preload inspired the initiation of this study. The purpose is to develop a fundamental knowledge base on how to determine a torque limit when a composite member is taken into account. Two simplified analytical models were used: a stress failure analysis model based on maximum stress criterion, and a strain failure analysis model based on maximum strain criterion.

A 6-week hip muscle strengthening and lumbopelvic-hip core stabilization program to improve pain, function, and quality of life in persons with patellofemoral osteoarthritis: a feasibility pilot study.

PubMed

Hoglund, Lisa T; Pontiggia, Laura; Kelly, John D

2018-01-01

Patellofemoral joint (PFJ) osteoarthritis (OA) is prevalent in middle-aged and older adults. Despite this, there are minimal studies which have examined conservative interventions for PFJ OA. Weakness of proximal lower extremity muscles is associated with PFJ OA. It is unknown if a hip muscle strengthening and lumbopelvic-hip core stabilization program will improve symptoms and function in persons with PFJ OA. This study examined the feasibility and impact of a 6-week hip muscle strengthening and core stabilization program on pain, symptoms, physical performance, peak muscle torques, and quality of life in persons with PFJ OA. Ten females with PFJ OA and ten age- and sex-matched controls participated in baseline tests. PFJ OA participants attended ten twice-a-week hip strengthening and core stabilization exercise sessions. Outcome measures included questionnaires, the Timed-Up-and-Go, and peak isometric torque of hip and quadriceps muscles. Data were tested for normality; parametric and non-parametric tests were used as appropriate. At baseline, the PFJ OA group had significantly worse symptoms, slower Timed-Up-and-Go performance, and lower muscle torques than control participants. PFJ OA group adherence to supervised exercise sessions was adequate. All PFJ OA participants attended at least nine exercise sessions. Five PFJ OA participants returned 6-month follow-up questionnaires, which was considered fair retention. The PFJ OA participants' self-reported pain, symptoms, function in daily living, function in sport, and quality of life all improved at 6 weeks ( P  < 0.05). Timed-Up-and-Go time score improved at 6 weeks ( P  = 0.005). Peak hip external rotator torque increased ( P  = 0.01). Improvements in pain and self-reported function were no longer significant 6 months following completion of the intervention. PFJ OA participants were adherent to the supervised sessions of the intervention. Improvement in symptoms, physical performance, and muscle torque were found after 6 weeks. Participant retention at 6 months was fair, and significant changes were no longer present. Our findings suggest that a hip strengthening and core stabilization program may be beneficial to improve symptoms, function, and physical performance in persons with PFJ OA. Future studies are needed, and additional measures should be taken to improve long-term adherence to exercise. ClinicalTrials.gov NCT02825238. Registered 6 July 2016 (retrospectively registered).

Design of a 7-DOF slave robot integrated with a magneto-rheological haptic master

NASA Astrophysics Data System (ADS)

Hwang, Yong-Hoon; Cha, Seung-Woo; Kang, Seok-Rae; Choi, Seung-Bok

2017-04-01

In this study, a 7-DOF slave robot integrated with the haptic master is designed and its dynamic motion is controlled. The haptic master is made using a controllable magneto-rheological (MR) clutch and brake and it provides the surgeon with a sense of touch by using both kinetic and kinesthetic information. Due to the size constraint of the slave robot, a wire actuating is adopted to make the desired motion of the end-effector which has 3-DOF instead of a conventional direct-driven motor. Another motions of the link parts that have 4-DOF use direct-driven motor. In total system, for working as a haptic device, the haptic master need to receive the information of repulsive forces applied on the slave robot. Therefore, repulsive forces on the end-effector are sensed by using three uniaxial torque transducer inserted in the wire actuating system and another repulsive forces applied on link part are sensed by using 6-axis transducer that is able to sense forces and torques. Using another 6-axis transducer, verify the reliability of force information on final end of slave robot. Lastly, integrated with a MR haptic master, psycho-physical test is conducted by different operators who can feel the different repulsive force or torque generated from the haptic master which is equivalent to the force or torque occurred on the end-effector to demonstrate the effectiveness of the proposed system.

Motor impairment factors related to brain injury timing in early hemiparesis Part I: expression of upper extremity weakness

PubMed Central

Sukal-Moulton, Theresa; Krosschell, Kristin J.; Gaebler-Spira, Deborah J.; Dewald, Julius P.A.

2014-01-01

Background Extensive neuromotor development occurs early in human life, but the time that a brain injury occurs during development has not been rigorously studied when quantifying motor impairments. Objective This study investigated the impact of timing of brain injury on magnitude and distribution of weakness in the paretic arm of individuals with childhood-onset hemiparesis. Methods Twenty-four individuals with hemiparesis were divided into time periods of injury before birth (PRE-natal, n=8), around the time of birth (PERI-natal, n=8) or after 6 months of age (POST-natal, n=8). They, along with 8 typically developing peers, participated in maximal isometric shoulder, elbow, wrist, and finger torque generation tasks using a multiple degree-of-freedom load cell to quantify torques in 10 directions. A mixed model ANOVA was used to determine the effect of group and task on a calculated relative weakness ratio between arms. Results There was a significant effect of both time of injury group (p<0.001) and joint torque direction (p<0.001) on the relative weakness of the paretic arm. Distal joints were more affected compared to proximal joints, especially in the POST-natal group. Conclusions The distribution of weakness provides evidence for the relative preservation of ipsilateral corticospinal motor pathways to the paretic limb in those individuals injured earlier, while those who sustained later injury may rely more on indirect ipsilateral cortico-bulbospinal projections during the generation of torques with the paretic arm. PMID:24009182

Motor impairment factors related to brain injury timing in early hemiparesis. Part I: expression of upper-extremity weakness.

PubMed

Sukal-Moulton, Theresa; Krosschell, Kristin J; Gaebler-Spira, Deborah J; Dewald, Julius P A

2014-01-01

Extensive neuromotor development occurs early in human life, but the time that a brain injury occurs during development has not been rigorously studied when quantifying motor impairments. This study investigated the impact of timing of brain injury on the magnitude and distribution of weakness in the paretic arm of individuals with childhood-onset hemiparesis. A total of 24 individuals with hemiparesis were divided into time periods of injury before birth (PRE-natal, n = 8), around the time of birth (PERI-natal, n = 8), or after 6 months of age (POST-natal, n = 8). They, along with 8 typically developing peers, participated in maximal isometric shoulder, elbow, wrist, and finger torque generation tasks using a multiple-degree-of-freedom load cell to quantify torques in 10 directions. A mixed-model ANOVA was used to determine the effect of group and task on a calculated relative weakness ratio between arms. There was a significant effect of both time of injury group (P < .001) and joint torque direction (P < .001) on the relative weakness of the paretic arm. Distal joints were more affected compared with proximal joints, especially in the POST-natal group. The distribution of weakness provides evidence for the relative preservation of ipsilateral corticospinal motor pathways to the paretic limb in those individuals injured earlier, whereas those who sustained later injury may rely more on indirect ipsilateral corticobulbospinal projections during the generation of torques with the paretic arm.

Effect of axial tibial torque direction on ACL relative strain and strain rate in an in vitro simulated pivot landing.

PubMed

Oh, Youkeun K; Kreinbrink, Jennifer L; Wojtys, Edward M; Ashton-Miller, James A

2012-04-01

Anterior cruciate ligament (ACL) injuries most frequently occur under the large loads associated with a unipedal jump landing involving a cutting or pivoting maneuver. We tested the hypotheses that internal tibial torque would increase the anteromedial (AM) bundle ACL relative strain and strain rate more than would the corresponding external tibial torque under the large impulsive loads associated with such landing maneuvers. Twelve cadaveric female knees [mean (SD) age: 65.0 (10.5) years] were tested. Pretensioned quadriceps, hamstring, and gastrocnemius muscle-tendon unit forces maintained an initial knee flexion angle of 15°. A compound impulsive test load (compression, flexion moment, and internal or external tibial torque) was applied to the distal tibia while recording the 3D knee loads and tibofemoral kinematics. AM-ACL relative strain was measured using a 3 mm DVRT. In this repeated measures experiment, the Wilcoxon signed-rank test was used to test the null hypotheses with p < 0.05 considered significant. The mean (±SD) peak AM-ACL relative strains were 5.4 ± 3.7% and 3.1 ± 2.8% under internal and external tibial torque, respectively. The corresponding mean (± SD) peak AM-ACL strain rates reached 254.4 ± 160.1%/s and 179.4 ± 109.9%/s, respectively. The hypotheses were supported in that the normalized mean peak AM-ACL relative strain and strain rate were 70 and 42% greater under internal than under external tibial torque, respectively (p = 0.023, p = 0.041). We conclude that internal tibial torque is a potent stressor of the ACL because it induces a considerably (70%) larger peak strain in the AM-ACL than does a corresponding external tibial torque. Copyright © 2011 Orthopaedic Research Society.

Displacement of screw-retained single crowns into implants with conical internal connections.

PubMed

Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2013-01-01

Internal conical implant-abutment connections without platforms may lead to axial displacement of crowns during screw tightening. This displacement may affect proximal contacts, incisal edge position, or occlusion. This study aimed to measure the displacement of screw-retained single crowns into an implant in three dimensions during screw tightening by hand or via torque driver. A stereolithic acrylic resin cast was created using computed tomography data from a patient missing the maxillary right central incisor. A 4.0- × 11-mm implant was placed in the edentulous site. Five porcelain-fused-to-metal single crowns were made using "cast-to" abutments. Crowns were tried on the stereolithic model, representing the patient, and hand tightened. The spatial relationship of crowns to the model after hand tightening was determined using three-dimensional digital image correlation (3D DIC), an optical measurement technique. The crowns were then tightened using a torque driver to 20 Ncm and the relative crown positions were again recorded. Testing was repeated three times for each crown, and displacement of the crowns was compared between the hand-tightened and torqued states. Commercial image correlation software was used to analyze the data. Mean vertical and horizontal crown displacement values were calculated after torqueing. The interproximal contacts were evaluated before and after torquing using an 8-μm aluminum foil shim. There were vertical and horizontal differences in crown positions between hand tightening and torqueing. Although these were small in magnitude, detectable displacements occurred in both apical and facial directions. After hand tightening, the 8-μm shim could be dragged without tearing. However, after torque tightening, the interproximal contacts were too tight and the 8-μm shim could not be dragged without tearing. Differences between hand tightening and torque tightening should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.

Does Humeral Component Lateralization in Reverse Shoulder Arthroplasty Affect Rotator Cuff Torque? Evaluation in a Cadaver Model.

PubMed

Chan, Kevin; Langohr, G Daniel G; Mahaffy, Matthew; Johnson, James A; Athwal, George S

2017-10-01

Humeral component lateralization in reverse total shoulder arthroplasty (RTSA) may improve the biomechanical advantage of the rotator cuff, which could improve the torque generated by the rotator cuff and increase internal and external rotation of the shoulder. The purpose of this in vitro biomechanical study was to evaluate the effect of humeral component lateralization (or lateral offset) on the torque of the anterior and posterior rotator cuff. Eight fresh-frozen cadaveric shoulders from eight separate donors (74 ± 8 years; six males, two females) were tested using an in vitro simulator. All shoulders were prescreened for soft tissue deficit and/or deformity before testing. A custom RTSA prosthesis was implanted that allowed five levels of humeral component lateralization (15, 20, 25, 30, 35 mm), which avoided restrictions imposed by commercially available designs. The torques exerted by the anterior and posterior rotator cuff were measured three times and then averaged for varying humeral lateralization, abduction angle (0°, 45°, 90°), and internal and external rotation (-60°, -30°, 0°, 30°, 60°). A three-way repeated measures ANOVA (abduction angle, humeral lateralization, internal rotation and external rotation angles) with a significance level of α = 0.05 was used for statistical analysis. Humeral lateralization only affected posterior rotator cuff torque at 0° abduction, where increasing humeral lateralization from 15 to 35 mm at 60° internal rotation decreased external rotation torque by 1.6 ± 0.4 Nm (95% CI, -0.07 -1.56 Nm; p = 0.06) from 4.0 ± 0.3 Nm to 2.4 ± 0.6 Nm, respectively, but at 60° external rotation increased external rotation torque by 2.2 ± 0.5 Nm (95% CI, -4.2 to -0.2 Nm; p = 0.029) from 6.2 ± 0.5 Nm to 8.3 ± 0.5 Nm, respectively. Anterior cuff torque was affected by humeral lateralization in more arm positions than the posterior cuff, where increasing humeral lateralization from 15 to 35 mm when at 60° internal rotation increased internal rotation torque at 0°, 45°, and 90° abduction by 3.2 ± 0.5 Nm (95% CI, 1.1-5.2 Nm; p = 0.004) from 6.6 ± 0.6 Nm to 9.7 ± 0.6 Nm, 4.0 ± 0.3 Nm (95% CI, 2.8-5.0 Nm; p < 0.001) from 1.7 ± 1.0 Nm to 5.6 ± 0.9 Nm, and 2.2 ± 0.2 Nm (95% CI, 1.4-2.9 Nm; p < 0.001) from 0.6 ± 0.6 Nm to 2.8 ± 0.6 Nm, respectively. In neutral internal and external rotation, increasing humeral lateral offset from 15 to 35 mm increased the internal rotation torque at 45˚ and 90˚ abduction by 1.5 ± 0.3 Nm (95% CI, 0.2-2.7 Nm; p = 0.02) and 1.3 ± 0.2 Nm (95% CI, 0.4-2.3 Nm; p < 0.001), respectively. Humeral component lateralization improves rotator cuff torque. The results of this preliminary in vitro cadaveric study suggest that the lateral offset of the RTSA humeral component plays an important role in the torque generated by the anterior and posterior rotator cuff. However, further studies are needed before clinical application of these results. Increasing humeral offset may have adverse effects, such as the increased risk of implant modularity, increasing tension of the cuff and soft tissues, increased costs often associated with design modifications, and other possible as yet unforeseen negative consequences.

Compensating for intersegmental dynamics across the shoulder, elbow, and wrist joints during feedforward and feedback control.

PubMed

Maeda, Rodrigo S; Cluff, Tyler; Gribble, Paul L; Pruszynski, J Andrew

2017-10-01

Moving the arm is complicated by mechanical interactions that arise between limb segments. Such intersegmental dynamics cause torques applied at one joint to produce movement at multiple joints, and in turn, the only way to create single joint movement is by applying torques at multiple joints. We investigated whether the nervous system accounts for intersegmental limb dynamics across the shoulder, elbow, and wrist joints during self-initiated planar reaching and when countering external mechanical perturbations. Our first experiment tested whether the timing and amplitude of shoulder muscle activity account for interaction torques produced during single-joint elbow movements from different elbow initial orientations and over a range of movement speeds. We found that shoulder muscle activity reliably preceded movement onset and elbow agonist activity, and was scaled to compensate for the magnitude of interaction torques arising because of forearm rotation. Our second experiment tested whether elbow muscles compensate for interaction torques introduced by single-joint wrist movements. We found that elbow muscle activity preceded movement onset and wrist agonist muscle activity, and thus the nervous system predicted interaction torques arising because of hand rotation. Our third and fourth experiments tested whether shoulder muscles compensate for interaction torques introduced by different hand orientations during self-initiated elbow movements and to counter mechanical perturbations that caused pure elbow motion. We found that the nervous system predicted the amplitude and direction of interaction torques, appropriately scaling the amplitude of shoulder muscle activity during self-initiated elbow movements and rapid feedback control. Taken together, our results demonstrate that the nervous system robustly accounts for intersegmental dynamics and that the process is similar across the proximal to distal musculature of the arm as well as between feedforward (i.e., self-initiated) and feedback (i.e., reflexive) control. NEW & NOTEWORTHY Intersegmental dynamics complicate the mapping between applied joint torques and the resulting joint motions. We provide evidence that the nervous system robustly predicts these intersegmental limb dynamics across the shoulder, elbow, and wrist joints during reaching and when countering external perturbations. Copyright © 2017 the American Physiological Society.

Improved Beam Jitter Control Methods for High Energy Laser Systems

DTIC Science & Technology

2009-12-01

Figure 16. The inner loop is a rate control loop composed of a gimbal, power amplifier , controller, and servo components (gyro, motor, and encoder...system characterization experiments 1. WFOV Control Loop a. Resonance Frequency Random signals were applied to the power amplifier and output...Loop Stabilization By applying a disturbance to the input of the power amplifier and measuring torque error, one is able to determine the torque

Key-and-keyway coupling for transmitting torque

DOEpatents

Blue, S.C.; Curtis, M.T.; Orthwein, W.C.; Stitt, D.H.

1975-11-18

The design of an improved key-and-keyway coupling for the transmission of torque is given. The coupling provides significant reductions in stress concentrations in the vicinity of the key and keyway. The keyway is designed with a flat-bottomed u-shaped portion whose inboard end terminates in a ramp which is dished transversely, so that the surface of the ramp as viewed in transverse section defines an outwardly concave arc.

Space suit glove design with advanced metacarpal phalangeal joints and robotic hand evaluation.

PubMed

Southern, Theodore; Roberts, Dustyn P; Moiseev, Nikolay; Ross, Amy; Kim, Joo H

2013-06-01

One area of space suits that is ripe for innovation is the glove. Existing models allow for some fine motor control, but the power grip--the act of grasping a bar--is cumbersome due to high torque requirements at the knuckle or metacarpal phalangeal joint (MCP). This area in particular is also a major source of complaints of pain and injury as reported by astronauts. This paper explores a novel fabrication and patterning technique that allows for more freedom of movement and less pain at this crucial joint in the manned space suit glove. The improvements are evaluated through unmanned testing, manned testing while depressurized in a vacuum glove box, and pressurized testing with a robotic hand. MCP joint flex score improved from 6 to 6.75 (out of 10) in the final glove relative to the baseline glove, and torque required for flexion decreased an average of 17% across all fingers. Qualitative assessments during unpressurized and depressurized manned testing also indicated the final glove was more comfortable than the baseline glove. The quantitative results from both human subject questionnaires and robotic torque evaluation suggest that the final iteration of the glove design enables flexion at the MCP joint with less torque and more comfort than the baseline glove.

Non-equilibrium dynamic reversal of in-plane ferromagnetic elliptical disk

NASA Astrophysics Data System (ADS)

Kim, June-Seo; Hwang, Hee-Kyeong; You, Chun-Yeol

2018-01-01

The ultrafast switching mechanism of an in-plane magnetized elliptical magnetic disk by applying dynamic out-of-plane magnetic field pulses is investigated by performing micromagnetic simulations. For the in-plane magnetized nanostructures, the out-of-plane magnetic field is able to rotate the direction of magnetization when the precession torque overcomes the shape anisotropy of the system. This type magnetization reversal is one of non-equilibrium dynamic within a certain transition time util the precession torque is equivalent to the damping torque. By controlling the rise time or fall times of dynamic out-of-plane field pulses, the transition time can be also successively tuned and then an ultrafast switching of an elliptical magnetic nano-disk is clearly achieved by controlling the precessional torque. As another reversal approach, sinusoidal magnetic fields in gigahertz range are applied to the system. Consequently, the thresholds of switching fields are drastically decreased. We also reveal that the ferromagnetic resonance frequencies at the center and the edge of the elliptical disk are most important for microwave sinusoidal out-of-plane magnetic field induced magnetization reversal.

Biophysical Characterization of a Thermoalkaliphilic Molecular Motor with a High Stepping Torque Gives Insight into Evolutionary ATP Synthase Adaptation*

PubMed Central

McMillan, Duncan G. G.; Watanabe, Rikiya; Ueno, Hiroshi; Cook, Gregory M.; Noji, Hiroyuki

2016-01-01

F1F0 ATP synthases are bidirectional molecular motors that translocate protons across the cell membrane by either synthesizing or hydrolyzing ATP. Alkaliphile ATP synthases are highly adapted, performing oxidative phosphorylation at high pH against an inverted pH gradient (acidin/alkalineout). Unlike mesophilic ATP synthases, alkaliphilic enzymes have tightly regulated ATP hydrolysis activity, which can be relieved in the presence of lauryldimethylamine oxide. Here, we characterized the rotary dynamics of the Caldalkalibacillus thermarum TA2.A1 F1 ATPase (TA2F1) with two forms of single molecule analysis, a magnetic bead duplex and a gold nanoparticle. TA2F1 rotated in a counterclockwise direction in both systems, adhering to Michaelis-Menten kinetics with a maximum rotation rate (Vmax) of 112.4 revolutions/s. TA2F1 displayed 120° unitary steps coupled with ATP hydrolysis. Torque measurements revealed the highest torque (52.4 piconewtons) derived from an F1 molecule using fluctuation theorem. The implications of high torque in terms of extreme environment adaptation are discussed. PMID:27624936

Effect of anisotropic thermal transport on the resistive plasma response to resonant magnetic perturbation field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue; Liu, Yueqiang; Gao, Zhe

Plasma response to the resonant magnetic perturbation (RMP) field is numerically investigated by an extended toroidal fluid model, which includes anisotropic thermal transport physics parallel and perpendicular to the total magnetic field. The thermal transport is found to be effective in eliminating the toroidal average curvature induced plasma screening (the so called Glasser-Green-Johnson, GGJ screening) at slow toroidal flow regime, whilst having minor effect on modifying the conventional plasma screening regimes at faster flow. Furthermore, this physics effect of interaction between thermal transport and GGJ screening is attributed to the modification of the radial structure of the shielding current, resultedmore » from the plasma response to the applied field. The modification of the plasma response (shielding current, response field, plasma displacement and the perturbed velocity) also has direct consequence on the toroidal torques produced by RMP. These modelling results show that thermal transport reduces the resonant electromagnetic torque as well as the torque associated with the Reynolds stress, but enhances the neoclassical toroidal viscous torque at slow plasma flow.« less

Effect of anisotropic thermal transport on the resistive plasma response to resonant magnetic perturbation field

DOE PAGES

Bai, Xue; Liu, Yueqiang; Gao, Zhe

2017-09-21

Plasma response to the resonant magnetic perturbation (RMP) field is numerically investigated by an extended toroidal fluid model, which includes anisotropic thermal transport physics parallel and perpendicular to the total magnetic field. The thermal transport is found to be effective in eliminating the toroidal average curvature induced plasma screening (the so called Glasser-Green-Johnson, GGJ screening) at slow toroidal flow regime, whilst having minor effect on modifying the conventional plasma screening regimes at faster flow. Furthermore, this physics effect of interaction between thermal transport and GGJ screening is attributed to the modification of the radial structure of the shielding current, resultedmore » from the plasma response to the applied field. The modification of the plasma response (shielding current, response field, plasma displacement and the perturbed velocity) also has direct consequence on the toroidal torques produced by RMP. These modelling results show that thermal transport reduces the resonant electromagnetic torque as well as the torque associated with the Reynolds stress, but enhances the neoclassical toroidal viscous torque at slow plasma flow.« less

Spatially and time-resolved magnetization dynamics driven by spin-orbit torques

NASA Astrophysics Data System (ADS)

Baumgartner, Manuel; Garello, Kevin; Mendil, Johannes; Avci, Can Onur; Grimaldi, Eva; Murer, Christoph; Feng, Junxiao; Gabureac, Mihai; Stamm, Christian; Acremann, Yves; Finizio, Simone; Wintz, Sebastian; Raabe, Jörg; Gambardella, Pietro

2017-10-01

Current-induced spin-orbit torques are one of the most effective ways to manipulate the magnetization in spintronic devices, and hold promise for fast switching applications in non-volatile memory and logic units. Here, we report the direct observation of spin-orbit-torque-driven magnetization dynamics in Pt/Co/AlOx dots during current pulse injection. Time-resolved X-ray images with 25 nm spatial and 100 ps temporal resolution reveal that switching is achieved within the duration of a subnanosecond current pulse by the fast nucleation of an inverted domain at the edge of the dot and propagation of a tilted domain wall across the dot. The nucleation point is deterministic and alternates between the four dot quadrants depending on the sign of the magnetization, current and external field. Our measurements reveal how the magnetic symmetry is broken by the concerted action of the damping-like and field-like spin-orbit torques and the Dzyaloshinskii-Moriya interaction, and show that reproducible switching events can be obtained for over 1012 reversal cycles.

A quasi-linear control theory analysis of timesharing skills

NASA Technical Reports Server (NTRS)

Agarwal, G. C.; Gottlieb, G. L.

1977-01-01

The compliance of the human ankle joint is measured by applying 0 to 50 Hz band-limited gaussian random torques to the foot of a seated human subject. These torques rotate the foot in a plantar-dorsal direction about a horizontal axis at a medial moleolus of the ankle. The applied torques and the resulting angular rotation of the foot are measured, digitized and recorded for off-line processing. Using such a best-fit, second-order model, the effective moment of inertia of the ankle joint, the angular viscosity and the stiffness are calculated. The ankle joint stiffness is shown to be a linear function of the level of tonic muscle contraction, increasing at a rate of 20 to 40 Nm/rad/Kg.m. of active torque. In terms of the muscle physiology, the more muscle fibers that are active, the greater the muscle stiffness. Joint viscosity also increases with activation. Joint stiffness is also a linear function of the joint angle, increasing at a rate of about 0.7 to 1.1 Nm/rad/deg from plantar flexion to dorsiflexion rotation.

Effect of anisotropic thermal transport on the resistive plasma response to resonant magnetic perturbation field

NASA Astrophysics Data System (ADS)

Bai, Xue; Liu, Yueqiang; Gao, Zhe

2017-10-01

Plasma response to the resonant magnetic perturbation (RMP) field is numerically investigated by an extended toroidal fluid model, which includes anisotropic thermal transport physics parallel and perpendicular to the total magnetic field. The thermal transport is found to be effective in eliminating the toroidal average curvature induced plasma screening (the so called Glasser-Green-Johnson, GGJ screening) in a slow toroidal flow regime, whilst having minor effect on modifying the conventional plasma screening regimes at faster flow. This physics effect of interaction between thermal transport and GGJ screening is attributed to the modification of the radial structure of the shielding current, which resulted from the plasma response to the applied field. The modification of the plasma response (shielding current, response field, plasma displacement, and the perturbed velocity) also has direct consequence on the toroidal torques produced by RMP. Modelling results show that thermal transport reduces the resonant electromagnetic torque as well as the torque associated with the Reynolds stress, but enhances the neoclassical toroidal viscous torque at slow plasma flow.

An isokinetic training program for reducing falls in a community-dwelling older adult: a case report.

PubMed

Beebe, Justin A; Hines, Roger W; McDaniel, Laura T; Shelden, Brenda L

2013-01-01

With the population older than 65 years, projected to double by the year 2030, falls in older adults are a substantial health concern. Muscle strength deficits are one of the multifactorial components linked to increased fall risk, and decreasing these deficits has been one of the goals of interventions designed to decrease fall risk. These interventions have traditionally focused on improving peak torque; however, recent research suggests that exercise protocols that focus on the rate of torque development (RTD) may be more effective in decreasing fall risk. This case report examines clinical outcomes following implementation of an isokinetic strengthening protocol coupled with a balance program designed to reduce fall risk in a community-dwelling older adult. The individual was a 70-year-old woman with a history of 3 falls over the past 8 months and no related medical etiology who had self-limited her activities because of fear of another fall. She was classified as having substantial risk for future falls because of fall history, increased fear of falling, and below age norms on the Berg Balance Scale (BBS), and the Timed Up and Go (TUG). The treatment program consisted of 12 weeks of high-intensity isokinetic knee extensor training, high challenge dynamic gait and balance activities, and core strengthening. The isokinetic protocol consisted of 4 sets of 10 concentric-only repetitions at speeds of 240°/sec and 300°/sec for a total of 8 work sets. Dynamic gait activities incorporating directional and obstacle drills, and rocker and balance boards were used for balance training activities. Progressive theraband exercises were used for core strengthening. As her home program, the participant was encouraged to return to line dancing twice per week. During the 12-week protocol, the participant completed two 90-minute therapy sessions and two 90-minute dance classes per week. After the 12 weeks of treatment, knee extensor peak torque at 150 ms improved on the right from 67.8 N to 107.1 N (57.9% increase), and on the left from 65.1 N to 97.6 N (49.9% increase). The BBS score improved from 45 to 52; and the TUG improved from 14.0 to 8.6 seconds. Both final scores exceeded fall risk cutoffs (BBS = 48; TUG = 13.5 seconds) and the change score exceeded minimal detectable change (BBS = 7; TUG 5.4 seconds). The treatment program produced improvements in knee extensor peak torque and RTD, but more importantly, the final scores on the clinical outcome measures placed the participant above established fall-risk cutoff scores. Although future research with increased numbers of participants and a control group should be conducted to confirm this study's results, these findings support the use of isokinetic training to reduce fall risk in older adults.

A home-based program of transcutaneous electrical nerve stimulation and task-related trunk training improves trunk control in patients with stroke: a randomized controlled clinical trial.

PubMed

Chan, Bill K S; Ng, Shamay S M; Ng, Gabriel Y F

2015-01-01

Impaired trunk motor control is common after stroke. Combining transcutaneous electrical nerve stimulation (TENS) with task-related trunk training (TRTT) has been shown to enhance the recovery of lower limb motor function. This study investigated whether combining TENS with TRTT would enhance trunk control after stroke. Methods. Thirty-seven subjects with stroke were recruited into a randomized controlled clinical trial. Subjects were randomly assigned to any one of the three 6-week home-based training groups: (1) TENS + TRTT, (2) placebo TENS + TRTT, or (3) control without active training. The outcome measures included isometric peak trunk flexion torque and extension torque; forward seated and lateral seated reaching distance to the affected and unaffected side; and Trunk Impairment Scale (TIS) scores. All outcome measures were assessed at baseline, after 3 and 6 weeks of training, and 4 weeks after training ended at follow-up. Both the TENS + TRTT and the placebo-TENS + TRTT groups had significantly greater improvements in isometric peak trunk flexion torque and extension torque, lateral seated reaching distance to affected and unaffected side, and TIS score than the control group after 3 weeks of training. The TENS + TRTT group had significantly greater and earlier improvement in its mean TIS score than the other 2 groups. Home-based TRTT is effective for improving trunk muscle strength, sitting functional reach and trunk motor control after stroke in subjects without somatosensory deficits. The addition of TENS to the trunk augments the effectiveness of the exercise in terms of TIS scores within the first 3 weeks of training. © The Author(s) 2014.

Bio-inspired sensing and control for disturbance rejection and stabilization

NASA Astrophysics Data System (ADS)

Gremillion, Gregory; Humbert, James S.

2015-05-01

The successful operation of small unmanned aircraft systems (sUAS) in dynamic environments demands robust stability in the presence of exogenous disturbances. Flying insects are sensor-rich platforms, with highly redundant arrays of sensors distributed across the insect body that are integrated to extract rich information with diminished noise. This work presents a novel sensing framework in which measurements from an array of accelerometers distributed across a simulated flight vehicle are linearly combined to directly estimate the applied forces and torques with improvements in SNR. In simulation, the estimation performance is quantified as a function of sensor noise level, position estimate error, and sensor quantity.

Examination of Disk-Type Multidegree-of-Freedom Ultrasonic Motor

NASA Astrophysics Data System (ADS)

Aoyagi, Manabu; Nakajima, Toshinori; Tomikawa, Yoshiro; Takano, Takehiro

2004-05-01

A multidegree-of-freedom (MDOF) ultrasonic motor using the multimode of a disk vibrator is realized. A spherical rotor can rotate around arbitrary axes. However, at the beginning of research on the MDOF ultrasonic motor, the MDOF ultrasonic motor did not have any mechanisms for supporting a spherical rotor. Since the preload was given by only the rotor’s own weight, the friction between the rotor and the stator vibrator was very small, but the torque characteristics of the MDOF motor were insufficient for practical use. The purpose of this study is to improve the motor performance further. In this paper, some support and preload mechanisms using a support plate were examined for the improvement of the motor performance. In addition to these methods, a sandwich structure in which two stator vibrators hold a spherical rotor is proposed. This structure has both a rotor support mechanism and a preload mechanism, and high torque by the torque composition of two stator vibrators can be obtained.

In-orbit performance of the ITOS improved attitude control system with Hall generator brushless motor and earth-splitting technique

NASA Technical Reports Server (NTRS)

Peacock, W. M.

1973-01-01

The National Aeronautics and Space Administration (NASA), launched ITOS-D with an improved attitude control system. A Hall generator brushless dc torque motor replaced the brush dc torque motor on Tiros-M and ITOS-A. Two CO2 attitude horizon sensors and one mirror replaced the four wideband horizon sensors and two mirrors on ITOS-1 and NOAA-1. Redundant pitch-control electronic boxes containing additional electronic circuitry for earth-splitting and brushless motor electronics were used. A method of generating a spacecraft earth-facing side reference for comparison to the time occurrence of the earth-splitting pulse was used to automatically correct pitch-attitude error. A single rotating flywheel, supported by a single bearing, provided gyroscopic stability and the required momentum interchange to keep one side of the satellite facing the earth. Magnetic torquing against the earth's magnetic field eliminated the requirement for expendable propellants which would limit satellite life in orbit.

Operating force information on-line acquisition of a novel slave manipulator for vascular interventional surgery.

PubMed

Zhao, Yan; Guo, Shuxiang; Xiao, Nan; Wang, Yuxin; Li, Youxiang; Jiang, Yuhua

2018-04-02

Vascular interventional surgery has its advantages compared to traditional operation. Master-slave robotic technology can further improve the operation accuracy, efficiency and safety of this complicated and high risk surgery. However, on-line acquisition of operating force information of catheter and guidewire remains to be a significant obstacle on the path to enhancing robotic surgery safety. Thus, a novel slave manipulator is proposed in this paper to realize on-line sensing of guidewire torsional operating torque and axial operation force during robotic assisted operations. A strain sensor is specially designed to detect the small scale torsional operation torque with low rotational frequency. Additionally, the axial operating force is detected via a load cell, which is incorporated into a sliding mechanism to eliminate the influence of friction. For validation, calibration and performance evaluation experiments are conducted. The results indicate that the proposed operation torque and force detection device is effective. Thus, it can provide the foundation for enabling accurate haptic feedback to the surgeon to improve surgical safety.

Decoupling analysis of a novel bearingless flux-switching permanent magnet motor

NASA Astrophysics Data System (ADS)

Zhao, Chenyin; Zhu, Huangqiu; Qin, Yuemei

2017-05-01

In this paper, a novel 12/10 stator/rotor pole bearingless flux-switching permanent magnet (BFSPM) motor is proposed to overcome the drawbacks of rotor permanent magnet type bearingless motors. The basic motor configuration, including motor configuration and winding configuration, is introduced firstly. Then, based on the principle of reverse direction magnetization for symmetrical rotor teeth, the radial suspension forces generation principle is analyzed in detail. Finally, decoupling performances between suspension force windings and torque windings are investigated. The results show that the proposed BFSPM not only ensures the merits of high torque output capability compared with conventional 12/10 stator/rotor pole FSPM motor, but also achieves stable radial suspension forces which have little mutual effect with torque. The validity of the proposed structure has been verified by finite element analysis (FEA).

'Neo-Suterian' pump-turbine characteristics and their benefits

NASA Astrophysics Data System (ADS)

Dörfler, P. K.

2010-08-01

Conventional representations of the various operation modes of a pump-turbine (4-quadrant characteristics) have important disadvantages. While curves of Q11 vs n11 have singularities at E=0 and multiple values in the 'unstable' ranges, the curves EnD(QnD) get singular at n=0. As a remedy, one may split the characteristics into separate parts, and switch between them. Another approach introduced by P. Suter (1966, [1]) defines a different set of variables which avoids singularity and always remains unique-valued. Suter described this artifice for non-regulated pumps; but using it for regulated machines without modifications is not practical due to large distortions at small guide vane opening. A decisive improvement has been described by C.S. Martin [4]. It avoids the distortion of the head-vs-flow curves at low load. The present paper describes how further improvement is possible, in particular with regard to the representation of torque. A modified torque parameter is obtained by subtracting the shutoff torque; this parameter can be handled in the same practical way as the discharge. Other improvements concern the correction for leakage at small guide vane opening, and the treatment of very small and zero opening. These details are concerned with the problem of closed gate where Suter's concept does not work. Applications are demonstrated, not only how to represent the hydraulic performance (head vs. discharge and torque vs. discharge), but also for other characteristics, such as the development of pressure and pressure pulsation in various locations, or the steady-state and unsteady guide vane torque. The advantage of a set of continuous, single-valued functions for all those physical properties greatly simplifies computation of their behavior during transients. Moreover, the, Suterized' properties of pump-turbines of different specific speed are less different from each other than the conventional ones, a fact that facilitates application of available test data for later projects.

Alternative Determination of Density of the Titan Atmosphere

NASA Technical Reports Server (NTRS)

Lee, Allan; Brown, Jay; Feldman, Antonette; Peer, Scott; Wamg. Eric

2009-01-01

An alternative has been developed to direct measurement for determining the density of the atmosphere of the Saturn moon Titan as a function of altitude. The basic idea is to deduce the density versus altitude from telemetric data indicative of the effects of aerodynamic torques on the attitude of the Cassini Saturn orbiter spacecraft as it flies past Titan at various altitudes. The Cassini onboard attitude-control software includes a component that can estimate three external per-axis torques exerted on the spacecraft. These estimates are available via telemetry.

Thermophoretic torque in colloidal particles with mass asymmetry

NASA Astrophysics Data System (ADS)

Olarte-Plata, Juan; Rubi, J. Miguel; Bresme, Fernando

2018-05-01

We investigate the response of anisotropic colloids suspended in a fluid under a thermal field. Using nonequilibrium molecular dynamics computer simulations and nonequilibrium thermodynamics theory, we show that an anisotropic mass distribution inside the colloid rectifies the rotational Brownian motion and the colloids experience transient torques that orient the colloid along the direction of the thermal field. This physical effect gives rise to distinctive changes in the dependence of the Soret coefficient with colloid mass, which features a maximum, unlike the monotonic increase of the thermophoretic force with mass observed in homogeneous colloids.

Evaluation of force-torque displays for use with space station telerobotic activities

NASA Technical Reports Server (NTRS)

Hendrich, Robert C.; Bierschwale, John M.; Manahan, Meera K.; Stuart, Mark A.; Legendre, A. Jay

1992-01-01

Recent experiments which addressed Space Station remote manipulation tasks found that tactile force feedback (reflecting forces and torques encountered at the end-effector through the manipulator hand controller) does not improve performance significantly. Subjective response from astronaut and non-astronaut test subjects indicated that force information, provided visually, could be useful. No research exists which specifically investigates methods of presenting force-torque information visually. This experiment was designed to evaluate seven different visual force-torque displays which were found in an informal telephone survey. The displays were prototyped in the HyperCard programming environment. In a within-subjects experiment, 14 subjects nullified forces and torques presented statically, using response buttons located at the bottom of the screen. Dependent measures included questionnaire data, errors, and response time. Subjective data generally demonstrate that subjects rated variations of pseudo-perspective displays consistently better than bar graph and digital displays. Subjects commented that the bar graph and digital displays could be used, but were not compatible with using hand controllers. Quantitative data show similar trends to the subjective data, except that the bar graph and digital displays both provided good performance, perhaps do to the mapping of response buttons to display elements. Results indicate that for this set of displays, the pseudo-perspective displays generally represent a more intuitive format for presenting force-torque information.

Solar and Heliospheric Observatory (SOHO) Flight Dynamics Simulations Using MATLAB (R)

NASA Technical Reports Server (NTRS)

Headrick, R. D.; Rowe, J. N.

1996-01-01

This paper describes a study to verify onboard attitude control laws in the coarse Sun-pointing (CSP) mode by simulation and to develop procedures for operational support for the Solar and Heliospheric Observatory (SOHO) mission. SOHO was launched on December 2, 1995, and the predictions of the simulation were verified with the flight data. This study used a commercial off the shelf product MATLAB(tm) to do the following: Develop procedures for computing the parasitic torques for orbital maneuvers; Simulate onboard attitude control of roll, pitch, and yaw during orbital maneuvers; Develop procedures for predicting firing time for both on- and off-modulated thrusters during orbital maneuvers; Investigate the use of feed forward or pre-bias torques to reduce the attitude handoff during orbit maneuvers - in particular, determine how to use the flight data to improve the feed forward torque estimates for use on future maneuvers. The study verified the stability of the attitude control during orbital maneuvers and the proposed use of feed forward torques to compensate for the attitude handoff. Comparison of the simulations with flight data showed: Parasitic torques provided a good estimate of the on- and off-modulation for attitude control; The feed forward torque compensation scheme worked well to reduce attitude handoff during the orbital maneuvers. The work has been extended to prototype calibration of thrusters from observed firing time and observed reaction wheel speed changes.

Temperature dependence of spin-orbit torques in Pt/Co/Pt multilayers

NASA Astrophysics Data System (ADS)

Chen, Shiwei; Li, Dong; Cui, Baoshan; Xi, Li; Si, Mingsu; Yang, Dezheng; Xue, Desheng

2018-03-01

We studied the current-induced spin-orbit torques in a perpendicularly magnetized Pt (1 nm)/Co (0.8 nm)/Pt (5 nm) heterojunction by harmonic Hall voltage measurements. Owing to similar Pt/Co/Pt interfaces, the spin-orbit torques originated from the Rashba effect are reduced, but the contribution from the spin Hall effect is still retained because of asymmetrical Pt thicknesses. When the temperature increases from 50 to 300 K, two orthogonal components of the effective field, induced by spin-orbit torques, reveal opposite temperature dependencies: the field-like term (transverse effective field) decreases from 2.3 to 2.1 (10-6 Oe (A cm-2)-1), whereas the damping-like term (longitudinal effective field) increases from 3.7 to 4.8 (10-6 Oe (A cm-2)-1). It is noticed that the damping-like term, usually smaller than the field-like term in the similar Pt/Co interfaces, is twice as large as the field-like term. As a result, the damping-like spin-orbit torque reaches an efficiency of 0.15 at 300 K. Such a temperature-dependent damping-like term in a Pt/Co/Pt heterojunction can efficiently reduce the switching current density which is 2.30  ×  106 A cm-2 at 300 K, providing an opportunity to further improve and understand spin-orbit torques induced by spin Hall effect.

Helical waves in easy-plane antiferromagnets

NASA Astrophysics Data System (ADS)

Semenov, Yuriy G.; Li, Xi-Lai; Xu, Xinyi; Kim, Ki Wook

2017-12-01

Effective spin torques can generate the Néel vector oscillations in antiferromagnets (AFMs). Here, it is theoretically shown that these torques applied at one end of a normal AFM strip can excite a helical type of spin wave in the strip whose properties are drastically different from characteristic spin waves. An analysis based on both a Néel vector dynamical equation and the micromagnetic simulation identifies the direction of magnetic anisotropy and the damping factor as the two key parameters determining the dynamics. Helical wave propagation requires the hard axis of the easy-plane AFM to be aligned with the traveling direction, while the damping limits its spatial extent. If the damping is neglected, the calculation leads to a uniform periodic domain wall structure. On the other hand, finite damping decelerates the helical wave rotation around the hard axis, ultimately causing stoppage of its propagation along the strip. With the group velocity staying close to spin-wave velocity at the wave front, the wavelength becomes correspondingly longer away from the excitation point. In a sufficiently short strip, a steady-state oscillation can be established whose frequency is controlled by the waveguide length as well as the excitation energy or torque.

Walking patterns and hip contact forces in patients with hip dysplasia.

PubMed

Skalshøi, Ole; Iversen, Christian Hauskov; Nielsen, Dennis Brandborg; Jacobsen, Julie; Mechlenburg, Inger; Søballe, Kjeld; Sørensen, Henrik

2015-10-01

Several studies have investigated walking characteristics in hip dysplasia patients, but so far none have described all hip rotational degrees of freedom during the whole gait cycle. This descriptive study reports 3D joint angles and torques, and furthermore extends previous studies with muscle and joint contact forces in 32 hip dysplasia patients and 32 matching controls. 3D motion capture data from walking and standing trials were analysed. Hip, knee, ankle and pelvis angles were calculated with inverse kinematics for both standing and walking trials. Hip, knee and ankle torques were calculated with inverse dynamics, while hip muscle and joint contact forces were calculated with static optimisation for the walking trials. No differences were found between the two groups while standing. While walking, patients showed decreased hip extension, increased ankle pronation and increased hip abduction and external rotation torques. Furthermore, hip muscle forces were generally lower and shifted to more posteriorly situated muscles, while the hip joint contact force was lower and directed more superiorly. During walking, patients showed lower and more superiorly directed hip joint contact force, which might alleviate pain from an antero-superiorly degenerated joint. Copyright © 2015 Elsevier B.V. All rights reserved.

Robot Position Sensor Fault Tolerance

NASA Technical Reports Server (NTRS)

Aldridge, Hal A.

1997-01-01

Robot systems in critical applications, such as those in space and nuclear environments, must be able to operate during component failure to complete important tasks. One failure mode that has received little attention is the failure of joint position sensors. Current fault tolerant designs require the addition of directly redundant position sensors which can affect joint design. A new method is proposed that utilizes analytical redundancy to allow for continued operation during joint position sensor failure. Joint torque sensors are used with a virtual passive torque controller to make the robot joint stable without position feedback and improve position tracking performance in the presence of unknown link dynamics and end-effector loading. Two Cartesian accelerometer based methods are proposed to determine the position of the joint. The joint specific position determination method utilizes two triaxial accelerometers attached to the link driven by the joint with the failed position sensor. The joint specific method is not computationally complex and the position error is bounded. The system wide position determination method utilizes accelerometers distributed on different robot links and the end-effector to determine the position of sets of multiple joints. The system wide method requires fewer accelerometers than the joint specific method to make all joint position sensors fault tolerant but is more computationally complex and has lower convergence properties. Experiments were conducted on a laboratory manipulator. Both position determination methods were shown to track the actual position satisfactorily. A controller using the position determination methods and the virtual passive torque controller was able to servo the joints to a desired position during position sensor failure.

Gastrocnemius Myoelectric Control of a Robotic Hip Exoskeleton Can Reduce the User's Lower-Limb Muscle Activities at Push Off

PubMed Central

Grazi, Lorenzo; Crea, Simona; Parri, Andrea; Molino Lova, Raffaele; Micera, Silvestro; Vitiello, Nicola

2018-01-01

We present a novel assistive control strategy for a robotic hip exoskeleton for assisting hip flexion/extension, based on a proportional Electromyography (EMG) strategy. The novelty of the proposed controller relies on the use of the Gastrocnemius Medialis (GM) EMG signal instead of a hip flexor muscle, to control the hip flexion torque. This strategy has two main advantages: first, avoiding the placement of the EMG electrodes at the human–robot interface can reduce discomfort issues for the user and motion artifacts of the recorded signals; second, using a powerful signal for control, such as the GM, could improve the reliability of the control system. The control strategy has been tested on eight healthy subjects, walking with the robotic hip exoskeleton on the treadmill. We evaluated the controller performance and the effect of the assistance on muscle activities. The tuning of the assistance timing in the controller was subject dependent and varied across subjects. Two muscles could benefit more from the assistive strategy, namely the Rectus Femoris (directly assisted) and the Tibialis Anterior (indirectly assisted). A significant correlation was found between the timing of the delivered assistance (i.e., synchronism with the biological hip torque), and reduction of the hip flexors muscular activity during walking; instead, no significant correlations were found for peak torque and peak power. Results suggest that the timing of the assistance is the most significant parameter influencing the effectiveness of the control strategy. The findings of this work could be important for future studies aimed at developing assistive strategies for walking assistance exoskeletons. PMID:29491830

Gastrocnemius Myoelectric Control of a Robotic Hip Exoskeleton Can Reduce the User's Lower-Limb Muscle Activities at Push Off.

PubMed

Grazi, Lorenzo; Crea, Simona; Parri, Andrea; Molino Lova, Raffaele; Micera, Silvestro; Vitiello, Nicola

2018-01-01

We present a novel assistive control strategy for a robotic hip exoskeleton for assisting hip flexion/extension, based on a proportional Electromyography (EMG) strategy. The novelty of the proposed controller relies on the use of the Gastrocnemius Medialis (GM) EMG signal instead of a hip flexor muscle, to control the hip flexion torque. This strategy has two main advantages: first, avoiding the placement of the EMG electrodes at the human-robot interface can reduce discomfort issues for the user and motion artifacts of the recorded signals; second, using a powerful signal for control, such as the GM, could improve the reliability of the control system. The control strategy has been tested on eight healthy subjects, walking with the robotic hip exoskeleton on the treadmill. We evaluated the controller performance and the effect of the assistance on muscle activities. The tuning of the assistance timing in the controller was subject dependent and varied across subjects. Two muscles could benefit more from the assistive strategy, namely the Rectus Femoris (directly assisted) and the Tibialis Anterior (indirectly assisted). A significant correlation was found between the timing of the delivered assistance (i.e., synchronism with the biological hip torque), and reduction of the hip flexors muscular activity during walking; instead, no significant correlations were found for peak torque and peak power. Results suggest that the timing of the assistance is the most significant parameter influencing the effectiveness of the control strategy. The findings of this work could be important for future studies aimed at developing assistive strategies for walking assistance exoskeletons.

Reduction of phase noise in nanowire spin orbit torque oscillators

PubMed Central

Yang, Liu; Verba, Roman; Tiberkevich, Vasil; Schneider, Tobias; Smith, Andrew; Duan, Zheng; Youngblood, Brian; Lenz, Kilian; Lindner, Jürgen; Slavin, Andrei N.; Krivorotov, Ilya N.

2015-01-01

Spin torque oscillators (STOs) are compact, tunable sources of microwave radiation that serve as a test bed for studies of nonlinear magnetization dynamics at the nanometer length scale. The spin torque in an STO can be created by spin-orbit interaction, but low spectral purity of the microwave signals generated by spin orbit torque oscillators hinders practical applications of these magnetic nanodevices. Here we demonstrate a method for decreasing the phase noise of spin orbit torque oscillators based on Pt/Ni80Fe20 nanowires. We experimentally demonstrate that tapering of the nanowire, which serves as the STO active region, significantly decreases the spectral linewidth of the generated signal. We explain the observed linewidth narrowing in the framework of the Ginzburg-Landau auto-oscillator model. The model reveals that spatial non-uniformity of the spin current density in the tapered nanowire geometry hinders the excitation of higher order spin-wave modes, thus stabilizing the single-mode generation regime. This non-uniformity also generates a restoring force acting on the excited self-oscillatory mode, which reduces thermal fluctuations of the mode spatial position along the wire. Both these effects improve the STO spectral purity. PMID:26592432

Relationships between explosive and maximal triple extensor muscle performance and vertical jump height.

PubMed

Chang, Eunwook; Norcross, Marc F; Johnson, Sam T; Kitagawa, Taichi; Hoffman, Mark

2015-02-01

The purpose of this study was to examine the relationships between maximum vertical jump height and (a) rate of torque development (RTD) calculated during 2 time intervals, 0-50 milliseconds (RTD50) and 0-200 milliseconds (RTD200) after torque onset and (b) peak torque (PT) for each of the triple extensor muscle groups. Thirty recreationally active individuals performed maximal isometric voluntary contractions (MVIC) of the hip, knee and ankle extensors, and a countermovement vertical jump. Rate of torque development was calculated from 0 to 50 (RTD50) and 0 to 200 (RTD200) milliseconds after the onset of joint torque. Peak torque was identified and defined as the maximum torque value during each MVIC trial. Greater vertical jump height was associated with greater knee and ankle extension RTD50, RTD200, and PT (p ≤ 0.05). However, hip extension RTD50, RTD200, and PT were not significantly related to maximal vertical jump height (p > 0.05). The results indicate that 47.6 and 32.5% of the variability in vertical jump height was explained by knee and ankle extensor RTD50, respectively. Knee and ankle extensor RTD50 also seemed to be more closely related to vertical jump performance than RTD200 (knee extensor: 28.1% and ankle extensor: 28.1%) and PT (knee extensor: 31.4% and ankle extensor: 13.7%). Overall, these results suggest that training specifically targeted to improve knee and ankle extension RTD, especially during the early phases of muscle contraction, may be effective for increasing maximal vertical jump performance.

77 FR 18970 - Airworthiness Directives; Bell Helicopter Textron Canada Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-29

... Model 407 Maintenance Manual and applied during manufacturing was incorrect and exceeded the torque... hardware (attachment hardware), and perform initial and recurring determinations of [[Page 18971

Prosthetic Engineering

MedlinePlus

... torque adapter in the pylons of transtibial amputees. Energy Storage & Release Many ambulatory lower limb amputees exhibit ... Future Directions Current Project Summaries Development of Controlled Energy Storage and Release Prosthetic Foot Development of Inverting- ...

Performance Monitoring Of A Computer Numerically Controlled (CNC) Lathe Using Pattern Recognition Techniques

NASA Astrophysics Data System (ADS)

Daneshmend, L. K.; Pak, H. A.

1984-02-01

On-line monitoring of the cutting process in CNC lathe is desirable to ensure unattended fault-free operation in an automated environment. The state of the cutting tool is one of the most important parameters which characterises the cutting process. Direct monitoring of the cutting tool or workpiece is not feasible during machining. However several variables related to the state of the tool can be measured on-line. A novel monitoring technique is presented which uses cutting torque as the variable for on-line monitoring. A classifier is designed on the basis of the empirical relationship between cutting torque and flank wear. The empirical model required by the on-line classifier is established during an automated training cycle using machine vision for off-line direct inspection of the tool.

The Direct Measurement of Engine Power on an Airplane in Flight with a Hub Type Dynamometer

NASA Technical Reports Server (NTRS)

Gove, W D; Green, M W

1927-01-01

This report describes tests made to obtain direct measurements of engine power in flight. Tests were made with a Bendemann hub dynamometer installed on a modified DH-4 Airplane, Liberty 12 Engine, to determine the suitability of this apparatus. This dynamometer unit, which was designed specially for use with a liberty 12 engine, is a special propeller hub in which is incorporated a system of pistons and cylinders interposed between the propeller and the engine crankshaft. The torque and thrust forces are balanced by fluid pressures, which are recorded by instruments in the cockpit. These tests have shown the suitability of this type of hub dynamometer for measurement of power in flight and for the determination of the torque and power coefficients of the propeller. (author)

TIDAL FRICTION AND TIDAL LAGGING. APPLICABILITY LIMITATIONS OF A POPULAR FORMULA FOR THE TIDAL TORQUE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Efroimsky, Michael; Makarov, Valeri V., E-mail: michael.efroimsky@usno.navy.mil, E-mail: vvm@usno.navy.mil

Tidal torques play a key role in rotational dynamics of celestial bodies. They govern these bodies' tidal despinning and also participate in the subtle process of entrapment of these bodies into spin-orbit resonances. This makes tidal torques directly relevant to the studies of habitability of planets and their moons. Our work begins with an explanation of how friction and lagging should be built into the theory of bodily tides. Although much of this material can be found in various publications, a short but self-consistent summary on the topic has been lacking in the hitherto literature, and we are filling themore » gap. After these preparations, we address a popular concise formula for the tidal torque, which is often used in the literature, for planets or stars. We explain why the derivation of this expression, offered in the paper by Goldreich and in the books by Kaula (Equation (4.5.29)) and Murray and Dermott (Equation (4.159)), implicitly sets the time lag to be frequency independent. Accordingly, the ensuing expression for the torque can be applied only to bodies having a very special (and very hypothetical) rheology which makes the time lag frequency independent, i.e., the same for all Fourier modes in the spectrum of tide. This expression for the torque should not be used for bodies of other rheologies. Specifically, the expression cannot be combined with an extra assertion of the geometric lag being constant, because at finite eccentricities the said assumption is incompatible with the constant-time-lag condition.« less

Measuring Micro-Friction Torque in MEMS Gas Bearings

PubMed Central

Fang, Xudong; Liu, Huan

2016-01-01

An in situ measurement of micro-friction torque in MEMS gas bearings, which has been a challenging research topic for years, is realized by a system designed in this paper. In the system, a high accuracy micro-force sensor and an electronically-driven table are designed, fabricated and utilized. With appropriate installation of the sensor and bearings on the table, the engine rotor can be driven to rotate with the sensor using a silicon lever beam. One end of the beam is fixed to the shaft of the gas bearing, while the other end is free and in contact with the sensor probe tip. When the sensor begins to rotate with the table, the beam is pushed by the sensor probe to rotate in the same direction. For the beam, the friction torque from the gas bearing is balanced by the torque induced by pushing force from the sensor probe. Thus, the friction torque can be calculated as a product of the pushing force measured by the sensor and the lever arm, which is defined as the distance from the sensor probe tip to the centerline of the bearing. Experimental results demonstrate the feasibility of this system, with a sensitivity of 1.285 mV/μN·m in a range of 0 to 11.76 μN·m when the lever arm is 20 mm long. The measuring range can be modified by varying the length of the lever arm. Thus, this system has wide potential applications in measuring the micro-friction torque of gas bearings in rotating MEMS machines. PMID:27213377

Forces associated with pneumatic power screwdriver operation: statics and dynamics.

PubMed

Lin, Jia-Hua; Radwin, Robert G; Fronczak, Frank J; Richard, Terry G

2003-10-10

The statics and dynamics of pneumatic power screwdriver operation were investigated in the context of predicting forces acting against the human operator. A static force model is described in the paper, based on tool geometry, mass, orientation in space, feed force, torque build up, and stall torque. Three common power hand tool shapes are considered, including pistol grip, right angle, and in-line. The static model estimates handle force needed to support a power nutrunner when it acts against the tightened fastener with a constant torque. A system of equations for static force and moment equilibrium conditions are established, and the resultant handle force (resolved in orthogonal directions) is calculated in matrix form. A dynamic model is formulated to describe pneumatic motor torque build-up characteristics dependent on threaded fastener joint hardness. Six pneumatic tools were tested to validate the deterministic model. The average torque prediction error was 6.6% (SD = 5.4%) and the average handle force prediction error was 6.7% (SD = 6.4%) for a medium-soft threaded fastener joint. The average torque prediction error was 5.2% (SD = 5.3%) and the average handle force prediction error was 3.6% (SD = 3.2%) for a hard threaded fastener joint. Use of these equations for estimating handle forces based on passive mechanical elements representing the human operator is also described. These models together should be useful for considering tool handle force in the selection and design of power screwdrivers, particularly for minimizing handle forces in the prevention of injuries and work related musculoskeletal disorders.

Torque Limit for Bolted Joint for Composites. Part A; TTTC Properties of Laminated Composites

NASA Technical Reports Server (NTRS)

Zhao, Yi

2003-01-01

The existing design code for torque limit of bolted joints for composites at Marshall Space Flight Center is MSFC-STD-486B, which was originally developed in 1960s for metallic materials. The theoretical basis for this code was a simplified mechanics analysis, which takes into account only the bolt, nut and washers, but not the structural members to be connected. The assumption was that metallic materials would not fail due to the bearing stress at the contact area between washer and the mechanical member. This is true for metallic materials; but for composite materials the results could be completely different. Unlike most metallic materials, laminated composite materials have superior mechanical properties (such as modulus and strength) in the in-plane direction, but not in the out-of-plane, or through-the-thickness (TTT) direction. During the torquing, TTT properties (particularly compressive modulus and compressive strength) play a dominant role in composite failure. Because of this concern, structural design engineers at Marshall are currently using a compromised empirical approach: using 50% of the torque value for composite members. Companies like Boeing is using a similar approach. An initial study was conducted last summer on this topic to develop theoretical model(s) that takes into consideration of composite members. Two simplified models were developed based on stress failure criterion and strain failure criterion, respective. However, these models could not be used to predict the torque limit because of the unavailability of material data, specifically, through-the-thickness compression (TTTC) modulus and strength. Therefore, the task for this summer is to experimentally determine the TTTC properties. Due to the time limitation, only one material has been tested: IM7/8552 with [0 degrees,plus or minus 45 degrees, 90 degree ] configuration. This report focuses the test results and their significance, while the experimentation will be described in a separate report by Mr. Kris Kostreva.

Dynamics of magnetization in ferromagnet with spin-transfer torque

NASA Astrophysics Data System (ADS)

Li, Zai-Dong; He, Peng-Bin; Liu, Wu-Ming

2014-11-01

We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.

Multiple-robot drug delivery strategy through coordinated teams of microswimmers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kei Cheang, U; Kim, Min Jun, E-mail: mkim@coe.drexel.edu; Lee, Kyoungwoo

2014-08-25

Untethered robotic microswimmers are very promising to significantly improve various types of minimally invasive surgeries by offering high accuracy at extremely small scales. A prime example is drug delivery, for which a large number of microswimmers is required to deliver sufficient dosages to target sites. For this reason, the controllability of groups of microswimmers is essential. In this paper, we demonstrate simultaneous control of multiple geometrically similar but magnetically different microswimmers using a single global rotating magnetic field. By exploiting the differences in their magnetic properties, we triggered different swimming behaviors from the microswimmers by controlling the frequency and themore » strength of the global field, for example, one swim and the other does not while exposed to the same control input. Our results show that the balance between the applied magnetic torque and the hydrodynamic torque can be exploited for simultaneous control of two microswimmers to swim in opposite directions, with different velocities, and with similar velocities. This work will serve to establish important concepts for future developments of control systems to manipulate multiple magnetically actuated microswimmers and a step towards using swarms of microswimmers as viable workforces for complex operations.« less

A Study of Spur Gears Lubricated With Grease-Observations From Seven Experiments

NASA Technical Reports Server (NTRS)

Krantz, Timothy L.; Handschuh, Robert F.

2005-01-01

To improve understanding of gears operating with a perfluoro type space-qualified grease, seven spur gear experiments were performed. Test conditions were selected to study the influences of torque, lubricant type, and atmosphere. Two testing torques provided nominal pitch-line Hertz stresses greater and lesser than the contact stress limit as recommended by the grease manufacturer. As was expected, all tests resulted in some gear tooth wear. Discoloration of the perfluoro type grease occurred for all tests. Tests in dry nitrogen produced some dark-grey colored perfluoro type grease. Testing in either ambient or dry air produced red debris after short test duration, and for tests of longer duration large amounts of red debris, red grease, and wear were evident. Tests using higher torques produced more debris. The first indications of discoloration occurred more quickly with higher test torques. Total amounts of wear were quite significant, up to four times the profile tolerance for AGMA Class 10 gears.

Surgeon-tool force/torque signatures--evaluation of surgical skills in minimally invasive surgery.

PubMed

Rosen, J; MacFarlane, M; Richards, C; Hannaford, B; Sinanan, M

1999-01-01

The best method of training for laparoscopic surgical skills is controversial. Some advocate observation in the operating room, while others promote animal and simulated models or a combination of surgical related tasks. The mode of proficiency evaluation common to all of these methods has been subjective evaluation by a skilled surgeon. In order to define an objective means of evaluating performance, an instrumented laparoscopic grasper was developed measuring the force/torque at the surgeon hand/tool interface. The measured database demonstrated substantial differences between experienced and novice surgeon groups. Analyzing forces and torques combined with the state transition during surgical procedures allows an objective measurement of skill in MIS. Teaching the novice surgeon to limit excessive loads and improve movement efficiency during surgical procedures can potentially result in less injury to soft tissues and less wasted time during laparoscopic surgery. Moreover the force/torque database measured in this study may be used for developing realistic virtual reality simulators and optimization of medical robots performance.

Effects of repeated ankle stretching on calf muscle-tendon and ankle biomechanical properties in stroke survivors

PubMed Central

Gao, Fan; Ren, Yupeng; Roth, Elliot J.; Harvey, Richard; Zhang, Li-Qun

2011-01-01

Background The objective of this study was to investigate changes in active and passive biomechanical properties of the calf muscle-tendon unit induced by controlled ankle stretching in stroke survivors. Methods Ten stroke survivors with ankle spasticity/contracture and ten healthy control subjects received intervention of 60-min ankle stretching. Joint biomechanical properties including resistance torque, stiffness and index of hysteresis were evaluated pre- and post-intervention. Achilles tendon length was measured using ultrasonography. The force output of the triceps surae muscles was characterized via the torque-angle relationship, by stimulating the calf muscles at a controlled intensity across different ankle positions. Findings Compared to healthy controls, the ankle position corresponding to the peak torque of the stroke survivors was shifted towards plantar flexion (P<0.001). Stroke survivors showed significantly higher resistance torques and joint stiffness (P<0.05), and these higher resistances were reduced significantly after the stretching intervention, especially in dorsiflexion (P = 0.013). Stretching significantly improved the force output of the impaired calf muscles in stroke survivors under matched stimulations (P<0.05). Ankle range of motion was also increased by stretching (P<0.001). Interpretation At the joint level, repeated stretching loosened the ankle joint with increased passive joint range of motion and decreased joint stiffness. At the muscle-tendon level, repeated stretching improved calf muscle force output, which might be associated with decreased muscle fascicle stiffness, increased fascicle length and shortening of the Achilles tendon. The study provided evidence of improvement in muscle tendon properties through stretching intervention. PMID:21211873

Fast Low-Current Spin-Orbit-Torque Switching of Magnetic Tunnel Junctions through Atomic Modifications of the Free-Layer Interfaces

NASA Astrophysics Data System (ADS)

Shi, Shengjie; Ou, Yongxi; Aradhya, S. V.; Ralph, D. C.; Buhrman, R. A.

2018-01-01

Future applications of spin-orbit torque will require new mechanisms to improve the efficiency of switching nanoscale magnetic tunnel junctions (MTJs), while also controlling the magnetic dynamics to achieve fast nanosecond-scale performance with low-write-error rates. Here, we demonstrate a strategy to simultaneously enhance the interfacial magnetic anisotropy energy and suppress interfacial spin-memory loss by introducing subatomic and monatomic layers of Hf at the top and bottom interfaces of the ferromagnetic free layer of an in-plane magnetized three-terminal MTJ device. When combined with a β -W spin Hall channel that generates spin-orbit torque, the cumulative effect is a switching current density of 5.4 ×106 A /cm2 .

New results in the theory of dust grain alignment

NASA Technical Reports Server (NTRS)

Cugnon, Pierre

1989-01-01

Two complementary approaches are used in an attempt to propose an appropriate formulation of the solution to the problem of magnetic alignment of grains in the diffuse and/or the more denser clouds, whatever the mechanism of rotational excitation can be. The interest of such a unified formulation is mainly that the same theoretical expression for polarization can be used everywhere, allowing for easier comparisons between regions where the physical conditions are highly different. The first consists in applying a Monte-Carlo method to a limited number of representative cases, for which all the torques acting on the grain are taken into account: impulsive random torques due to direct collisions with gas atoms, to evaporation of atoms from the surface, and to exo-energetic recombinations forming hydrogen molecules, followed by violent ejections from peculiar sites; magnetic torques. Three characteristic times are associated with these torques: the collisional damping time, the time necessary to change completely the actual sites configuration narrowly bound to the correlation time of the suprathermal torque; and the magnetic damping time. The second approach starts from a heuristic point of view. It consists in a generalization of results (Cugnon, 1983; see also Purcell and Spitzer, 1971; Greenberg, 1978) obtained for thermal alignment to the suprathermal case. It appears indeed that in two extreme cases, the thermal formulation may be used after redefinition of involved times and temperatures.

Rotational effect of buoyancy in frontcrawl: Does it really cause the legs to sink?

PubMed

Yanai, T

2001-02-01

The purposes of this study were to quantify the rotational effect of buoyant force (buoyant torque) during the performance of front crawl and to reexamine the mechanics of horizontal alignment of the swimmers. Three-dimensional videography was used to measure the position and orientation of the body segments of 11 competitive swimmers performing front crawl stroke at a sub-maximum sprinting speed. The dimensions of each body segment were defined mathematically to match the body segment parameters (mass, density, and centroid position) reported in the literature. The buoyant force and torque were computed for every video-field (60fields/s), assuming that the water surface followed a sine curve along the length of the swimmer. The average buoyant torque over the stroke cycle (mean=22Nm) was directed to raise the legs and lower the head, primarily because the recovery arm and a part of the head were lifted out of the water and the center of buoyancy shifted toward the feet. This finding contradicts the prevailing speculation that buoyancy only causes the legs to sink throughout the stroke cycle. On the basis of a theoretical analysis of the results, it is postulated that the buoyant torque, and perhaps the forces generated by kicks, function to counteract the torque generated by the hydrodynamic forces acting on the hands, so as to maintain the horizontal alignment of the body in front crawl.

Subspace methods for identification of human ankle joint stiffness.

PubMed

Zhao, Y; Westwick, D T; Kearney, R E

2011-11-01

Joint stiffness, the dynamic relationship between the angular position of a joint and the torque acting about it, describes the dynamic, mechanical behavior of a joint during posture and movement. Joint stiffness arises from both intrinsic and reflex mechanisms, but the torques due to these mechanisms cannot be measured separately experimentally, since they appear and change together. Therefore, the direct estimation of the intrinsic and reflex stiffnesses is difficult. In this paper, we present a new, two-step procedure to estimate the intrinsic and reflex components of ankle stiffness. In the first step, a discrete-time, subspace-based method is used to estimate a state-space model for overall stiffness from the measured overall torque and then predict the intrinsic and reflex torques. In the second step, continuous-time models for the intrinsic and reflex stiffnesses are estimated from the predicted intrinsic and reflex torques. Simulations and experimental results demonstrate that the algorithm estimates the intrinsic and reflex stiffnesses accurately. The new subspace-based algorithm has three advantages over previous algorithms: 1) It does not require iteration, and therefore, will always converge to an optimal solution; 2) it provides better estimates for data with high noise or short sample lengths; and 3) it provides much more accurate results for data acquired under the closed-loop conditions, that prevail when subjects interact with compliant loads.

The control of mono-articular muscles in multijoint leg extensions in man.

PubMed Central

van Ingen Schenau, G J; Dorssers, W M; Welter, T G; Beelen, A; de Groot, G; Jacobs, R

1995-01-01

1. Movements often require control of direction and a magnitude of force exerted externally on the environment. Bi-articular upper leg muscles appear to play a unique role in the regulation of the net torques about the hip and knee joints, necessary for the control of this external force. 2. The aim of this study was to test the hypothesis that the mono-articular muscles act as work generators in powerful dynamic leg extensions, which means that they should be activated primarily in the phases during which they can contribute to work, irrespective of the net joint torques required to control the external force. 3. Cycling movements of six trained subjects were analysed by means of inverse dynamics, yielding net joint torques as well as activity patterns and shortening velocities of four mono- and four bi-articular leg muscles. 4. The results show that the mono-articular muscles exert force only in the phase in which these muscles shorten, whereas this appears not to be the case for the bi-articular muscles. 5. Reciprocal patterns of activation of the rectus femoris and hamstring muscles appear to tune the distribution of net joint torques about the hip and knee joints, necessary to control the (changing) direction of the force on the pedal. 6. An analysis of running in man and additional related literature based on animal studies appears to provide further support for the hypothesis that mono- and bi-articular muscles have essentially different roles in these powerful multijoint leg extension tasks. PMID:7602524

Sex Comparison of Knee Extensor Size, Strength and Fatigue Adaptation to Sprint Interval Training.

PubMed

Bagley, Liam; Al-Shanti, Nasser; Bradburn, Steven; Baig, Osamah; Slevin, Mark; McPhee, Jamie S

2018-03-12

Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for males and females. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship and fatigability adaptations to 12 weeks SIT. Sixteen males and fifteen females (mean (SEM) age: 41 (±2.5) yrs) completed measurements of total body composition assessed by DXA, quadriceps muscle cross-sectional area (CSAQ) assessed by MRI, the knee extensor torque-velocity relationship (covering 0 - 240°·sec) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·sec. SIT consisted of 4 x 20 second sprints on a cycle ergometer set at an initial power output of 175% of power at VO2max, three times per week for 12 weeks. CSAQ increased by 5% (p=0.023) and fatigue resistance improved 4.8% (p=0.048), with no sex differences in these adaptations (sex comparisons: p=0.140 and p=0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both males and females (p>0.05 for all velocities). 12 weeks SIT, totalling 4 minutes very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in males and females, but did not significantly increase torque in males or females. These results suggest that SIT is a time-effective training modality for males and females to increase leg muscle size and fatigue resistance.

Validation of Kinetic-Turbulent-Neoclassical Theory for Edge Intrinsic Rotation in DIII-D Plasmas

NASA Astrophysics Data System (ADS)

Ashourvan, Arash

2017-10-01

Recent experiments on DIII-D with low-torque neutral beam injection (NBI) have provided a validation of a new model of momentum generation in a wide range of conditions spanning L- and H-mode with direct ion and electron heating. A challenge in predicting the bulk rotation profile for ITER has been to capture the physics of momentum transport near the separatrix and steep gradient region. A recent theory has presented a model for edge momentum transport which predicts the value and direction of the main-ion intrinsic velocity at the pedestal-top, generated by the passing orbits in the inhomogeneous turbulent field. In this study, this model-predicted velocity is tested on DIII-D for a database of 44 low-torque NBI discharges comprised of bothL- and H-mode plasmas. For moderate NBI powers (PNBI<4 MW), model prediction agrees well with the experiments for both L- and H-mode. At higher NBI power the experimental rotation is observed to saturate and even degrade compared to theory. TRANSP-NUBEAM simulations performed for the database show that for discharges with nominally balanced - but high powered - NBI, the net injected torque through the edge can exceed 1 N.m in the counter-current direction. The theory model has been extended to compute the rotation degradation from this counter-current NBI torque by solving a reduced momentum evolution equation for the edge and found the revised velocity prediction to be in agreement with experiment. Projecting to the ITER baseline scenario, this model predicts a value for the pedestal-top rotation (ρ 0.9) comparable to 4 kRad/s. Using the theory modeled - and now tested - velocity to predict the bulk plasma rotation opens up a path to more confidently projecting the confinement and stability in ITER. Supported by the US DOE under DE-AC02-09CH11466 and DE-FC02-04ER54698.

Local mechanical response of cells to the controlled rotation of magnetic nanorods.

PubMed

Castillo, Matias; Ebensperger, Roberto; Wirtz, Denis; Walczak, Magdalena; Hurtado, Daniel E; Celedon, Alfredo

2014-11-01

The mechanical response of the cytoplasm was investigated by the intracellular implantation of magnetic nanorods and exposure to low-frequency rotatory magnetic fields. Nanorods (Pt-Ni, ∼200 nm diameter) fabricated by electrodeposition in templates of porous alumina with lengths of approximately 2 and 5 µm were inserted into NIH/3T3 fibroblasts and manipulated with a rotational magnetic field. Nanorod rotation was observed only for torques greater than 3.0 × 10(-16) Nm, suggesting a Bingham-type behavior of the cytoplasm. Higher torques produced considerable deformation of the intracellular material. The cell nucleus and cell membrane were significantly deformed by nanorods actuated by 4.5 × 10(-15) Nm torques. Our results demonstrate that nanorods under magnetic fields are an effective tool to mechanically probe the intracellular environment. We envision that our findings may contribute to the noninvasive and direct mechanical characterization of the cytoplasm. © 2014 Wiley Periodicals, Inc.

Local mechanical response of cells to the controlled rotation of magnetic nanorods

PubMed Central

Castillo, Matias; Ebensperger, Roberto; Wirtz, Denis; Walczak, Magdalena; Hurtado, Daniel E.; Celedon, Alfredo

2015-01-01

The mechanical response of the cytoplasm was investigated by the intracellular implantation of magnetic nanorods and exposure to low-frequency rotatory magnetic fields. Nanorods (Pt-Ni, ~200 nm diameter) fabricated by electrodeposition in templates of porous alumina with lengths of approximately 2 and 5 μm were inserted into NIH/ 3T3 fibroblasts and manipulated with a rotational magnetic field. Nanorod rotation was observed only for torques greater than 3.0 × 10−16 Nm, suggesting a Bingham-type behavior of the cytoplasm. Higher torques produced considerable deformation of the intracellular material. The cell nucleus and cell membrane were significantly deformed by nanorods actuated by 4.5 × 10−15 Nm torques. Our results demonstrate that nanorods under magnetic fields are an effective tool to mechanically probe the intracellular environment. We envision that our findings may contribute to the noninvasive and direct mechanical characterization of the cytoplasm. PMID:24700696

Antidamping-Torque-Induced Switching in Biaxial Antiferromagnetic Insulators

NASA Astrophysics Data System (ADS)

Chen, X. Z.; Zarzuela, R.; Zhang, J.; Song, C.; Zhou, X. F.; Shi, G. Y.; Li, F.; Zhou, H. A.; Jiang, W. J.; Pan, F.; Tserkovnyak, Y.

2018-05-01

We investigate the current-induced switching of the Néel order in NiO (001 )/Pt heterostructures, which is manifested electrically via the spin Hall magnetoresistance. Significant reversible changes in the longitudinal and transverse resistances are found at room temperature for a current threshold lying in the range of 1 07 A /cm2 . The order-parameter switching is ascribed to the antiferromagnetic dynamics triggered by the (current-induced) antidamping torque, which orients the Néel order towards the direction of the writing current. This is in stark contrast to the case of antiferromagnets such as Mn2Au and CuMnAs, where fieldlike torques induced by the Edelstein effect drive the Néel switching, therefore resulting in an orthogonal alignment between the Néel order and the writing current. Our findings can be readily generalized to other biaxial antiferromagnets, providing broad opportunities for all-electrical writing and readout in antiferromagnetic spintronics.

Experimental Robot Position Sensor Fault Tolerance Using Accelerometers and Joint Torque Sensors

NASA Technical Reports Server (NTRS)

Aldridge, Hal A.; Juang, Jer-Nan

1997-01-01

Robot systems in critical applications, such as those in space and nuclear environments, must be able to operate during component failure to complete important tasks. One failure mode that has received little attention is the failure of joint position sensors. Current fault tolerant designs require the addition of directly redundant position sensors which can affect joint design. The proposed method uses joint torque sensors found in most existing advanced robot designs along with easily locatable, lightweight accelerometers to provide a joint position sensor fault recovery mode. This mode uses the torque sensors along with a virtual passive control law for stability and accelerometers for joint position information. Two methods for conversion from Cartesian acceleration to joint position based on robot kinematics, not integration, are presented. The fault tolerant control method was tested on several joints of a laboratory robot. The controllers performed well with noisy, biased data and a model with uncertain parameters.

Optimal spacecraft attitude control using collocation and nonlinear programming

NASA Astrophysics Data System (ADS)

Herman, A. L.; Conway, B. A.

1992-10-01

Direct collocation with nonlinear programming (DCNLP) is employed to find the optimal open-loop control histories for detumbling a disabled satellite. The controls are torques and forces applied to the docking arm and joint and torques applied about the body axes of the OMV. Solutions are obtained for cases in which various constraints are placed on the controls and in which the number of controls is reduced or increased from that considered in Conway and Widhalm (1986). DCLNP works well when applied to the optimal control problem of satellite attitude control. The formulation is straightforward and produces good results in a relatively small amount of time on a Cray X/MP with no a priori information about the optimal solution. The addition of joint acceleration to the controls significantly reduces the control magnitudes and optimal cost. In all cases, the torques and acclerations are modest and the optimal cost is very modest.

Output of skeletal muscle contractions. a study of isokinetic plantar flexion in athletes.

PubMed

Fugl-Meyer, A R; Mild, K H; Hörnsten, J

1982-06-01

Maximum torques, total work and mean power of isokinetic plantar flexions were measured with simultaneous registrations. The integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. The method applied offers possibilities for adequate description of dynamic muscular work which in the case of plantar flexion in trained man declines as a negative exponential function of angular motion velocity. The decline is parallel to that of maximum torques. The summed triceps surae iEMG was inversely proportional to the velocity and direct proportional to time suggesting that structural rather than neural factors determine the relationships between velocity of angular motion and maximum torque/total work of single Mmaneuvers. Moreover, the fact that maximum mean power as well as maximum electrical efficiency were reached at the functional velocity of toe-off during gait suggests an influence of pragmatic demands on plantar flexion mechanical output.

Spin-transfer torque in multiferroic tunnel junctions with composite dielectric/ferroelectric barriers

NASA Astrophysics Data System (ADS)

Velev, Julian P.; Merodio, Pablo; Pollack, Cesar; Kalitsov, Alan; Chshiev, Mairbek; Kioussis, Nicholas

2017-12-01

Using model calculations, we demonstrate a very high level of control of the spin-transfer torque (STT) by electric field in multiferroic tunnel junctions with composite dielectric/ferroelectric barriers. We find that, for particular device parameters, toggling the polarization direction can switch the voltage-induced part of STT between a finite value and a value close to zero, i.e. quench and release the torque. Additionally, we demonstrate that under certain conditions the zero-voltage STT, i.e. the interlayer exchange coupling, can switch sign with polarization reversal, which is equivalent to reversing the magnetic ground state of the tunnel junction. This bias- and polarization-tunability of the STT could be exploited to engineer novel functionalities such as softening/hardening of the bit or increasing the signal-to-noise ratio in magnetic sensors, which can have important implications for magnetic random access memories or for combined memory and logic devices.

The 2001 April Burst Activation of SGR 1900-14: Pulse Properties and Torque

NASA Technical Reports Server (NTRS)

Woods, P. M.; Kouveliotou, C.; Goegues, E.; Finger, M. H.; Feroci, M.; Mereghetti, S.; Swank, J. H.; Hurley, K.; Heise, J.; Smith D.

2003-01-01

We report on observations of SGR 1900+14 made with the Rossi X-Ray Timing Explorer (RXTE) and BeppoSAXduring the 2001 April burst activation of the source. Using these data, we measure the spin-down torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to the gamma-ray profile during the April 18 intermediate flare and show that (1) their shapes are similar and (1) the gamma-ray profile aligns closely in phase with the X-ray pulsations. The good phase alignment of the gamma-ray and X-ray profiles suggests that there was no rapid spin-down following this flare of the magnitude inferred for the August 27 giant flare. We discuss how these observations further constrain magnetic field reconfiguration models for the large flares of SGRs.

Acoustical radiation torque and force for spheres and Bessel beam extinction efficiency

NASA Astrophysics Data System (ADS)

Marston, Philip L.; Zhang, Likun

2014-11-01

The scattering of optical and acoustical beams is relevant to the levitation and manipulation of drops. Here we examine theoretical developments in the acoustical case. We previously showed how the optical theorem for extinction can be extended to invariant beams. The example of a sphere in a Bessel beam facilitates the direct comparison with a circular disc computed using Babinet's principle and the Kirchhoff approximation. In related work, by considering traveling or standing wave first-order vortex beams we previously showed that the radiation torque is the ratio of the absorbed power and the radian acoustic frequency. By modifying the scattering to account for the viscosity of the surrounding fluid in the analysis of the absorbed power, approximations for radiation torque and force are obtained at long wavelengths in special cases and these can be compared with results published elsewhere.

Muscle function in aged women in response to a water-based exercises program and progressive resistance training.

PubMed

Bento, Paulo Cesar Barauce; Rodacki, André Luiz Felix

2015-11-01

The purpose of the present study was to determine the effects of a water-based exercise program on muscle function compared with regular high-intensity resistance training. Older women (n = 87) were recruited from the local community. The inclusion criteria were, to be aged 60 years or older, able to walk and able to carry out daily living activities independently. Participants were randomly assigned to one of the following groups: water-based exercises (WBG), resistance training (RTG) or control (CG). The experimental groups carried out 12 weeks of an excise program performed on water or on land. The dynamic strength, the isometric peak, and rate of torque development for the lower limbs were assessed before and after interventions. The water-based program provided a similar improvement in dynamic strength in comparison with resistance training. The isometric peak torque increased around the hip and ankle joints in the water-based group, and around the knee joint in the resistance-training group (P < 0.05). The rate of torque development increased only in the water-based group around the hip extensors muscles (P < 0.05). Water-based programs constitute an attractive alternative to promote relevant strength gains using moderate loads and fast speed movements, which were also effective to improve the capacity to generate fast torques. © 2014 Japan Geriatrics Society.

Parallel elastic elements improve energy efficiency on the STEPPR bipedal walking robot

DOE PAGES

Mazumdar, Anirban; Spencer, Steven J.; Hobart, Clinton; ...

2016-11-23

This study describes how parallel elastic elements can be used to reduce energy consumption in the electric motor driven, fully-actuated, STEPPR bipedal walking robot without compromising or significantly limiting locomotive behaviors. A physically motivated approach is used to illustrate how selectively-engaging springs for hip adduction and ankle flexion predict benefits for three different flat ground walking gaits: human walking, human-like robot walking and crouched robot walking. Based on locomotion data, springs are designed and substantial reductions in power consumption are demonstrated using a bench dynamometer. These lessons are then applied to STEPPR (Sandia Transmission-Efficient Prototype Promoting Research), a fully actuatedmore » bipedal robot designed to explore the impact of tailored joint mechanisms on walking efficiency. Featuring high-torque brushless DC motors, efficient low-ratio transmissions, and high fidelity torque control, STEPPR provides the ability to incorporate novel joint-level mechanisms without dramatically altering high level control. Unique parallel elastic designs are incorporated into STEPPR, and walking data shows that hip adduction and ankle flexion springs significantly reduce the required actuator energy at those joints for several gaits. These results suggest that parallel joint springs offer a promising means of supporting quasi-static joint torques due to body mass during walking, relieving motors of the need to support these torques and substantially improving locomotive energy efficiency.« less

Parallel elastic elements improve energy efficiency on the STEPPR bipedal walking robot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazumdar, Anirban; Spencer, Steven J.; Hobart, Clinton

This study describes how parallel elastic elements can be used to reduce energy consumption in the electric motor driven, fully-actuated, STEPPR bipedal walking robot without compromising or significantly limiting locomotive behaviors. A physically motivated approach is used to illustrate how selectively-engaging springs for hip adduction and ankle flexion predict benefits for three different flat ground walking gaits: human walking, human-like robot walking and crouched robot walking. Based on locomotion data, springs are designed and substantial reductions in power consumption are demonstrated using a bench dynamometer. These lessons are then applied to STEPPR (Sandia Transmission-Efficient Prototype Promoting Research), a fully actuatedmore » bipedal robot designed to explore the impact of tailored joint mechanisms on walking efficiency. Featuring high-torque brushless DC motors, efficient low-ratio transmissions, and high fidelity torque control, STEPPR provides the ability to incorporate novel joint-level mechanisms without dramatically altering high level control. Unique parallel elastic designs are incorporated into STEPPR, and walking data shows that hip adduction and ankle flexion springs significantly reduce the required actuator energy at those joints for several gaits. These results suggest that parallel joint springs offer a promising means of supporting quasi-static joint torques due to body mass during walking, relieving motors of the need to support these torques and substantially improving locomotive energy efficiency.« less

Torque limit of PM motors for field-weakening region operation

DOEpatents

Royak, Semyon [Beachwood, OH; Harbaugh, Mark M [Richfield, OH

2012-02-14

The invention includes a motor controller and technique for controlling a permanent magnet motor. In accordance with one aspect of the present technique, a permanent magnet motor is controlled by receiving a torque command, determining a physical torque limit based on a stator frequency, determining a theoretical torque limit based on a maximum available voltage and motor inductance ratio, and limiting the torque command to the smaller of the physical torque limit and the theoretical torque limit. Receiving the torque command may include normalizing the torque command to obtain a normalized torque command, determining the physical torque limit may include determining a normalized physical torque limit, determining a theoretical torque limit may include determining a normalized theoretical torque limit, and limiting the torque command may include limiting the normalized torque command to the smaller of the normalized physical torque limit and the normalized theoretical torque limit.

An experimental comparison of the relative benefits of work and torque assistance in ankle exoskeletons.

PubMed

Jackson, Rachel W; Collins, Steven H

2015-09-01

Techniques proposed for assisting locomotion with exoskeletons have often included a combination of active work input and passive torque support, but the physiological effects of different assistance techniques remain unclear. We performed an experiment to study the independent effects of net exoskeleton work and average exoskeleton torque on human locomotion. Subjects wore a unilateral ankle exoskeleton and walked on a treadmill at 1.25 m·s(-1) while net exoskeleton work rate was systematically varied from -0.054 to 0.25 J·kg(-1)·s(-1), with constant (0.12 N·m·kg(-1)) average exoskeleton torque, and while average exoskeleton torque was systematically varied from approximately zero to 0.18 N·m·kg(-1), with approximately zero net exoskeleton work. We measured metabolic rate, center-of-mass mechanics, joint mechanics, and muscle activity. Both techniques reduced effort-related measures at the assisted ankle, but this form of work input reduced metabolic cost (-17% with maximum net work input) while this form of torque support increased metabolic cost (+13% with maximum average torque). Disparate effects on metabolic rate seem to be due to cascading effects on whole body coordination, particularly related to assisted ankle muscle dynamics and the effects of trailing ankle behavior on leading leg mechanics during double support. It would be difficult to predict these results using simple walking models without muscles or musculoskeletal models that assume fixed kinematics or kinetics. Data from this experiment can be used to improve predictive models of human neuromuscular adaptation and guide the design of assistive devices. Copyright © 2015 the American Physiological Society.

The effect of grip force, stroke rotation and frequency on discomfort for a torqueing tasks.

PubMed

Bano, Farheen; Mallick, Zulqernian; Khan, Abid Ali

2015-08-08

Occupational tasks involve awkward upper limb postures, especially movement of forearm with repetitive combined gripping and torqueing exertions, which may lead to development of WMSDs. From the literature survey it was observed that there was a lack of studies focussed on the combined effect of torque and grip exertions on forearm discomfort. The present study was to investigate the effects of grip force, stroke rotation and frequency of exertions on discomfort and Electromyography (EMG) activities of the forearm muscles in a repetitive torqueing task. Twenty-seven male participants volunteered in this study. The participants performed repetitive exertions for a 5 minutes duration for each combination of the different levels of stroke rotation, grip force and frequency of exertions. Three levels of stroke rotation, three levels of grip force and three levels of frequency of exertion were chosen as independent variables. Therefore a 3 × 3 customized factorial design was used for the experiment for each level of grip force. Hence, the study was divided into three groups on the basis of grip force (50N, 70N and 90N). The ANOVA showed that stroke rotation and frequency of exertion were significant on discomfort. Further Students Newmann test (SNK) revealed that discomfort was increased with increasing stroke rotation and frequency of exertion. The multivariate analysis of variances (MANOVA) performed on EMG data instead of ANOVA because EMG activities of five muscles simultaneously were recorded. The Results found that extensor muscles were more fatigued in torqueing with gripping task. It was found that stroke rotation for the torqueing tasks must be kept below 45°. It was concluded that it is important to control stroke rotation to improve performance of repetitive torqueing activity.

Correlation of Shoulder and Elbow Kinetics With Ball Velocity in Collegiate Baseball Pitchers.

PubMed

Post, Eric G; Laudner, Kevin G; McLoda, Todd A; Wong, Regan; Meister, Keith

2015-06-01

Throwing a baseball is a dynamic and violent act that places large magnitudes of stress on the shoulder and elbow. Specific injuries at the elbow and glenohumeral joints have been linked to several kinetic variables throughout the throwing motion. However, very little research has directly examined the relationship between these kinetic variables and ball velocity. To examine the correlation of peak ball velocity with elbow-valgus torque, shoulder external-rotation torque, and shoulder-distraction force in a group of collegiate baseball pitchers. Cross-sectional study. Motion-analysis laboratory. Sixty-seven asymptomatic National Collegiate Athletic Association Division I baseball pitchers (age = 19.5 ± 1.2 years, height = 186.2 ± 5.7 cm, mass = 86.7 ± 7.0 kg; 48 right handed, 19 left handed). We measured peak ball velocity using a radar gun and shoulder and elbow kinetics of the throwing arm using 8 electronically synchronized, high-speed digital cameras. We placed 26 reflective markers on anatomical landmarks of each participant to track 3-dimensional coordinate data. The average data from the 3 highest-velocity fastballs thrown for strikes were used for data analysis. We calculated a Pearson correlation coefficient to determine the associations between ball velocity and peak elbow-valgus torque, shoulder-distraction force, and shoulder external-rotation torque (P < .05). A weak positive correlation was found between ball velocity and shoulder-distraction force (r = 0.257; 95% confidence interval [CI] = 0.02, 0.47; r(2) = 0.066; P = .018). However, no significant correlations were noted between ball velocity and elbow-valgus torque (r = 0.199; 95% CI = -0.043, 0.419; r(2) = 0.040; P = .053) or shoulder external-rotation torque (r = 0.097; 95% CI = -0.147, 0.329; r(2) = 0.009; P = .217). Although a weak positive correlation was present between ball velocity and shoulder-distraction force, no significant association was seen between ball velocity and elbow-valgus torque or shoulder external-rotation torque. Therefore, other factors, such as improper pitching mechanics, may contribute more to increases in joint kinetics than peak ball velocity.

Correlation of Shoulder and Elbow Kinetics With Ball Velocity in Collegiate Baseball Pitchers

PubMed Central

Post, Eric G.; Laudner, Kevin G.; McLoda, Todd A.; Wong, Regan; Meister, Keith

2015-01-01

Context Throwing a baseball is a dynamic and violent act that places large magnitudes of stress on the shoulder and elbow. Specific injuries at the elbow and glenohumeral joints have been linked to several kinetic variables throughout the throwing motion. However, very little research has directly examined the relationship between these kinetic variables and ball velocity. Objective To examine the correlation of peak ball velocity with elbow-valgus torque, shoulder external-rotation torque, and shoulder-distraction force in a group of collegiate baseball pitchers. Design Cross-sectional study. Setting Motion-analysis laboratory. Patients or Other Participants Sixty-seven asymptomatic National Collegiate Athletic Association Division I baseball pitchers (age = 19.5 ± 1.2 years, height = 186.2 ± 5.7 cm, mass = 86.7 ± 7.0 kg; 48 right handed, 19 left handed). Main Outcome Measure(s) We measured peak ball velocity using a radar gun and shoulder and elbow kinetics of the throwing arm using 8 electronically synchronized, high-speed digital cameras. We placed 26 reflective markers on anatomical landmarks of each participant to track 3-dimensional coordinate data. The average data from the 3 highest-velocity fastballs thrown for strikes were used for data analysis. We calculated a Pearson correlation coefficient to determine the associations between ball velocity and peak elbow-valgus torque, shoulder-distraction force, and shoulder external-rotation torque (P < .05). Results A weak positive correlation was found between ball velocity and shoulder-distraction force (r = 0.257; 95% confidence interval [CI] = 0.02, 0.47; r2 = 0.066; P = .018). However, no significant correlations were noted between ball velocity and elbow-valgus torque (r = 0.199; 95% CI = −0.043, 0.419; r2 = 0.040; P = .053) or shoulder external-rotation torque (r = 0.097; 95% CI = −0.147, 0.329; r2 = 0.009; P = .217). Conclusions Although a weak positive correlation was present between ball velocity and shoulder-distraction force, no significant association was seen between ball velocity and elbow-valgus torque or shoulder external-rotation torque. Therefore, other factors, such as improper pitching mechanics, may contribute more to increases in joint kinetics than peak ball velocity. PMID:25756790

A Biomechanical Comparison of Proportional Electromyography Control to Biological Torque Control Using a Powered Hip Exoskeleton.

PubMed

Young, Aaron J; Gannon, Hannah; Ferris, Daniel P

2017-01-01

Despite a large increase in robotic exoskeleton research, there are few studies that have examined human performance with different control strategies on the same exoskeleton device. Direct comparison studies are needed to determine how users respond to different types of control. The purpose of this study was to compare user performance using a robotic hip exoskeleton with two different controllers: a controller that targeted a biological hip torque profile and a proportional myoelectric controller. We tested both control approaches on 10 able-bodied subjects using a pneumatically powered hip exoskeleton. The state machine controller targeted a biological hip torque profile. The myoelectric controller used electromyography (EMG) of lower limb muscles to produce a proportional control signal for the hip exoskeleton. Each subject performed two 30-min exoskeleton walking trials (1.0 m/s) using each controller and a 10-min trial with the exoskeleton unpowered. During each trial, we measured subjects' metabolic cost of walking, lower limb EMG profiles, and joint kinematics and kinetics (torques and powers) using a force treadmill and motion capture. Compared to unassisted walking in the exoskeleton, myoelectric control significantly reduced metabolic cost by 13% ( p  = 0.005) and biological hip torque control reduced metabolic cost by 7% ( p  = 0.261). Subjects reduced muscle activity relative to the unpowered condition for a greater number of lower limb muscles using myoelectric control compared to the biological hip torque control. More subjects subjectively preferred the myoelectric controller to the biological hip torque control. Myoelectric control had more advantages (metabolic cost and muscle activity reduction) compared to a controller that targeted a biological torque profile for walking with a robotic hip exoskeleton. However, these results were obtained with a single exoskeleton device with specific control configurations while level walking at a single speed. Further testing on different exoskeleton hardware and with more varied experimental protocols, such as testing over multiple types of terrain, is needed to fully elucidate the potential benefits of myoelectric control for exoskeleton technology.

An entropy and viscosity corrected potential method for rotor performance prediction

NASA Technical Reports Server (NTRS)

Bridgeman, John O.; Strawn, Roger C.; Caradonna, Francis X.

1988-01-01

An unsteady Full-Potential Rotor code (FPR) has been enhanced with modifications directed at improving its drag prediction capability. The shock generated entropy has been included to provide solutions comparable to the Euler equations. A weakly interacted integral boundary layer has also been coupled to FPR in order to estimate skin-friction drag. Pressure distributions, shock positions, and drag comparisons are made with various data sets derived from two-dimensional airfoil, hovering, and advancing high speed rotor tests. In all these comparisons, the effect of the nonisentropic modification improves (i.e., weakens) the shock strength and wave drag. In addition, the boundary layer method yields reasonable estimates of skin-friction drag. Airfoil drag and hover torque data comparisons are excellent, as are predicted shock strength and positions for a high speed advancing rotor.

Step-to-Step Ankle Inversion/Eversion Torque Modulation Can Reduce Effort Associated with Balance.

PubMed

Kim, Myunghee; Collins, Steven H

2017-01-01

Below-knee amputation is associated with higher energy expenditure during walking, partially due to difficulty maintaining balance. We previously found that once-per-step push-off work control can reduce balance-related effort, both in simulation and in experiments with human participants. Simulations also suggested that changing ankle inversion/eversion torque on each step, in response to changes in body state, could assist with balance. In this study, we investigated the effects of ankle inversion/eversion torque modulation on balance-related effort among amputees ( N = 5) using a multi-actuated ankle-foot prosthesis emulator. In stabilizing conditions, changes in ankle inversion/eversion torque were applied so as to counteract deviations in side-to-side center-of-mass acceleration at the moment of intact-limb toe off; higher acceleration toward the prosthetic limb resulted in a corrective ankle inversion torque during the ensuing stance phase. Destabilizing controllers had the opposite effect, and a zero gain controller made no changes to the nominal inversion/eversion torque. To separate the balance-related effects of step-to-step control from the potential effects of changes in average mechanics, average ankle inversion/eversion torque and prosthesis work were held constant across conditions. High-gain stabilizing control lowered metabolic cost by 13% compared to the zero gain controller ( p = 0.05). We then investigated individual responses to subject-specific stabilizing controllers following an enforced exploration period. Four of five participants experienced reduced metabolic rate compared to the zero gain controller (-15, -14, -11, -6, and +4%) an average reduction of 9% ( p = 0.05). Average prosthesis mechanics were unchanged across all conditions, suggesting that improvements in energy economy might have come from changes in step-to-step corrections related to balance. Step-to-step modulation of inversion/eversion torque could be used in new, active ankle-foot prostheses to reduce walking effort associated with maintaining balance.

Explosive sport training and torque kinetics in children.

PubMed

Dotan, Raffy; Mitchell, Cameron J; Cohen, Rotem; Gabriel, David; Klentrou, Panagiota; Falk, Bareket

2013-07-01

A high rate of force development (RFD) is often more important than maximal force in daily and sports activities. In children, resistance training has been shown to increase maximal force. It is unclear whether, or to what extent, can children improve RFD and force kinetics. For this study, we compared strength and force kinetics of boy gymnasts with those of untrained boys and untrained men. Eight boy gymnasts (age, 9.5 ± 1.2 y), 20 untrained boys (age, 10.1 ± 1.3 y), and 20 untrained men (age, 22.9 ± 4.4 y) performed maximal, explosive, isometric elbow flexions (EF) and knee flexions (KF). Peak torque (maximal voluntary contraction (MVC)), elapsed times to 10%-100% MVC, peak rate of torque development (RTDpk), and other kinetics parameters were determined. When gymnasts were compared with untrained boys, size-normalized EF MVC was 11%-20% higher, RTDpk was 32% higher, and times to 30% and 80% MVC were 16% and 55% shorter, respectively (p < 0.05). No corresponding differences were observed in KF. Furthermore, although the normalized EF MVC was 28% lower in gymnasts than in men (p < 0.001), their torque kinetics parameters were similar. These findings highlight the specificity of gymnastics training, which markedly elevated the torque kinetics of young, prepubertal boys to adult levels, but only moderately affected peak torque. It is suggested that neurologic adaptations, such as enhanced firing and activation rates or increased type II motor-unit recruitment, as well as changes in musculotendinous stiffness, could explain these findings.

The effect of different screw-tightening techniques on the strain generated on an internal-connection implant superstructure. Part 2: Models created with a splinted impression technique.

PubMed

Choi, Jung-Han

2011-01-01

This study aimed to evaluate the effect of different screw-tightening sequences, torques, and methods on the strains generated on an internal-connection implant (Astra Tech) superstructure with good fit. An edentulous mandibular master model and a metal framework directly connected to four parallel implants with a passive fit to each other were fabricated. Six stone casts were made from a dental stone master model by a splinted impression technique to represent a well-fitting situation with the metal framework. Strains generated by four screw-tightening sequences (1-2-3-4, 4-3-2-1, 2-4-3-1, and 2-3-1-4), two torques (10 and 20 Ncm), and two methods (one-step and two-step) were evaluated. In the two-step method, screws were tightened to the initial torque (10 Ncm) in a predetermined screw-tightening sequence and then to the final torque (20 Ncm) in the same sequence. Strains were recorded twice by three strain gauges attached to the framework (superior face midway between abutments). Deformation data were analyzed using multiple analysis of variance at a .05 level of statistical significance. In all stone casts, strains were produced by connection of the superstructure, regardless of screw-tightening sequence, torque, and method. No statistically significant differences in superstructure strains were found based on screw-tightening sequences (range, -409.8 to -413.8 μm/m), torques (-409.7 and -399.1 μm/m), or methods (-399.1 and -410.3 μm/m). Within the limitations of this in vitro study, screw-tightening sequence, torque, and method were not critical factors for the strain generated on a well-fitting internal-connection implant superstructure by the splinted impression technique. Further studies are needed to evaluate the effect of screw-tightening techniques on the preload stress in various different clinical situations.

Asteroid Geophysics through a Tidal-BYORP Equilibrium

NASA Astrophysics Data System (ADS)

Jacobson, S. A.; Scheeres, D. J.

2012-12-01

There exists a long-term stable orbital equilibrium for singly synchronous binary asteroids balancing the contractive BYORP (binary Yarkovsky-O'Keefe-Radzievskii-Paddack) effect and the expansive tidal torque from the secondary onto the primary [Jacobson & Scheeres 2011]. Observations of 1996 FG3 determined that this object is consistent with occupying the predicted equilibrium [Scheirich, et al., 2012]. From the torque balance, the important tidal parameters of the primary and BYORP coefficient of the secondary can be directly determined for the first time, albeit degenerately. Singly synchronous systems consist of a rapidly spinning primary and a tidally locked secondary. Two torques evolve the mutual orbit of the system. First, the secondary raises a tidal torque on the primary, and this process expands the semi-major axis of the mutual orbit according to two parameters. The tidal Love number k is related to the strength (rigidity) of the body. The tidal dissipation number Q describes the mechanical energy dissipation. Second, the BYORP torque is the summed torques from all of the incident and exigent photons on the secondary acting on the barycenter of the system. Unless there is a spin-orbit resonance, the torques sum to zero. McMahon & Scheeres [2010] showed that showed that to first order in eccentricity the evolution of the semi-major axis and eccentricity depends only upon a single constant coefficient B determined by the shape of the secondary (size-independent). The BYORP torque can either contract or expand the mutual orbit, however it evolves the eccentricity with the opposite sign. Jacobson & Scheeres [2011] determined that when the BYORP torque is contractive, it can balance the expansive tidal torque. The system evolves to an equilibrium semi-major axis that is stable in eccentricity due to tidal decay overcoming BYORP excitation. If the singly synchronous population occupies this equilibrium, then the three unknown (i.e. unobserved) parameters: Bs Qp/k_p, as shown in the figure. Since the BYORP coefficient is defined to be size independent, the tidal parameters Qp/k_p ∝ Rp. This inverse dependence is different than the predicted dependencies of the classical tidal Love number kp ∝ Rp2 and the ``rubble-pile'' tidal Love number predicted in Goldreich & Sari [2009] kp ∝ Rp. Calculated Bs Qp/ kp for each observed singly synchronous binary asteroid system. The circled system is 1996 FG3. The solid line is the fit Bs Qp/k_p = 2557 Rp and the dashed lines are a facto r of 10 and a factor of 0.01 different.

Torque Induced on Lipid Microtubules with Optical Tweezers

NASA Astrophysics Data System (ADS)

wichean, T. Na; Charrunchon, S.; Pattanaporkratana, A.; Limtrakul, J.; Chattham, N.

2017-09-01

Chiral Phospholipids are found self-assembled into cylindrical tubules of 500 nm in diameter by helical winding of bilayer stripes under cooling in ethanol and water solution. Theoretical prediction and experimental evidence reported so far confirmed the modulated tilt direction in a helical striped pattern of the tubules. This molecular orientation morphology results in optically birefringent tubules. We investigate an individual lipid microtubule under a single optical trap of 532 nm linearly polarized laser. Spontaneous rotation of a lipid tubule induced by radiation torque was observed with only one sense of rotation caused by chirality of a lipid tubule. Rotation discontinued once the high refractive index axis of a lipid tubule aligned with a polarization axis of the laser. We further explored a lipid tubule under circularly polarized optical trap. It was found that a lipid tubule was continuously rotated confirming the tubule birefringent property. We modified the shape of optical trap by cylindrical lens obtaining an elliptical profile optical trap. A lipid tubule can be aligned along the elongated length of optical trap. We reported an investigation of competition between polarized light torque on a birefringent lipid tubule versus torque from intensity gradient of an elongated optical trap.

Haptic feedback can provide an objective assessment of arthroscopic skills.

PubMed

Chami, George; Ward, James W; Phillips, Roger; Sherman, Kevin P

2008-04-01

The outcome of arthroscopic procedures is related to the surgeon's skills in arthroscopy. Currently, evaluation of such skills relies on direct observation by a surgeon trainer. This type of assessment, by its nature, is subjective and time-consuming. The aim of our study was to identify whether haptic information generated from arthroscopic tools could distinguish between skilled and less skilled surgeons. A standard arthroscopic probe was fitted with a force/torque sensor. The probe was used by five surgeons with different levels of experience in knee arthroscopy performing 11 different tasks in 10 standard knee arthroscopies. The force/torque data from the hand and tool interface were recorded and synchronized with a video recording of the procedure. The torque magnitude and patterns generated were analyzed and compared. A computerized system was used to analyze the force/torque signature based on general principles for quality of performance using such measures as economy in movement, time efficiency, and consistency in performance. The results showed a considerable correlation between three haptic parameters and the surgeon's experience, which could be used in an automated objective assessment system for arthroscopic surgery. Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Current-driven second-harmonic domain wall resonance in ferromagnetic metal/nonmagnetic metal bilayers: A field-free method for spin Hall angle measurements

NASA Astrophysics Data System (ADS)

Hajiali, M. R.; Hamdi, M.; Roozmeh, S. E.; Mohseni, S. M.

2017-10-01

We study the ac current-driven domain wall motion in bilayer ferromagnetic metal (FM)/nonmagnetic metal (NM) nanowires. The solution of the modified Landau-Lifshitz-Gilbert equation including all the spin transfer torques is used to describe motion of the domain wall in the presence of the spin Hall effect. We show that the domain wall center has a second-harmonic frequency response in addition to the known first-harmonic excitation. In contrast to the experimentally observed second-harmonic response in harmonic Hall measurements of spin-orbit torque in magnetic thin films, this second-harmonic response directly originates from spin-orbit torque driven domain wall dynamics. Based on the spin current generated by domain wall dynamics, the longitudinal spin motive force generated voltage across the length of the nanowire is determined. The second-harmonic response introduces additionally a practical field-free and all-electrical method to probe the effective spin Hall angle for FM/NM bilayer structures that could be applied in experiments. Our results also demonstrate the capability of utilizing FM/NM bilayer structures in domain wall based spin-torque signal generators and resonators.

Measurements of Inertial Torques on Sedimenting Fibers

NASA Astrophysics Data System (ADS)

Hamati, Rami; Roy, Anubhab; Koch, Don; Voth, Greg

2017-11-01

Stokes flow solutions predict that ellipsoids sedimenting in quiescent fluid keep their initial orientation. However, preferential alignment in low Reynolds number sedimentation is easily observed. For example, sun dogs form from alignment of sedimenting ice crystals. The cause of this preferential alignment is a torque due to non-zero fluid inertia that aligns particles with a long axis in the horizontal direction. These torques are predicted analytically for slender fibers with low Reynolds number based on the fiber diameter (ReD) by Khayat and Cox (JFM 209:435, 1989). Despite increasingly widespread use of these expressions, we did not find experimental measurements of these inertial torques at parameters where the theory was valid, so we performed a set of sedimentation experiments using fore-aft symmetric cylinders and asymmetric cylinders with their center of mass offset from their center of drag. Measured rotation rates as a function of orientation using carefully prepared glass capillaries in silicon oil show good agreement with the theory. We quantify the effect of finite tank size and compare with other experiments in water where the low ReD condition is not met. Supported by Army Research Office Grant W911NF1510205.

Low torque hydrodynamic lip geometry for bi-directional rotation seals

DOEpatents

Dietle, Lannie L [Houston, TX; Schroeder, John E [Richmond, TX

2009-07-21

A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.

Low torque hydrodynamic lip geometry for bi-directional rotation seals

DOEpatents

Dietle, Lannie L [Houston, TX; Schroeder, John E [Richmond, TX

2011-11-15

A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.

Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

DOEpatents

Woolley, R.D.

1998-09-08

A method and apparatus are disclosed for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators. 6 figs.

Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

DOEpatents

Woolley, Robert D.

1998-01-01

A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.

Torque teno virus: an improved indicator for viral pathogens in drinking waters.

PubMed

Griffin, Jennifer S; Plummer, Jeanine D; Long, Sharon C

2008-10-03

Currently applied indicator organism systems, such as coliforms, are not fully protective of public health from enteric viruses in water sources. Waterborne disease outbreaks have occurred in systems that tested negative for coliforms, and positive coliform results do not necessarily correlate with viral risk. It is widely recognized that bacterial indicators do not co-occur exclusively with infectious viruses, nor do they respond in the same manner to environmental or engineered stressors. Thus, a more appropriate indicator of health risks from infectious enteric viruses is needed. Torque teno virus is a small, non-enveloped DNA virus that likely exhibits similar transport characteristics to pathogenic enteric viruses. Torque teno virus is unique among enteric viral pathogens in that it appears to be ubiquitous in humans, elicits seemingly innocuous infections, and does not exhibit seasonal fluctuations or epidemic spikes. Torque teno virus is transmitted primarily via the fecal-oral route and can be assayed using rapid molecular techniques. We hypothesize that Torque teno virus is a more appropriate indicator of viral pathogens in drinking waters than currently used indicator systems based solely on bacteria. To test the hypothesis, a multi-phased research approach is needed. First, a reliable Torque teno virus assay must be developed. A rapid, sensitive, and specific PCR method using established nested primer sets would be most appropriate for routine monitoring of waters. Because PCR detects both infectious and inactivated virus, an in vitro method to assess infectivity also is needed. The density and occurrence of Torque teno virus in feces, wastewater, and source waters must be established to define spatial and temporal stability of this potential indicator. Finally, Torque teno virus behavior through drinking water treatment plants must be determined with co-assessment of traditional indicators and enteric viral pathogens to assess whether correlations exist. If substantiated, Torque teno virus could provide a completely new, reliable, and efficient indicator system for viral pathogen risk. This indicator would have broad application to drinking water utilities, watershed managers, and protection agencies and would provide a better means to assess viral risk and protect public health.

Torque teno virus: an improved indicator for viral pathogens in drinking waters

PubMed Central

Griffin, Jennifer S; Plummer, Jeanine D; Long, Sharon C

2008-01-01

Background Currently applied indicator organism systems, such as coliforms, are not fully protective of public health from enteric viruses in water sources. Waterborne disease outbreaks have occurred in systems that tested negative for coliforms, and positive coliform results do not necessarily correlate with viral risk. It is widely recognized that bacterial indicators do not co-occur exclusively with infectious viruses, nor do they respond in the same manner to environmental or engineered stressors. Thus, a more appropriate indicator of health risks from infectious enteric viruses is needed. Presentation of the hypothesis Torque teno virus is a small, non-enveloped DNA virus that likely exhibits similar transport characteristics to pathogenic enteric viruses. Torque teno virus is unique among enteric viral pathogens in that it appears to be ubiquitous in humans, elicits seemingly innocuous infections, and does not exhibit seasonal fluctuations or epidemic spikes. Torque teno virus is transmitted primarily via the fecal-oral route and can be assayed using rapid molecular techniques. We hypothesize that Torque teno virus is a more appropriate indicator of viral pathogens in drinking waters than currently used indicator systems based solely on bacteria. Testing the hypothesis To test the hypothesis, a multi-phased research approach is needed. First, a reliable Torque teno virus assay must be developed. A rapid, sensitive, and specific PCR method using established nested primer sets would be most appropriate for routine monitoring of waters. Because PCR detects both infectious and inactivated virus, an in vitro method to assess infectivity also is needed. The density and occurrence of Torque teno virus in feces, wastewater, and source waters must be established to define spatial and temporal stability of this potential indicator. Finally, Torque teno virus behavior through drinking water treatment plants must be determined with co-assessment of traditional indicators and enteric viral pathogens to assess whether correlations exist. Implications of the hypothesis If substantiated, Torque teno virus could provide a completely new, reliable, and efficient indicator system for viral pathogen risk. This indicator would have broad application to drinking water utilities, watershed managers, and protection agencies and would provide a better means to assess viral risk and protect public health. PMID:18834517

Vibration characteristics of OH-58A helicopter main rotor transmission

NASA Technical Reports Server (NTRS)

Lewicki, David G.; Coy, John J.

1987-01-01

Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.

Dual rotating shaft seal apparatus

DOEpatents

Griggs, J.E.; Newman, H.J.

1983-06-16

The report is directed to apparatus suitable for transferring torque and rotary motion through a wall in a manner which is essentially gas impermeable. The apparatus can be used for pressurizing, agitating, and mixing fluids and features two ferrofluidic, i.e., ferrometic seals. Each seal is disposed on one of two supported shafts and each shaft is operably connected at one end to a gear mechanism and at its other end to an adjustable coupling means which is to be connected to a rotatable shaft extending through a wall through which torque and rotary motion are to be transferred.

Spinal circuits can accommodate interaction torques during multijoint limb movements.

PubMed

Buhrmann, Thomas; Di Paolo, Ezequiel A

2014-01-01

The dynamic interaction of limb segments during movements that involve multiple joints creates torques in one joint due to motion about another. Evidence shows that such interaction torques are taken into account during the planning or control of movement in humans. Two alternative hypotheses could explain the compensation of these dynamic torques. One involves the use of internal models to centrally compute predicted interaction torques and their explicit compensation through anticipatory adjustment of descending motor commands. The alternative, based on the equilibrium-point hypothesis, claims that descending signals can be simple and related to the desired movement kinematics only, while spinal feedback mechanisms are responsible for the appropriate creation and coordination of dynamic muscle forces. Partial supporting evidence exists in each case. However, until now no model has explicitly shown, in the case of the second hypothesis, whether peripheral feedback is really sufficient on its own for coordinating the motion of several joints while at the same time accommodating intersegmental interaction torques. Here we propose a minimal computational model to examine this question. Using a biomechanics simulation of a two-joint arm controlled by spinal neural circuitry, we show for the first time that it is indeed possible for the neuromusculoskeletal system to transform simple descending control signals into muscle activation patterns that accommodate interaction forces depending on their direction and magnitude. This is achieved without the aid of any central predictive signal. Even though the model makes various simplifications and abstractions compared to the complexities involved in the control of human arm movements, the finding lends plausibility to the hypothesis that some multijoint movements can in principle be controlled even in the absence of internal models of intersegmental dynamics or learned compensatory motor signals.

Research on parallel load sharing principle of piezoelectric six-dimensional heavy force/torque sensor

NASA Astrophysics Data System (ADS)

Liu, Wei; Li, Ying-jun; Jia, Zhen-yuan; Zhang, Jun; Qian, Min

2011-01-01

In working process of huge heavy-load manipulators, such as the free forging machine, hydraulic die-forging press, forging manipulator, heavy grasping manipulator, large displacement manipulator, measurement of six-dimensional heavy force/torque and real-time force feedback of the operation interface are basis to realize coordinate operation control and force compliance control. It is also an effective way to raise the control accuracy and achieve highly efficient manufacturing. Facing to solve dynamic measurement problem on six-dimensional time-varying heavy load in extremely manufacturing process, the novel principle of parallel load sharing on six-dimensional heavy force/torque is put forward. The measuring principle of six-dimensional force sensor is analyzed, and the spatial model is built and decoupled. The load sharing ratios are analyzed and calculated in vertical and horizontal directions. The mapping relationship between six-dimensional heavy force/torque value to be measured and output force value is built. The finite element model of parallel piezoelectric six-dimensional heavy force/torque sensor is set up, and its static characteristics are analyzed by ANSYS software. The main parameters, which affect load sharing ratio, are analyzed. The experiments for load sharing with different diameters of parallel axis are designed. The results show that the six-dimensional heavy force/torque sensor has good linearity. Non-linearity errors are less than 1%. The parallel axis makes good effect of load sharing. The larger the diameter is, the better the load sharing effect is. The results of experiments are in accordance with the FEM analysis. The sensor has advantages of large measuring range, good linearity, high inherent frequency, and high rigidity. It can be widely used in extreme environments for real-time accurate measurement of six-dimensional time-varying huge loads on manipulators.

Displacement of screw-retained splinted and nonsplinted restorations into implants with conical internal connections.

PubMed

Yilmaz, Burak; Seidt, Jeremy D; Clelland, Nancy L

2014-01-01

Variable abutment displacement could potentially affect proximal contacts, incisal edge position, or occlusion of implant-supported prostheses. This study aimed to measure and compare displacements of splinted and nonsplinted restorations into implants featuring internal conical connections as screws were tightened by hand or by torque driver. A stereolithic resin model was printed using computed tomography data from a patient missing mandibular left first and second molars. Two 5.0 × 11-mm implants were placed in the edentulous site using a surgical guide. Two sets (splinted and nonsplinted) of gold screw-retained prostheses were made indirectly to fit the implants in the stereolithic model representing the patient. The axial position of the crowns relative to a fixed location on the model was recorded following hand tightening using the three-dimensional image correlation technique and image correlation software. A pair of high-resolution digital cameras provided a synchronized view of the model during the experiment. Relative crown positions were again recorded after tightening with a torque driver to 25 Ncm. Testing was repeated randomly three times for each set of crowns. Displacement data after torque tightening were compared using a factorial analysis of variance with JMP 9.0 software (SAS) followed by a Tukey-Kramer post hoc test (α = .05). Interproximal contacts were evaluated using an 8-μm tin foil shim after tightening by hand and torque driver. Displacements for splinted and nonsplinted restorations differed only in a buccal direction. The nonsplinted crowns displaced significantly more than splinted crowns. Discernible differences were observed for the tin foil shim when dragged through proximal contacts following hand versus torque tightening. Differences between screw tightening by hand or torque driver should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.

Three-Dimensional Displacement of Nine Different Abutments for an Implant with an Internal Hexagon Platform.

PubMed

Gilbert, Andy B; Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L; Chien, Hua-Hong

2015-01-01

Clinicians need to know whether there are any differences among the many abutment options available for restoring a particular implant. This study aims to compare nine abutments for one implant system for positional changes between hand tightening and torqueing. Nine Tapered Screw-Vent (TSV) implants were placed into a resin block. Five specimens of nine different abutments (n = 45) were tried in one of the nine implants. Initially, the abutments were torqued to 20 Ncm to represent hand tightening. Abutments were tightened to 30 Ncm using a torque driver as recommended by the manufacturer for final seating. Images were recorded in 12-second intervals for approximately 10 minutes after the torque was applied. The spatial relationship of the abutments to the resin block was determined using three-dimensional digital image correlation. Commercial image correlation software was used to analyze the displacements. Mean displacements for the nine different abutments were calculated in all three dimensions and for overall displacement in space. A t test with a step-down Bonferroni correction was used for a pairwise comparison of each abutment's mean displacements to the other abutments to determine statistical differences (α = .05). The Atlantis titanium, Inclusive titanium, and Legacy zirconia abutments showed mean displacements that were statistically significantly higher than other abutments in the horizontal direction. The overall three-dimensional displacement of the Atlantis titanium abutment after an applied 30-Ncm torque was significantly higher than that of six of the other eight abutments (P < .0144). Within the limitations of this in vitro study, the Zimmer PSA demonstrated less displacement between hand tightening and torqueing than the Atlantis titanium or Inclusive titanium abutments when used to restore a TSV implant.

A thin membrane artificial muscle rotary motor

NASA Astrophysics Data System (ADS)

Anderson, Iain A.; Hale, Thom; Gisby, Todd; Inamura, Tokushu; McKay, Thomas; O'Brien, Benjamin; Walbran, Scott; Calius, Emilio P.

2010-01-01

Desirable rotary motor attributes for robotics include the ability to develop high torque in a low mass body and to generate peak power at low rotational speeds. Electro-active polymer artificial muscles offer promise as actuator elements for robotic motors. A promising artificial muscle technology for use as a driving mechanism for rotary motion is the dielectric elastomer actuator (DEA). We present a membrane DEA motor in which phased actuation of electroded sectors of the motor membrane impart orbital motion to a central drive that turns a rotor. The motor is inherently scalable, flexible, flat, silent in operation, amenable to deposition-based manufacturing approaches, and uses relatively inexpensive materials. As a membrane it can also form part of the skin of a robot. We have investigated the torque and power of stacked membrane layers. Specific power and torque ratios when calculated using active membrane mass only were 20.8 W/kg and 4.1 Nm/kg, respectively. These numbers compare favorably with a commercially available stepper motor. Multi-membrane fabrication substantially boosts torque and power and increases the active mass of membrane relative to supporting framework. Through finite element modeling, we show the mechanisms governing the maximum torque the device can generate and how the motor can be improved.

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE PAGES

Pace, D. C.; Collins, C. S.; Crowley, B.; ...

2016-09-28

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

An Electromyographic-driven Musculoskeletal Torque Model using Neuro-Fuzzy System Identification: A Case Study

PubMed Central

Jafari, Zohreh; Edrisi, Mehdi; Marateb, Hamid Reza

2014-01-01

The purpose of this study was to estimate the torque from high-density surface electromyography signals of biceps brachii, brachioradialis, and the medial and lateral heads of triceps brachii muscles during moderate-to-high isometric elbow flexion-extension. The elbow torque was estimated in two following steps: First, surface electromyography (EMG) amplitudes were estimated using principal component analysis, and then a fuzzy model was proposed to illustrate the relationship between the EMG amplitudes and the measured torque signal. A neuro-fuzzy method, with which the optimum number of rules could be estimated, was used to identify the model with suitable complexity. Utilizing the proposed neuro-fuzzy model, the clinical interpretability was introduced; contrary to the previous linear and nonlinear black-box system identification models. It also reduced the estimation error compared with that of the most recent and accurate nonlinear dynamic model introduced in the literature. The optimum number of the rules for all trials was 4 ± 1, that might be related to motor control strategies and the % variance accounted for criterion was 96.40 ± 3.38 which in fact showed considerable improvement compared with the previous methods. The proposed method is thus a promising new tool for EMG-Torque modeling in clinical applications. PMID:25426427

Characteristics of a multilayer one-touch-point ultrasonic motor for high torque

NASA Astrophysics Data System (ADS)

Jeong, Seong-Su; Park, Tae-Gone; Park, Jong-Kyu

2013-04-01

In this paper, a one-touch-point ultrasonic motor is proposed. Fabricating the stator is easy because of its simple structure and the use of a punching technique. Also, a thin stator is advantageous to use in tight spaces. A thin metal plate was used as a V-shaped stator and two to the upper and two to the lower ceramic plates were attached to the upper and the lower surfaces respectively of the metal plate. When two sinusoidal sources with a phase difference of 90 degrees were applied to the stator, an elliptical displacement was generated at contact tip of the stator. Modeling of the ultrasonic motor was done and the displacement characteristics were defined by using a finite element analysis program (ATILA). To improve the speed and the torque of the ultrasonic motor, we analyzed the effects of the leg angle and the number of ceramic layers. In addition, a model with large x-axis and y-axis displacements was fabricated, and the speed and the torque were measured under various conditions. The elliptical motion of the contact tip of the stator was consistently obtained at the resonance frequency. The maximum speed and torque were obtained by using maximum elliptical displacement model. The speed and the torque increased linearly with increasing voltage.

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, D. C.; Collins, C. S.; Crowley, B.

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

Matching initial torque with different stimulation parameters influences skeletal muscle fatigue.

PubMed

Bickel, C Scott; Gregory, Chris M; Azuero, Andres

2012-01-01

A fundamental barrier to using electrical stimulation in the clinical setting is an inability to maintain torque production secondary to muscle fatigue. Electrical stimulation parameters are manipulated to influence muscle torque production, and they may also influence fatigability during repetitive stimulation. Our purpose was to determine the response of the quadriceps femoris to three different fatigue protocols using the same initial torque obtained by altering stimulator parameter settings. Participants underwent fatigue protocols in which either pulse frequency (lowHz), pulse duration (lowPD), or voltage (lowV) was manipulated to obtain an initial torque that equaled 25% of maximum voluntary isometric contraction. Muscle soreness was reported on a visual analog scale 48 h after each fatigue test. The lowHz protocol resulted in the least fatigue (25% +/- 14%); the lowPD (50% +/- 13%) and lowV (48% +/- 14%) protocols had similar levels of fatigue. The lowHz protocol resulted in significantly less muscle soreness than the higher frequency protocols. Stimulation protocols that use a lower frequency coupled with long pulse durations and high voltages result in lesser amounts of muscle fatigue and perceived soreness. The identification of optimal stimulation patterns to maximize muscle performance will reduce the effect of muscle fatigue and potentially improve clinical efficacy.

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

NASA Astrophysics Data System (ADS)

Pace, D. C.; Collins, C. S.; Crowley, B.; Grierson, B. A.; Heidbrink, W. W.; Pawley, C.; Rauch, J.; Scoville, J. T.; Van Zeeland, M. A.; Zhu, Y. B.; The DIII-D Team

2017-01-01

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak (Luxon 2002 Nucl. Fusion 42 614). Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significant changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. Developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.

A Critical Review on Tubercles Design for Propellers

NASA Astrophysics Data System (ADS)

Seeni, A.; Rajendran, P.; Kutty, H. A.

2018-05-01

The design of propellers in aeronautics is still earning high interest. This has led to the application of biomimetic for improving aerodynamic performance. One such design is the usage of tubercles in either leading or trailing edge of airfoils. So the usage of tubercles has so far been in the design of wing or wind-turbines. Recent studies have aimed to study tubercles for the design of a propeller. The studies have so far gained reputations in improving the aerodynamic performance on a few but not all of the airfoil shapes. Similar results have been identified for propeller designs with improvement in thrust at low torque. We have so far led research works on developing new propeller designs with the aim to improve the thrust and torque performance of propeller. A review of recent studies has been performed to study the state-of-the-art. The results of this work will be discussed in this paper.

Torque undergone by assemblies of single-domain magnetic nanoparticles submitted to a rotating magnetic field

NASA Astrophysics Data System (ADS)

Carrey, J.; Hallali, N.

2016-11-01

In the last 10 years, it has been shown in various types of experiments that it is possible to induce biological effects in cells using the torque generated by magnetic nanoparticles submitted to an alternating or a rotating magnetic field. In biological systems, particles are generally found under the form of assemblies because they accumulate at the cell membrane, are internalized inside lysosomes, or are synthesized under the form of beads containing several particles. The torque undergone by assemblies of single-domain magnetic nanoparticles has not been addressed theoretically so far and is the subject of the present article. The results shown in the present article have been obtained using kinetic Monte Carlo simulations, in which thermal activation is taken into account, so the torque undergone by ferromagnetic and superparamagnetic nanoparticles could both be simulated. The first system under study is a single ferromagnetic particle with its easy axis in the plane of the rotating magnetic field. Then, elements adding complexity to the problem are introduced progressively and the properties of the resulting system presented and analyzed: random anisotropy axes, thermal activation, assemblies, and finally magnetic interactions. The most complex studied systems are particularly relevant for applications and are assemblies of interacting superparamagnetic nanoparticles with randomly oriented anisotropy axes. Whenever it is possible, analytical equations describing the torque properties are provided, as well as their domain of validity. Although the properties of an assembly naturally derive from those of single particles, it is shown here that several of them were unexpected and are particularly interesting with regard to the maximization of torque amplitude in biological applications. In particular, it is shown that, in a given range of parameters, the torque of an assembly increases dramatically in the direction perpendicular to the plane of the rotating magnetic field. This effect results from a breaking of time reversal symmetry when the field is rotated and is comprehensively explained. This strong enhancement occurs only if the magnetic field rotates, not if it oscillates. When this enhancement does not occur, the total torque of an assembly scales with the square root of the number of particles in the assembly. In the enhancement regime, the total torque scales with a power exponent larger than 1/2. It is also found that, in superparamagnetic nanoparticles, this enhancement is induced by the presence of magnetic interactions so that, in a rather large range of parameters, interacting superparamagnetic particles display a much larger torque than otherwise identical ferromagnetic particles. In all cases studied, the conditions required to obtain this enhancement are provided. The concepts presented in this article should help chemists and biologists in synthesizing nano-objects with optimized torque properties. For physicists, it would be interesting to test experimentally the results described in this article. For this purpose, torque measurements on well-characterized assemblies of nanoparticles should be performed and compared with numerical simulations.

A comparative study of Cr-X-N (X=Zr, Si) coatings for the improvement of the low-speed torque efficiency of a hydraulic piston pump

NASA Astrophysics Data System (ADS)

Hong, Yeh-Sun; Lee, Sang-Yul

2008-02-01

The internal parts of hydraulic pumps operating at variable speed should be protected from insufficient lubrication. The axial piston type pumps employ a steel-base cylinder barrel rotating on a soft bronze valves plate with a slide contact, where the insufficient lubrication of these components can cause rapid wear of the valve plate and increase the friction loss. In this study, the cylinder barrel surface was deposited with CrZrN coatings, which were expected to improve the tribological contact with a valve plate under low-speed mixed lubrication conditions. Its effect on the improvement of the low-speed torque efficiency of a hydraulic piston pump was investigated and compared with that from the CrSiN coating. The coated cylinder barrels showed much lower friction coefficients and wear rates of the valve plates than the uncoated plasma-nitride one. In particular, the CrZrN coatings revealed better performance than the CrSiN coatings. By representing the improvement in the torque efficiency of the whole pump based upon the degree of the friction coefficient reduction, the CrZrN coatings exhibited approximately a 0.35% higher improvement at 300 bar and 100 rpm than CrSiN coatings. The possible failure modes of the coatings coated on the barrel were sugested and the microstructures of the coatings seemed to have a strong effect on the film failure mode.

An Evaluation of Relative Damage to the Powertrain System in Tracked Vehicles

PubMed Central

Lee, Sang-Ho; Lee, Jeong-Hwan; Goo, Sang-Hwa; Cho, Yong-Cheol; Cho, Ho-Young

2009-01-01

The objective of this study was to improve the reliability of the endurance test for the powertrain system of military tracked vehicles. The measurement system that measures the driving duty applied to the powertrain system caused by mobility on roads consists of eight analog channels and two pulse channels, including the propeller shaft output torques for the left and right sides. The data obtained from this measurement system can be used to introduce a new technology that produces the output torque of a torque converter and that can be applied to analyze the revolution counting for the endurance and road mobility in the front unit and represent the relative fatigue damages analysis technique and its results according to the driven roads through a cumulative fatigue method. PMID:22573990

A study of the dynamic tire properties over a range of tire constructions

NASA Technical Reports Server (NTRS)

Nybakken, G. H.; Dodge, R. N.; Clark, S. K.

1973-01-01

The dynamic properties of four model aircraft tires of various construction were evaluated experimentally and compared with available theory. The experimental investigation consisted of measuring the cornering force and the self-aligning torque developed by the tires undergoing sinusoidal steering inputs while operating on a small scale, road-wheel tire testing apparatus. The force and moment data from the different tires are compared with both finite- and point-contact patch string theory predictions. In general, agreement between finite contact patch theory and experimental observation is good. A modified string theory is also presented in which coefficients for cornering force and self-aligning torque are determined separately. This theory improves the correspondence between the experimental and analytical data, particularly on tires with relatively high self-aligning torques.

Optimal control of the gear shifting process for shift smoothness in dual-clutch transmissions

NASA Astrophysics Data System (ADS)

Li, Guoqiang; Görges, Daniel

2018-03-01

The control of the transmission system in vehicles is significant for the driving comfort. In order to design a controller for smooth shifting and comfortable driving, a dynamic model of a dual-clutch transmission is presented in this paper. A finite-time linear quadratic regulator is proposed for the optimal control of the two friction clutches in the torque phase for the upshift process. An integral linear quadratic regulator is introduced to regulate the relative speed difference between the engine and the slipping clutch under the optimization of the input torque during the inertia phase. The control objective focuses on smoothing the upshift process so as to improve the driving comfort. Considering the available sensors in vehicles for feedback control, an observer design is presented to track the immeasurable variables. Simulation results show that the jerk can be reduced both in the torque phase and inertia phase, indicating good shift performance. Furthermore, compared with conventional controllers for the upshift process, the proposed control method can reduce shift jerk and improve shift quality.

Design and Performance Analysis of a new Rotary Hydraulic Joint

NASA Astrophysics Data System (ADS)

Feng, Yong; Yang, Junhong; Shang, Jianzhong; Wang, Zhuo; Fang, Delei

2017-07-01

To improve the driving torque of the robots joint, a wobble plate hydraulic joint is proposed, and the structure and working principle are described. Then mathematical models of kinematics and dynamics was established. On the basis of this, dynamic simulation and characteristic analysis are carried out. Results show that the motion curve of the joint is continuous and the impact is small. Moreover the output torque of the joint characterized by simple structure and easy processing is large and can be rotated continuously.

Electromagnetically driven westward drift and inner-core superrotation in Earth's core.

PubMed

Livermore, Philip W; Hollerbach, Rainer; Jackson, Andrew

2013-10-01

A 3D numerical model of the earth's core with a viscosity two orders of magnitude lower than the state of the art suggests a link between the observed westward drift of the magnetic field and superrotation of the inner core. In our model, the axial electromagnetic torque has a dominant influence only at the surface and in the deepest reaches of the core, where it respectively drives a broad westward flow rising to an axisymmetric equatorial jet and imparts an eastward-directed torque on the solid inner core. Subtle changes in the structure of the internal magnetic field may alter not just the magnitude but the direction of these torques. This not only suggests that the quasi-oscillatory nature of inner-core superrotation [Tkalčić H, Young M, Bodin T, Ngo S, Sambridge M (2013) The shuffling rotation of the earth's inner core revealed by earthquake doublets. Nat Geosci 6:497-502.] may be driven by decadal changes in the magnetic field, but further that historical periods in which the field exhibited eastward drift were contemporaneous with a westward inner-core rotation. The model further indicates a strong internal shear layer on the tangent cylinder that may be a source of torsional waves inside the core.

Nearly axisymmetric hot plasmas in a highly rippled tokamak

NASA Astrophysics Data System (ADS)

Bellan, Paul

2002-11-01

Tokamak ohmic heating current flowing along toroidally rippled flux surfaces results in a poloidal torque. Since pressure gradients cannot offset torques, the torque drives plasma flows which convect plasma toroidally from ripple necks (high B_pol^2) to ripple bulges (low B_pol^2). Stagnation of the oppositely directed toroidal flows at the ripple bulges thermalizes the directed flow velocity ˜ B_pol/μ_0ρ , giving β _pol ˜1. These flows also convect frozen-in poloidal field lines which accumulate at the bulges enhancing the pinch force there and so reducing the bulge. Thus, a nearly axisymmetric β_pol ˜1 equilibrium is achieved using only a few TF coils. Particles bouncing in step between approaching flows will be Fermi accelerated to form a high energy tail. The ST tokamak magnetic mountain experiment [1] showed that, compared to a 1.8% ripple configuration, a 28% ripple configuration had four times the neutron production, and only a modest degradation of overall confinement; the former is consistent with the notion of Fermi acceleration of particles bouncing between colliding toroidal flows and the latter is consistent with ripple reduction due to toroidal convection of poloidal field lines. [1] W. Stodiek et al, Proc. 4th Intl. Conf. Plasma Phys. and Contr. Nuc. Fusion Res., (Madison, 1971), Vol. 1, p. 465

Control strategies for wind farm power optimization: LES study

NASA Astrophysics Data System (ADS)

Ciri, Umberto; Rotea, Mario; Leonardi, Stefano

2017-11-01

Turbines in wind farms operate in off-design conditions as wake interactions occur for particular wind directions. Advanced wind farm control strategies aim at coordinating and adjusting turbine operations to mitigate power losses in such conditions. Coordination is achieved by controlling on upstream turbines either the wake intensity, through the blade pitch angle or the generator torque, or the wake direction, through yaw misalignment. Downstream turbines can be adapted to work in waked conditions and limit power losses, using the blade pitch angle or the generator torque. As wind conditions in wind farm operations may change significantly, it is difficult to determine and parameterize the variations of the coordinated optimal settings. An alternative is model-free control and optimization of wind farms, which does not require any parameterization and can track the optimal settings as conditions vary. In this work, we employ a model-free optimization algorithm, extremum-seeking control, to find the optimal set-points of generator torque, blade pitch and yaw angle for a three-turbine configuration. Large-Eddy Simulations are used to provide a virtual environment to evaluate the performance of the control strategies under realistic, unsteady incoming wind. This work was supported by the National Science Foundation, Grants No. 1243482 (the WINDINSPIRE project) and IIP 1362033 (I/UCRC WindSTAR). TACC is acknowledged for providing computational time.

Electromagnetically driven westward drift and inner-core superrotation in Earth’s core

PubMed Central

Livermore, Philip W.; Hollerbach, Rainer; Jackson, Andrew

2013-01-01

A 3D numerical model of the earth’s core with a viscosity two orders of magnitude lower than the state of the art suggests a link between the observed westward drift of the magnetic field and superrotation of the inner core. In our model, the axial electromagnetic torque has a dominant influence only at the surface and in the deepest reaches of the core, where it respectively drives a broad westward flow rising to an axisymmetric equatorial jet and imparts an eastward-directed torque on the solid inner core. Subtle changes in the structure of the internal magnetic field may alter not just the magnitude but the direction of these torques. This not only suggests that the quasi-oscillatory nature of inner-core superrotation [Tkalčić H, Young M, Bodin T, Ngo S, Sambridge M (2013) The shuffling rotation of the earth’s inner core revealed by earthquake doublets. Nat Geosci 6:497–502.] may be driven by decadal changes in the magnetic field, but further that historical periods in which the field exhibited eastward drift were contemporaneous with a westward inner-core rotation. The model further indicates a strong internal shear layer on the tangent cylinder that may be a source of torsional waves inside the core. PMID:24043841

A Novel Method for Characterizing Spacesuit Mobility Through Metabolic Cost

NASA Technical Reports Server (NTRS)

McFarland, Shane M.; Norcross, Jason R.

2014-01-01

Historically, spacesuit mobility has been characterized by directly measuring both range of motion and joint torque of individual anatomic joints. The work detailed herein aims to improve on this method, which is often prone to uncertainly, lack of repeatability, and a general lack of applicability to real-world functional tasks. Specifically, the goal of this work is to characterize suited mobility performance by directly measuring the metabolic performance of the occupant. Pilot testing was conducted in 2013, employing three subjects performing a range of functional tasks in two different suits prototypes, the Mark III and Z-1. Cursory analysis of the results shows the approach has merit, with consistent performance trends toward one suit over the other. Forward work includes the need to look at more subjects, a refined task set, and another suit in a different mass/mobility regime to validate the approach.

Engine-driven preparation of curved root canals: measuring cyclic fatigue and other physical parameters.

PubMed

Peters, Ove A; Kappeler, Stefan; Bucher, Willi; Barbakow, Fred

2002-04-01

An increasing number of engine-driven rotary systems are marketed to shape root canals. Although these systems may improve the quality of canal preparations, the risk for instrument fracture is also increased. Unfortunately, the stresses generated in rotary instruments when shaping curved root canals have not been adequately studied. Consequently, the aim of an ongoing project was to develop a measurement platform that could more accurately detail physical parameters generated in a simulated clinical situation. Such a platform was constructed by fitting a torque-measuring device between the rotating endodontic instrument and the motor driving it. Apically directed force and instrument insertion depth were also recorded. Additional devices were constructed to assess cyclic fatigue and static fracture loads. The current pilot study evaluated GT rotary instruments during the shaping of curved canals in plastic blocks as well as "ISO 3630-1 torque to fracture" and number of rotations required for fatigue fracture. Results indicated that torques in excess of 40 Nmm were generated by rotary GT-Files, a significantly higher figure than static fracture loads (less than 13 Nmm for the size 20. 12 GT-File). Furthermore, the number of rotations needed to shape simulated canals with a 5 mm radius of curvature in plastic blocks was 10 times lower than the number of rotations needed to fracture instruments in a "cyclic fatigue test". Apical forces were always greater than 1 N, and in some specimens, scores of 8 N or more were recorded. Further studies are required using extracted natural teeth, with their wide anatomical variation, in order to reduce the incidence of fracture of rotary instruments. In this way, the clinical potential of engine-driven rotary instruments to safely prepare curved canals can be fully appreciated.

Roughness and wettability effect on histological and mechanical response of self-drilling orthodontic mini-implants.

PubMed

Espinar-Escalona, Eduardo; Bravo-Gonzalez, Luis-Alberto; Pegueroles, Marta; Gil, Francisco Javier

2016-06-01

Self-drilling orthodontic mini-implants can be used as temporary devices for orthodontic treatments. Our main goal was to evaluate surface characteristics, roughness and wettability, of surface modified mini-implants to increase their stability during orthodontic treatment without inducing bone fracture and tissue destruction during unscrewing. Modified mini-implants by acid etching, grit-blasting and its combination were implanted in 20 New Zealand rabbits during 10 weeks. After that, the bone-to-implant (BIC) parameter was determined and the torque during unscrewing was measured. The surface characteristics, roughness and wettability, were also measured, onto modified Ti c.p. discs. Acid-etched mini-implants (R a ≈ 1.7 μm, contact angle (CA) ≈ 66°) significantly improved the bone-to-implant parameter, 26 %, compared to as-machined mini-implants (R a ≈ 0.3 μm, CA ≈ 68°, BIC = 19 %) due to its roughness. Moreover, this surface treatment did not modify torque during unscrewing due to their statistically similar wettability (p > 0.05). Surface treatments with higher roughness and hydrophobicity (R a ≈ 4.5 μm, CA ≈ 74°) lead to a greater BIC and to a higher removal torque during unscrewing, causing bone fracture, compared to as-machined mini-implants. Based on these in vivo findings, we conclude that acid-etching surface treatment can support temporary anchoring of titanium mini-implants. This treatment represents a step forward in the direction of reducing the time prior to mini-implant loading by increasing their stability during orthodontic treatment, without inducing bone fracture and tissue destruction during unscrewing.

Promoting balance and strength in the middle-aged workforce.

PubMed

Granacher, U; Wick, C; Rueck, N; Esposito, C; Roth, R; Zahner, L

2011-01-01

The prevalence of sustaining fall-related injuries is high in the middle-aged workforce. Deficits in postural control/muscle strength represent important fall-risk factors. The objective of this study was to examine the impact of balance and strength training followed by detraining on postural control and muscle strength in the workforce. Thirty-two adults with sedentary office work participated in this study and were assigned to an intervention (age 56.0 ± 3.7 yrs) or a control group (age 55.5 ± 3.4 yrs). The intervention group participated in 8 weeks of balance and strength training conducted at the worksite, followed by 8 weeks of detraining. Tests included the measurement of (a) total centre of pressure (COP) displacements during one-legged standing, (b) gait velocity and stride-to-stride variability, (c) peak isometric/isokinetic torque and rate of torque development (RTD) of the plantar flexors, and (d) jumping height. After training, significant improvements in COP displacements, gait velocity, peak isometric/isokinetic torque, RTD, and jumping height were observed. During detraining, muscle strength deteriorated, whereas postural control improved. This fall-preventive training program conducted at the worksite proved to be feasible and effective. It is suggested that this training program should be permanently conducted to maintain/improve muscle strength. © Georg Thieme Verlag KG Stuttgart · New York.

Human movement onset detection from isometric force and torque measurements: a supervised pattern recognition approach.

PubMed

Soda, Paolo; Mazzoleni, Stefano; Cavallo, Giuseppe; Guglielmelli, Eugenio; Iannello, Giulio

2010-09-01

Recent research has successfully introduced the application of robotics and mechatronics to functional assessment and motor therapy. Measurements of movement initiation in isometric conditions are widely used in clinical rehabilitation and their importance in functional assessment has been demonstrated for specific parts of the human body. The determination of the voluntary movement initiation time, also referred to as onset time, represents a challenging issue since the time window characterizing the movement onset is of particular relevance for the understanding of recovery mechanisms after a neurological damage. Establishing it manually as well as a troublesome task may also introduce oversight errors and loss of information. The most commonly used methods for automatic onset time detection compare the raw signal, or some extracted measures such as its derivatives (i.e., velocity and acceleration) with a chosen threshold. However, they suffer from high variability and systematic errors because of the weakness of the signal, the abnormality of response profiles as well as the variability of movement initiation times among patients. In this paper, we introduce a technique to optimise onset detection according to each input signal. It is based on a classification system that enables us to establish which deterministic method provides the most accurate onset time on the basis of information directly derived from the raw signal. The approach was tested on annotated force and torque datasets. Each dataset is constituted by 768 signals acquired from eight anatomical districts in 96 patients who carried out six tasks related to common daily activities. The results show that the proposed technique improves not only on the performance achieved by each of the deterministic methods, but also on that attained by a group of clinical experts. The paper describes a classification system detecting the voluntary movement initiation time and adaptable to different signals. By using a set of features directly derived from raw data, we obtained promising results. Furthermore, although the technique has been developed within the scope of isometric force and torque signal analysis, it can be applied to other detection problems where several simple detectors are available. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Skill transfer from symmetric and asymmetric bimanual training using a robotic system to single limb performance

PubMed Central

2012-01-01

Background Humans are capable of fast adaptation to new unknown dynamics that affect their movements. Such motor learning is also believed to be an important part of motor rehabilitation. Bimanual training can improve post-stroke rehabilitation outcome and is associated with interlimb coordination between both limbs. Some studies indicate partial transfer of skills among limbs of healthy individuals. Another aspect of bimanual training is the (a)symmetry of bimanual movements and how these affect motor learning and possibly post-stroke rehabilitation. Methods A novel bimanual 2-DOF robotic system was used for both bimanual and unimanual reaching movements. 35 young healthy adults participated in the study. They were divided into 5 test groups that performed movements under different conditions (bimanual or unimanual movements and symmetric or asymmetric bimanual arm loads). The subjects performed a simple tracking exercise with the bimanual system. The exercise was developed to stimulate motor learning by applying a velocity-dependent disturbance torque to the handlebar. Each subject performed 255 trials divided into three phases: baseline without disturbance torque, training phase with disturbance torque and evaluation phase with disturbance torque. Results Performance was assessed with the maximal values of rotation errors of the handlebar. After exposure to disturbance torque, the errors decreased for both unimanual and bimanual training. Errors in unimanual evaluation following the bimanual training phase were not significantly different from errors in unimanual evaluation following unimanual training. There was no difference in performance following symmetric or asymmetric training. Changing the arm force symmetry during bimanual movements from asymmetric to symmetric had little influence on performance. Conclusions Subjects could adapt to an unknown disturbance torque that was changing the dynamics of the movements. The learning effect was present during both unimanual and bimanual training. Transfer of learned skills from bimanual training to unimanual movements was also observed, as bimanual training also improved single limb performance with the dominant arm. Changes of force symmetry did not have an effect on motor learning. As motor learning is believed to be an important mechanism of rehabilitation, our findings could be tested for future post-stroke rehabilitation systems. PMID:22805223

Closed kinetic chain exercises with or without additional hip strengthening exercises in management of patellofemoral pain syndrome: a randomized controlled trial.

PubMed

Ismail, M M; Gamaleldein, M H; Hassa, K A

2013-10-01

Patellofemoral pain syndrome (PFPS) is a common musculoskeletal pain condition, especially in females. Decreased hip muscle strength has been implicated as a contributing factor. Isolated open kinetic chain hip abductors and lateral rotators exercises were added by many authors to the rehabilitation program. However, Closed Kinetic Chain (CKC) exercises focusing on hip and knee muscles were not investigated if they can produce similar effect of hip strengthening and decreasing pain without the need of isolated exercises for hip musculature. The aim of the present study was to determine the effect of a CKC exercises program with or without additional hip strengthening exercises on pain and hip abductors and lateral rotators peak torque. Prospective randomized clinical trial. Patients with patellofemoral pain syndrome referred to the outpatient physical therapy clinic of the faculty of physical therapy, cairo university. Thirty two patients who had patellofemoral pain syndrome with age ranged from eighteen to thirty years. Patients were randomly assigned into two groups: CKC group and CKC with hip muscles strengthening exercises as a control (CO) group. Treatment was given 3 times/week, for 6 weeks. Patients were evaluated pre- and post-treatment for their pain severity using VAS, function of knee joint using Kujala questionnaire, hip abductors and external rotators concentric/eccentric peak torque. There were significant improvements in pain, function and hip muscles peak torque in both groups (P<0.05). However, there was no statistically significant difference between groups in hip muscles torque (P<0.05) but pain and function improvements were significantly greater in the CO group (P<0.05). Six weeks CKC program focusing on knee and hip strengthening has similar effect in improving hip muscles torque in patients with PFPS as a CKC exercises with additional hip strengthening exercises. However, adding isolated hip strengthening exercises has the advantage of more pain relief. CKC exercises with additional hip strengthening could be more beneficial in decreasing pain in PFPS than CKC exercises alone.

Advanced emergency braking under split friction conditions and the influence of a destabilising steering wheel torque

NASA Astrophysics Data System (ADS)

Tagesson, Kristoffer; Cole, David

2017-07-01

The steering system in most heavy trucks is such that it causes a destabilising steering wheel torque when braking on split friction, that is, different friction levels on the two sides of the vehicle. Moreover, advanced emergency braking systems are now mandatory in most heavy trucks, making vehicle-induced split friction braking possible. This imposes higher demands on understanding how the destabilising steering wheel torque affects the driver, which is the focus here. Firstly, an experiment has been carried out involving 24 subjects all driving a truck where automatic split friction braking was emulated. Secondly, an existing driver-vehicle model has been adapted and implemented to improve understanding of the observed outcome. A common conclusion drawn, after analysing results, is that the destabilising steering wheel torque only has a small effect on the motion of the vehicle. The underlying reason is a relatively slow ramp up of the disturbance in comparison to the observed cognitive delay amongst subjects; also the magnitude is low and initially suppressed by passive driver properties.

Validation of a Biofeedback System for Wheelchair Propulsion Training

PubMed Central

Guo, Liyun; Kwarciak, Andrew M.; Rodriguez, Russell; Sarkar, Nilanjan; Richter, W. Mark

2011-01-01

This paper describes the design and validation of the OptiPush Biofeedback System, a commercially available, instrumented wheel system that records handrim biomechanics and provides stroke-by-stroke biofeedback and targeting for 11 propulsion variables. Testing of the system revealed accurate measurement of wheel angle (0.02% error), wheel speed (0.06% error), and handrim loads. The maximum errors in static force and torque measurements were 3.80% and 2.05%, respectively. Measured forces were also found to be highly linear (0.985 < slope < 1.011) and highly correlated to the reference forces (r 2 > .998). Dynamic measurements of planar forces (F x and F y) and axle torque also had low error (−0.96 N to 0.83 N for force and 0.10 Nm to 0.14 Nm for torque) and were highly correlated (r > .986) with expected force and torque values. Overall, the OptiPush Biofeedback System provides accurate measurement of wheel dynamics and handrim biomechanics and may be a useful tool for improving manual wheelchair propulsion. PMID:22110977

Development of a precise controller for an electrohydraulic total artificial heart. Improvement of the motor's dynamic response.

PubMed

Ahn, J M; Masuzawa, T; Taenaka, Y; Tatsumi, E; Ohno, T; Choi, W W; Toda, K; Miyazaki, K; Baba, Y; Nakatani, T; Takano, H; Min, B G

1996-01-01

In an electrohydraulic total artificial heart developed at the National Cardiovascular Center (Osaka, Japan), two blood pumps are pushed alternatively by means of the bidirectional motion of a brushless DC motor for pump systole and diastole. Improvement in the dynamic response of the motor is very important to obtain better pump performance; this was accomplished by using power electronic simulation. For the motor to have the desired dynamic response, it must be commutated properly and the damping ratio (zeta), which represents transient characteristics of the motor, must lie between 0.4 and 0.8. Consequently, all satisfactory specifications with respect to power consumption must be obtained. Based on the simulated results, the design criteria were determined and the precise controller designed to reduce torque ripple and motor vibration, and determine motor stop time at every direction change. In in vitro tests, evaluation of the controller and dynamic response of the motor was justified in terms of zeta, power consumption, and motor stop time. The results indicated that the power consumption of the controller and the input power of the motor were decreased by 1.2 and 2.5 W at zeta = 0.6, respectively, compared to the previous system. An acceptable dynamic response of the motor, necessary for the reduction of torque ripple and motor vibration, was obtained between zeta = 0.5 and zeta = 0.7, with an increase in system efficiency from 10% to 12%. The motor stop time required for stable motor reoperation was determined to be over 10 msec, for a savings in power consumption of approximately 1.5 W. Therefore, the improved dynamic response of the motor can contribute to the stability and reliability of the pump.

A systems-based investigation into vitamin D and skeletal muscle repair, regeneration, and hypertrophy.

PubMed

Owens, Daniel J; Sharples, Adam P; Polydorou, Ioanna; Alwan, Nura; Donovan, Timothy; Tang, Jonathan; Fraser, William D; Cooper, Robert G; Morton, James P; Stewart, Claire; Close, Graeme L

2015-12-15

Skeletal muscle is a direct target for vitamin D. Observational studies suggest that low 25[OH]D correlates with functional recovery of skeletal muscle following eccentric contractions in humans and crush injury in rats. However, a definitive association is yet to be established. To address this gap in knowledge in relation to damage repair, a randomised, placebo-controlled trial was performed in 20 males with insufficient concentrations of serum 25(OH)D (45 ± 25 nmol/l). Prior to and following 6 wk of supplemental vitamin D3 (4,000 IU/day) or placebo (50 mg of cellulose), participants performed 20 × 10 damaging eccentric contractions of the knee extensors, with peak torque measured over the following 7 days of recovery. Parallel experimentation using isolated human skeletal muscle-derived myoblast cells from biopsies of 14 males with low serum 25(OH)D (37 ± 11 nmol/l) were subjected to mechanical wound injury, which enabled corresponding in vitro studies of muscle repair, regeneration, and hypertrophy in the presence and absence of 10 or 100 nmol 1α,25(OH)2D3. Supplemental vitamin D3 increased serum 25(OH)D and improved recovery of peak torque at 48 h and 7 days postexercise. In vitro, 10 nmol 1α,25(OH)2D3 improved muscle cell migration dynamics and resulted in improved myotube fusion/differentiation at the biochemical, morphological, and molecular level together with increased myotube hypertrophy at 7 and 10 days postdamage. Together, these preliminary data are the first to characterize a role for vitamin D in human skeletal muscle regeneration and suggest that maintaining serum 25(OH)D may be beneficial for enhancing reparative processes and potentially for facilitating subsequent hypertrophy. Copyright © 2015 the American Physiological Society.

An experimental investigation on fluid dynamics of an automotive torque converter

NASA Astrophysics Data System (ADS)

Dong, Yu

The objective of the automotive torque converter fluid dynamics experimental investigation is to understand the flow field inside the torque converter, improve the performance, and increase the fuel economy of vehicles. A high-frequency response five-hole probe was developed for the unsteady flow measurement. The dynamic performance of this probe was examined, and the corresponding data processing technique was also developed. The accuracy of this probe unsteady flow measurement was assessed using a hot-film sensor and a high-frequency response total pressure Pitot probe. The pump passage relative flow field was measured by a rotating five-hole probe system at three chord-wise locations. The rotating probe system is designed and developed for both pump and turbine flow measurement, and it was proved to be accurate and successful. A strong secondary flow is observed to dominate the flow structure at the pump mid-chord. At the pump 3/4 chord, the flow concentration on the pressure side is clearly observed. The secondary flow is found to change direction of rotation between the 3/4 chord and the 4/4 chord. High losses are found in the core-suction corner "wake" flow. The pump exit and turbine exit unsteady flow fields were measured by a high-frequency response five-hole probe in the stationary frame. At the pump exit, the flow is concentrated on the pressure side due to the strong secondary flow in the pump passage. A strong secondary flow is observed. At the turbine exit, a fully developed flow is found caused by the turbulent mixing. The stator exit steady flow was measured by a conventional five-hole probe. A strong secondary flow is found due to the inlet vorticity and axial velocity deficit near the core. The radially inward velocity and the secondary flow produce a large radial transport of mass flow in the stator passage. The stator passage flow is found to be turbulent at the normal operating condition by the measurement using the surface hot-film sensors mounted on the stator blade surface. Based on the experimental data and analysis, recommendations are proposed for the hydraulic design and the fluid dynamics research of the torque converter.