Single neural adaptive controller and neural network identifier based on PSO algorithm for spherical actuators with 3D magnet array

NASA Astrophysics Data System (ADS)

Yan, Liang; Zhang, Lu; Zhu, Bo; Zhang, Jingying; Jiao, Zongxia

2017-10-01

Permanent magnet spherical actuator (PMSA) is a multi-variable featured and inter-axis coupled nonlinear system, which unavoidably compromises its motion control implementation. Uncertainties such as external load and friction torque of ball bearing and manufacturing errors also influence motion performance significantly. Therefore, the objective of this paper is to propose a controller based on a single neural adaptive (SNA) algorithm and a neural network (NN) identifier optimized with a particle swarm optimization (PSO) algorithm to improve the motion stability of PMSA with three-dimensional magnet arrays. The dynamic model and computed torque model are formulated for the spherical actuator, and a dynamic decoupling control algorithm is developed. By utilizing the global-optimization property of the PSO algorithm, the NN identifier is trained to avoid locally optimal solution and achieve high-precision compensations to uncertainties. The employment of the SNA controller helps to reduce the effect of compensation errors and convert the system to a stable one, even if there is difference between the compensations and uncertainties due to external disturbances. A simulation model is established, and experiments are conducted on the research prototype to validate the proposed control algorithm. The amplitude of the parameter perturbation is set to 5%, 10%, and 15%, respectively. The strong robustness of the proposed hybrid algorithm is validated by the abundant simulation data. It shows that the proposed algorithm can effectively compensate the influence of uncertainties and eliminate the effect of inter-axis couplings of the spherical actuator.

Multi-parameter actuation of a neutrally stable shell: a flexible gear-less motor.

PubMed

Hamouche, W; Maurini, C; Vidoli, S; Vincenti, A

2017-08-01

We have designed and tested experimentally a morphing structure consisting of a neutrally stable thin cylindrical shell driven by a multi-parameter piezoelectric actuation. The shell is obtained by plastically deforming an initially flat copper disc, so as to induce large isotropic and almost uniform inelastic curvatures. Following the plastic deformation, in a perfectly isotropic system, the shell is theoretically neutrally stable, having a continuous set of stable cylindrical shapes corresponding to the rotation of the axis of maximal curvature. Small imperfections render the actual structure bistable, giving preferred orientations. A three-parameter piezoelectric actuation, exerted through micro-fibre-composite actuators, allows us to add a small perturbation to the plastic inelastic curvature and to control the direction of maximal curvature. This actuation law is designed through a geometrical analogy based on a fully nonlinear inextensible uniform-curvature shell model. We report on the fabrication, identification and experimental testing of a prototype and demonstrate the effectiveness of the piezoelectric actuators in controlling its shape. The resulting motion is an apparent rotation of the shell, controlled by the voltages as in a 'gear-less motor', which is, in reality, a precession of the axis of principal curvature.

Multi-parameter actuation of a neutrally stable shell: a flexible gear-less motor

NASA Astrophysics Data System (ADS)

Hamouche, W.; Maurini, C.; Vidoli, S.; Vincenti, A.

2017-08-01

We have designed and tested experimentally a morphing structure consisting of a neutrally stable thin cylindrical shell driven by a multi-parameter piezoelectric actuation. The shell is obtained by plastically deforming an initially flat copper disc, so as to induce large isotropic and almost uniform inelastic curvatures. Following the plastic deformation, in a perfectly isotropic system, the shell is theoretically neutrally stable, having a continuous set of stable cylindrical shapes corresponding to the rotation of the axis of maximal curvature. Small imperfections render the actual structure bistable, giving preferred orientations. A three-parameter piezoelectric actuation, exerted through micro-fibre-composite actuators, allows us to add a small perturbation to the plastic inelastic curvature and to control the direction of maximal curvature. This actuation law is designed through a geometrical analogy based on a fully nonlinear inextensible uniform-curvature shell model. We report on the fabrication, identification and experimental testing of a prototype and demonstrate the effectiveness of the piezoelectric actuators in controlling its shape. The resulting motion is an apparent rotation of the shell, controlled by the voltages as in a `gear-less motor', which is, in reality, a precession of the axis of principal curvature.

Effect of the number and position of nozzle holes on in- and near-nozzle dynamic characteristics of diesel injection

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

Moon, Seoksu; Gao, Yuan; Park, Suhan

Despite the fact that all modern diesel engines use multi-hole injectors, single-hole injectors are frequently used to understand the fundamental properties of high-pressure diesel injections due to their axisymmetric design of the injector nozzles. A multi-hole injector accommodates many holes around the nozzle axis to deliver adequate amount of fuel with small orifices. The off-axis arrangement of the multi-hole injectors significantly alters the inter- and near-nozzle flow patterns compared to those of the single-hole injectors. This study compares the transient needle motion and near-nozzle flow characteristics of the single- and multi-hole (3-hole and 6-hole) diesel injectors to understand how themore » difference in hole arrangement and number affects the initial flow development of the diesel injectors. A propagation-based X-ray phase-contrast imaging technique was applied to compare the transient needle motion and near-nozzle flow characteristics of the single- and multi-hole injectors. The comparisons were made by dividing the entire injection process by three sub-stages: opening-transient, quasi-steady and closing-transient. (C) 2015 Elsevier Ltd. All rights reserved.« less

Three axis electronic flight motion simulator real time control system design and implementation

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

Gao, Zhiyuan; Miao, Zhonghua, E-mail: zhonghua-miao@163.com; Wang, Xiaohua

2014-12-15

A three axis electronic flight motion simulator is reported in this paper including the modelling, the controller design as well as the hardware implementation. This flight motion simulator could be used for inertial navigation test and high precision inertial navigation system with good dynamic and static performances. A real time control system is designed, several control system implementation problems were solved including time unification with parallel port interrupt, high speed finding-zero method of rotary inductosyn, zero-crossing management with continuous rotary, etc. Tests were carried out to show the effectiveness of the proposed real time control system.

Three axis electronic flight motion simulator real time control system design and implementation.

PubMed

Gao, Zhiyuan; Miao, Zhonghua; Wang, Xuyong; Wang, Xiaohua

2014-12-01

A three axis electronic flight motion simulator is reported in this paper including the modelling, the controller design as well as the hardware implementation. This flight motion simulator could be used for inertial navigation test and high precision inertial navigation system with good dynamic and static performances. A real time control system is designed, several control system implementation problems were solved including time unification with parallel port interrupt, high speed finding-zero method of rotary inductosyn, zero-crossing management with continuous rotary, etc. Tests were carried out to show the effectiveness of the proposed real time control system.

Fast Auroral Snapshot performance using a multi-body dynamic simulation

NASA Technical Reports Server (NTRS)

Zimbelman, Darrell; Walker, Mary

1993-01-01

This paper examines the complex dynamic interaction between two 2.6 m long stacer booms, four 30 m long flexible wire booms and the attitude control system of the Fast Auroral SnapshoT (FAST) spacecraft. The FAST vehicle will nominally operate as a negative orbit spinner, positioned in a 83 deg inclination, 350 x 4200 km orbit. For this study, a three-axis, non-linear, seven body dynamic simulation is developed using the TREETOPS software package. The significance of this approach is the ability to model each component of the FAST spacecraft as an individual member and connect them together in order to better understand the dynamic coupling between structures and the control system. Both the wire and stacer booms are modeled as separate bodies attached to a rigid central body. The wire booms are oriented perpendicular to the spin axis at right angles relative to each other, whereas the stacer booms are aligned with the spin axis. The analysis consists of a comparison between the simulated in-plane and out-of-plane boom motions with theoretically derived frequencies, and an examination of the dynamic coupling between the control system and boom oscillations. Results show that boom oscillations of up to 0.36 deg are acceptable in order to meet the performance requirements. The dynamic motion is well behaved when the precession coil is operating, however, activation of the spin coil produces an erratic trend in the spin rate which approaches the spin rate requirement.

The 3-axis Dynamic Motion Simulator (DMS) system

NASA Technical Reports Server (NTRS)

1975-01-01

A three-axis dynamic motion simulator (DMS) consisting of a test table with three degrees of freedom and an electronics control system was designed, constructed, delivered, and tested. Documentation, as required in the Data Requirements List (DRL), was also provided.

Variations in the axis of motion during head repositioning--a comparison of subjects with whiplash-associated disorders or non-specific neck pain and healthy controls.

PubMed

Grip, Helena; Sundelin, Gunnevi; Gerdle, Björn; Karlsson, J Stefan

2007-10-01

The ability to reproduce head position can be affected in patients after a neck injury. The repositioning error is commonly used as a measure of proprioception, but variations in the movement might provide additional information. The axis of motion and target performance were analyzed during a head repositioning task (flexion, extension and side rotations) for 24 control subjects, 22 subjects with whiplash-associated disorders and 21 with non-specific neck pain. Questionnaires regarding pain intensity and fear avoidance were collected. Head position and axis of motion parameters were calculated using a helical axis model with a moving window of 4 degrees . During flexion the whiplash group had a larger constant repositioning error than the control group (-1.8(2.9) degrees vs. 0.1(2.4) degrees , P=0.04). The axis was more inferior in both neck pain groups (12.0(1.6)cm vs. 14.5(2.0)cm, P<0.05) indicating movement at a lower level in the spine. Including pain intensity from shoulder and neck region as covariates showed an effect on the axis position (P=0.03 and 0.04). During axial rotation to the left there was more variation in axis direction for neckpain groups as compared with controls (4.0(1.7) degrees and 3.7(2.4) degrees vs. 2.3(1.9) degrees , P=0.01 and 0.05). No significant difference in fear avoidance was found between the two neck pain groups. Measuring variation in the axis of motion together with target performance gives objective measures on proprioceptive ability that are difficult to quantify by visual inspection. Repositioning errors were in general small, suggesting it is not sufficient as a single measurement variable in a clinical situation, but should be measured in combination with other tests, such as range of motion.

Off-axis current drive and real-time control of current profile in JT-60U

NASA Astrophysics Data System (ADS)

Suzuki, T.; Ide, S.; Oikawa, T.; Fujita, T.; Ishikawa, M.; Seki, M.; Matsunaga, G.; Hatae, T.; Naito, O.; Hamamatsu, K.; Sueoka, M.; Hosoyama, H.; Nakazato, M.; JT-60 Team

2008-04-01

Aiming at optimization of current profile in high-β plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor (qmin) using the off-axis current drive has been developed. The off-axis current drive can raise the safety factor in the centre and help to avoid instability that limits the performance of the plasma. The system controls the injection power of lower-hybrid waves, and hence its off-axis driven current in order to control qmin. The real-time control of qmin is demonstrated in a high-β plasma, where qmin follows the temporally changing reference qmin,ref from 1.3 to 1.7. Applying the control to another high-β discharge (βN = 1.7, βp = 1.5) with m/n = 2/1 neo-classical tearing mode (NTM), qmin was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using the motional Stark effect diagnostic. Spatially localized NBCD profile was clearly observed at the normalized minor radius ρ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward shifted than the measurement.

John Glenn Prepares for a Test in the Multi-Axis Space Test Inertia Facility

NASA Image and Video Library

1960-02-21

Mercury astronaut John Glenn prepares for a test in the Multi-Axis Space Test Inertia Facility (MASTIF) inside the Altitude Wind Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. The MASTIF was a three-axis test rig with a pilot’s chair mounted in the center. The device was designed to train Project Mercury pilots to bring a spinning spacecraft under control. An astronaut was secured in a foam couch in the center of the rig. The rig was then spun on three axes from 2 to 50 rotations per minute. Small nitrogen gas thrusters were used by the astronauts to bring the MASTIF under control. In February and March 1960, the seven Project Mercury astronauts traveled to Cleveland to train on the MASTIF. Warren North and a team of air force physicians were on hand to monitor their health. After being briefed by Lewis pilot Joe Algranti and researcher James Useller, the rider would climb into the rig and be secured in the chair, as seen in this photograph. A Lewis engineer would then slowly set the MASTIF in motion. It was the astronaut’s job to bring it under control. Each individual was required to accumulate 4.5 to 5 hours of MASTIF time. Glenn became the first American to orbit the earth on February 20, 1962 in the Friendship 7 Mercury capsule. In March 1999, the Lewis Research Center was renamed the John H. Glenn Research Center at Lewis Field.

Multi-photon vertical cross-sectional imaging with a dynamically-balanced thin-film PZT z-axis microactuator.

PubMed

Choi, Jongsoo; Duan, Xiyu; Li, Haijun; Wang, Thomas D; Oldham, Kenn R

2017-10-01

Use of a thin-film piezoelectric microactuator for axial scanning during multi-photon vertical cross-sectional imaging is described. The actuator uses thin-film lead-zirconate-titanate (PZT) to generate upward displacement of a central mirror platform, micro-machined from a silicon-on-insulator (SOI) wafer to dimensions compatible with endoscopic imaging instruments. Device modeling in this paper focuses on existence of frequencies near device resonance producing vertical motion with minimal off-axis tilt even in the presence of multiple vibration modes and non-uniformity in fabrication outcomes. Operation near rear resonance permits large stroke lengths at low voltages relative to other vertical microactuators. Highly uniform vertical motion of the mirror platform is a key requirement for vertical cross-sectional imaging in the remote scan architecture being used for multi-photon instrument prototyping. The stage is installed in a benchtop testbed in combination with an electrostatic mirror that performs in-plane scanning. Vertical sectional images are acquired from 15 μm diameter beads and excised mouse colon tissue.

Synchronized motion control and precision positioning compensation of a 3-DOFs macro-micro parallel manipulator fully actuated by piezoelectric actuators

NASA Astrophysics Data System (ADS)

Zhang, Quan; Li, Chaodong; Zhang, Jiantao; Zhang, Xu

2017-11-01

The macro-micro combined approach, as an effective way to realize trans-scale nano-precision positioning with multi-dimensions and high velocity, plays a significant role in integrated circuit manufacturing field. A 3-degree-of-freedoms (3-DOFs) macro-micro manipulator is designed and analyzed to compromise the conflictions among the large stroke, high precision and multi-DOFs. The macro manipulator is a 3-Prismatic-Revolute-Revolute (3-PRR) structure parallel manipulator which is driven by three linear ultrasonic motors. The dynamic model and the cross-coupling error based synchronized motion controller of the 3-PRR parallel manipulator are theoretical analyzed and experimental tested. To further improve the positioning accuracy, a 3-DOFs monolithic compliant manipulator actuated by three piezoelectric stack actuators is designed. Then a multilayer BP neural network based inverse kinematic model identifier is developed to perform the positioning control. Finally, by forming the macro-micro structure, the dual stage manipulator successfully achieved the positioning task from the point (2 mm, 2 mm, 0 rad) back to the original point (0 mm, 0 mm, 0 rad) with the translation errors in X and Y directions less than ±50 nm and the rotation error around Z axis less than ±1 μrad, respectively.

The Structure, Design, and Closed-Loop Motion Control of a Differential Drive Soft Robot.

PubMed

Wu, Pang; Jiangbei, Wang; Yanqiong, Fei

2018-02-01

This article presents the structure, design, and motion control of an inchworm inspired pneumatic soft robot, which can perform differential movement. This robot mainly consists of two columns of pneumatic multi-airbags (actuators), one sensor, one baseboard, front feet, and rear feet. According to the different inflation time of left and right actuators, the robot can perform both linear and turning movements. The actuators of this robot are composed of multiple airbags, and the design of the airbags is analyzed. To deal with the nonlinear performance of the soft robot, we use radial basis function neural networks to train the turning ability of this robot on three different surfaces and create a mathematical model among coefficient of friction, deflection angle, and inflation time. Then, we establish the closed-loop automatic control model using three-axis electronic compass sensor. Finally, the automatic control model is verified by linear and turning movement experiments. According to the experiment, the robot can finish the linear and turning movements under the closed-loop control system.

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

Three-dimensional control of Tetrahymena pyriformis using artificial magnetotaxis

NASA Astrophysics Data System (ADS)

Hyung Kim, Dal; Seung Soo Kim, Paul; Agung Julius, Anak; Jun Kim, Min

2012-01-01

We demonstrate three-dimensional control with the eukaryotic cell Tetrahymena pyriformis (T. pyriformis) using two sets of Helmholtz coils for xy-plane motion and a single electromagnet for z-direction motion. T. pyriformis is modified to have artificial magnetotaxis with internalized magnetite. To track the cell's z-axis position, intensity profiles of non-motile cells at varying distances from the focal plane are used. During vertical motion along the z-axis, the intensity difference is used to determine the position of the cell. The three-dimensional control of the live microorganism T. pyriformis as a cellular robot shows great potential for practical applications in microscale tasks, such as target transport and cell therapy.

Optimal sagittal motion axis for trunk extension and flexion tests in chronic low back trouble.

PubMed

Rantanen, P; Nykvist, F

2000-11-01

To find the optimal height for sagittal motion axis for trunk strength test in chronic low back trouble. Cross-sectional study. The strength of trunk muscles of low back pain patients is decreased. The measured strength depends on the height of the sagittal motion axis but the differences between patients and controls are not known. 114 (67 female) patients with chronic low back trouble are classified according to Quebec Task Force, 50 (31 female) patients with rheumatic disorder, but without low back trouble, and 33 (22 female) healthy controls, no appreciable physical differences but clear differences in Oswestry score. Isometric trunk extension-flexion test with different heights for the pelvic fulcrum. Force decreased in extension, increased in flexion, and torque increased both in flexion and extension in every group (P<0.001) as the fulcrum was moved caudally. The male controls were stronger than patients with low back trouble (P<0.01). The female controls were stronger only if the fulcrum was set at the hip joint level (P<0.05). There were no differences between patients with rheumatic disorder and low back trouble, except in extension if the fulcrum was at the hip joint level (P<0.02). The rotation axis in trunk extension-flexion strength test should be set at the level of the hip joint. Trunk muscle weakness is a common sign of different rheumatic disorders. Proper setting of sagittal motion axis and concomitant measurement of trunk and hip extensor or flexor muscles increases the specificity of the strength test for low back trouble.

Reduced hypothalamic-pituitary-adrenal axis activity in chronic multi-site musculoskeletal pain: partly masked by depressive and anxiety disorders.

PubMed

Generaal, Ellen; Vogelzangs, Nicole; Macfarlane, Gary J; Geenen, Rinie; Smit, Johannes H; Penninx, Brenda W J H; Dekker, Joost

2014-07-09

Studies on hypothalamic-pituitary-adrenal axis (HPA-axis) function amongst patients with chronic pain show equivocal results and well-controlled cohort studies are rare in this field. The goal of our study was to examine whether HPA-axis dysfunction is associated with the presence and the severity of chronic multi-site musculoskeletal pain. Data are from the Netherlands Study of Depression and Anxiety including 1125 subjects with and without lifetime depressive and anxiety disorders. The Chronic Pain Grade questionnaire was used to determine the presence and severity of chronic multi-site musculoskeletal pain. Subjects were categorized into a chronic multi-site musculoskeletal pain group (n = 471) and a control group (n = 654). Salivary cortisol samples were collected to assess HPA-axis function (awakening level, 1-h awakening response, evening level, diurnal slope and post-dexamethasone level). In comparison with the control group, subjects with chronic multi-site musculoskeletal pain showed significantly lower cortisol level at awakening, lower evening level and a blunted diurnal slope. Lower cortisol level at awakening and a blunted diurnal slope appeared to be restricted to those without depressive and/or anxiety disorders, who also showed a lower 1-h awakening response. Our results suggest hypocortisolemia in chronic multi-site musculoskeletal pain. However, if chronic pain is accompanied by a depressive or anxiety disorder, typically related to hypercortisolemia, the association between cortisol levels and chronic multi-site musculoskeletal pain appears to be partly masked. Future studies should take psychopathology into account when examining HPA-axis function in chronic pain.

Reduced hypothalamic-pituitary-adrenal axis activity in chronic multi-site musculoskeletal pain: partly masked by depressive and anxiety disorders

PubMed Central

2014-01-01

Background Studies on hypothalamic-pituitary-adrenal axis (HPA-axis) function amongst patients with chronic pain show equivocal results and well-controlled cohort studies are rare in this field. The goal of our study was to examine whether HPA-axis dysfunction is associated with the presence and the severity of chronic multi-site musculoskeletal pain. Methods Data are from the Netherlands Study of Depression and Anxiety including 1125 subjects with and without lifetime depressive and anxiety disorders. The Chronic Pain Grade questionnaire was used to determine the presence and severity of chronic multi-site musculoskeletal pain. Subjects were categorized into a chronic multi-site musculoskeletal pain group (n = 471) and a control group (n = 654). Salivary cortisol samples were collected to assess HPA-axis function (awakening level, 1-h awakening response, evening level, diurnal slope and post-dexamethasone level). Results In comparison with the control group, subjects with chronic multi-site musculoskeletal pain showed significantly lower cortisol level at awakening, lower evening level and a blunted diurnal slope. Lower cortisol level at awakening and a blunted diurnal slope appeared to be restricted to those without depressive and/or anxiety disorders, who also showed a lower 1-h awakening response. Conclusions Our results suggest hypocortisolemia in chronic multi-site musculoskeletal pain. However, if chronic pain is accompanied by a depressive or anxiety disorder, typically related to hypercortisolemia, the association between cortisol levels and chronic multi-site musculoskeletal pain appears to be partly masked. Future studies should take psychopathology into account when examining HPA-axis function in chronic pain. PMID:25007969

Design of optical axis jitter control system for multi beam lasers based on FPGA

NASA Astrophysics Data System (ADS)

Ou, Long; Li, Guohui; Xie, Chuanlin; Zhou, Zhiqiang

2018-02-01

A design of optical axis closed-loop control system for multi beam lasers coherent combining based on FPGA was introduced. The system uses piezoelectric ceramics Fast Steering Mirrors (FSM) as actuator, the Fairfield spot detection of multi beam lasers by the high speed CMOS camera for optical detecting, a control system based on FPGA for real-time optical axis jitter suppression. The algorithm for optical axis centroid detecting and PID of anti-Integral saturation were realized by FPGA. Optimize the structure of logic circuit by reuse resource and pipeline, as a result of reducing logic resource but reduced the delay time, and the closed-loop bandwidth increases to 100Hz. The jitter of laser less than 40Hz was reduced 40dB. The cost of the system is low but it works stably.

Magnetic fish-robot based on multi-motion control of a flexible magnetic actuator.

PubMed

Kim, Sung Hoon; Shin, Kyoosik; Hashi, Shuichiro; Ishiyama, Kazushi

2012-09-01

This paper presents a biologically inspired fish-robot driven by a single flexible magnetic actuator with a rotating magnetic field in a three-axis Helmholtz coil. Generally, magnetic fish-robots are powered by alternating and gradient magnetic fields, which provide a single motion such as bending the fish-robot's fins. On the other hand, a flexible magnetic actuator driven by an external rotating magnetic field can create several gaits such as the bending vibration, the twisting vibration, and their combination. Most magnetic fish-like micro-robots do not have pectoral fins on the side and are simply propelled by the tail fin. The proposed robot can swim and perform a variety of maneuvers with the addition of pectoral fins and control of the magnetic torque direction. In this paper, we find that the robot's dynamic actuation correlates with the magnetic actuator and the rotating magnetic field. The proposed robot is also equipped with new features, such as a total of six degrees of freedom, a new control method that stabilizes posture, three-dimensional swimming, a new velocity control, and new turning abilities.

Master-slave micromanipulator apparatus

DOEpatents

Morimoto, A.K.; Kozlowski, D.M.; Charles, S.T.; Spalding, J.A.

1999-08-31

An apparatus is disclosed based on precision X-Y stages that are stacked. Attached to arms projecting from each X-Y stage are a set of two axis gimbals. Attached to the gimbals is a rod, which provides motion along the axis of the rod and rotation around its axis. A dual-planar apparatus that provides six degrees of freedom of motion precise to within microns of motion. Precision linear stages along with precision linear motors, encoders, and controls provide a robotics system. The motors can be positioned in a remote location by incorporating a set of bellows on the motors and can be connected through a computer controller that will allow one to be a master and the other one to be a slave. Position information from the master can be used to control the slave. Forces of interaction of the slave with its environment can be reflected back to the motor control of the master to provide a sense of force sensed by the slave. Forces import onto the master by the operator can be fed back into the control of the slave to reduce the forces required to move it. 12 figs.

Master-slave micromanipulator method

DOEpatents

Morimoto, Alan K.; Kozlowski, David M.; Charles, Steven T.; Spalding, James A.

1999-01-01

A method based on precision X-Y stages that are stacked. Attached to arms projecting from each X-Y stage are a set of two axis gimbals. Attached to the gimbals is a rod, which provides motion along the axis of the rod and rotation around its axis. A dual-planar apparatus that provides six degrees of freedom of motion precise to within microns of motion. Precision linear stages along with precision linear motors, encoders, and controls provide a robotics system. The motors can be remotized by incorporating a set of bellows on the motors and can be connected through a computer controller that will allow one to be a master and the other one to be a slave. Position information from the master can be used to control the slave. Forces of interaction of the slave with its environment can be reflected back to the motor control of the master to provide a sense of force sensed by the slave. Forces import onto the master by the operator can be fed back into the control of the slave to reduce the forces required to move it.

Master-slave micromanipulator apparatus

DOEpatents

Morimoto, Alan K.; Kozlowski, David M.; Charles, Steven T.; Spalding, James A.

1999-01-01

An apparatus based on precision X-Y stages that are stacked. Attached to arms projecting from each X-Y stage are a set of two axis gimbals. Attached to the gimbals is a rod, which provides motion along the axis of the rod and rotation around its axis. A dual-planar apparatus that provides six degrees of freedom of motion precise to within microns of motion. Precision linear stages along with precision linear motors, encoders, and controls provide a robotics system. The motors can be positioned in a remote location by incorporating a set of bellows on the motors and can be connected through a computer controller that will allow one to be a master and the other one to be a slave. Position information from the master can be used to control the slave. Forces of interaction of the slave with its environment can be reflected back to the motor control of the master to provide a sense of force sensed by the slave. Forces import onto the master by the operator can be fed back into the control of the slave to reduce the forces required to move it.

Method and apparatus for characterizing and enhancing the dynamic performance of machine tools

DOEpatents

Barkman, William E; Babelay, Jr., Edwin F

2013-12-17

Disclosed are various systems and methods for assessing and improving the capability of a machine tool. The disclosure applies to machine tools having at least one slide configured to move along a motion axis. Various patterns of dynamic excitation commands are employed to drive the one or more slides, typically involving repetitive short distance displacements. A quantification of a measurable merit of machine tool response to the one or more patterns of dynamic excitation commands is typically derived for the machine tool. Examples of measurable merits of machine tool performance include dynamic one axis positional accuracy of the machine tool, dynamic cross-axis stability of the machine tool, and dynamic multi-axis positional accuracy of the machine tool.

A One-Axis-Controlled Magnetic Bearing and Its Performance

NASA Astrophysics Data System (ADS)

Li, Lichuan; Shinshi, Tadahiko; Kuroki, Jiro; Shimokohbe, Akira

Magnetic bearings (MBs) are complex machines in which sensors and controllers must be used to stabilize the rotor. A standard MB requires active control of five motion axes, imposing significant complexity and high cost. In this paper we report a very simple MB and its experimental testing. In this MB, the rotor is stabilized by active control of only one motion axis. The other four motion axes are passively stabilized by permanent magnets and appropriate magnetic circuit design. In rotor radial translational motion, which is passively stabilized, a resonant frequency of 205Hz is achieved for a rotor mass of 11.5×10-3kg. This MB features virtually zero control current and zero rotor iron loss (hysteresis and eddy current losses). Although the rotational speed and accuracy are limited by the resonance of passively stabilized axes, the MB is still suitable for applications where cost is critical but performance is not, such as cooling fans and auxiliary support for aerodynamic bearings.

Design and testing of a novel multi-stroke micropositioning system with variable resolutions.

PubMed

Xu, Qingsong

2014-02-01

Multi-stroke stages are demanded in micro-/nanopositioning applications which require smaller and larger motion strokes with fine and coarse resolutions, respectively. This paper presents the conceptual design of a novel multi-stroke, multi-resolution micropositioning stage driven by a single actuator for each working axis. It eliminates the issue of the interference among different drives, which resides in conventional multi-actuation stages. The stage is devised based on a fully compliant variable stiffness mechanism, which exhibits unequal stiffnesses in different strokes. Resistive strain sensors are employed to offer variable position resolutions in the different strokes. To quantify the design of the motion strokes and coarse/fine resolution ratio, analytical models are established. These models are verified through finite-element analysis simulations. A proof-of-concept prototype XY stage is designed, fabricated, and tested to demonstrate the feasibility of the presented ideas. Experimental results of static and dynamic testing validate the effectiveness of the proposed design.

Optimization of blade motion of vertical axis turbine

NASA Astrophysics Data System (ADS)

Ma, Yong; Zhang, Liang; Zhang, Zhi-yang; Han, Duan-feng

2016-04-01

In this paper, a method is proposed to improve the energy efficiency of the vertical axis turbine. First of all, a single disk multiple stream-tube model is used to calculate individual fitness. Genetic algorithm is adopted to optimize blade pitch motion of vertical axis turbine with the maximum energy efficiency being selected as the optimization objective. Then, a particular data processing method is proposed, fitting the result data into a cosine-like curve. After that, a general formula calculating the blade motion is developed. Finally, CFD simulation is used to validate the blade pitch motion formula. The results show that the turbine's energy efficiency becomes higher after the optimization of blade pitch motion; compared with the fixed pitch turbine, the efficiency of variable-pitch turbine is significantly improved by the active blade pitch control; the energy efficiency declines gradually with the growth of speed ratio; besides, compactness has lager effect on the blade motion while the number of blades has little effect on it.

Evaluation of the New B-REX Fatigue Testing System for Multi-Megawatt Wind Turbine Blades: Preprint

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

White, D.; Musial, W.; Engberg, S.

2004-12-01

The National Renewable Energy Laboratory (NREL) recently developed a new hybrid fatigue testing system called the Blade Resonance Excitation (B-REX) test system. The new system uses 65% less energy to test large wind turbine blades in half the time of NREL's dual-axis forced-displacement test method with lower equipment and operating costs. The B-REX is a dual-axis test system that combines resonance excitation with forced hydraulic loading to reduce the total test time required while representing the operating strains on the critical inboard blade stations more accurately than a single-axis test system. The analysis and testing required to fully implement themore » B-REX was significant. To control unanticipated blade motion and vibrations caused by dynamic coupling between the flap, lead-lag, and torsional directions, we needed to incorporate additional test hardware and control software. We evaluated the B-REX test system under stable operating conditions using a combination of various sensors. We then compared our results with results from the same blade, tested previously using NREL's dual-axis forced-displacement test method. Experimental results indicate that strain levels produced by the B-REX system accurately replicated the forced-displacement method. This paper describes the challenges we encountered while developing the new blade fatigue test system and the experimental results that validate its accuracy.« less

Design of a Minimum Surface-Effect Three Degree-of-Freedom Micromanipulator

NASA Technical Reports Server (NTRS)

Goldfarb, Michael; Speich, John E.

1997-01-01

This paper describes the fundamental physical motivations for small-scale minimum surface-effect design, and presents a three degree-of-freedom micromanipulator design that incorporates a minimum surface-effect approach. The primary focus of the design is the split-tube flexure, a unique small-scale revolute joint that exhibits a considerably larger range of motion and significantly better multi-axis revolute joint characteristics than a conventional flexure. The development of this joint enables the implementation of a small-scale spatially-loaded revolute joint-based manipulator with well-behaved kinematic characteristics and without the backlash and stick-slip behavior that would otherwise prevent precision control

Sensitivity of finite helical axis parameters to temporally varying realistic motion utilizing an idealized knee model.

PubMed

Johnson, T S; Andriacchi, T P; Erdman, A G

2004-01-01

Various uses of the screw or helical axis have previously been reported in the literature in an attempt to quantify the complex displacements and coupled rotations of in vivo human knee kinematics. Multiple methods have been used by previous authors to calculate the axis parameters, and it has been theorized that the mathematical stability and accuracy of the finite helical axis (FHA) is highly dependent on experimental variability and rotation increment spacing between axis calculations. Previous research has not addressed the sensitivity of the FHA for true in vivo data collection, as required for gait laboratory analysis. This research presents a controlled series of experiments simulating continuous data collection as utilized in gait analysis to investigate the sensitivity of the three-dimensional finite screw axis parameters of rotation, displacement, orientation and location with regard to time step increment spacing, utilizing two different methods for spatial location. Six-degree-of-freedom motion parameters are measured for an idealized rigid body knee model that is constrained to a planar motion profile for the purposes of error analysis. The kinematic data are collected using a multicamera optoelectronic system combined with an error minimization algorithm known as the point cluster method. Rotation about the screw axis is seen to be repeatable, accurate and time step increment insensitive. Displacement along the axis is highly dependent on time step increment sizing, with smaller rotation angles between calculations producing more accuracy. Orientation of the axis in space is accurate with only a slight filtering effect noticed during motion reversal. Locating the screw axis by a projected point onto the screw axis from the mid-point of the finite displacement is found to be less sensitive to motion reversal than finding the intersection of the axis with a reference plane. A filtering effect of the spatial location parameters was noted for larger time step increments during periods of little or no rotation.

Multi-axis planar slide system

DOEpatents

Bieg, Lothar F.

2002-01-01

An apparatus for positioning an item that provides two-dimensional, independent orthogonal motion of a platform in a X-Y plane. A pair of master and slave disks engages opposite sides of the platform. Rotational drivers are connected to master disks so the disks rotate eccentrically about axes of rotation. Opposing slave disks are connected to master disks on opposite sides of the platform by a timing belt, or are electronically synchronized together using stepper motors, to effect coordinated motion. The coordinated eccentric motion of the pairs of master/slave disks compels smooth linear motion of the platform in the X-Y plane without backlash. The apparatus can be a planar mechanism implemented in a MEMS device.

Sacroiliac joint motion in patients with degenerative lumbar spine disorders.

PubMed

Nagamoto, Yukitaka; Iwasaki, Motoki; Sakaura, Hironobu; Sugiura, Tsuyoshi; Fujimori, Takahito; Matsuo, Yohei; Kashii, Masafumi; Murase, Tsuyoshi; Yoshikawa, Hideki; Sugamoto, Kazuomi

2015-08-01

OBJECT Usually additional anchors into the ilium are necessary in long fusion to the sacrum for degenerative lumbar spine disorders (DLSDs), especially for adult spine deformity. Although the use of anchors is becoming quite common, surgeons must always keep in mind that the sacroiliac (SI) joint is mobile and they should be aware of the kinematic properties of the SI joint in patients with DLSDs, including adult spinal deformity. No previous study has clarified in vivo kinematic changes in the SI joint with respect to patient age, sex, or parturition status or the presence of DLSDs. The authors conducted a study to clarify the mobility and kinematic characteristics of the SI joint in patients with DLSDs in comparison with healthy volunteers by using in vivo 3D motion analysis with voxel-based registration, a highly accurate, noninvasive method. METHODS Thirteen healthy volunteers (the control group) and 20 patients with DLSDs (the DLSD group) underwent low-dose 3D CT of the lumbar spine and pelvis in 3 positions (neutral, maximal trunk flexion, and maximal trunk extension). SI joint motion was calculated by computer processing of the CT images (voxel-based registration). 3D motion of the SI joint was expressed as both 6 df by Euler angles and translations on the coordinate system and a helical axis of rotation. The correlation between joint motion and the cross-sectional area of the trunk muscles was also investigated. RESULTS SI joint motion during trunk flexion-extension was minute in healthy volunteers. The mean rotation angles during trunk flexion were 0.07° around the x axis, -0.02° around the y axis, and 0.16° around the z axis. The mean rotation angles during trunk extension were 0.38° around the x axis, -0.08° around the y axis, and 0.08° around the z axis. During trunk flexion-extension, the largest amount of motion occurred around the x axis. In patients with DLSDs, the mean rotation angles during trunk flexion were 0.57° around the x axis, 0.01° around the y axis, and 0.19° around the z axis. The mean rotation angles during trunk extension were 0.68° around the x axis, -0.11° around the y axis, and 0.05° around the z axis. Joint motion in patients with DLSDs was significantly greater, with greater individual difference, than in healthy volunteers. Among patients with DLSDs, women had significantly more motion than men did during trunk extension. SI joint motion was significantly negatively correlated with the cross-sectional area of the trunk muscles during both flexion and extension of the trunk. CONCLUSIONS The authors elucidated the mobility and kinematic characteristics of the SI joint in patients with DLSDs compared with healthy volunteers for the first time. This information is useful for spine surgeons because of the recent increase in spinopelvic fusion for the treatment of DLSDs.

The DREO (Defence Research Establishment Ottawa) Inertial Navigation Laboratory: Development and Test Capabilities,

DTIC Science & Technology

1984-06-01

TABLE AND ASSOCIATED ELECTRONICS The laboratory motion table is a Contraves -Goerz Corporation Model 57CD, two-axis table controlled by a 30H MPACS...Figure 2-2 Contraves -Goerz 57CD/30H 2-axis Motion Table rr r Vr 14 Ow6 7.a Figr 2- Motion Tal oto lcrnc +,4W Figure 2-4 Table Top Breakouts and Fixturing...noted that both power supplies are synch loss and line power protected preventing overshoot during power supply recovery after failure. 2.4

Motion control of multi-actuator hydraulic systems for mobile machineries: Recent advancements and future trends

NASA Astrophysics Data System (ADS)

Xu, Bing; Cheng, Min

2018-06-01

This paper presents a survey of recent advancements and upcoming trends in motion control technologies employed in designing multi-actuator hydraulic systems for mobile machineries. Hydraulic systems have been extensively used in mobile machineries due to their superior power density and robustness. However, motion control technologies of multi-actuator hydraulic systems have faced increasing challenges due to stringent emission regulations. In this study, an overview of the evolution of existing throttling control technologies is presented, including open-center and load sensing controls. Recent advancements in energy-saving hydraulic technologies, such as individual metering, displacement, and hybrid controls, are briefly summarized. The impact of energy-saving hydraulic technologies on dynamic performance and control solutions are also discussed. Then, the advanced operation methods of multi-actuator mobile machineries are reviewed, including coordinated and haptic controls. Finally, challenges and opportunities of advanced motion control technologies are presented by providing an overall consideration of energy efficiency, controllability, cost, reliability, and other aspects.

Single Axis Attitude Control and DC Bus Regulation with Two Flywheels

NASA Technical Reports Server (NTRS)

Kascak, Peter E.; Jansen, Ralph H.; Kenny, Barbara; Dever, Timothy P.

2002-01-01

A computer simulation of a flywheel energy storage single axis attitude control system is described. The simulation models hardware which will be experimentally tested in the future. This hardware consists of two counter rotating flywheels mounted to an air table. The air table allows one axis of rotational motion. An inertia DC bus coordinator is set forth that allows the two control problems, bus regulation and attitude control, to be separated. Simulation results are presented with a previously derived flywheel bus regulator and a simple PID attitude controller.

Stabilization of a programmed rotation mode for a satellite with electrodynamic attitude control system

NASA Astrophysics Data System (ADS)

Aleksandrov, A. Yu.; Aleksandrova, E. B.; Tikhonov, A. A.

2018-07-01

The paper deals with a dynamically symmetric satellite in a circular near-Earth orbit. The satellite is equipped with an electrodynamic attitude control system based on Lorentz and magnetic torque properties. The programmed satellite attitude motion is such that the satellite slowly rotates around the axis of its dynamical symmetry. Unlike previous publications, we consider more complex and practically more important case where the axis is fixed in the orbital frame in an inclined position with respect to the local vertical axis. The satellite stabilization in the programmed attitude motion is studied. The gravitational disturbing torque acting on the satellite attitude dynamics is taken into account since it is the largest disturbing torque. The novelty of the proposed approach is based on the usage of electrodynamic attitude control system. With the aid of original construction of a Lyapunov function, new conditions under which electrodynamic control solves the problem are obtained. Sufficient conditions for asymptotic stability of the programmed motion are found in terms of inequalities for the values of control parameters. The results of a numerical simulation are presented to demonstrate the effectiveness of the proposed approach.

Attitude guidance and tracking for spacecraft with two reaction wheels

NASA Astrophysics Data System (ADS)

Biggs, James D.; Bai, Yuliang; Henninger, Helen

2018-04-01

This paper addresses the guidance and tracking problem for a rigid-spacecraft using two reaction wheels (RWs). The guidance problem is formulated as an optimal control problem on the special orthogonal group SO(3). The optimal motion is solved analytically as a function of time and is used to reduce the original guidance problem to one of computing the minimum of a nonlinear function. A tracking control using two RWs is developed that extends previous singular quaternion stabilisation controls to tracking controls on the rotation group. The controller is proved to locally asymptotically track the generated reference motions using Lyapunov's direct method. Simulations of a 3U CubeSat demonstrate that this tracking control is robust to initial rotation errors and angular velocity errors in the controlled axis. For initial angular velocity errors in the uncontrolled axis and under significant disturbances the control fails to track. However, the singular tracking control is combined with a nano-magnetic torquer which simply damps the angular velocity in the uncontrolled axis and is shown to provide a practical control method for tracking in the presence of disturbances and initial condition errors.

Method for spinning up a three-axis controlled spacecraft

NASA Technical Reports Server (NTRS)

Vorlicek, Preston L. (Inventor)

1988-01-01

A three-axis controlled spacecraft (1), typically a satellite, is spun up about its roll axis (20) prior to firing a motor (2), i.e., a perigee kick motor, to achieve the requisite degree of angular momentum stiffness. Thrusters (21) for imparting rotation about the roll axis (20) are activated in open-loop fashion, typically at less than full duty cycle. Cross-axis torques induced by this rotational motion are compensated for by means of closed control loops for each of the pitch and yaw axes (30, 40, respectively). Each closed control loop combines a prebias torque (72) with torques (75, 74) representative of position and rate feedback information, respectively. A deadband (52) within each closed control loop can be widened during the spinup, to conserve fuel. Position feedback information (75) in each of the control loops is disabled upon saturation of the gyroscope associated with the roll axis (20).

Design and Verification of a Digital Controller for a 2-Piece Hemispherical Resonator Gyroscope.

PubMed

Lee, Jungshin; Yun, Sung Wook; Rhim, Jaewook

2016-04-20

A Hemispherical Resonator Gyro (HRG) is the Coriolis Vibratory Gyro (CVG) that measures rotation angle or angular velocity using Coriolis force acting the vibrating mass. A HRG can be used as a rate gyro or integrating gyro without structural modification by simply changing the control scheme. In this paper, differential control algorithms are designed for a 2-piece HRG. To design a precision controller, the electromechanical modelling and signal processing must be pre-performed accurately. Therefore, the equations of motion for the HRG resonator with switched harmonic excitations are derived with the Duhamel Integral method. Electromechanical modeling of the resonator, electric module and charge amplifier is performed by considering the mode shape of a thin hemispherical shell. Further, signal processing and control algorithms are designed. The multi-flexing scheme of sensing, driving cycles and x, y-axis switching cycles is appropriate for high precision and low maneuverability systems. The differential control scheme is easily capable of rejecting the common mode errors of x, y-axis signals and changing the rate integrating mode on basis of these studies. In the rate gyro mode the controller is composed of Phase-Locked Loop (PLL), amplitude, quadrature and rate control loop. All controllers are designed on basis of a digital PI controller. The signal processing and control algorithms are verified through Matlab/Simulink simulations. Finally, a FPGA and DSP board with these algorithms is verified through experiments.

Simulation study of the ROMPS robot control system

NASA Technical Reports Server (NTRS)

Nguyen, Charles C.; Liu, HUI-I.

1994-01-01

This is a report presenting the progress of a research grant funded by NASA for work performed from June 1, 1993 to August 1, 1993. The report deals with the Robot Operated Material Processing System (ROMPS). It presents results of a computer simulation study conducted to investigate the performance of the control systems controlling the azimuth, elevation, and radial axes of the ROMPS and its gripper. Four study cases are conducted. The first case investigates the control of free motion of the three areas. In the second case, the compliant motion in the elevation axis with the wrist compliant device is studied in terms of position accuracy and impact forces. The third case focuses on the behavior of the control system in controlling the robot motion along the radial axis when pulling the pallet out of the rack. In the fourth case, the compliant motion of the gripper grasping a solid object under the effect of the gripper passive compliance is studied in terms of position accuracy and contact forces. For each of the above cases, a set of PIR gains will be selected to optimize the controller performance and computer simulation results will be presented and discussed.

Simultaneous, proportional, multi-axis prosthesis control using multichannel surface EMG.

PubMed

Yatsenko, Dimitri; McDonnall, Daniel; Guillory, K Shane

2007-01-01

Most upper limb prosthesis controllers only allow the individual selection and control of single joints of the limb. The main limiting factor for simultaneous multi-joint control is usually the availability of reliable independent control signals that can intuitively be used. In this paper, a novel method is presented for extraction of individual muscle source signals from surface EMG array recordings, based on EMG energy orthonormalization along principle movement vectors. In cases where independently-controllable muscles are present in residual limbs, this method can be used to provide simultaneous, multi-axis, proportional control of prosthetic systems. Initial results are presented for simultaneous control of wrist rotation, wrist flexion/extension, and grip open/close for two intact subjects under both isometric and non-isometric conditions and for one subject with transradial amputation.

Stirling engine control mechanism and method

DOEpatents

Dineen, John J.

1983-01-01

A reciprocating-to-rotating motion conversion and power control device for a Stirling engine includes a hub mounted on an offset portion of the output shaft for rotation relative to the shaft and for sliding motion therealong which causes the hub to tilt relative to the axis of rotation of the shaft. This changes the angle of inclination of the hub relative to the shaft axis and changes the axial stroke of a set of arms connected to the hub and nutating therewith. A hydraulic actuating mechanism is connected to the hub for moving its axial position along the shaft. A balancing wheel is linked to the hub and changes its angle of inclination as the angle of inclination of the hub changes to maintain the mechanism in perfect balance throughout its range of motion.

Design of a Space Borne Autonomous Infrared Tracking System

DTIC Science & Technology

2004-03-01

8217, hsv (6),’FaceColor’,’flat ’); theta_last = 0;%axis([-.2 .2 -.2 .2 -.2 .2]); axis square;break % Motion for ii= 1 :num_pts %transform... 1 Space Control...88 ix List of Figures Figure Page 1

Robotic Prostate Biopsy in Closed MRI Scanner

DTIC Science & Technology

2009-02-01

radioactive seeds or diagnosis by harvesting tissue samples inside the mag- net bore, under remote control of the physician without mov- ing the patient out...and allows fast removal for reloading brachytherapy needles or col- lecting harvested biopsy tissue. The primary actuated motions of the robot...include two prismatic motions and two rotational motions for aligning the needle axis. In addition to these base motions, application-specific motions are

Scientific Visualization of Radio Astronomy Data using Gesture Interaction

NASA Astrophysics Data System (ADS)

Mulumba, P.; Gain, J.; Marais, P.; Woudt, P.

2015-09-01

MeerKAT in South Africa (Meer = More Karoo Array Telescope) will require software to help visualize, interpret and interact with multidimensional data. While visualization of multi-dimensional data is a well explored topic, little work has been published on the design of intuitive interfaces to such systems. More specifically, the use of non-traditional interfaces (such as motion tracking and multi-touch) has not been widely investigated within the context of visualizing astronomy data. We hypothesize that a natural user interface would allow for easier data exploration which would in turn lead to certain kinds of visualizations (volumetric, multidimensional). To this end, we have developed a multi-platform scientific visualization system for FITS spectral data cubes using VTK (Visualization Toolkit) and a natural user interface to explore the interaction between a gesture input device and multidimensional data space. Our system supports visual transformations (translation, rotation and scaling) as well as sub-volume extraction and arbitrary slicing of 3D volumetric data. These tasks were implemented across three prototypes aimed at exploring different interaction strategies: standard (mouse/keyboard) interaction, volumetric gesture tracking (Leap Motion controller) and multi-touch interaction (multi-touch monitor). A Heuristic Evaluation revealed that the volumetric gesture tracking prototype shows great promise for interfacing with the depth component (z-axis) of 3D volumetric space across multiple transformations. However, this is limited by users needing to remember the required gestures. In comparison, the touch-based gesture navigation is typically more familiar to users as these gestures were engineered from standard multi-touch actions. Future work will address a complete usability test to evaluate and compare the different interaction modalities against the different visualization tasks.

Rotary fast tool servo system and methods

DOEpatents

Montesanti, Richard C.; Trumper, David L.

2007-10-02

A high bandwidth rotary fast tool servo provides tool motion in a direction nominally parallel to the surface-normal of a workpiece at the point of contact between the cutting tool and workpiece. Three or more flexure blades having all ends fixed are used to form an axis of rotation for a swing arm that carries a cutting tool at a set radius from the axis of rotation. An actuator rotates a swing arm assembly such that a cutting tool is moved in and away from the lathe-mounted, rotating workpiece in a rapid and controlled manner in order to machine the workpiece. A pair of position sensors provides rotation and position information for a swing arm to a control system. A control system commands and coordinates motion of the fast tool servo with the motion of a spindle, rotating table, cross-feed slide, and in-feed slide of a precision lathe.

Rotary fast tool servo system and methods

DOEpatents

Montesanti, Richard C [Cambridge, MA; Trumper, David L [Plaistow, NH; Kirtley, Jr., James L.

2009-08-18

A high bandwidth rotary fast tool servo provides tool motion in a direction nominally parallel to the surface-normal of a workpiece at the point of contact between the cutting tool and workpiece. Three or more flexure blades having all ends fixed are used to form an axis of rotation for a swing arm that carries a cutting tool at a set radius from the axis of rotation. An actuator rotates a swing arm assembly such that a cutting tool is moved in and away from the lathe-mounted, rotating workpiece in a rapid and controlled manner in order to machine the workpiece. One or more position sensors provides rotation and position information for a swing arm to a control system. A control system commands and coordinates motion of the fast tool servo with the motion of a spindle, rotating table, cross-feed slide, and in-feed slide of a precision lathe.

Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator.

PubMed

Raabe, D; Harrison, A; Ireland, A; Alemzadeh, K; Sandy, J; Dogramadzi, S; Melhuish, C; Burgess, S

2012-03-01

This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator. Experimental studies of wear using this simulator demonstrate that integrating the biological feature of combined force/position hybrid control in dental material testing improves the linearity and reduces the variability of results. In addition, it has been shown that present biaxially operated dental wear simulators are likely to provide misleading results in comparative in vitro/in vivo one-contact studies due to neglecting the occlusal sliding motion in one plane which could introduce an error of up to 49% since occlusal sliding motion D and volumetric wear loss V(loss) are proportional.

Identification of Time-Varying Pilot Control Behavior in Multi-Axis Control Tasks

NASA Technical Reports Server (NTRS)

Zaal, Peter M. T.; Sweet, Barbara T.

2012-01-01

Recent developments in fly-by-wire control architectures for rotorcraft have introduced new interest in the identification of time-varying pilot control behavior in multi-axis control tasks. In this paper a maximum likelihood estimation method is used to estimate the parameters of a pilot model with time-dependent sigmoid functions to characterize time-varying human control behavior. An experiment was performed by 9 general aviation pilots who had to perform a simultaneous roll and pitch control task with time-varying aircraft dynamics. In 8 different conditions, the axis containing the time-varying dynamics and the growth factor of the dynamics were varied, allowing for an analysis of the performance of the estimation method when estimating time-dependent parameter functions. In addition, a detailed analysis of pilots adaptation to the time-varying aircraft dynamics in both the roll and pitch axes could be performed. Pilot control behavior in both axes was significantly affected by the time-varying aircraft dynamics in roll and pitch, and by the growth factor. The main effect was found in the axis that contained the time-varying dynamics. However, pilot control behavior also changed over time in the axis not containing the time-varying aircraft dynamics. This indicates that some cross coupling exists in the perception and control processes between the roll and pitch axes.

Two-dimensional straightness measurement based on optical knife-edge sensing

NASA Astrophysics Data System (ADS)

Wang, Chen; Zhong, Fenghe; Ellis, Jonathan D.

2017-09-01

Straightness error is a parasitic translation along a perpendicular direction to the primary displacement axis of a linear stage. The parasitic translations could be coupled into other primary displacement directions of a multi-axis platform. Hence, its measurement and compensation are critical in precision multi-axis metrology, calibration, and manufacturing. This paper presents a two-dimensional (2D) straightness measurement configuration based on 2D optical knife-edge sensing, which is simple, light-weight, compact, and easy to align. It applies a 2D optical knife-edge to manipulate the diffraction pattern sensed by a quadrant photodetector, whose output voltages could derive 2D straightness errors after a calibration process. This paper analyzes the physical model of the configuration and performs simulations and experiments to study the system sensitivity, measurement nonlinearity, and error sources. The results demonstrate that the proposed configuration has higher sensitivity and insensitive to beam's vibration, compared with the conventional configurations without using the knife-edge, and could achieve ±0.25 μ m within a ±40 μ m measurement range along a 40 mm primary axial motion.

Design and Verification of a Digital Controller for a 2-Piece Hemispherical Resonator Gyroscope

PubMed Central

Lee, Jungshin; Yun, Sung Wook; Rhim, Jaewook

2016-01-01

A Hemispherical Resonator Gyro (HRG) is the Coriolis Vibratory Gyro (CVG) that measures rotation angle or angular velocity using Coriolis force acting the vibrating mass. A HRG can be used as a rate gyro or integrating gyro without structural modification by simply changing the control scheme. In this paper, differential control algorithms are designed for a 2-piece HRG. To design a precision controller, the electromechanical modelling and signal processing must be pre-performed accurately. Therefore, the equations of motion for the HRG resonator with switched harmonic excitations are derived with the Duhamel Integral method. Electromechanical modeling of the resonator, electric module and charge amplifier is performed by considering the mode shape of a thin hemispherical shell. Further, signal processing and control algorithms are designed. The multi-flexing scheme of sensing, driving cycles and x, y-axis switching cycles is appropriate for high precision and low maneuverability systems. The differential control scheme is easily capable of rejecting the common mode errors of x, y-axis signals and changing the rate integrating mode on basis of these studies. In the rate gyro mode the controller is composed of Phase-Locked Loop (PLL), amplitude, quadrature and rate control loop. All controllers are designed on basis of a digital PI controller. The signal processing and control algorithms are verified through Matlab/Simulink simulations. Finally, a FPGA and DSP board with these algorithms is verified through experiments. PMID:27104539

Wireless control system for two-axis linear oscillating motion applying CBR technology

NASA Astrophysics Data System (ADS)

Kuzyakov, O. N.; Andreeva, M. A.

2018-03-01

The paper presents the aspects of elaborating a movement control system. The system is to implement determination of movement characteristics of the object controlled, which performs an oscillating linear motion in a two-axis direction. The system has an electronic-optical principle of action: light receivers are attached to a controlled object, and a laser light emitter is attached to a static construction. While the object performs movement along the construction, the light emitter signal is registered by light receivers, based on which determination of the object position and characteristic of its movement are performed. An algorithm of system implementation is elaborated. Signal processing is performed on the basis of the case-based reasoning method. The system is to be used in machine-building industry in controlling relative displacement of the dynamic object or its assembly.

Vista/F-16 Multi-Axis Thrust Vectoring (MATV) control law design and evaluation

NASA Technical Reports Server (NTRS)

Zwerneman, W. D.; Eller, B. G.

1994-01-01

For the Multi-Axis Thrust Vectoring (MATV) program, a new control law was developed using multi-axis thrust vectoring to augment the aircraft's aerodynamic control power to provide maneuverability above the normal F-16 angle of attack limit. The control law architecture was developed using Lockheed Fort Worth's offline and piloted simulation capabilities. The final flight control laws were used in flight test to demonstrate tactical benefits gained by using thrust vectoring in air-to-air combat. Differences between the simulator aerodynamics data base and the actual aircraft aerodynamics led to significantly different lateral-directional flying qualities during the flight test program than those identified during piloted simulation. A 'dial-a-gain' flight test control law update was performed in the middle of the flight test program. This approach allowed for inflight optimization of the aircraft's flying qualities. While this approach is not preferred over updating the simulator aerodynamic data base and then updating the control laws, the final selected gain set did provide adequate lateral-directional flying qualities over the MATV flight envelope. The resulting handling qualities and the departure resistance of the aircraft allowed the 422nd_squadron pilots to focus entirely on evaluating the aircraft's tactical utility.

Testing a satellite automatic nutation control system. [on synchronous meteorological satellite

NASA Technical Reports Server (NTRS)

Hrasiar, J. A.

1974-01-01

Testing of a particular nutation control system for the synchronous meteorological satellite (SMS) is described. The test method and principles are applicable to nutation angle control for other satellites with similar requirements. During its ascent to synchronous orbit, a spacecraft like the SMS spins about its minimum-moment-of-inertia axis. An uncontrolled spacecraft in this state is unstable because torques due to fuel motion increase the nutation angle. However, the SMS is equipped with an automatic nutation control (ANC) system which will keep the nutation angle close to zero. Because correct operation of this system is critical to mission success, it was tested on an air-bearing table. The ANC system was mounted on the three-axis air-bearing table which was scaled to the SMS and equipped with appropriate sensors and thrusters. The table was spun up in an altitude chamber and nutation induced so that table motion simulated spacecraft motion. The ANC system was used to reduce the nutation angle. This dynamic test of the ANC system met all its objectives and provided confidence that the ANC system will control the SMS nutation angle.

Subendocardial motion in hypertrophic cardiomyopathy: assessment from long- and short-axis views by pulsed tissue Doppler imaging

NASA Technical Reports Server (NTRS)

Tabata, T.; Oki, T.; Yamada, H.; Abe, M.; Onose, Y.; Thomas, J. D.

2000-01-01

BACKGROUND: Tissue Doppler imaging (TDI) is a recently developed technique that allows the instantaneous measurement of intrinsic regional myocardial motion velocity. Pulsed TDI is capable of separately assessing left ventricular (LV) regional motion velocity caused by circumferential and longitudinal fiber contraction. This particular feature of function is still controversial in patients with hypertrophic cardiomyopathy (HC). METHODS: To better characterize intrinsic circumferential and longitudinal LV systolic myocardial function in HC, we used pulsed TDI to measure short- and long-axis LV motion velocities, respectively. The subendocardial motion velocity patterns at the middle of the LV posterior wall (PW) and ventricular septum (IVS) in LV parasternal and apical long-axis views were recorded by pulsed TDI in 19 patients with nonobstructive HC and in 21 normal controls (NC). RESULTS: Peak short- and long-axis systolic subendocardial velocities in both the LV PW and IVS were significantly smaller in the HC group than in the NC group, and the time to peak velocity was significantly delayed. Furthermore, peak PW systolic velocity was significantly greater along the long axis than along the short axis in the NC group (8.8 +/- 1.5 cm/s vs 8.2 +/- 1.4 cm/s, P <.05), whereas the opposite was observed in the HC group (6.1 +/- 1.2 cm/s vs 7.5 +/- 1.0 cm/s, P <.0001). No significant differences were found in either group between the long- and short-axis IVS velocities (HC: 5.9 +/- 1.4 cm/s vs 5.5 +/- 1.3 cm/s; NC: 7.8 +/- 1.3 cm/s vs 7.9 +/- 1.6 cm/s). CONCLUSIONS: By using the capability of pulsed TDI for the evaluation of intrinsic myocardial velocity instantaneously in a specific region and direction, we found impairment of LV myocardial systolic function in patients with HC not only in the hypertrophied IVS but also in the nonhypertrophied LV PW. We also found a greater decrease in LV PW velocities along the long axis than the short axis, suggesting greater impairment of long-axis contraction in patients with HC. Because our HC patients did not appear to have excessive intracavitary pressure, these results suggest that the relatively normal-appearing PW is directly affected by the HC pathologic process.

Coordinate measuring system

DOEpatents

Carlisle, Keith [Discovery Bay, CA

2003-04-08

An apparatus and method is utilized to measure relative rigid body motion between two bodies by measuring linear motion in the principal axis and linear motion in an orthogonal axis. From such measurements it is possible to obtain displacement, departure from straightness, and angular displacement from the principal axis of a rigid body.

Research on the unsteady hydrodynamic characteristics of vertical axis tidal turbine

NASA Astrophysics Data System (ADS)

Zhang, Xue-wei; Zhang, Liang; Wang, Feng; Zhao, Dong-ya; Pang, Cheng-yan

2014-03-01

The unsteady hydrodynamic characteristics of vertical axis tidal turbine are investigated by numerical simulation based on viscous CFD method. The starting mechanism of the turbine is revealed through analyzing the interaction of its motion and dynamics during starting process. The operating hydrodynamic characteristics of the turbine in wave-current condition are also explored by combining with the linear wave theory. According to possible magnification of the cyclic loads in the maximum power tracking control of vertical axis turbine, a novel torque control strategy is put forward, which can improve the structural characteristics significantly without effecting energy efficiency.

Vection during conflicting multisensory information about the axis, magnitude, and direction of self-motion.

PubMed

Ash, April; Palmisano, Stephen

2012-01-01

We examined the vection induced by consistent and conflicting multisensory information about self-motion. Observers viewed displays simulating constant-velocity self-motion in depth while physically oscillating their heads left-right or back-forth in time with a metronome. Their tracked head movements were either ignored or incorporated directly into the self-motion display (as an added simulated self-acceleration). When this head oscillation was updated into displays, sensory conflict was generated by simulating oscillation along: (i) an orthogonal axis to the head movement; or (ii) the same axis, but in a non-ecological direction. Simulated head oscillation always produced stronger vection than 'no display oscillation'--even when the axis/direction of this display motion was inconsistent with the physical head motion. When head-and-display oscillation occurred along the same axis: (i) consistent (in-phase) horizontal display oscillation produced stronger vection than conflicting (out-of-phase) horizontal display oscillation; however, (ii) consistent and conflicting depth oscillation conditions did not induce significantly different vection. Overall, orthogonal-axis oscillation was found to produce very similar vection to same-axis oscillation. Thus, we conclude that while vection appears to be very robust to sensory conflict, there are situations where sensory consistency improves vection.

Rapid fabrication of miniature lens arrays by four-axis single point diamond machining

PubMed Central

McCall, Brian; Tkaczyk, Tomasz S.

2013-01-01

A novel method for fabricating lens arrays and other non-rotationally symmetric free-form optics is presented. This is a diamond machining technique using 4 controlled axes of motion – X, Y, Z, and C. As in 3-axis diamond micro-milling, a diamond ball endmill is mounted to the work spindle of a 4-axis ultra-precision computer numerical control (CNC) machine. Unlike 3-axis micro-milling, the C-axis is used to hold the cutting edge of the tool in contact with the lens surface for the entire cut. This allows the feed rates to be doubled compared to the current state of the art of micro-milling while producing an optically smooth surface with very low surface form error and exceptionally low radius error. PMID:23481813

Multi-axis transient vibration testing of space objects: Test philosophy, test facility, and control strategy

NASA Technical Reports Server (NTRS)

Lachenmayr, Georg

1992-01-01

IABG has been using various servohydraulic test facilities for many years for the reproduction of service loads and environmental loads on all kinds of test objects. For more than 15 years, a multi-axis vibration test facility has been under service, originally designed for earthquake simulation but being upgraded to the demands of space testing. First tests with the DFS/STM showed good reproduction accuracy and demonstrated the feasibility of transient vibration testing of space objects on a multi-axis hydraulic shaker. An approach to structural qualification is possible by using this test philosophy. It will be outlined and its obvious advantages over the state-of-the-art single-axis test will be demonstrated by example results. The new test technique has some special requirements to the test facility exceeding those of earthquake testing. Most important is the high reproduction accuracy demanded for a sophisticated control system. The state-of-the-art approach of analog closed-loop control circuits for each actuator combined with a static decoupling network and an off-line iterative waveform control is not able to meet all the demands. Therefore, the future over-all control system is implemented as hierarchical full digital closed-loop system on a highly parallel transputer network. The innermost layer is the digital actuator controller, the second one is the MDOF-control of the table movement. The outermost layer would be the off-line iterative waveform control, which is dedicated only to deal with the interaction of test table and test object or non-linear effects. The outline of the system will be presented.

Disturbing effects of attitude control maneuvers on the orbital motion of the Helios spacecraft

NASA Technical Reports Server (NTRS)

Georgevic, R. M.

1976-01-01

The position of the spin axis of the Helios A spacecraft has been maintained and updated by a series of attitude control maneuvers, by means of a sequence of unbalanced jet forces which produce an additional disturbed motion of the spacecraft's center of mass. The character of this motion, its magnitude and direction was studied. For practical purposes of the orbit determination of the spacecraft, a computer program is given which shows how the components of the disturbing acceleration in the spacecraft-fixed reference frame can be easily computed.

Multi-axis control based on movement control cards in NC systems

NASA Astrophysics Data System (ADS)

Jiang, Tingbiao; Wei, Yunquan

2005-12-01

Today most movement control cards need special control software of topper computers and are only suitable for fixed-axis controls. Consequently, the number of axes which can be controlled is limited. Advanced manufacture technology develops at a very high speed, and that development brings forth. New requirements for movement control in mechanisms and electronics. This paper introduces products of the 5th generation of movement control cards, PMAC 2A-PC/104, made by the Delta Tau Company in the USA. Based on an analysis of PMAC 2A-PC/104, this paper first describes two aspects relevant to the hardware structure of movement control cards and the interrelated software of the topper computers. Then, two methods are presented for solving these problems. The first method is to set limit switches on the movement control cards; all of them can be used to control each moving axis. The second method is to program applied software with existing programming language (for example, VC ++, Visual Basic, Delphi, and so forth). This program is much easier to operate and expand by its users. By using a limit switch, users can choose different axes in movement control cards. Also, users can change parts of the parameters in the control software of topper computers to realize different control axes. Combining these 2 methods proves to be convenient for realizing multi-axis control in numerical control systems.

A novel single thruster control strategy for spacecraft attitude stabilization

NASA Astrophysics Data System (ADS)

Godard; Kumar, Krishna Dev; Zou, An-Min

2013-05-01

Feasibility of achieving three axis attitude stabilization using a single thruster is explored in this paper. Torques are generated using a thruster orientation mechanism with which the thrust vector can be tilted on a two axis gimbal. A robust nonlinear control scheme is developed based on the nonlinear kinematic and dynamic equations of motion of a rigid body spacecraft in the presence of gravity gradient torque and external disturbances. The spacecraft, controlled using the proposed concept, constitutes an underactuated system (a system with fewer independent control inputs than degrees of freedom) with nonlinear dynamics. Moreover, using thruster gimbal angles as control inputs make the system non-affine (control terms appear nonlinearly in the state equation). This necessitates the control algorithms to be developed based on nonlinear control theory since linear control methods are not directly applicable. The stability conditions for the spacecraft attitude motion for robustness against uncertainties and disturbances are derived to establish the regions of asymptotic 3-axis attitude stabilization. Several numerical simulations are presented to demonstrate the efficacy of the proposed controller and validate the theoretical results. The control algorithm is shown to compensate for time-varying external disturbances including solar radiation pressure, aerodynamic forces, and magnetic disturbances; and uncertainties in the spacecraft inertia parameters. The numerical results also establish the robustness of the proposed control scheme to negate disturbances caused by orbit eccentricity.

Forward/up directional incompatibilities during cursor placement within graphical user interfaces.

PubMed

Phillips, James G; Triggs, Thomas J; Meehan, James W

2005-05-15

Within graphical user interfaces, an indirect relationship between display and control may lead to directional incompatibilities when a forward mouse movement codes upward cursor motions. However, this should not occur for left/right movements or direct cursor controllers (e.g. touch sensitive screens). In a four-choice reaction time task, 12 participants performed movements from a central start location to a target situated at one of four cardinal points (top, bottom, left, right). A 2 x 2 x 2 design varied directness of controller (moving cursor on computer screen or pen on graphics tablet), compatibility of orientation of cursor controller with screen (horizontal or vertical) and axis of desired cursor motion (left/right or up/down). Incompatibility between orientation of controller and motion of cursor did not affect response latencies, possibly because both forward and upward movements are away from the midline and go up the visual field. However, directional incompatibilities between display and controller led to slower movement with prolonged accelerative phases. Indirect relationships between display and control led to less efficient movements with prolonged decelerative phases and a tendency to undershoot movements along the bottom/top axis. More direct cursor control devices, such as touch sensitive screens, should enhance the efficiency of aspects of cursor trajectories.

Optimal Navigation of Self-Propelled Colloids in Microstructured Mazes

NASA Astrophysics Data System (ADS)

Yang, Yuguang; Bevan, Michael

Controlling navigation of self-propelled microscopic `robots' subject to random Brownian motion in complex microstructured environments (e.g., porous media, tumor vasculature) is important to many emerging applications (e.g., enhanced oil recovery, drug delivery). In this work, we design an optimal feedback policy to navigate an active self-propelled colloidal rod in complex mazes with various obstacle types. Actuation of the rods is modelled based on a light-controlled osmotic flow mechanism, which produces different propulsion velocities along the rod's long axis. Actuator-parameterized Langevin equations, with soft rod-obstacle repulsive interactions, are developed to describe the system dynamics. A Markov decision process (MDP) framework is used for optimal policy calculations with design goals of colloidal rods reaching target end points in minimum time. Simulations show that optimal MDP-based policies are able to control rod trajectories to reach target regions order-of-magnitudes faster than uncontrolled rods, which diverges as maze complexity increases. An efficient multi-graph based implementation for MDP is also presented, which scales linearly with the maze dimension.

Altered sensory-motor control of the head as an etiological factor in space-motion sickness

NASA Technical Reports Server (NTRS)

Lackner, J. R.; DiZio, P.

1989-01-01

Mechanical unloading during head movements in weightlessness may be an etiological factor in space-motion sickness. We simulated altered head loading on Earth without affecting vestibular stimulation by having subjects wear a weighted helmet. Eight subjects were exposed to constant velocity rotation about a vertical axis with direction reversals every 60 sec. for eight reversals with the head loaded and eight with the head unloaded. The severity of motion sickness elicited was significantly higher when the head was loaded. This suggests that altered sensory-motor control of the head is also an etiological factor in space-motion sickness.

X- And y-axis driver for rotating microspheres

DOEpatents

Weinstein, Berthold W.

1979-01-01

Apparatus for precise control of the motion and position of microspheres for examination of their interior and/or exterior. The apparatus includes an x- and y-axis driver mechanism controlled, for example, by a minicomputer for selectively rotating microspheres retained between a pair of manipulator arms having flat, smooth end surfaces. The driver mechanism includes an apertured plate and ball arrangement which provided for coupled equal and opposite movement of the manipulator arms in two perpendicular directions.

B-dot algorithm steady-state motion performance

NASA Astrophysics Data System (ADS)

Ovchinnikov, M. Yu.; Roldugin, D. S.; Tkachev, S. S.; Penkov, V. I.

2018-05-01

Satellite attitude motion subject to the well-known B-dot magnetic control is considered. Unlike the majority of studies the present work focuses on the slowly rotating spacecraft. The attitude and the angular velocity acquired after detumbling the satellite is determined. This task is performed using two relatively simple geomagnetic field models. First the satellite is considered moving in the simplified dipole model. Asymptotically stable rotation around the axis of the maximum moment of inertia is found. This axis direction in the inertial space and the rotation rate are found. This result is then refined using the direct dipole geomagnetic field. Simple stable rotation transforms into the periodical motion, the rotation rate is also refined. Numerical analysis with the gravitational torque and the inclined dipole model verifies the analytical results.

Accuracy Improvement of Multi-Axis Systems Based on Laser Correction of Volumetric Geometric Errors

NASA Astrophysics Data System (ADS)

Teleshevsky, V. I.; Sokolov, V. A.; Pimushkin, Ya I.

2018-04-01

The article describes a volumetric geometric errors correction method for CNC- controlled multi-axis systems (machine-tools, CMMs etc.). The Kalman’s concept of “Control and Observation” is used. A versatile multi-function laser interferometer is used as Observer in order to measure machine’s error functions. A systematic error map of machine’s workspace is produced based on error functions measurements. The error map results into error correction strategy. The article proposes a new method of error correction strategy forming. The method is based on error distribution within machine’s workspace and a CNC-program postprocessor. The postprocessor provides minimal error values within maximal workspace zone. The results are confirmed by error correction of precision CNC machine-tools.

A Method for Integrating Thrust-Vectoring and Actuated Forebody Strakes with Conventional Aerodynamic Controls on a High-Performance Fighter Airplane

NASA Technical Reports Server (NTRS)

Lallman, Frederick J.; Davidson, John B.; Murphy, Patrick C.

1998-01-01

A method, called pseudo controls, of integrating several airplane controls to achieve cooperative operation is presented. The method eliminates conflicting control motions, minimizes the number of feedback control gains, and reduces the complication of feedback gain schedules. The method is applied to the lateral/directional controls of a modified high-performance airplane. The airplane has a conventional set of aerodynamic controls, an experimental set of thrust-vectoring controls, and an experimental set of actuated forebody strakes. The experimental controls give the airplane additional control power for enhanced stability and maneuvering capabilities while flying over an expanded envelope, especially at high angles of attack. The flight controls are scheduled to generate independent body-axis control moments. These control moments are coordinated to produce stability-axis angular accelerations. Inertial coupling moments are compensated. Thrust-vectoring controls are engaged according to their effectiveness relative to that of the aerodynamic controls. Vane-relief logic removes steady and slowly varying commands from the thrust-vectoring controls to alleviate heating of the thrust turning devices. The actuated forebody strakes are engaged at high angles of attack. This report presents the forward-loop elements of a flight control system that positions the flight controls according to the desired stability-axis accelerations. This report does not include the generation of the required angular acceleration commands by means of pilot controls or the feedback of sensed airplane motions.

A four-axis hand controller for helicopter flight control

NASA Technical Reports Server (NTRS)

Demaio, Joe

1993-01-01

A proof-of-concept hand controller for controlling lateral and longitudinal cyclic pitch, collective pitch and tail rotor thrust was developed. The purpose of the work was to address problems of operator fatigue, poor proprioceptive feedback and cross-coupling of axes associated with many four-axis controller designs. The present design is an attempt to reduce cross-coupling to a level that can be controlled with breakout force, rather than to eliminate it entirely. The cascaded design placed lateral and longitudinal cyclic in their normal configuration. Tail rotor thrust was placed atop the cyclic controller. A left/right twisting motion with the wrist made the control input. The axis of rotation was canted outboard (clockwise) to minimize cross-coupling with the cyclic pitch axis. The collective control was a twist grip, like a motorcycle throttle. Measurement of the amount of cross-coupling involved in pure, single-axis inputs showed cross coupling under 10 percent of full deflection for all axes. This small amount of cross-coupling could be further reduced with better damping and force gradient control. Fatigue was not found to be a problem, and proprioceptive feedback was adequate for all flight tasks executed.

Malaligned dynamic anterior cervical plate: a biomechanical analysis of effectiveness.

PubMed

Lawrence, Brandon D; Patel, Alpesh A; Guss, Andrew; Ryan Spiker, W; Brodke, Darrel S

2014-12-01

Biomechanical evaluation. To evaluate the kinematic and load-sharing differences of dynamic anterior cervical plates when placed in-line at 0° and off-axis at 20°. The use of dynamic anterior cervical plating systems has recently gained popularity due to the theoretical benefit of improved load sharing with graft subsidence. Occasionally, due to anatomical restraints, the anterior cervical plate may be placed off-axis in the coronal plane. This may potentially decrease the dynamization capability of the plate, leading to less load sharing and potentially decreased fusion rates. The purpose of this study was to comprehensively evaluate the kinematic and load-sharing differences of a dynamic plate placed in-line versus off-axis in the coronal plane. Thirteen fresh-frozen human cadaveric cervical spines (C2-T1) were used. Nondestructive range-of-motion testing was performed with a pneumatically controlled spine simulator in flexion/extension, lateral bending, and axial rotation using the OptoTrak motion measurement system. A C5 corpectomy was performed, and a custom interbody spacer with an integrated load cell collected load-sharing data under axial compression at varying loads. A dynamic anterior cervical plate was placed in-line at 0° and then off-axis at 20°. Testing conditions ensued using a full-length spacer, followed by simulated subsidence by removing 10% of the height of the original spacer. There were no kinematic differences noted in the in-line model versus the off-axis model. After simulated subsidence, the small decreases in stiffness and increases in motion were similar whether the plate was placed in-line or off-axis in all 3 planes of motion. There were also no significant differences in the load-sharing characteristics of the in-line plate versus the off-axis plate in either the full-length model or the subsided interbody model. This study suggests that off-axis dynamic plate positioning does not significantly impact construct kinematics or graft load sharing. As such, we do not recommend removal or repositioning of an off-axis placed dynamic plate because the kinematic and load-sharing biomechanical properties are similar. N/A.

Dynamics modeling and periodic control of horizontal-axis wind turbines

NASA Astrophysics Data System (ADS)

Stol, Karl Alexander

2001-07-01

The development of large multi-megawatt wind turbines has increased the need for active feedback control to meet multiple performance objectives. Power regulation is still of prime concern but there is an increasing interest in mitigating loads for these very large, dynamically soft and highly integrated power systems. This work explores the opportunities for utilizing state space modeling, modal analysis, and multi-objective controllers in advanced horizontal-axis wind turbines. A linear state-space representation of a generic, multiple degree-of-freedom wind turbine is developed to test various control methods and paradigms. The structural model, SymDyn, provides for limited flexibility in the tower, drive train and blades assuming a rigid component architecture with joint springs and dampers. Equations of motion are derived symbolically, verified by numerical simulation, and implemented in the Matlab with Simulink computational environment. AeroDyn, an industry-standard aerodynamics package for wind turbines, provides the aerodynamic load data through interfaced subroutines. Linearization of the structural model produces state equations with periodic coefficients due to the interaction of rotating and non-rotating components. Floquet theory is used to extract the necessary modal properties and several parametric studies identify the damping levels and dominant dynamic coupling influences. Two separate issues of control design are investigated: full-state feedback and state estimation. Periodic gains are developed using time-varying LQR techniques and many different time-invariant control designs are constructed, including a classical PID controller. Disturbance accommodating control (DAC) allows the estimation of wind speed for minimization of the disturbance effects on the system. Controllers are tested in simulation for multiple objectives using measurement of rotor position and rotor speed only and actuation of independent blade pitch. It is found that periodic control is capable of reducing cyclic blade bending moments while regulating speed but that optimal performance requires additional sensor information. Periodic control is also the only design found that could successfully control the yaw alignment although blade loads are increased as a consequence. When speed regulation is the only performance objective then a time-invariant state-space design or PID is appropriate.

Effectiveness enhancement of a cycloidal wind turbine by individual active control of blade motion

NASA Astrophysics Data System (ADS)

Hwang, In Seong; Lee, Yun Han; Kim, Seung Jo

2007-04-01

In this paper, a research for the effectiveness enhancement of a Cycloidal Wind Turbine by individual active control of blade motion is described. To improve the performance of the power generation system, which consists of several straight blades rotating about axis in parallel direction, the cycloidal blade system and the individual active blade control method are adopted. It has advantages comparing with horizontal axis wind turbine or conventional vertical axis wind turbine because it maintains optimal blade pitch angles according to wind speed, wind direction and rotor rotating speed to produce high electric power at any conditions. It can do self-starting and shows good efficiency at low wind speed and complex wind condition. Optimal blade pitch angle paths are obtained through CFD analysis according to rotor rotating speed and wind speed. The individual rotor blade control system consists of sensors, actuators and microcontroller. To realize the actuating device, servo motors are installed to each rotor blade. Actuating speed and actuating force are calculated to compare with the capacities of servo motor, and some delays of blade pitch angles are corrected experimentally. Performance experiment is carried out by the wind blowing equipment and Labview system, and the rotor rotates from 50 to 100 rpm according to the electric load. From this research, it is concluded that developing new vertical axis wind turbine, Cycloidal Wind Turbine which is adopting individual active blade pitch control method can be a good model for small wind turbine in urban environment.

Attitude motion compensation for imager on Fengyun-4 geostationary meteorological satellite

NASA Astrophysics Data System (ADS)

Lyu, Wang; Dai, Shoulun; Dong, Yaohai; Shen, Yili; Song, Xiaozheng; Wang, Tianshu

2017-09-01

A compensation method is used in Chinese Fengyun-4 satellite to counteracting the line-of-sight influence by attitude motion during imaging. The method is acted on-board by adding the compensation amount to the instrument scanning control circuit. The mathematics simulation and the three-axis air-bearing test results show that the method works effectively.

Coordinated X-Y stage apparatus

DOEpatents

Morimoto, Alan K.; Kozlowski, David M.; Charles, Steven T.; Spalding, James A.

2000-01-01

An apparatus based on precision X-Y stages that are stacked. Attached to arms projecting from each X-Y stage are a set of two axis gimbals. Attached to the gimbals is a rod, which provides motion along the axis of the rod and rotation around its axis. A dual-planar apparatus that provides six degrees of freedom of motion precise to within microns of motion.

Lumbar joint torque estimation based on simplified motion measurement using multiple inertial sensors.

PubMed

Miyajima, Saori; Tanaka, Takayuki; Imamura, Yumeko; Kusaka, Takashi

2015-01-01

We estimate lumbar torque based on motion measurement using only three inertial sensors. First, human motion is measured by a 6-axis motion tracking device that combines a 3-axis accelerometer and a 3-axis gyroscope placed on the shank, thigh, and back. Next, the lumbar joint torque during the motion is estimated by kinematic musculoskeletal simulation. The conventional method for estimating joint torque uses full body motion data measured by an optical motion capture system. However, in this research, joint torque is estimated by using only three link angles of the body, thigh, and shank. The utility of our method was verified by experiments. We measured motion of bendung knee and waist simultaneously. As the result, we were able to estimate the lumbar joint torque from measured motion.

Tunable polarization plasma channel undulator for narrow bandwidth photon emission

DOE PAGES

Rykovanov, S. G.; Wang, J. W.; Kharin, V. Yu.; ...

2016-09-09

The theory of a plasma undulator excited by a short intense laser pulse in a parabolic plasma channel is presented. The undulator fields are generated either by the laser pulse incident off-axis and/or under the angle with respect to the channel axis. Linear plasma theory is used to derive the wakefield structure. It is shown that the electrons injected into the plasma wakefields experience betatron motion and undulator oscillations. Optimal electron beam injection conditions are derived for minimizing the amplitude of the betatron motion, producing narrow-bandwidth undulator radiation. Polarization control is readily achieved by varying the laser pulse injection conditions.

Research on Robot Pose Control Technology Based on Kinematics Analysis Model

NASA Astrophysics Data System (ADS)

Liu, Dalong; Xu, Lijuan

2018-01-01

In order to improve the attitude stability of the robot, proposes an attitude control method of robot based on kinematics analysis model, solve the robot walking posture transformation, grasping and controlling the motion planning problem of robot kinematics. In Cartesian space analytical model, using three axis accelerometer, magnetometer and the three axis gyroscope for the combination of attitude measurement, the gyroscope data from Calman filter, using the four element method for robot attitude angle, according to the centroid of the moving parts of the robot corresponding to obtain stability inertia parameters, using random sampling RRT motion planning method, accurate operation to any position control of space robot, to ensure the end effector along a prescribed trajectory the implementation of attitude control. The accurate positioning of the experiment is taken using MT-R robot as the research object, the test robot. The simulation results show that the proposed method has better robustness, and higher positioning accuracy, and it improves the reliability and safety of robot operation.

Analysis of cardiac interventricular septum motion in different respiratory states

NASA Astrophysics Data System (ADS)

Tautz, Lennart; Feng, Li; Otazo, Ricardo; Hennemuth, Anja; Axel, Leon

2016-03-01

The interaction between the left and right heart ventricles (LV and RV) depends on load and pressure conditions that are affected by cardiac contraction and respiration cycles. A novel MRI sequence, XD-GRASP, allows the acquisition of multi-dimensional, respiration-sorted and cardiac-synchronized free-breathing image data. In these data, effects of the cardiac and respiratory cycles on the LV/RV interaction can be observed independently. To enable the analysis of such data, we developed a semi-automatic exploration workflow. After tracking a cross-sectional line positioned over the heart, over all motion states, the septum and heart wall border locations are detected by analyzing the grey-value profile under the lines. These data are used to quantify septum motion, both in absolute units and as a fraction of the heart size, to compare values for different subjects. In addition to conventional visualization techniques, we used color maps for intuitive exploration of the variable values for this multi-dimensional data set. We acquired short-axis image data of nine healthy volunteers, to analyze the position and the motion of the interventricular septum in different breathing states and different cardiac cycle phases. The results indicate a consistent range of normal septum motion values, and also suggest that respiratory phase-dependent septum motion is greatest near end-diastolic phases. These new methods are a promising tool to assess LV/RV ventricle interaction and the effects of respiration on this interaction.

Multi-mode sliding mode control for precision linear stage based on fixed or floating stator.

PubMed

Fang, Jiwen; Long, Zhili; Wang, Michael Yu; Zhang, Lufan; Dai, Xufei

2016-02-01

This paper presents the control performance of a linear motion stage driven by Voice Coil Motor (VCM). Unlike the conventional VCM, the stator of this VCM is regulated, which means it can be adjusted as a floating-stator or fixed-stator. A Multi-Mode Sliding Mode Control (MMSMC), including a conventional Sliding Mode Control (SMC) and an Integral Sliding Mode Control (ISMC), is designed to control the linear motion stage. The control is switched between SMC and IMSC based on the error threshold. To eliminate the chattering, a smooth function is adopted instead of a signum function. The experimental results with the floating stator show that the positioning accuracy and tracking performance of the linear motion stage are improved with the MMSMC approach.

Design, Fabrication, and Modeling of a Novel Dual-Axis Control Input PZT Gyroscope.

PubMed

Chang, Cheng-Yang; Chen, Tsung-Lin

2017-10-31

Conventional gyroscopes are equipped with a single-axis control input, limiting their performance. Although researchers have proposed control algorithms with dual-axis control inputs to improve gyroscope performance, most have verified the control algorithms through numerical simulations because they lacked practical devices with dual-axis control inputs. The aim of this study was to design a piezoelectric gyroscope equipped with a dual-axis control input so that researchers may experimentally verify those control algorithms in future. Designing a piezoelectric gyroscope with a dual-axis control input is more difficult than designing a conventional gyroscope because the control input must be effective over a broad frequency range to compensate for imperfections, and the multiple mode shapes in flexural deformations complicate the relation between flexural deformation and the proof mass position. This study solved these problems by using a lead zirconate titanate (PZT) material, introducing additional electrodes for shielding, developing an optimal electrode pattern, and performing calibrations of undesired couplings. The results indicated that the fabricated device could be operated at 5.5±1 kHz to perform dual-axis actuations and position measurements. The calibration of the fabricated device was completed by system identifications of a new dynamic model including gyroscopic motions, electromechanical coupling, mechanical coupling, electrostatic coupling, and capacitive output impedance. Finally, without the assistance of control algorithms, the "open loop sensitivity" of the fabricated gyroscope was 1.82 μV/deg/s with a nonlinearity of 9.5% full-scale output. This sensitivity is comparable with those of other PZT gyroscopes with single-axis control inputs.

Dynamics and control of tethered antennas/reflectors in orbit

NASA Astrophysics Data System (ADS)

Liu, Liangdong; Bainum, Peter M.

The system linear equations for the motion of a tethered shallow spherical shell in orbit with its symmetry axis nominally following the local vertical are developed. The shell roll, yaw, tether out-of-plane swing motion and elastic vibrations are decoupled from the shell and tether in-plane pitch motions and elastic vibrations. The neutral gravity stability conditions for the special case of a constant length rigid tether are given for in-plane motion and out-of-plant motion. It is proved that the in-plane motion of the system could be asymptotically stable based on Rupp's tension control law, for a variable length tether. However, the system simulation results indicate that the transient responses can be improved significantly, especially for the damping of the tether and shell pitch motion, by an optimal feedback control law for the rigid variable length tether model. It is also seen that the system could be unstable when the effect of tether flexibility is included if the control gains are not chosen carefully. The transient responses for three different tension control laws are compared during typical station keeping operations.

An air-bearing weight offload system for ground test of heavy LSS structures

NASA Technical Reports Server (NTRS)

Rice, R. B.

1989-01-01

The capability and use of the Gravity Offload Facility (GOF) are discussed. Briefly explained are the: truss and base casting; carriage assembly; carriage weldment; vertical lift axis control; lifting cylinder; payload gimbal; motion base layout; and control processor.

FRIENDS OF HOT JUPITERS. II. NO CORRESPONDENCE BETWEEN HOT-JUPITER SPIN-ORBIT MISALIGNMENT AND THE INCIDENCE OF DIRECTLY IMAGED STELLAR COMPANIONS

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

Ngo, Henry; Knutson, Heather A.; Hinkley, Sasha

Multi-star systems are common, yet little is known about a stellar companion's influence on the formation and evolution of planetary systems. For instance, stellar companions may have facilitated the inward migration of hot Jupiters toward to their present day positions. Many observed short-period gas giant planets also have orbits that are misaligned with respect to their star's spin axis, which has also been attributed to the presence of a massive outer companion on a non-coplanar orbit. We present the results of a multi-band direct imaging survey using Keck NIRC2 to measure the fraction of short-period gas giant planets found inmore » multi-star systems. Over three years, we completed a survey of 50 targets ('Friends of Hot Jupiters') with 27 targets showing some signature of multi-body interaction (misaligned or eccentric orbits) and 23 targets in a control sample (well-aligned and circular orbits). We report the masses, projected separations, and confirmed common proper motion for the 19 stellar companions found around 17 stars. Correcting for survey incompleteness, we report companion fractions of 48% ± 9%, 47% ± 12%, and 51% ± 13% in our total, misaligned/eccentric, and control samples, respectively. This total stellar companion fraction is 2.8σ larger than the fraction of field stars with companions approximately 50-2000 AU. We observe no correlation between misaligned/eccentric hot Jupiter systems and the incidence of stellar companions. Combining this result with our previous radial velocity survey, we determine that 72% ± 16% of hot Jupiters are part of multi-planet and/or multi-star systems.« less

Evaluation of simulation motion fidelity criteria in the vertical and directional axes

NASA Technical Reports Server (NTRS)

Schroeder, Jeffery A.

1993-01-01

An evaluation of existing motion fidelity criteria was conducted on the NASA Ames Vertical Motion Simulator. Experienced test pilots flew single-axis repositioning tasks in both the vertical and the directional axes. Using a first-order approximation of a hovering helicopter, tasks were flown with variations only in the filters that attenuate the commands to the simulator motion system. These filters had second-order high-pass characteristics, and the variations were made in the filter gain and natural frequency. The variations spanned motion response characteristics from nearly full math-model motion to fixed-base. Between configurations, pilots recalibrated their motion response perception by flying the task with full motion. Pilots subjectively rated the motion fidelity of subsequent configurations relative to this full motion case, which was considered the standard for comparison. The results suggested that the existing vertical-axis criterion was accurate for combinations of gain and natural frequency changes. However, if only the gain or the natural frequency was changed, the rated motion fidelity was better than the criterion predicted. In the vertical axis, the objective and subjective results indicated that a larger gain reduction was tolerated than the existing criterion allowed. The limited data collected in the yaw axis revealed that pilots had difficulty in distinguishing among the variations in the pure yaw motion cues.

Rapid rotational/translational maneuvering experiments of a flexible steel beam

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Yang, Li-Farn; Huanag, Jen-Kuang; Macauley, Richard

1989-01-01

Future space manipulators may need translational base motion to expand the access region of a manipulator. An experiment was conducted to demonstrate slewing of flexible structures with coupled rotational and translational axes while simultaneously suppressing vibrational motion during the maneuver. In the experiment, a flexible steel beam carried by a translational cart was maneuvered by an active controller to perform position-control tasks. Experimental results are presented to show how the flexibility of the steel beam influences the multi-input multi-output feedback controller.

Coordination of multiple robot arms

NASA Technical Reports Server (NTRS)

Barker, L. K.; Soloway, D.

1987-01-01

Kinematic resolved-rate control from one robot arm is extended to the coordinated control of multiple robot arms in the movement of an object. The structure supports the general movement of one axis system (moving reference frame) with respect to another axis system (control reference frame) by one or more robot arms. The grippers of the robot arms do not have to be parallel or at any pre-disposed positions on the object. For multiarm control, the operator chooses the same moving and control reference frames for each of the robot arms. Consequently, each arm then moves as though it were carrying out the commanded motions by itself.

Single-axis gyroscopic motion with uncertain angular velocity about spin axis

NASA Technical Reports Server (NTRS)

Singh, S. N.

1977-01-01

A differential game approach is presented for studying the response of a gyro by treating the controlled angular velocity about the input axis as the evader, and the bounded but uncertain angular velocity about the spin axis as the pursuer. When the uncertain angular velocity about the spin axis desires to force the gyro to saturation a differential game problem with two terminal surfaces results, whereas when the evader desires to attain the equilibrium state the usual game with single terminal manifold arises. A barrier, delineating the capture zone (CZ) in which the gyro can attain saturation and the escape zone (EZ) in which the evader avoids saturation is obtained. The CZ is further delineated into two subregions such that the states in each subregion can be forced on a definite target manifold. The application of the game theoretic approach to Control Moment Gyro is briefly discussed.

Electron beam deflection control system of a welding and surface modification installation

NASA Astrophysics Data System (ADS)

Koleva, E.; Dzharov, V.; Gerasimov, V.; Tsvetkov, K.; Mladenov, G.

2018-03-01

In the present work, we examined the patterns of the electron beam motion when controlling the transverse with respect to the axis of the beam homogeneous magnetic field created by the coils of the deflection system the electron gun. During electron beam processes, the beam motion is determined the process type (welding, surface modification, etc.), the technological mode, the design dimensions of the electron gun and the shape of the processed samples. The electron beam motion is defined by the cumulative action of two cosine-like control signals generated by a functional generator. The signal control is related to changing the amplitudes, frequencies and phases (phase differences) of the generated voltages. We realized the motion control by applying a graphical user interface developed by us and an Arduino Uno programmable microcontroller. The signals generated were calibrated using experimental data from the available functional generator. The free and precise motion on arbitrary trajectories determines the possible applications of an electron beam process to carrying out various scientific research tasks in material processing.

Fused smart sensor network for multi-axis forward kinematics estimation in industrial robots.

PubMed

Rodriguez-Donate, Carlos; Osornio-Rios, Roque Alfredo; Rivera-Guillen, Jesus Rooney; Romero-Troncoso, Rene de Jesus

2011-01-01

Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint's angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot.

Undisturbed upright stance control in the elderly: Part 2. Postural-control impairments of elderly fallers.

PubMed

Berger, L; Chuzel, M; Buisson, G; Rougier, P

2005-09-01

A common way of predicting falling risks in elderly people can be to study center of pressure (CP) trajectories during undisturbed upright stance maintenance. By estimating the difference between CP and center of gravity (CG) motions (CP - CGv), one can estimate the neuromuscular activity. The results of this study, which included 34 sedentary elderly persons aged over 75 years (21 fallers and 13 nonfallers), demonstrated significantly increased CGh and CP - CGv motions in both axes for the fallers. In addition, the fallers presented larger CGh motions in the mediolateral axis, suggesting an enlarged loading-unloading mechanism, which could have reflected the adoption of a step-initiating strategy. As highlighted by fractional Brownian motion modeling, the distance covered by the CP - CGv motions before the successive control mechanisms switched was enhanced for the fallers in both axes, therefore increasing the risk that the CG would be outside of the base of support.

Progress in geophysical aspects of the rotation of the earth

NASA Technical Reports Server (NTRS)

Lambeck, K.

1978-01-01

The geophysical causes and consequences of the Earth's rotation are reviewed. Specific topics covered include: (1) the motion of the rotation axis in space, precession and nutation; (2) the motion of the rotation axis relative to the Earth, polar motion; and (3) the rate of rotation about this axis, or changes in the length of day. Secular decrease in obliquity and evolution of the Earth-Moon system are also discussed.

Rotorcraft flight control design using quantitative feedback theory and dynamic crossfeeds

NASA Technical Reports Server (NTRS)

Cheng, Rendy P.

1995-01-01

A multi-input, multi-output controls design with robust crossfeeds is presented for a rotorcraft in near-hovering flight using quantitative feedback theory (QFT). Decoupling criteria are developed for dynamic crossfeed design and implementation. Frequency dependent performance metrics focusing on piloted flight are developed and tested on 23 flight configurations. The metrics show that the resulting design is superior to alternative control system designs using conventional fixed-gain crossfeeds and to feedback-only designs which rely on high gains to suppress undesired off-axis responses. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets current handling qualities specifications relative to the decoupling of off-axis responses. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensator successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective.

Multi-level manual and autonomous control superposition for intelligent telerobot

NASA Technical Reports Server (NTRS)

Hirai, Shigeoki; Sato, T.

1989-01-01

Space telerobots are recognized to require cooperation with human operators in various ways. Multi-level manual and autonomous control superposition in telerobot task execution is described. The object model, the structured master-slave manipulation system, and the motion understanding system are proposed to realize the concept. The object model offers interfaces for task level and object level human intervention. The structured master-slave manipulation system offers interfaces for motion level human intervention. The motion understanding system maintains the consistency of the knowledge through all the levels which supports the robot autonomy while accepting the human intervention. The superposing execution of the teleoperational task at multi-levels realizes intuitive and robust task execution for wide variety of objects and in changeful environment. The performance of several examples of operating chemical apparatuses is shown.

Adaptive Multi-Layer LMS Controller Design and Application to Active Vibration Suppression on a Truss and Proposed Impact Analysis Technique

DTIC Science & Technology

2001-06-01

Setup and Initiation ........................................................ 83 2. Simulation 1 (19 Hz, Y-axis of Node 18, Piezo #2...175 INITIAL DISTRIBUTION LIST ................................................................................... 187 ix...system for the sake of testing and simplicity. The Adaptive Multi-Layered LMS Controller was developed one piece at a time. After initial experimental

Large Angle Reorientation of a Solar Sail Using Gimballed Mass Control

NASA Astrophysics Data System (ADS)

Sperber, E.; Fu, B.; Eke, F. O.

2016-06-01

This paper proposes a control strategy for the large angle reorientation of a solar sail equipped with a gimballed mass. The algorithm consists of a first stage that manipulates the gimbal angle in order to minimize the attitude error about a single principal axis. Once certain termination conditions are reached, a regulator is employed that selects a single gimbal angle for minimizing both the residual attitude error concomitantly with the body rate. Because the force due to the specular reflection of radiation is always directed along a reflector's surface normal, this form of thrust vector control cannot generate torques about an axis normal to the plane of the sail. Thus, in order to achieve three-axis control authority a 1-2-1 or 2-1-2 sequence of rotations about principal axes is performed. The control algorithm is implemented directly in-line with the nonlinear equations of motion and key performance characteristics are identified.

Lumbar Facet Joint Motion in Patients with Degenerative Disc Disease at Affected and Adjacent Levels

PubMed Central

Li, Weishi; Wang, Shaobai; Xia, Qun; Passias, Peter; Kozanek, Michal; Wood, Kirkham; Li, Guoan

2013-01-01

Study Design Controlled laboratory study. Objective To evaluate the effect of lumbar degenerative disc diseases (DDDs) on motion of the facet joints during functional weight-bearing activities. Summary of Background Data It has been suggested that DDD adversely affects the biomechanical behavior of the facet joints. Altered facet joint motion, in turn, has been thought to associate with various types of lumbar spine pathology including facet degeneration, neural impingement, and DDD progression. However, to date, no data have been reported on the motion patterns of the lumbar facet joint in DDD patients. Methods Ten symptomatic patients of DDD at L4–S1 were studied. Each participant underwent magnetic resonance images to obtain three-dimensional models of the lumbar vertebrae (L2–S1) and dual fluoroscopic imaging during three characteristic trunk motions: left-right torsion, left-right bending, and flexion-extension. In vivo positions of the vertebrae were reproduced by matching the three-dimensional models of the vertebrae to their outlines on the fluoroscopic images. The kinematics of the facet joints and the ranges of motion (ROMs) were compared with a group of healthy participants reported in a previous study. Results In facet joints of the DDD patients, there was no predominant axis of rotation and no difference in ROMs was found between the different levels. During left-right torsion, the ROMs were similar between the DDD patients and the healthy participants. During left-right bending, the rotation around mediolateral axis at L4–L5, in the DDD patients, was significantly larger than that of the healthy participants. During flexion-extension, the rotations around anterioposterior axis at L4–L5 and around craniocaudal axis at the adjacent level (L3–L4), in the DDD patients, were also significantly larger, whereas the rotation around mediolateral axis at both L2–L3 and L3–L4 levels in the DDD patients were significantly smaller than those of the healthy participants. Conclusion DDD alters the ROMs of the facet joints. The rotations can increase significantly not only at the DDD levels but also at their adjacent levels when compared to those of the healthy participants. The increase in rotations did not occur around the primary rotation axis of the torso motion but around the coupled axes. This hypermobility in coupled rotations might imply a biomechanical mechanism related to DDD. PMID:21270686

A Foundation for Systems Anthropometry.

DTIC Science & Technology

1980-12-31

List of Tables Table Page 1 Screw Axis Analysis for Hip Motion 12 2 Screw Axis Analysis for Sacroiliac Motion 12 𔃾 S, 1.0 Introduction The application...Following are two examples: 1) a sample of living subjects seated in a hard-seat and 2) the hip and sacroiliac kinematics of one unembalmed cadaver. In...axes for relative motion at the hip and sacroiliac joints. Each of the three bones was targeted with three pointmarks and an axis system calculated

Periodic motions of generalized conservative mechanical systems whose equations of motion contain a large parameter

NASA Astrophysics Data System (ADS)

Sazonov, V. V.

An analysis is made of a generalized conservative mechanical system whose equations of motion contain a large parameter characterizing local forces acting along certain generalized coordinates. It is shown that the equations have periodic solutions which are close to periodic solutions to the corresponding degenerate equations. As an example, the periodic motions of a satellite with respect to its center of mass due to gravitational and restoring aerodynamic moments are examined for the case where the aerodynamic moment is much larger than the gravitational moment. Such motions can be treated as nominal unperturbed motions of a satellite under conditions of single-axis aerodynamic attitude control.

Pilot Jerrie Cobb Trains in the Multi-Axis Space Test Inertia Facility

NASA Image and Video Library

1960-04-21

Jerrie Cobb prepares to operate the Multi-Axis Space Test Inertia Facility (MASTIF) inside the Altitude Wind Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. The MASTIF was a three-axis rig with a pilot’s chair mounted in the center to train Project Mercury pilots to bring a spinning spacecraft under control. An astronaut was secured in a foam couch in the center of the rig. The rig was then spun on three axes from 2 to 50 rotations per minute. The pilots were tested on each of the three axis individually, then all three simultaneously. The two controllers in Cobb’s hands activated the small nitrogen gas thrusters that were used to bring the MASTIF under control. A makeshift spacecraft control panel was set up in front of the trainee’s face. Cobb was one of several female pilots who underwent the skill and endurance testing that paralleled that of the Project Mercury astronauts. In 1961 Jerrie Cobb was the first female to pass all three phases of the Mercury Astronaut Program. NASA rules, however, stipulated that only military test pilots could become astronauts and there were no female military test pilots. The seven Mercury astronauts had taken their turns on the MASTIF in February and March 1960.

A passively controlled appendage deployment system for the San Marco D/L spacecraft

NASA Technical Reports Server (NTRS)

Lang, W. E.; Frisch, H. P.; Schwartz, D. A.

1984-01-01

The analytical simulation of deployment dynamics of these two axis concepts as well as the evolution of practical designs for the add on deployable inertia boom units is described. With the boom free to swing back in response to Coriolis forces as well as outwards in response to centrifugal forces, the kinematics of motion are complex but admit the possibility of absorbing deployment energy in frictional or other damping devices about the radial axis, where large amplitude motions can occur and where the design envelope allows more available volume. An acceptable range is defined for frictional damping for any given spin rate. Inadequate damping allows boom motions which strike the spacecraft; excessive damping causes the boom to swing out and latch with damaging violence. The acceptable range is a design parameter and must accommodate spin rate tolerance and also the tolerance and repeatability of the damping mechanisms.

Multi-type Tectonic Responses to Plate Motion Changes of Mega-Offset Transform Faults at the Pacific-Antarctic Ridge

NASA Astrophysics Data System (ADS)

Zhang, F.; Lin, J.; Yang, H.; Zhou, Z.

2017-12-01

Magmatic and tectonic responses of a mid-ocean ridge system to plate motion changes can provide important constraints on the mechanisms of ridge-transform interaction and lithospheric properties. Here we present new analysis of multi-type responses of the mega-offset transform faults at the Pacific-Antarctic Ridge (PAR) system to plate motion changes in the last 12 Ma. Detailed analysis of the Heezen, Tharp, and Udintsev transform faults showed that the extensional stresses induced by plate motion changes could have been released through a combination of magmatic and tectonic processes: (1) For a number of ridge segments with abundant magma supply, plate motion changes might have caused the lateral transport of magma along the ridge axis and into the abutting transform valley, forming curved "hook" ridges at the ridge-transform intersection. (2) Plate motion changes might also have caused vertical deformation on steeply-dipping transtensional faults that were developed along the Heezen, Tharp, and Udintsev transform faults. (3) Distinct zones of intensive tectonic deformation, resembling belts of "rift zones", were found to be sub-parallel to the investigated transform faults. These rift-like deformation zones were hypothesized to have developed when the stresses required to drive the vertical deformation on the steeply-dipping transtensional faults along the transform faults becomes excessive, and thus deformation on off-transform "rift zones" became favored. (4) However, to explain the observed large offsets on the steeply-dipping transtensional faults, the transform faults must be relatively weak with low apparent friction coefficient comparing to the adjacent lithospheric plates.

Ion trajectory simulations of axial ac dipolar excitation in the Orbitrap

NASA Astrophysics Data System (ADS)

Wu, Guangxiang; Noll, Robert J.; Plass, Wolfgang R.; Hu, Qizhi; Perry, Richard H.; Cooks, R. Graham

2006-07-01

The newly developed version of the multi-particle ion trajectory simulation program, ITSIM 6.0, was applied to simulate ac dipolar excitation of ion axial motion in the Orbitrap. The Orbitrap inner and outer electrodes were generated in AutoCAD, a 3D drawing program. The electrode geometry was imported into the 3D field solver COMSOL; the field array was then imported into ITSIM 6.0. Ion trajectories were calculated by solving Newton's equations using Runge-Kutta integration methods. Compared to the analytical solution, calculated radial components of the field at the device's "equator" (z = 0) were within 0.5% and calculated axial components midway between the inner and outer electrodes were within 0.2%. The experiments simulated here involved the control of axial motion of ions in the Orbitrap by the application of dipolar ac signals to the split outer electrodes, as described in a recently published paper from this laboratory [Hu et al., J. Phys. Chem. A 110 (2006) 2682]. In these experiments, ac signal was applied at the axial resonant frequency of a selected ion. Axial excitation and eventual ion ejection resulted when the ac was in phase with, i.e., had 0° phase relative to ion axial motion. De-excitation of ion axial motion until the ions were at z = 0 and at rest with respect to the z-axis resulted if the applied ac was out of phase with ion motion, with re-excitation of ion axial motion occurring if the dipolar ac was continued beyond this point. Both de-excitation and re-excitation could be achieved mass-selectively and depended on the amplitude and duration (number of cycles) of the applied ac. The effects of ac amplitude, frequency, phase relative to ion motion, and bandwidth of applied waveform were simulated. All simulation results were compared directly with the experimental data and good agreement was observed. Such ion motion control experiments and their simulation provide the possibility to improve Orbitrap performance and to develop tandem mass spectrometry (MS/MS) capabilities inside the Orbitrap.

High frequency, multi-axis dynamic stiffness analysis of a fractionally damped elastomeric isolator using continuous system theory

NASA Astrophysics Data System (ADS)

Fredette, Luke; Singh, Rajendra

2017-02-01

A spectral element approach is proposed to determine the multi-axis dynamic stiffness terms of elastomeric isolators with fractional damping over a broad range of frequencies. The dynamic properties of a class of cylindrical isolators are modeled by using the continuous system theory in terms of homogeneous rods or Timoshenko beams. The transfer matrix type dynamic stiffness expressions are developed from exact harmonic solutions given translational or rotational displacement excitations. Broadband dynamic stiffness magnitudes (say up to 5 kHz) are computationally verified for axial, torsional, shear, flexural, and coupled stiffness terms using a finite element model. Some discrepancies are found between finite element and spectral element models for the axial and flexural motions, illustrating certain limitations of each method. Experimental validation is provided for an isolator with two cylindrical elements (that work primarily in the shear mode) using dynamic measurements, as reported in the prior literature, up to 600 Hz. Superiority of the fractional damping formulation over structural or viscous damping models is illustrated via experimental validation. Finally, the strengths and limitations of the spectral element approach are briefly discussed.

Sensor Data Fusion for Body State Estimation in a Bipedal Robot and Its Feedback Control Application for Stable Walking

PubMed Central

Chen, Ching-Pei; Chen, Jing-Yi; Huang, Chun-Kai; Lu, Jau-Ching; Lin, Pei-Chun

2015-01-01

We report on a sensor data fusion algorithm via an extended Kalman filter for estimating the spatial motion of a bipedal robot. Through fusing the sensory information from joint encoders, a 6-axis inertial measurement unit and a 2-axis inclinometer, the robot’s body state at a specific fixed position can be yielded. This position is also equal to the CoM when the robot is in the standing posture suggested by the detailed CAD model of the robot. In addition, this body state is further utilized to provide sensory information for feedback control on a bipedal robot with walking gait. The overall control strategy includes the proposed body state estimator as well as the damping controller, which regulates the body position state of the robot in real-time based on instant and historical position tracking errors. Moreover, a posture corrector for reducing unwanted torque during motion is addressed. The body state estimator and the feedback control structure are implemented in a child-size bipedal robot and the performance is experimentally evaluated. PMID:25734644

Relation of motion sickness susceptibility to vestibular and behavioral measures of orientation

NASA Technical Reports Server (NTRS)

Peterka, Robert J.

1994-01-01

The objective of this proposal is to determine the relationship of motion sickness susceptibility to vestibulo-ocular reflexes (VOR), motion perception, and behavioral utilization of sensory orientation cues for the control of postural equilibrium. The work is focused on reflexes and motion perception associated with pitch and roll movements that stimulate the vertical semicircular canals and otolith organs of the inner ear. This work is relevant to the space motion sickness problem since 0 g related sensory conflicts between vertical canal and otolith motion cues are a likely cause of space motion sickness. Results of experimentation are summarized and modifications to a two-axis rotation device are described. Abstracts of a number of papers generated during the reporting period are appended.

The dynamics and control of large flexible asymmetric spacecraft

NASA Astrophysics Data System (ADS)

Humphries, T. T.

1991-02-01

This thesis develops the equations of motion for a large flexible asymmetric Earth observation satellite and finds the characteristics of its motion under the influence of control forces. The mathematical model of the structure is produced using analytical methods. The equations of motion are formed using an expanded momentum technique which accounts for translational motion of the spacecraft hub and employs orthogonality relations between appendage and vehicle modes. The controllability and observability conditions of the full spacecraft motions using force and torque actuators are defined. A three axis reaction wheel control system is implemented for both slewing the spacecraft and controlling its resulting motions. From minor slew results it is shown that the lowest frequency elastic mode of the spacecraft is more important than higher frequency modes, when considering the effects of elastic motion on instrument pointing from the hub. Minor slews of the spacecraft configurations considered produce elastic deflections resulting in rotational attitude motions large enough to contravene pointing accuracy requirements of instruments aboard the spacecraft hub. Active vibration damping is required to reduce these hub motions to acceptable bounds in sufficiently small time. A comparison between hub mounted collocated and hub/appendage mounted non-collocated control systems verifies that provided the non-collocated system is stable, it can more effectively damp elastic modes whilst maintaining adequate damping of rigid modes. Analysis undertaken shows that the reaction wheel controller could be replaced by a thruster control system which decouples the modes of the spacecraft motion, enabling them to be individually damped.

Error-compensation model for simultaneous measurement of five degrees of freedom motion errors of a rotary axis

NASA Astrophysics Data System (ADS)

Bao, Chuanchen; Li, Jiakun; Feng, Qibo; Zhang, Bin

2018-07-01

This paper introduces an error-compensation model for our measurement method to measure five motion errors of a rotary axis based on fibre laser collimation. The error-compensation model is established in a matrix form using the homogeneous coordinate transformation theory. The influences of the installation errors, error crosstalk, and manufacturing errors are analysed. The model is verified by both ZEMAX simulation and measurement experiments. The repeatability values of the radial and axial motion errors are significantly suppressed by more than 50% after compensation. The repeatability experiments of five degrees of freedom motion errors and the comparison experiments of two degrees of freedom motion errors of an indexing table were performed by our measuring device and a standard instrument. The results show that the repeatability values of the angular positioning error ε z and tilt motion error around the Y axis ε y are 1.2″ and 4.4″, and the comparison deviations of the two motion errors are 4.0″ and 4.4″, respectively. The repeatability values of the radial and axial motion errors, δ y and δ z , are 1.3 and 0.6 µm, respectively. The repeatability value of the tilt motion error around the X axis ε x is 3.8″.

Motion-base simulator results of advanced supersonic transport handling qualities with active controls

NASA Technical Reports Server (NTRS)

Feather, J. B.; Joshi, D. S.

1981-01-01

Handling qualities of the unaugmented advanced supersonic transport (AST) are deficient in the low-speed, landing approach regime. Consequently, improvement in handling with active control augmentation systems has been achieved using implicit model-following techniques. Extensive fixed-based simulator evaluations were used to validate these systems prior to tests with full motion and visual capabilities on a six-axis motion-base simulator (MBS). These tests compared the handling qualities of the unaugmented AST with several augmented configurations to ascertain the effectiveness of these systems. Cooper-Harper ratings, tracking errors, and control activity data from the MBS tests have been analyzed statistically. The results show the fully augmented AST handling qualities have been improved to an acceptable level.

Kinematics of Hooke universal joint robot wrists

NASA Technical Reports Server (NTRS)

Mckinney, William S., Jr.

1988-01-01

The singularity problem associated with wrist mechanisms commonly found on industrial manipulators can be alleviated by redesigning the wrist so that it functions as a three-axis gimbal system. This paper discussess the kinematics of gimbal robot wrists made of one and two Hooke universal joints. Derivations of the resolved rate motion control equations for the single and double Hooke universal joint wrists are presented using the three-axis gimbal system as a theoretical wrist model.

A movable mass control system to detumble a disabled space vehicle

NASA Technical Reports Server (NTRS)

Edwards, T. L.

1973-01-01

An internal autonomous control system to either completely detumble a spacecraft or lessen the tumbling motions until the rescue craft arrives is discussed. Such a device would become active upon loss of control. The development of a movable mass control system to convert the tumbling motions of a disabled vehicle into simple spin is presented. A simple spin state would greatly facilitate crew evacuation and final despinning by an external means. The system moves a control mass, according to a selected control law, in the acceleration environment created by the tumbling motion. By moving the mass properly, the rotational kinetic energy of the system may be increased or decreased creating simple spin states about the minimum or maximum moment of inertia axis, respectively. The control system is designed for the latter case due to its associated stability in the presence of perturbing forces.

Steerable vertical to horizontal energy transducer for mobile robots

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Feddema, John T.

2001-01-01

The present invention provides a steerable vertical to horizontal energy transducer for mobile robots that less complex and requires less power than two degree of freedom tilt mechanisms. The present invention comprises an end effector that, when mounted with a hopping actuator, translates along axis (typically vertical) actuation into combined vertical and horizontal motion. The end effector, or foot, mounts with an end of the actuator that moves toward the support surface (typically a floor or the earth). The foot is shaped so that the first contact with the support surface is off the axis of the actuator. Off-axis contact with the support surface generates an on-axis force (typically resulting in vertical motion) and a moment orthogonal to the axis. The moment initiates a horizontal tumbling motion, and tilts the actuator so that its axis is oriented with a horizontal component and continued actuation generates both vertical and horizontal force.

Periodic-disturbance accommodating control of the space station for asymptotic momentum management

NASA Technical Reports Server (NTRS)

Warren, Wayne; Wie, Bong

1989-01-01

Periodic maneuvering control is developed for asymptotic momentum management of control gyros used as primary actuating devices for the Space Station. The proposed controller utilizes the concepts of quaternion feedback control and periodic-disturbance accommodation to achieve oscillations about the constant torque equilibrium attitude, while minimizing the control effort required. Three-axis coupled equations of motion, written in terms of quaternions, are derived for roll/yaw controller design and stability analysis. It is shown that the quaternion feedback controller is very robust for a wide range of pitch angles. It is also shown that the proposed controller tunes the open-loop unstable vehicle to a stable oscillatory motion which minimizes the control effort needed for steady-state operations.

Interlimb Differences in Coordination of Unsupported Reaching Movements

PubMed Central

Schaffer, Jacob E.; Sainburg, Robert L.

2017-01-01

Previous research suggests that interlimb differences in coordination associated with handedness might result from specialized control mechanisms that are subserved by different cerebral hemispheres. Based largely on the results of horizontal plane reaching studies, we have proposed that the hemisphere contralateral to the dominant arm is specialized for predictive control of limb dynamics, while the non-dominant hemisphere is specialized for controlling limb impedance. The current study explores interlimb differences in control of 3-D unsupported reaching movements. While the task was presented in the horizontal plane, participant’s arms were unsupported and free to move within a range of the vertical axis, which was redundant to the task plane. Results indicated significant dominant arm advantages for both initial direction accuracy and final position accuracy. The dominant arm showed greater excursion along a redundant axis that was perpendicular to the task, and parallel to gravitational forces. In contrast, the non-dominant arm better impeded motion out of the task-plane. Nevertheless, left arm task errors varied substantially more with shoulder rotation excursion than did dominant arm task errors. These findings suggest that the dominant arm controller was able to take advantage of the redundant degrees of freedom of the task, while non-dominant task errors appeared enslaved to motion along the redundant axis. These findings are consistent with a dominant controller that is specialized for intersegmental coordination, and a non-dominant controller that is specialized for impedance control. However, the findings are inconsistent with previously documented conclusions from planar tasks, in which non-dominant control leads to greater final position accuracy. PMID:28344068

Atomic force microscopy capable of vibration isolation with low-stiffness Z-axis actuation.

PubMed

Ito, Shingo; Schitter, Georg

2018-03-01

For high-resolution imaging without bulky external vibration isolation, this paper presents an atomic force microscope (AFM) capable of vibration isolation with its internal Z-axis (vertical) actuators moving the AFM probe. Lorentz actuators (voice coil actuators) are used for the Z-axis actuation, and flexures guiding the motion are designed to have a low stiffness between the mover and the base. The low stiffness enables a large Z-axis actuation of more than 700 µm and mechanically isolates the probe from floor vibrations at high frequencies. To reject the residual vibrations, the probe tracks the sample by using a displacement sensor for feedback control. Unlike conventional AFMs, the Z-axis actuation attains a closed-loop control bandwidth that is 35 times higher than the first mechanical resonant frequency. The closed-loop AFM system has robustness against the flexures' nonlinearity and uses the first resonance for better sample tracking. For further improvement, feedforward control with a vibration sensor is combined, and the resulting system rejects 98.4% of vibrations by turning on the controllers. The AFM system is demonstrated by successful AFM imaging in a vibrational environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Transverse beam motion on the second axis of the dual axis radiographic hydrodynamic test facility

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

Caporaso, G J; Chen, Y J; Fawley, W M

1999-03-23

The accelerator on the second-axis of the Dual-Axis Radiographic Hydrodynamic Test (DARHT-II) facility will generate a 20 MeV, 2-4 kA, 2 µs long electron beam with an energy variation {<=} ± 0.5%. Four short current pulses with various lengths will be selected out of this 2 µs long current pulse and delivered to an x-ray converter target. The DARHT-II radiographic resolution requires these electron pulses to be focused to sub-millimeter spots on Bremsstrahlung targets with peak-to-peak transverse beam motion less than a few hundred microns. We have modeled the transverse beam motion, including the beam breakup instability, corkscrew motion, transversemore » resistive wall instability and beam induced transverse deflection in the kicker system, from the DARHT-II injector exit to the x-ray converter target. Simulations show that the transverse motion at the x-ray converters satisfies the DARHT-II radiographic requirements.« less

Dual-Arm Generalized Compliant Motion With Shared Control

NASA Technical Reports Server (NTRS)

Backes, Paul G.

1994-01-01

Dual-Arm Generalized Compliant Motion (DAGCM) primitive computer program implementing improved unified control scheme for two manipulator arms cooperating in task in which both grasp same object. Provides capabilities for autonomous, teleoperation, and shared control of two robot arms. Unifies cooperative dual-arm control with multi-sensor-based task control and makes complete task-control capability available to higher-level task-planning computer system via large set of input parameters used to describe desired force and position trajectories followed by manipulator arms. Some concepts discussed in "A Generalized-Compliant-Motion Primitive" (NPO-18134).

Machine imparting complex rotary motion for lapping a spherical inner diameter

DOEpatents

Carroll, Thomas A.; Yetter, Harold H.

1986-01-01

An apparatus for imparting complex rotary motion is used to lap an inner spherical diameter surface of a workpiece. A lapping tool consists of a dome and rod mounted along the dome's vertical axis. The workpiece containing the lapping tool is held in a gimbal which uses power derived from a secondary takeoff means to impart rotary motion about a horizontal axis. The gimbal is rotated about a vertical axis by a take means while mounted at a radially outward position on a rotating arm.

Machine imparting complex rotary motion for lapping a spherical inner diameter

DOEpatents

Carroll, T.A.; Yetter, H.H.

1985-01-30

An apparatus for imparting complex rotary motion is used to lap an inner spherical diameter surface of a workpiece. A lapping tool consists of a dome and rod mounted along the dome's vertical axis. The workpiece containing the lapping tool is held in a gimbal which uses power derived from a secondary takeoff means to impart rotary motion about a horizontal axis. The gimbal is rotated about a vertical axis by a take means while mounted at a radially outward position on a rotating arm.

Controls design with crossfeeds for hovering rotorcraft using quantitative feedback theory

NASA Technical Reports Server (NTRS)

Tischler, Mark B.; Biezad, Daniel J.; Cheng, Rendy

1996-01-01

A multi-input, multi-output controls design with dynamic crossfeed pre-compensation is presented for rotorcraft in near-hovering flight using Quantitative Feedback Theory (QFT). The resulting closed-loop control system bandwidth allows the rotorcraft to be considered for use as an inflight simulator. The use of dynamic, robust crossfeeds prior to the QFT design reduces the magnitude of required feedback gain and results in performance that meets most handling qualities specifications relative to the decoupling of off-axis responses. Handling qualities are Level 1 for both low-gain tasks and high-gain tasks in the roll, pitch, and yaw axes except for the 10 deg/sec moderate-amplitude yaw command where the rotorcraft exhibits Level 2 handling qualities in the yaw axis caused by phase lag. The combined effect of the QFT feedback design following the implementation of low-order, dynamic crossfeed compensators successfully decouples ten of twelve off-axis channels. For the other two channels it was not possible to find a single, low-order crossfeed that was effective. This is an area to be investigated in future research.

The Mechanism for Processing Random-Dot Motion at Various Speeds in Early Visual Cortices

PubMed Central

An, Xu; Gong, Hongliang; McLoughlin, Niall; Yang, Yupeng; Wang, Wei

2014-01-01

All moving objects generate sequential retinotopic activations representing a series of discrete locations in space and time (motion trajectory). How direction-selective neurons in mammalian early visual cortices process motion trajectory remains to be clarified. Using single-cell recording and optical imaging of intrinsic signals along with mathematical simulation, we studied response properties of cat visual areas 17 and 18 to random dots moving at various speeds. We found that, the motion trajectory at low speed was encoded primarily as a direction signal by groups of neurons preferring that motion direction. Above certain transition speeds, the motion trajectory is perceived as a spatial orientation representing the motion axis of the moving dots. In both areas studied, above these speeds, other groups of direction-selective neurons with perpendicular direction preferences were activated to encode the motion trajectory as motion-axis information. This applied to both simple and complex neurons. The average transition speed for switching between encoding motion direction and axis was about 31°/s in area 18 and 15°/s in area 17. A spatio-temporal energy model predicted the transition speeds accurately in both areas, but not the direction-selective indexes to random-dot stimuli in area 18. In addition, above transition speeds, the change of direction preferences of population responses recorded by optical imaging can be revealed using vector maximum but not vector summation method. Together, this combined processing of motion direction and axis by neurons with orthogonal direction preferences associated with speed may serve as a common principle of early visual motion processing. PMID:24682033

Wrist joint assembly

NASA Technical Reports Server (NTRS)

Kersten, L.; Johnson, J. D. (Inventor)

1978-01-01

A wrist joint assembly is provided for use with a mechanical manipulator arm for finely positioning an end-effector carried by the wrist joint on the terminal end of the manipulator arm. The wrist joint assembly is pivotable about a first axis to produce a yaw motion, a second axis is to produce a pitch motion, and a third axis to produce a roll motion. The wrist joint assembly includes a disk segment affixed to the terminal end of the manipulator arm and a first housing member, a second housing member, and a third housing member. The third housing member and the mechanical end-effector are moved in the yaw, pitch, and roll motion. Drive means are provided for rotating each of the housings about their respective axis which includes a cluster of miniature motors having spur gears carried on the output drive shaft which mesh with a center drive gear affixed on the housing to be rotated.

Motion perception during variable-radius swing motion in darkness.

PubMed

Rader, A A; Oman, C M; Merfeld, D M

2009-10-01

Using a variable-radius roll swing motion paradigm, we examined the influence of interaural (y-axis) and dorsoventral (z-axis) force modulation on perceived tilt and translation by measuring perception of horizontal translation, roll tilt, and distance from center of rotation (radius) at 0.45 and 0.8 Hz using standard magnitude estimation techniques (primarily verbal reports) in darkness. Results show that motion perception was significantly influenced by both y- and z-axis forces. During constant radius trials, subjects' perceptions of tilt and translation were generally almost veridical. By selectively pairing radius (1.22 and 0.38 m) and frequency (0.45 and 0.8 Hz, respectively), the y-axis acceleration could be tailored in opposition to gravity so that the combined y-axis gravitoinertial force (GIF) variation at the subject's ears was reduced to approximately 0.035 m/s(2) - in effect, the y-axis GIF was "nulled" below putative perceptual threshold levels. With y-axis force nulling, subjects overestimated their tilt angle and underestimated their horizontal translation and radius. For some y-axis nulling trials, a radial linear acceleration at twice the tilt frequency (0.25 m/s(2) at 0.9 Hz, 0.13 m/s(2) at 1.6 Hz) was simultaneously applied to reduce the z-axis force variations caused by centripetal acceleration and by changes in the z-axis component of gravity during tilt. For other trials, the phase of this radial linear acceleration was altered to double the magnitude of the z-axis force variations. z-axis force nulling further increased the perceived tilt angle and further decreased perceived horizontal translation and radius relative to the y-axis nulling trials, while z-axis force doubling had the opposite effect. Subject reports were remarkably geometrically consistent; an observer model-based analysis suggests that perception was influenced by knowledge of swing geometry.

Improved motor control method with measurements of fiber optics gyro (FOG) for dual-axis rotational inertial navigation system (RINS).

PubMed

Song, Tianxiao; Wang, Xueyun; Liang, Wenwei; Xing, Li

2018-05-14

Benefiting from frame structure, RINS can improve the navigation accuracy by modulating the inertial sensor errors with proper rotation scheme. In the traditional motor control method, the measurements of the photoelectric encoder are always adopted to drive inertial measurement unit (IMU) to rotate. However, when carrier conducts heading motion, the inertial sensor errors may no longer be zero-mean in navigation coordinate. Meanwhile, some high-speed carriers like aircraft need to roll a certain angle to balance the centrifugal force during the heading motion, which may result in non-negligible coupling errors, caused by the FOG installation errors and scale factor errors. Moreover, the error parameters of FOG are susceptible to the temperature and magnetic field, and the pre-calibration is a time-consuming process which is difficult to completely suppress the FOG-related errors. In this paper, an improved motor control method with the measurements of FOG is proposed to address these problems, with which the outer frame can insulate the carrier's roll motion and the inner frame can simultaneously achieve the rotary modulation on the basis of insulating the heading motion. The results of turntable experiments indicate that the navigation performance of dual-axis RINS has been significantly improved over the traditional method, which could still be maintained even with large FOG installation errors and scale factor errors, proving that the proposed method can relax the requirements for the accuracy of FOG-related errors.

Non-destructive evaluation means and method of flaw reconstruction utilizing an ultrasonic multi-viewing transducer data acquistion system

DOEpatents

Thompson, Donald O.; Wormley, Samuel J.

1989-03-28

A multi-viewing ultrasound transducer acquisition system for non-destructive evaluation, flaw detection and flaw reconstruction in materials. A multiple transducer assembly includes a central transducer surrounded by a plurality of perimeter transducers, each perimeter transducer having an axis of transmission which can be angularly oriented with respect to the axis of transmission of the central transducer to intersect the axis of transmission of the central transducer. A control apparatus automatically and remotely positions the transducer assembly with respect to the material by a positioning apparatus and adjusts the pe GRANT REFERENCE This invention was conceived and reduced to practice at least in part under a grant from the Department of Energy under Contract No. W-7407-ENG-82.

Regional myocardial velocity imaged by magnetic resonance in patients with ischaemic heart disease.

PubMed Central

Karwatowski, S P; Mohiaddin, R H; Yang, G Z; Firmin, D N; St John Sutton, M; Underwood, S R

1994-01-01

OBJECTIVE--To assess the pattern of global and regional left ventricular long axis motion during early diastole in patients with ischaemic heart disease with and without myocardial infarction using magnetic resonance velocity mapping. DESIGN--Prospective study of 26 patients with a history of myocardial infarction (age 29-78, mean 55 years) and 21 patients with coronary artery disease without infarction (age range 39-71, mean 58 years). Values were compared with a control group (19 controls, age 35-76, mean 52 years) with a low likelihood of cardiovascular disease. RESULTS--Regional long axis velocity varied with time and position around the ventricle. All measurements were taken at the time of maximum early diastolic long axis velocity. Patients with coronary artery disease without infarction had lower values for maximum (mean (SD)) (99 (30) v 125 (33) mm/s, P < 0.05) and mean peak early diastolic wall motion (63 (13) v 82 (22) mm/s, P < 0.05) than controls. The coefficient of variation showed greater inhomogeneity of relaxation in patients than in controls (38 (18)% v 27 (10)%). All values were lower in patients with previous infarction than in patients with coronary artery disease without infarction and normal subjects. In patients with previous myocardial infarction the maximum (mean (SD)) early diastolic velocity was 80 (22) mm/s (P < 0.01 compared with controls and P < 0.05 compared with patients without infarction) and the mean (SD) velocity was 47 (18) mm/s (P < 0.01 compared with controls). The coefficient of variation was greater (52 (33)%) than for controls (P < 0.05) and patients with coronary artery disease without infarction. 18 of 26 patients with previous myocardial infarction and 13 of 21 patients with coronary artery disease without infarction had regional abnormalities corresponding to areas of fixed or reversible ischaemia on exercise electrocardiography or thallium myocardial perfusion tomography. CONCLUSIONS--Magnetic resonance velocity mapping can be used to assess regional long axis myocardial velocity. Ischaemic heart disease causes alterations in the patterns of left ventricular long axis velocity during early diastole. Images PMID:7833190

Kinematics and Dynamics of Motion Control Based on Acceleration Control

NASA Astrophysics Data System (ADS)

Ohishi, Kiyoshi; Ohba, Yuzuru; Katsura, Seiichiro

The first IEEE International Workshop on Advanced Motion Control was held in 1990 pointed out the importance of physical interpretation of motion control. The software servoing technology is now common in machine tools, robotics, and mechatronics. It has been intensively developed for the numerical control (NC) machines. Recently, motion control in unknown environment will be more and more important. Conventional motion control is not always suitable due to the lack of adaptive capability to the environment. A more sophisticated ability in motion control is necessary for compliant contact with environment. Acceleration control is the key technology of motion control in unknown environment. The acceleration control can make a motion system to be a zero control stiffness system without losing the robustness. Furthermore, a realization of multi-degree-of-freedom motion is necessary for future human assistance. A human assistant motion will require various control stiffness corresponding to the task. The review paper focuses on the modal coordinate system to integrate the various control stiffness in the virtual axes. A bilateral teleoperation is a good candidate to consider the future human assistant motion and integration of decentralized systems. Thus the paper reviews and discusses the bilateral teleoperation from the control stiffness and the modal control design points of view.

The Vestibular System and Human Dynamic Space Orientation

NASA Technical Reports Server (NTRS)

Meiry, J. L.

1966-01-01

The motion sensors of the vestibular system are studied to determine their role in human dynamic space orientation and manual vehicle control. The investigation yielded control models for the sensors, descriptions of the subsystems for eye stabilization, and demonstrations of the effects of motion cues on closed loop manual control. Experiments on the abilities of subjects to perceive a variety of linear motions provided data on the dynamic characteristics of the otoliths, the linear motion sensors. Angular acceleration threshold measurements supplemented knowledge of the semicircular canals, the angular motion sensors. Mathematical models are presented to describe the known control characteristics of the vestibular sensors, relating subjective perception of motion to objective motion of a vehicle. The vestibular system, the neck rotation proprioceptors and the visual system form part of the control system which maintains the eye stationary relative to a target or a reference. The contribution of each of these systems was identified through experiments involving head and body rotations about a vertical axis. Compensatory eye movements in response to neck rotation were demonstrated and their dynamic characteristics described by a lag-lead model. The eye motions attributable to neck rotations and vestibular stimulation obey superposition when both systems are active. Human operator compensatory tracking is investigated in simple vehicle orientation control system with stable and unstable controlled elements. Control of vehicle orientation to a reference is simulated in three modes: visual, motion and combined. Motion cues sensed by the vestibular system through tactile sensation enable the operator to generate more lead compensation than in fixed base simulation with only visual input. The tracking performance of the human in an unstable control system near the limits of controllability is shown to depend heavily upon the rate information provided by the vestibular sensors.

Fused Smart Sensor Network for Multi-Axis Forward Kinematics Estimation in Industrial Robots

PubMed Central

Rodriguez-Donate, Carlos; Osornio-Rios, Roque Alfredo; Rivera-Guillen, Jesus Rooney; de Jesus Romero-Troncoso, Rene

2011-01-01

Flexible manipulator robots have a wide industrial application. Robot performance requires sensing its position and orientation adequately, known as forward kinematics. Commercially available, motion controllers use high-resolution optical encoders to sense the position of each joint which cannot detect some mechanical deformations that decrease the accuracy of the robot position and orientation. To overcome those problems, several sensor fusion methods have been proposed but at expenses of high-computational load, which avoids the online measurement of the joint’s angular position and the online forward kinematics estimation. The contribution of this work is to propose a fused smart sensor network to estimate the forward kinematics of an industrial robot. The developed smart processor uses Kalman filters to filter and to fuse the information of the sensor network. Two primary sensors are used: an optical encoder, and a 3-axis accelerometer. In order to obtain the position and orientation of each joint online a field-programmable gate array (FPGA) is used in the hardware implementation taking advantage of the parallel computation capabilities and reconfigurability of this device. With the aim of evaluating the smart sensor network performance, three real-operation-oriented paths are executed and monitored in a 6-degree of freedom robot. PMID:22163850

Validation of an Actuator Line Model Coupled to a Dynamic Stall Model for Pitching Motions Characteristic to Vertical Axis Turbines

NASA Astrophysics Data System (ADS)

Mendoza, Victor; Bachant, Peter; Wosnik, Martin; Goude, Anders

2016-09-01

Vertical axis wind turbines (VAWT) can be used to extract renewable energy from wind flows. A simpler design, low cost of maintenance, and the ability to accept flow from all directions perpendicular to the rotor axis are some of the most important advantages over conventional horizontal axis wind turbines (HAWT). However, VAWT encounter complex and unsteady fluid dynamics, which present significant modeling challenges. One of the most relevant phenomena is dynamic stall, which is caused by the unsteady variation of angle of attack throughout the blade rotation, and is the focus of the present study. Dynamic stall is usually used as a passive control for VAWT operating conditions, hence the importance of predicting its effects. In this study, a coupled model is implemented with the open-source CFD toolbox OpenFOAM for solving the Navier-Stokes equations, where an actuator line model and dynamic stall model are used to compute the blade loading and body force. Force coefficients obtained from the model are validated with experimental data of pitching airfoil in similar operating conditions as an H-rotor type VAWT. Numerical results show reasonable agreement with experimental data for pitching motion.

Periodic-disturbance accommodating control of the space station for asymptotic momentum management

NASA Technical Reports Server (NTRS)

Warren, Wayne; Wie, Bong; Geller, David

1989-01-01

Periodic-disturbance accommodating control is investigated for asymptotic momentum management of control moment gyros used as primary actuating devices for the Space Station. The proposed controller utilizes the concepts of quaternion feedback control and periodic-disturbance accommodation to achieve oscillations about the constant torque equilibrium attitude, while minimizing the control effort required. Three-axis coupled equations of motion, written in terms of quaternions, are derived for roll/yaw controller design and stability analysis. The quaternion feedback controller designed using the linear-quadratic regulator synthesis technique is shown to be robust for a wide range of pitch angles. It is also shown that the proposed controller tunes the open-loop unstable vehicle to a stable oscillatory motion which minimizes the control effort needed for steady-state operations.

Automatic spacecraft detumbling by internal mass motion

NASA Technical Reports Server (NTRS)

Edwards, T. L.; Kaplan, M. H.

1974-01-01

In the operation of future manned space vehicles, there will always be a finite probability that an accident will occur which results in uncontrolled tumbling of a craft. Hard docking by a manned rescue vehicle is not acceptable because of the hazardous environment to which rescue crewmen would be exposed and excessive maneuvering accelerations during docking operations. A movable-mass control concept, which is activated upon initiation of tumbling and is autonomous, can convert tumbling motion into simple spin. The complete equations of motion for an asymmetric rigid spacecraft containing a movable mass are presented, and appropriate control law and system parameters are selected to minimize kinetic energy, resulting in simple spin about the major principal axis. Simulations indicate that for a large space station experiencing a collision, which results in tumbling, a 1% movable mass is capable of stabilizing motion in 2 hr.

Human heart rate variability relation is unchanged during motion sickness

NASA Technical Reports Server (NTRS)

Mullen, T. J.; Berger, R. D.; Oman, C. M.; Cohen, R. J.

1998-01-01

In a study of 18 human subjects, we applied a new technique, estimation of the transfer function between instantaneous lung volume (ILV) and instantaneous heart rate (HR), to assess autonomic activity during motion sickness. Two control recordings of ILV and electrocardiogram (ECG) were made prior to the development of motion sickness. During the first, subjects were seated motionless, and during the second they were seated rotating sinusoidally about an earth vertical axis. Subjects then wore prism goggles that reverse the left-right visual field and performed manual tasks until they developed moderate motion sickness. Finally, ILV and ECG were recorded while subjects maintained a relatively constant level of sickness by intermittent eye closure during rotation with the goggles. Based on analyses of ILV to HR transfer functions from the three conditions, we were unable to demonstrate a change in autonomic control of heart rate due to rotation alone or due to motion sickness. These findings do not support the notion that moderate motion sickness is manifested as a generalized autonomic response.

Predictive momentum management for a space station measurement and computation requirements

NASA Technical Reports Server (NTRS)

Adams, John Carl

1986-01-01

An analysis is made of the effects of errors and uncertainties in the predicting of disturbance torques on the peak momentum buildup on a space station. Models of the disturbance torques acting on a space station in low Earth orbit are presented, to estimate how accurately they can be predicted. An analysis of the torque and momentum buildup about the pitch axis of the Dual Keel space station configuration is formulated, and a derivation of the Average Torque Equilibrium Attitude (ATEA) is presented, for the case of no MRMS (Mobile Remote Manipulation System) motion, Y vehicle axis MRMS motion, and Z vehicle axis MRMS motion. Results showed the peak momentum buildup to be approximately 20000 N-m-s and to be relatively insensitive to errors in the predicting torque models, for Z axis motion of the MRMS was found to vary significantly with model errors, but not exceed a value of approximately 15000 N-m-s for the Y axis MRMS motion with 1 deg attitude hold error. Minimum peak disturbance momentum was found not to occur at the ATEA angle, but at a slightly smaller angle. However, this minimum peak momentum attitude was found to produce significant disturbance momentum at the end of the predicting time interval.

Adaptive PI control strategy for flat permanent magnet linear synchronous motor vibration suppression

NASA Astrophysics Data System (ADS)

Meng, Fanwei; Liu, Chengying; Li, Zhijun; Wang, Liping

2013-01-01

Due to low damping ratio, flat permanent magnet linear synchronous motor's vibration is difficult to be damped and the accuracy is limited. The vibration suppressing results are not good enough in the existing research because only the longitudinal direction vibration is considered while the normal direction vibration is neglected. The parameters of the direct-axis current controller are set to be the same as those of the quadrature-axis current controller commonly. This causes contradiction between signal noise and response. To suppress the vibration, the electromagnetic force model of the flat permanent magnet synchronous linear motor is formulated first. Through the analysis of the effect that direct-axis current noise and quadrature-axis current noise have on both direction vibration, it can be declared that the conclusion that longitudinal direction vibration is only related to the quadrature-axis current noise while the normal direction vibration is related to both the quadrature-axis current noise and direct-axis current noise. Then, the simulation test on current loop with a low-pass filter is conducted and the results show that the low-pass filter can not suppress the vibration but makes the vibration more severe. So a vibration suppressing strategy that the proportional gain of direct-axis current controller adapted according to quadrature-axis reference current is proposed. This control strategy can suppress motor vibration by suppressing direct-axis current noise. The experiments results about the effect of K p and T i on normal direction vibration, longitudinal vibration and the position step response show that this strategy suppresses vibration effectively while the motor's motion performance is not affected. The maximum reduction of vibration can be up to 40%. In addition, current test under rated load condition is also conducted and the results show that the control strategy can avoid the conflict between the direct-axis current and the quadrature-axis current under typical load. Adaptive PI control strategy can effectively suppress the flat permanent magnet linear synchronous motor's vibration without affecting the motor's performance.

Single Vector Calibration System for Multi-Axis Load Cells and Method for Calibrating a Multi-Axis Load Cell

NASA Technical Reports Server (NTRS)

Parker, Peter A. (Inventor)

2003-01-01

A single vector calibration system is provided which facilitates the calibration of multi-axis load cells, including wind tunnel force balances. The single vector system provides the capability to calibrate a multi-axis load cell using a single directional load, for example loading solely in the gravitational direction. The system manipulates the load cell in three-dimensional space, while keeping the uni-directional calibration load aligned. The use of a single vector calibration load reduces the set-up time for the multi-axis load combinations needed to generate a complete calibration mathematical model. The system also reduces load application inaccuracies caused by the conventional requirement to generate multiple force vectors. The simplicity of the system reduces calibration time and cost, while simultaneously increasing calibration accuracy.

Autonomous Motion Learning for Intra-Vehicular Activity Space Robot

NASA Astrophysics Data System (ADS)

Watanabe, Yutaka; Yairi, Takehisa; Machida, Kazuo

Space robots will be needed in the future space missions. So far, many types of space robots have been developed, but in particular, Intra-Vehicular Activity (IVA) space robots that support human activities should be developed to reduce human-risks in space. In this paper, we study the motion learning method of an IVA space robot with the multi-link mechanism. The advantage point is that this space robot moves using reaction force of the multi-link mechanism and contact forces from the wall as space walking of an astronaut, not to use a propulsion. The control approach is determined based on a reinforcement learning with the actor-critic algorithm. We demonstrate to clear effectiveness of this approach using a 5-link space robot model by simulation. First, we simulate that a space robot learn the motion control including contact phase in two dimensional case. Next, we simulate that a space robot learn the motion control changing base attitude in three dimensional case.

How NASA KSC Controls Interfaces with the use of Motion Skeletons and Product Structure

NASA Technical Reports Server (NTRS)

Jones, Corey

2013-01-01

This presentation will show how NASA KSC controls interfaces for Modular Product Architecture (MPA) using Locator Skeletons, Interface Skeletons, and Product Structure, to be combined together within a Motion Skeleton. The user will learn how to utilize skeleton models to communicate interface data, as successfully done at NASA KSC in their use of Motion Skeletons to control interfaces for multi-launch systems. There will be discussion of the methodology used to control design requirements through WTParts, and how to utilize product structure for non-CAD documents.

Controlled droplet transport to target on a high adhesion surface with multi-gradients

PubMed Central

Deng, Siyan; Shang, Weifeng; Feng, Shile; Zhu, Shiping; Xing, Yan; Li, Dan; Hou, Yongping; Zheng, Yongmei

2017-01-01

We introduce multi-gradients including Laplace pressure gradient, wettable gradient and wettable different gradient on a high adhesion surface via special wedge-pattern and improved anodic oxidation method. As a result of the cooperative effect mentioned above, controlled directional motion of a droplet on a high adhesion surface is realized, even when the surface is turned upside down. The droplet motion can be predicted and the movement distances can be controlled by simply adjusting the wedge angle and droplet volume. More interestingly, when Laplace pressure gradient is introduced on a V-shaped wettable gradient surface, two droplets can move toward one another as designed. PMID:28368020

An advanced scanning method for space-borne hyper-spectral imaging system

NASA Astrophysics Data System (ADS)

Wang, Yue-ming; Lang, Jun-Wei; Wang, Jian-Yu; Jiang, Zi-Qing

2011-08-01

Space-borne hyper-spectral imagery is an important means for the studies and applications of earth science. High cost efficiency could be acquired by optimized system design. In this paper, an advanced scanning method is proposed, which contributes to implement both high temporal and spatial resolution imaging system. Revisit frequency and effective working time of space-borne hyper-spectral imagers could be greatly improved by adopting two-axis scanning system if spatial resolution and radiometric accuracy are not harshly demanded. In order to avoid the quality degradation caused by image rotation, an idea of two-axis rotation has been presented based on the analysis and simulation of two-dimensional scanning motion path and features. Further improvement of the imagers' detection ability under the conditions of small solar altitude angle and low surface reflectance can be realized by the Ground Motion Compensation on pitch axis. The structure and control performance are also described. An intelligent integration technology of two-dimensional scanning and image motion compensation is elaborated in this paper. With this technology, sun-synchronous hyper-spectral imagers are able to pay quick visit to hot spots, acquiring both high spatial and temporal resolution hyper-spectral images, which enables rapid response of emergencies. The result has reference value for developing operational space-borne hyper-spectral imagers.

Vibration measurements of the Daniel K. Inouye Solar Telescope mount, Coudé rotator, and enclosure assemblies

NASA Astrophysics Data System (ADS)

McBride, William R.; McBride, Daniel R.

2016-08-01

The Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar telescope in the world, with a 4-meter off-axis primary mirror and 16 meter rotating Coudé laboratory within the telescope pier. The off-axis design requires a mount similar to an 8-meter on-axis telescope. Both the telescope mount and the Coudé laboratory utilize a roller bearing technology in place of the more commonly used hydrostatic bearings. The telescope enclosure utilizes a crawler mechanism for the altitude axis. As these mechanisms have not previously been used in a telescope, understanding the vibration characteristics and the potential impact on the telescope image is important. This paper presents the methodology used to perform jitter measurements of the enclosure and the mount bearings and servo system in a high-noise environment utilizing seismic accelerometers and high dynamic-range data acquisition equipment, along with digital signal processing (DSP) techniques. Data acquisition and signal processing were implemented in MATLAB. In the factory acceptance testing of the telescope mount, multiple accelerometers were strategically located to capture the six axes-of-motion of the primary and secondary mirror dummies. The optical sensitivity analysis was used to map these mirror mount displacements and rotations into units of image motion on the focal plane. Similarly, tests were done with the Coudé rotator, treating the entire rotating instrument lab as a rigid body. Testing was performed by recording accelerometer data while the telescope control system performed tracking operations typical of various observing scenarios. The analysis of the accelerometer data utilized noise-averaging fast Fourier transform (FFT) routines, spectrograms, and periodograms. To achieve adequate dynamic range at frequencies as low as 3Hz, the use of special filters and advanced windowing functions were necessary. Numerous identical automated tests were compared to identify and select the data sets with the lowest level of external interference. Similar testing was performed on the telescope enclosure during the factory test campaign. The vibration of the enclosure altitude and azimuth mechanisms were characterized. This paper details jitter tests using accelerometers placed in locations that allowed the motion of the assemblies to be measured while the control system performed various moves typical of on-sky observations. The measurements were converted into the rigid body motion of the structures and mapped into image motion using the telescope's optical sensitivity analysis.

Planning 4-Dimensional Computed Tomography (4DCT) Cannot Adequately Represent Daily Intrafractional Motion of Abdominal Tumors

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

Ge, Jiajia; Santanam, Lakshmi; Noel, Camille

2013-03-15

Purpose: To evaluate whether planning 4-dimensional computed tomography (4DCT) can adequately represent daily motion of abdominal tumors in regularly fractionated and stereotactic body radiation therapy (SBRT) patients. Methods and Materials: Intrafractional tumor motion of 10 patients with abdominal tumors (4 pancreas-fractionated and 6 liver-stereotactic patients) with implanted fiducials was measured based on daily orthogonal fluoroscopic movies over 38 treatment fractions. The needed internal margin for at least 90% of tumor coverage was calculated based on a 95th and fifth percentile of daily 3-dimensional tumor motion. The planning internal margin was generated by fusing 4DCT motion from all phase bins. The disagreementmore » between needed and planning internal margin was analyzed fraction by fraction in 3 motion axes (superior-inferior [SI], anterior-posterior [AP], and left-right [LR]). The 4DCT margin was considered as an overestimation/underestimation of daily motion when disagreement exceeded at least 3 mm in the SI axis and/or 1.2 mm in the AP and LR axes (4DCT image resolution). The underlying reasons for this disagreement were evaluated based on interfractional and intrafractional breathing variation. Results: The 4DCT overestimated daily 3-dimensional motion in 39% of the fractions in 7 of 10 patients and underestimated it in 53% of the fractions in 8 of 10 patients. Median underestimation was 3.9 mm, 3.0 mm, and 1.7 mm in the SI axis, AP axis, and LR axis, respectively. The 4DCT was found to capture irregular deep breaths in 3 of 10 patients, with 4DCT motion larger than mean daily amplitude by 18 to 21 mm. The breathing pattern varied from breath to breath and day to day. The intrafractional variation of amplitude was significantly larger than intrafractional variation (2.7 mm vs 1.3 mm) in the primary motion axis (ie, SI axis). The SBRT patients showed significantly larger intrafractional amplitude variation than fractionated patients (3.0 mm vs 2.1 mm, P<.05). Conclusions: It may not be appropriate to use 4DCT without monitoring of patient motion on a regular basis for patients with abdominal tumors, especially SBRT patients.« less

Dynamics of thin-film piezoelectric microactuators with large vertical stroke subject to multi-axis coupling and fabrication asymmetries

NASA Astrophysics Data System (ADS)

Choi, Jongsoo; Wang, Thomas; Oldham, Kenn

2018-01-01

The high performance and small size of MEMS based scanners has allowed various optical imaging techniques to be realized in a small form factor. Many such devices are resonant scanners, and thus their linear and nonlinear dynamic behaviors have been studied in the past. Thin-film piezoelectric materials, in contrast, provide sufficient energy density to achieve both large static displacements and high-frequency resonance, but large deformation can in turn influence dynamic scanner behavior. This paper reports on the influence of very large stroke translation of a piezoelectric vertical actuator on its resonant behavior, which may not be otherwise explained fully by common causes of resonance shift such as beam stiffening or nonlinear forcing. To examine the change of structural compliance over the course of scanner motion, a model has been developed that includes internal forces from residual stress and the resultant additional multi-axis coupling among actuator leg structures. Like some preceding vertical scanning micro-actuators, the scanner of this work has four legs, with each leg featuring four serially connected thin-film PZT unimorphs that allow the scanner to generate larger than 400 µm of vertical displacement at 14 V DC. Using an excitation near one or more resonances, the input voltage can be lowered, and complementary multi-axis rotations can be also generated, but change of the resonant frequencies with scanner height needs to be understood to maximize scanner performance. The presented model well predicts the experimental observation of the decrease of the resonant frequencies of the scanner with the increase of a dc bias voltage. Also, the effects of the magnitude and uniformity of residual stress across the scanner structure on the natural frequencies have been studied.

Using the Xbox Kinect sensor for positional data acquisition

NASA Astrophysics Data System (ADS)

Ballester, Jorge; Pheatt, Chuck

2013-01-01

The Kinect sensor was introduced in November 2010 by Microsoft for the Xbox 360 video game system. It is designed to be positioned above or below a video display to track player body and hand movements in three dimensions (3D). The sensor contains a red, green, and blue (RGB) camera, a depth sensor, an infrared (IR) light source, a three-axis accelerometer, and a multi-array microphone, as well as hardware required to transmit sensor information to an external receiver. In this article, we evaluate the capabilities of the Kinect sensor as a 3D data-acquisition platform for use in physics experiments. Data obtained for a simple pendulum, a spherical pendulum, projectile motion, and a bouncing basketball are presented. Overall, the Kinect sensor is found to be a useful data-acquisition tool for motion studies in the physics laboratory.

An Investigation of the Ability to Recover from Transients Following Failures for Single-Pilot Rotorcraft

NASA Technical Reports Server (NTRS)

Mansur, M. Hossein; Schroeder, Jeffery A.

1988-01-01

A moving-base simulation was conducted to investigate a pilot's ability to recover from transients following single-axis hard-over failures of the flight-control system. The investigation was performed in conjunction with a host simulation that examined the influence of control modes on a single pilot's ability to perform various mission elements under high-workload conditions. The NASA Ames large-amplitude-motion Vertical Motion Simulator (VMS) was utilized, and the experimental variables were the failure axis, the severity of the failure, and the airspeed at which the failure occurred. Other factors, such as pilot workload and terrain and obstacle proximity at the time of failure, were kept as constant as possible within the framework of the host simulation task scenarios. No explicit failure warnings were presented to the pilot. Data from the experiment are shown, and pilot ratings are compared with the proposed handling-qualities requirements for military rotorcraft. Results indicate that the current proposed failure transient requirements may need revision.

A model for the pilot's use of motion cues in roll-axis tracking tasks

NASA Technical Reports Server (NTRS)

Levison, W. H.; Junker, A. M.

1977-01-01

Simulated target-following and disturbance-regulation tasks were explored with subjects using visual-only and combined visual and motion cues. The effects of motion cues on task performance and pilot response behavior were appreciably different for the two task configurations and were consistent with data reported in earlier studies for similar task configurations. The optimal-control model for pilot/vehicle systems provided a task-independent framework for accounting for the pilot's use of motion cues. Specifically, the availability of motion cues was modeled by augmenting the set of perceptual variables to include position, rate, acceleration, and accleration-rate of the motion simulator, and results were consistent with the hypothesis of attention-sharing between visual and motion variables. This straightforward informational model allowed accurate model predictions of the effects of motion cues on a variety of response measures for both the target-following and disturbance-regulation tasks.

Lateral-Directional Parameter Estimation on the X-48B Aircraft Using an Abstracted, Multi-Objective Effector Model

NASA Technical Reports Server (NTRS)

Ratnayake, Nalin A.; Waggoner, Erin R.; Taylor, Brian R.

2011-01-01

The problem of parameter estimation on hybrid-wing-body aircraft is complicated by the fact that many design candidates for such aircraft involve a large number of aerodynamic control effectors that act in coplanar motion. This adds to the complexity already present in the parameter estimation problem for any aircraft with a closed-loop control system. Decorrelation of flight and simulation data must be performed in order to ascertain individual surface derivatives with any sort of mathematical confidence. Non-standard control surface configurations, such as clamshell surfaces and drag-rudder modes, further complicate the modeling task. In this paper, time-decorrelation techniques are applied to a model structure selected through stepwise regression for simulated and flight-generated lateral-directional parameter estimation data. A virtual effector model that uses mathematical abstractions to describe the multi-axis effects of clamshell surfaces is developed and applied. Comparisons are made between time history reconstructions and observed data in order to assess the accuracy of the regression model. The Cram r-Rao lower bounds of the estimated parameters are used to assess the uncertainty of the regression model relative to alternative models. Stepwise regression was found to be a useful technique for lateral-directional model design for hybrid-wing-body aircraft, as suggested by available flight data. Based on the results of this study, linear regression parameter estimation methods using abstracted effectors are expected to perform well for hybrid-wing-body aircraft properly equipped for the task.

A New Fuzzy-Evidential Controller for Stabilization of the Planar Inverted Pendulum System

PubMed Central

Tang, Yongchuan; Zhou, Deyun

2016-01-01

In order to realize the stability control of the planar inverted pendulum system, which is a typical multi-variable and strong coupling system, a new fuzzy-evidential controller based on fuzzy inference and evidential reasoning is proposed. Firstly, for each axis, a fuzzy nine-point controller for the rod and a fuzzy nine-point controller for the cart are designed. Then, in order to coordinate these two controllers of each axis, a fuzzy-evidential coordinator is proposed. In this new fuzzy-evidential controller, the empirical knowledge for stabilization of the planar inverted pendulum system is expressed by fuzzy rules, while the coordinator of different control variables in each axis is built incorporated with the dynamic basic probability assignment (BPA) in the frame of fuzzy inference. The fuzzy-evidential coordinator makes the output of the control variable smoother, and the control effect of the new controller is better compared with some other work. The experiment in MATLAB shows the effectiveness and merit of the proposed method. PMID:27482707

A New Fuzzy-Evidential Controller for Stabilization of the Planar Inverted Pendulum System.

PubMed

Tang, Yongchuan; Zhou, Deyun; Jiang, Wen

2016-01-01

In order to realize the stability control of the planar inverted pendulum system, which is a typical multi-variable and strong coupling system, a new fuzzy-evidential controller based on fuzzy inference and evidential reasoning is proposed. Firstly, for each axis, a fuzzy nine-point controller for the rod and a fuzzy nine-point controller for the cart are designed. Then, in order to coordinate these two controllers of each axis, a fuzzy-evidential coordinator is proposed. In this new fuzzy-evidential controller, the empirical knowledge for stabilization of the planar inverted pendulum system is expressed by fuzzy rules, while the coordinator of different control variables in each axis is built incorporated with the dynamic basic probability assignment (BPA) in the frame of fuzzy inference. The fuzzy-evidential coordinator makes the output of the control variable smoother, and the control effect of the new controller is better compared with some other work. The experiment in MATLAB shows the effectiveness and merit of the proposed method.

A motion-tolerant approach for monitoring SpO2 and heart rate using photoplethysmography signal with dual frame length processing and multi-classifier fusion.

PubMed

Fan, Feiyi; Yan, Yuepeng; Tang, Yongzhong; Zhang, Hao

2017-12-01

Monitoring pulse oxygen saturation (SpO 2 ) and heart rate (HR) using photoplethysmography (PPG) signal contaminated by a motion artifact (MA) remains a difficult problem, especially when the oximeter is not equipped with a 3-axis accelerometer for adaptive noise cancellation. In this paper, we report a pioneering investigation on the impact of altering the frame length of Molgedey and Schuster independent component analysis (ICAMS) on performance, design a multi-classifier fusion strategy for selecting the PPG correlated signal component, and propose a novel approach to extract SpO 2 and HR readings from PPG signal contaminated by strong MA interference. The algorithm comprises multiple stages, including dual frame length ICAMS, a multi-classifier-based PPG correlated component selector, line spectral analysis, tree-based HR monitoring, and post-processing. Our approach is evaluated by multi-subject tests. The root mean square error (RMSE) is calculated for each trial. Three statistical metrics are selected as performance evaluation criteria: mean RMSE, median RMSE and the standard deviation (SD) of RMSE. The experimental results demonstrate that a shorter ICAMS analysis window probably results in better performance in SpO 2 estimation. Notably, the designed multi-classifier signal component selector achieved satisfactory performance. The subject tests indicate that our algorithm outperforms other baseline methods regarding accuracy under most criteria. The proposed work can contribute to improving the performance of current pulse oximetry and personal wearable monitoring devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mandibular kinematics represented by a non-orthogonal floating axis joint coordinate system.

PubMed

Leader, Joseph K; Boston, J Robert; Debski, Richard E; Rudy, Thomas E

2003-02-01

There are many methods used to represent joint kinematics (e.g., roll, pitch, and yaw angles; instantaneous center of rotation; kinematic center; helical axis). Often in biomechanics internal landmarks are inferred from external landmarks. This study represents mandibular kinematics using a non-orthogonal floating axis joint coordinate system based on 3-D geometric models with parameters that are "clinician friendly" and mathematically rigorous. Kinematics data for two controls were acquired from passive fiducial markers attached to a custom dental clutch. The geometric models were constructed from MRI data. The superior point along the arc of the long axis of the condyle was used to define the coordinate axes. The kinematic data and geometric models were registered through fiducial markers visible during both protocols. The mean absolute maxima across the subjects for sagittal rotation, coronal rotation, axial rotation, medial-lateral translation, anterior-posterior translation, and inferior-superior translation were 34.10 degrees, 1.82 degrees, 1.14 degrees, 2.31, 21.07, and 6.95 mm, respectively. All the parameters, except for one subject's axial rotation, were reproducible across two motion recording sessions. There was a linear correlation between sagittal rotation and translation, the dominant motion plane, with approximately 1.5 degrees of rotation per millimeter of translation. The novel approach of combining the floating axis system with geometric models succinctly described mandibular kinematics with reproducible and clinician friendly parameters.

Combined pitch and roll and cybersickness in a virtual environment.

PubMed

Bonato, Frederick; Bubka, Andrea; Palmisano, Stephen

2009-11-01

Stationary subjects who perceive visually induced illusions of self-motion, or vection, in virtual reality (VR) often experience cybersickness, the symptoms of which are similar to those experienced during motion sickness. An experiment was conducted to test the effects of single and dual-axis rotation of a virtual environment on cybersickness. It was predicted that VR displays which induced illusory dual-axis (as opposed to single-axis) self-rotations in stationary subjects would generate more sensory conflict and subsequently more cybersickness. There were 19 individuals (5 men, 14 women, mean age = 19.8 yr) who viewed the interior of a virtual cube that steadily rotated (at 60 degrees x s(-1)) about either the pitch axis or both the pitch and roll axes simultaneously. Subjects completed the Simulator Sickness Questionnaire (SSQ) before a trial and after 5 min of stimulus viewing. Post-treatment total SSQ scores and subscores for nausea, oculomotor, and disorientation were significantly higher in the dual-axis condition. These results support the hypothesis that a vection-inducing VR stimulus that rotates about two axes generates more cybersickness compared to aVR stimulus that rotates about only one. In the single-axis condition, sensory conflict and pseudo-Coriolis effects may have led to symptoms. However, in the dual-axis condition, not only was perceived self-motion more complex (two axes compared to one), the inducing stimulus was consistent with twice as much self-motion. Hence, the increased likelihood/magnitude of sensory conflict and pseudo-Coriolis effects may have subsequently resulted in a higher degree of cybersickness in the dual-axis condition.

Reverse control for humanoid robot task recognition.

PubMed

Hak, Sovannara; Mansard, Nicolas; Stasse, Olivier; Laumond, Jean Paul

2012-12-01

Efficient methods to perform motion recognition have been developed using statistical tools. Those methods rely on primitive learning in a suitable space, for example, the latent space of the joint angle and/or adequate task spaces. Learned primitives are often sequential: A motion is segmented according to the time axis. When working with a humanoid robot, a motion can be decomposed into parallel subtasks. For example, in a waiter scenario, the robot has to keep some plates horizontal with one of its arms while placing a plate on the table with its free hand. Recognition can thus not be limited to one task per consecutive segment of time. The method presented in this paper takes advantage of the knowledge of what tasks the robot is able to do and how the motion is generated from this set of known controllers, to perform a reverse engineering of an observed motion. This analysis is intended to recognize parallel tasks that have been used to generate a motion. The method relies on the task-function formalism and the projection operation into the null space of a task to decouple the controllers. The approach is successfully applied on a real robot to disambiguate motion in different scenarios where two motions look similar but have different purposes.

Role of curvatures in determining the characteristics of a string vibrating against a doubly curved obstacle

NASA Astrophysics Data System (ADS)

Singh, Harkirat; Wahi, Pankaj

2017-08-01

The motion of a string in the presence of a doubly curved obstacle is investigated. A mathematical model has been developed for a general shape of the obstacle. However, detailed analysis has been performed for a shape relevant to the Indian stringed musical instruments like Tanpura and Sitar. In particular, we explore the effect of obstacle's curvature in the plane perpendicular to the string axis on its motion. This geometrical feature of the obstacle introduces a coupling between motions in mutually perpendicular directions over and above the coupling due to the stretching nonlinearity. We find that only one planar motion is possible for our system. Small amplitude planar motions are stable to perturbations in the perpendicular direction resulting in non-whirling motions while large amplitude oscillations lead to whirling motions. The critical amplitude of oscillations, across which there is a transition in the qualitative behavior of the non-planar trajectories, is determined using Floquet theory. Our analysis reveals that a small obstacle curvature in a direction perpendicular to the string axis leads to a considerable reduction in the critical amplitudes required for initiation of whirling motions. Hence, this obstacle curvature has a destabilizing effect on the planar motions in contrast to the curvature along the string axis which stabilizes planar motions.

Direct measurements of safety factor profiles with motional Stark effect for KSTAR tokamak discharges with internal transport barriers

NASA Astrophysics Data System (ADS)

Ko, J.; Chung, J.

2017-06-01

The safety factor profile evolutions have been measured from the plasma discharges with the external current drive mechanism such as the multi-ion-source neutral beam injection for the Korea Superconducting Tokamak Advanced Research (KSTAR) for the first time. This measurement has been possible by the newly installed motional Stark effect (MSE) diagnostic system that utilizes the polarized Balmer-alpha emission from the energetic neutral deuterium atoms induced by the Stark effect under the Lorentz electric field. The 25-channel KSTAR MSE diagnostic is based on the conventional photoelastic modulator approach with the spatial and temporal resolutions less than 2 cm (for the most of the channels except 2 to 3 channels inside the magnetic axis) and about 10 ms, respectively. The strong Faraday rotation imposed on the optical elements in the diagnostic system is calibrated out from a separate and well-designed polarization measurement procedure using an in-vessel reference polarizer during the toroidal-field ramp-up phase before the plasma experiment starts. The combination of the non-inductive current drive during the ramp-up and shape control enables the formation of the internal transport barrier where the pitch angle profiles indicate flat or slightly hollow profiles in the safety factor.

Visual guidance of forward flight in hummingbirds reveals control based on image features instead of pattern velocity.

PubMed

Dakin, Roslyn; Fellows, Tyee K; Altshuler, Douglas L

2016-08-02

Information about self-motion and obstacles in the environment is encoded by optic flow, the movement of images on the eye. Decades of research have revealed that flying insects control speed, altitude, and trajectory by a simple strategy of maintaining or balancing the translational velocity of images on the eyes, known as pattern velocity. It has been proposed that birds may use a similar algorithm but this hypothesis has not been tested directly. We examined the influence of pattern velocity on avian flight by manipulating the motion of patterns on the walls of a tunnel traversed by Anna's hummingbirds. Contrary to prediction, we found that lateral course control is not based on regulating nasal-to-temporal pattern velocity. Instead, birds closely monitored feature height in the vertical axis, and steered away from taller features even in the absence of nasal-to-temporal pattern velocity cues. For vertical course control, we observed that birds adjusted their flight altitude in response to upward motion of the horizontal plane, which simulates vertical descent. Collectively, our results suggest that birds avoid collisions using visual cues in the vertical axis. Specifically, we propose that birds monitor the vertical extent of features in the lateral visual field to assess distances to the side, and vertical pattern velocity to avoid collisions with the ground. These distinct strategies may derive from greater need to avoid collisions in birds, compared with small insects.

A manipulative instrument with simultaneous gesture and end-effector trajectory planning and controlling

NASA Astrophysics Data System (ADS)

Lin, Hsien-I.; Nguyen, Xuan-Anh

2017-05-01

To operate a redundant manipulator to accomplish the end-effector trajectory planning and simultaneously control its gesture in online programming, incorporating the human motion is a useful and flexible option. This paper focuses on a manipulative instrument that can simultaneously control its arm gesture and end-effector trajectory via human teleoperation. The instrument can be classified by two parts; first, for the human motion capture and data processing, marker systems are proposed to capture human gesture. Second, the manipulator kinematics control is implemented by an augmented multi-tasking method, and forward and backward reaching inverse kinematics, respectively. Especially, the local-solution and divergence problems of a multi-tasking method are resolved by the proposed augmented multi-tasking method. Computer simulations and experiments with a 7-DOF (degree of freedom) redundant manipulator were used to validate the proposed method. Comparison among the single-tasking, original multi-tasking, and augmented multi-tasking algorithms were performed and the result showed that the proposed augmented method had a good end-effector position accuracy and the most similar gesture to the human gesture. Additionally, the experimental results showed that the proposed instrument was realized online.

Causal evidence for retina dependent and independent visual motion computations in mouse cortex

PubMed Central

Hillier, Daniel; Fiscella, Michele; Drinnenberg, Antonia; Trenholm, Stuart; Rompani, Santiago B.; Raics, Zoltan; Katona, Gergely; Juettner, Josephine; Hierlemann, Andreas; Rozsa, Balazs; Roska, Botond

2017-01-01

How neuronal computations in the sensory periphery contribute to computations in the cortex is not well understood. We examined this question in the context of visual-motion processing in the retina and primary visual cortex (V1) of mice. We disrupted retinal direction selectivity – either exclusively along the horizontal axis using FRMD7 mutants or along all directions by ablating starburst amacrine cells – and monitored neuronal activity in layer 2/3 of V1 during stimulation with visual motion. In control mice, we found an overrepresentation of cortical cells preferring posterior visual motion, the dominant motion direction an animal experiences when it moves forward. In mice with disrupted retinal direction selectivity, the overrepresentation of posterior-motion-preferring cortical cells disappeared, and their response at higher stimulus speeds was reduced. This work reveals the existence of two functionally distinct, sensory-periphery-dependent and -independent computations of visual motion in the cortex. PMID:28530661

Perception of Invariance Over Perspective Transformations in Five Month Old Infants.

ERIC Educational Resources Information Center

Gibson, Eleanor; And Others

This experiment asked whether infants at 5 months perceived an invariant over four types of rigid motion (perspective transformations), and thereby differentiated rigid motion from deformation. Four perspective transformations of a sponge rubber object (rotation around the vertical axis, rotation around the horizontal axis, rotation in the frontal…

Detumbling of a rigid spacecraft via torque wheel assisted gyroscopic motion

NASA Astrophysics Data System (ADS)

Lin, Yiing-Yuh; Wang, Chin-Tzuo

2014-01-01

A time and energy efficient two-part method for detumbling a rigid spacecraft using an onboard torque wheel and a set of three-axis magnetic torquer is presented in this paper. Part-1 of the method manipulates the speed of the wheel, whose spin axis is parallel to a designated body axis of a tumbling spacecraft, and induces a desired gyroscopic-like motion to align the designated axis with its total angular momentum, H. The procedure in effect detumbles the spacecraft to rotate about the designated axis and distributes H, which is conserved during this control period, between the body and the wheel. After the alignment is achieved, Part-2 control, activated with a specified momentum transfer parameter, η, can either quickly stop the body rotation by transferring its angular momentum to the wheel or offload most of the momentum into space, using the wheel and the magnetic torquer. Convergence criteria and control laws for both parts are derived from the Lyapunov stability analysis and the method of feedback linearization. The wheel performs as a momentum storing and transferring device regulating the angular momentum between the wheel and the body. It can also provide gyroscopic stiffness to stabilize the system while the magnetic torquer is offloading the momentum. Simulation results from the included cases indicate that significantly fast detumbling of the spacecraft can be achieved with Part-1 of the proposed method. The results also show that, under the same condition, either by transferring almost all H to the wheel or dumping it, the two-part method, with a chosen η and final residual momentum condition, requires much less time and energy needed than the B-dot method does. Moreover, the stability nature of the two-part method is heuristically substantiated as the wheel torques and the dipole moment were constrained in the simulation.

The KALI multi-arm robot programming and control environment

NASA Technical Reports Server (NTRS)

Backes, Paul; Hayati, Samad; Hayward, Vincent; Tso, Kam

1989-01-01

The KALI distributed robot programming and control environment is described within the context of its use in the Jet Propulsion Laboratory (JPL) telerobot project. The purpose of KALI is to provide a flexible robot programming and control environment for coordinated multi-arm robots. Flexibility, both in hardware configuration and software, is desired so that it can be easily modified to test various concepts in robot programming and control, e.g., multi-arm control, force control, sensor integration, teleoperation, and shared control. In the programming environment, user programs written in the C programming language describe trajectories for multiple coordinated manipulators with the aid of KALI function libraries. A system of multiple coordinated manipulators is considered within the programming environment as one motion system. The user plans the trajectory of one controlled Cartesian frame associated with a motion system and describes the positions of the manipulators with respect to that frame. Smooth Cartesian trajectories are achieved through a blending of successive path segments. The manipulator and load dynamics are considered during trajectory generation so that given interface force limits are not exceeded.

The Influence of Tactual Seat-motion Cues on Training and Performance in a Roll-axis Compensatory Tracking Task Setting

DTIC Science & Technology

2008-05-01

AFRL-RH-WP-SR-2009-0002 The Influence of Tactual Seat-motion Cues on Training and Performance in a Roll-axis Compensatory Tracking Task...and Performance in a Roll-axis Compensatory Tracking Task Setting 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62202F 6. AUTHOR(S...simulated vehicle having aircraft-like dynamics. A centrally located compensatory display, subtending about nine degrees, provided visual roll error

Analytical Methods of Decoupling the Automotive Engine Torque Roll Axis

NASA Astrophysics Data System (ADS)

JEONG, TAESEOK; SINGH, RAJENDRA

2000-06-01

This paper analytically examines the multi-dimensional mounting schemes of an automotive engine-gearbox system when excited by oscillating torques. In particular, the issue of torque roll axis decoupling is analyzed in significant detail since it is poorly understood. New dynamic decoupling axioms are presented an d compared with the conventional elastic axis mounting and focalization methods. A linear time-invariant system assumption is made in addition to a proportionally damped system. Only rigid-body modes of the powertrain are considered and the chassis elements are assumed to be rigid. Several simplified physical systems are considered and new closed-form solutions for symmetric and asymmetric engine-mounting systems are developed. These clearly explain the design concepts for the 4-point mounting scheme. Our analytical solutions match with the existing design formulations that are only applicable to symmetric geometries. Spectra for all six rigid-body motions are predicted using the alternate decoupling methods and the closed-form solutions are verified. Also, our method is validated by comparing modal solutions with prior experimental and analytical studies. Parametric design studies are carried out to illustrate the methodology. Chief contributions of this research include the development of new or refined analytical models and closed-form solutions along with improved design strategies for the torque roll axis decoupling.

Design of multi-energy Helds coupling testing system of vertical axis wind power system

NASA Astrophysics Data System (ADS)

Chen, Q.; Yang, Z. X.; Li, G. S.; Song, L.; Ma, C.

2016-08-01

The conversion efficiency of wind energy is the focus of researches and concerns as one of the renewable energy. The present methods of enhancing the conversion efficiency are mostly improving the wind rotor structure, optimizing the generator parameters and energy storage controller and so on. Because the conversion process involves in energy conversion of multi-energy fields such as wind energy, mechanical energy and electrical energy, the coupling effect between them will influence the overall conversion efficiency. In this paper, using system integration analysis technology, a testing system based on multi-energy field coupling (MEFC) of vertical axis wind power system is proposed. When the maximum efficiency of wind rotor is satisfied, it can match to the generator function parameters according to the output performance of wind rotor. The voltage controller can transform the unstable electric power to the battery on the basis of optimizing the parameters such as charging times, charging voltage. Through the communication connection and regulation of the upper computer system (UCS), it can make the coupling parameters configure to an optimal state, and it improves the overall conversion efficiency. This method can test the whole wind turbine (WT) performance systematically and evaluate the design parameters effectively. It not only provides a testing method for system structure design and parameter optimization of wind rotor, generator and voltage controller, but also provides a new testing method for the whole performance optimization of vertical axis wind energy conversion system (WECS).

Three-Dimensional Modeling of Aircraft High-Lift Components with Vehicle Sketch Pad

NASA Technical Reports Server (NTRS)

Olson, Erik D.

2016-01-01

Vehicle Sketch Pad (OpenVSP) is a parametric geometry modeler that has been used extensively for conceptual design studies of aircraft, including studies using higher-order analysis. OpenVSP can model flap and slat surfaces using simple shearing of the airfoil coordinates, which is an appropriate level of complexity for lower-order aerodynamic analysis methods. For three-dimensional analysis, however, there is not a built-in method for defining the high-lift components in OpenVSP in a realistic manner, or for controlling their complex motions in a parametric manner that is intuitive to the designer. This paper seeks instead to utilize OpenVSP's existing capabilities, and establish a set of best practices for modeling high-lift components at a level of complexity suitable for higher-order analysis methods. Techniques are described for modeling the flap and slat components as separate three-dimensional surfaces, and for controlling their motion using simple parameters defined in the local hinge-axis frame of reference. To demonstrate the methodology, an OpenVSP model for the Energy-Efficient Transport (EET) AR12 wind-tunnel model has been created, taking advantage of OpenVSP's Advanced Parameter Linking capability to translate the motions of the high-lift components from the hinge-axis coordinate system to a set of transformations in OpenVSP's frame of reference.

Simulation of a flexible spinning vehicle

NASA Technical Reports Server (NTRS)

Baudry, W. A.

1972-01-01

Results are presented of experimental investigation of the controlled and uncontrolled dynamical behavior of a rotating or artificial gravity space station including flexible body effects. A dynamically scaled model was supported by a spherical air bearing which provided a nearly moment free environment. Reaction jet system were provided for spin-up and spin-down and for damping of wobble motion. Two single-gimbal gyros were arranged as a control moment gyro wobble damping system. Remotely controllable movable masses were provided to simulate mass shift disturbances such as arise from crew motions. An active mass balance wobble damping system which acted to minimize the wobble motions induced by crew motions was also installed. Flexible body effects were provided by a pair of inertia augmentation booms. Inertia augmentation booms are contemplated for use on rotating space stations to cause the spin axis moment of inertia to be the largest of the three moments of inertia as is necessary to assure gyroscopic stability. Test runs were made with each of the control systems with the booms locked (rigid body) and unlocked (flexible body).

Experimental Sloshing Reference Test

NASA Astrophysics Data System (ADS)

Lada, C.; Such-Taboada, M.; Ngan, I.; Grigore, L.; Appolloni, M.; Roure, S.; Murray, N.; Mendes Leal, M.; de Wilde, D.; Longo, J.; Bureo-Dacal, R.; Cozzani, A.; Laine, B.

2014-06-01

This article describes the sloshing experiment performed on the HYDRA multi-axis hydraulic shaker at ESTEC. Two tank geometries, a rectangular tank and a pill shaped tank, were excited in the lateral direction. Both tanks, manufactured from a transparent material in order to provide high visibility of the phenomenon, were filled with water and several fill ratios were tested, varying the amplitude of the input and the sweep rate. The results of the test are presented from a structural point of view, with the main objective to study the interface force due to dynamic fluid sloshing motion. An investigation of the behaviour of the water around the main resonance of the assembly is conducted through the observation of the identified modes and the damping values. The experimental results confirm the amplification effect at low frequency caused by water sloshing motion and a comparison with data from numerical simulation is provided.

Low-Friction, Low-Profile, High-Moment Two-Axis Joint

NASA Technical Reports Server (NTRS)

Lewis, James L.; Le, Thang; Carroll, Monty B.

2010-01-01

The two-axis joint is a mechanical device that provides two-degrees-of-freedom motion between connected components. A compact, moment-resistant, two-axis joint is used to connect an electromechanical actuator to its driven structural members. Due to the requirements of the overall mechanism, the joint has a low profile to fit within the allowable space, low friction, and high moment-reacting capability. The mechanical arrangement of this joint can withstand high moments when loads are applied. These features allow the joint to be used in tight spaces where a high load capability is required, as well as in applications where penetrating the mounting surface is not an option or where surface mounting is required. The joint consists of one base, one clevis, one cap, two needle bearings, and a circular shim. The base of the joint is the housing (the base and the cap together), and is connected to the grounding structure via fasteners and a bolt pattern. Captive within the housing, between the base and the cap, are the rotating clevis and the needle bearings. The clevis is attached to the mechanical system (linear actuator) via a pin. This pin, and the rotational movement of the clevis with respect to the housing, provides two rotational degrees of freedom. The larger diameter flange of the clevis is sandwiched between a pair of needle bearings, one on each side of the flange. During the assembly of the two-axis joint, the circular shims are used to adjust the amount of preload that is applied to the needle bearings. The above arrangement enables the joint to handle high moments with minimal friction. To achieve the high-moment capability within a low-profile joint, the use of depth of engagement (like that of a conventional rotating shaft) to react moment is replaced with planar engagement parallel to the mounting surface. The needle bearings with the clevis flange provide the surface area to react the clevis loads/moments into the joint housing while providing minimal friction during rotation. The diameter of the flange and the bearings can be increased to react higher loads and still maintain a compact surface mounting capability. This type of joint can be used in a wide variety of mechanisms and mechanical systems. It is especially effective where precise, smooth, continuous motion is required. For example, the joint can be used at the end of a linear actuator that is required to extend and rotate simultaneously. The current design application is for use in a spacecraft docking-system capture mechanism. Other applications might include industrial robotic or assembly line apparatuses, positioning systems, or in the motion-based simulator industry that employs complex, multi-axis manipulators for various types of motions.

Undisturbed upright stance control in the elderly: Part 1. Age-related changes in undisturbed upright stance control.

PubMed

Berger, L; Chuzel, M; Buisson, G; Rougier, P

2005-09-01

The authors investigated age-related changes in postural control in 33 healthy young adults (18-31 years), 29 seniors (62-75 years), and 22 elderly people (75-96 years). A force platform recorded the results. The horizontal motions of the center of gravity (CGh) and their difference in the plane of support CP - CGv were deduced from the complex center of pressure (CP) trajectories. With fractional Brownian modeling, one can establish that the aging process seems to induce a transition phase in which seniors take more time to initiate the corrective process in the mediolateral (ML) axis than do younger people. The elderly develop a new strategy characterized by the mobilization of higher neuromuscular energy to maintain equilibrium. In the ML axis, the larger displacements could be caused mainly by a hip strategy that could facilitate step initiation. In the anteroposterior (AP) axis, seniors and elderly individuals maintain a relative ability to stabilize their CG into the base of support compared with younger people.

Suppressing beam-centroid motion in a long-pulse linear induction accelerator

NASA Astrophysics Data System (ADS)

Ekdahl, Carl; Abeyta, E. O.; Archuleta, R.; Bender, H.; Broste, W.; Carlson, C.; Cook, G.; Frayer, D.; Harrison, J.; Hughes, T.; Johnson, J.; Jacquez, E.; McCuistian, B. Trent; Montoya, N.; Nath, S.; Nielsen, K.; Rose, C.; Schulze, M.; Smith, H. V.; Thoma, C.; Tom, C. Y.

2011-12-01

The second axis of the dual-axis radiography of hydrodynamic testing (DARHT) facility produces up to four radiographs within an interval of 1.6μs. It does this by slicing four micropulses out of a 2-μs long electron beam pulse and focusing them onto a bremsstrahlung converter target. The 1.8-kA beam pulse is created by a dispenser cathode diode and accelerated to more than 16 MeV by the unique DARHT Axis-II linear induction accelerator (LIA). Beam motion in the accelerator would be a problem for multipulse flash radiography. High-frequency motion, such as from beam-breakup (BBU) instability, would blur the individual spots. Low-frequency motion, such as produced by pulsed-power variation, would produce spot-to-spot differences. In this article, we describe these sources of beam motion, and the measures we have taken to minimize it. Using the methods discussed, we have reduced beam motion at the accelerator exit to less than 2% of the beam envelope radius for the high-frequency BBU, and less than 1/3 of the envelope radius for the low-frequency sweep.

Implementation of Unsteady Double-Axis of Rotation Motion to Predict Pitch-Damping Moment

DTIC Science & Technology

2016-10-18

2014;51(5). 4. Dupuis A. Aeroballistic range and wind tunnel tests of the basic finner reference projectile from subsonic to high supersonic velocities... modelled . Typically, when computing aerodynamic coefficients, motion about each axis is considered individually (i.e., spin around body-axis, pitch about...has a diameter, , of 0.03 m (1 caliber) and consists of a 10° half- angle cone that is 2.84-calibers long, followed by a 7.16-caliber cylindrical

Flight Test of a Propulsion-Based Emergency Control System on the MD-11 Airplane with Emphasis on the Lateral Axis

NASA Technical Reports Server (NTRS)

Burken, John J.; Burcham, Frank W., Jr.; Maine, Trindel A.; Feather, John; Goldthorpe, Steven; Kahler, Jeffrey A.

1996-01-01

A large, civilian, multi-engine transport MD-11 airplane control system was recently modified to perform as an emergency backup controller using engine thrust only. The emergency backup system, referred to as the propulsion-controlled aircraft (PCA) system, would be used if a major primary flight control system fails. To allow for longitudinal and lateral-directional control, the PCA system requires at least two engines and is implemented through software modifications. A flight-test program was conducted to evaluate the PCA system high-altitude flying characteristics and to demonstrate its capacity to perform safe landings. The cruise flight conditions, several low approaches and one landing without any aerodynamic flight control surface movement, were demonstrated. This paper presents results that show satisfactory performance of the PCA system in the longitudinal axis. Test results indicate that the lateral-directional axis of the system performed well at high attitude but was sluggish and prone to thermal upsets during landing approaches. Flight-test experiences and test techniques are also discussed with emphasis on the lateral-directional axis because of the difficulties encountered in flight test.

Postural illusions experienced during Z-axis recumbent rotation and their dependence upon somatosensory stimulation of the body surface

NASA Technical Reports Server (NTRS)

Lackner, J. R.; Graybiel, A.

1978-01-01

A blindfolded recumbent subject experiences a variety of postural illusions when rotated about his Z axis. Initially, during the acceleratory phase of rotation, turning about his Z axis is experienced; but, as rotary velocity increases, a spiraling of the body outward in the direction opposite to true rotation is experienced as well. Above 15-20 rpm, only orbital motion of the body is experienced, with the subject feeling that he is always facing in the same direction. One cycle of the apparent orbit is completed each time the subject actually rotates 360 deg. The reverse sequence of illusory motion is experienced during deceleration. The illusory motion all subjects experience during Z-axis recumbent rotation is shown to depend upon the touch and pressure stimulation of the body surface generated by contact forces of support.

Multi-Axis Prosthetic Knee Resembles Alpine Skiing Movements of an Intact Leg

PubMed Central

Demšar, Ivan; Duhovnik, Jože; Lešnik, Blaž; Supej, Matej

2015-01-01

The purpose of the study was to analyse the flexion angles of the ski boot, ankle and knee joints of an above-knee prosthesis and to compare them with an intact leg and a control group of skiers. One subject with an above-knee amputation of the right leg and eight healthy subjects simulated the movement of a skiing turn by performing two-leg squats in laboratory conditions. By adding additional loads in proportion to body weight (BW; +1/3 BW, +2/3 BW, +3/3 BW), various skiing regimes were simulated. Change of Flexion Angle (CoFA) and Range of Motion (RoM) in the ski boot, ankle and knee joints were calculated and compared. An average RoM in the skiing boot on the side of prosthesis (4.4 ± 1.1°) was significantly lower compared to an intact leg (5.9 ± 1.8°) and the control group (6.5 ± 2.3°). In the ankle joint, the average RoM was determined to be 13.2±2.9° in the prosthesis, 12.7 ± 2.8° in an intact leg and 14.8±3.6 in the control group. However, the RoM of the knee joint in the prosthesis (42.2 ± 4.2°) was significantly larger than that of the intact leg (34.7 ± 4.4°). The average RoM of the knee joint in the control group was 47.8 ± 5.4°. The influences of additional loads on the kinematics of the lower extremities were different on the side of the prosthesis and on the intact leg. In contrast, additional loads did not produce any significant differences in the control group. Although different CoFAs in the ski boot, ankle and knee joints were used, an above-knee prosthesis with a built-in multi-axis prosthetic knee enables comparable leg kinematics in simulated alpine skiing. Key points The RoM in the ski boot on the side of the prosthetic leg was smaller than the RoM of the intact leg and the control group of healthy subjects. The RoM in the ankle joint of prosthetic leg was comparable to that of the intact leg and the control group of healthy subjects. The RoM in the prosthetic knee joint was greater than the RoM in the knee joint of the intact leg and smaller than that of the control group. The total knee flexions in the laboratory measurements were comparable with field measurements. Additional load affects the RoM of the ski boot, ankle and knee joints for the amputated skier in both legs. No significant influence from the additional load was found on the RoM in the control group of healthy subjects. The above-knee prosthesis with a multiple-axis prosthetic knee reproduces the alpine skiing kinematics of an intact leg. PMID:26664282

Multi-Axis Test Facility Orientation

NASA Image and Video Library

1960-03-01

Seven Astronauts and William North undergo Multi Axis Space Test Inertia Facility (MASTIF) orientation: This film contains footage Gus Grissom leaving "Astro-Penthouse" and beginning tests, pilot Joe Algranti explaining the MASTIF to Scott Carpenter, Walter Schirra testing the controls and being strapped in, Deke Slayton climbing into the rig, and John Glenn preparing for test and being briefed by Algranti. Also seen are Alan Shepherd talking with Algranti and James Useller prior to climbing into rig and beginning test, Gordon Cooper being strapped in and beginning his test, Cooper and Algranti briefing to William North prior to his test. North was a test pilot on the NASA committee which selected the Mercury 7 astronauts.

Evaluation of a motion artifacts removal approach on breath-hold cine-magnetic resonance images of hypertrophic cardiomyopathy subjects

NASA Astrophysics Data System (ADS)

Betancur, Julián.; Simon, Antoine; Schnell, Frédéric; Donal, Erwan; Hernández, Alfredo; Garreau, Mireille

2013-11-01

The acquisition of ECG-gated cine magnetic resonance images of the heart is routinely performed in apnea in order to suppress the motion artifacts caused by breathing. However, many factors including the 2D nature of the acquisition and the use of di erent beats to acquire the multiple-view cine images, cause this kind of artifacts to appear. This paper presents the qualitative evaluation of a method aiming to remove motion artifacts in multipleview cine images acquired on patients with hypertrophic cardiomyopathy diagnosis. The approach uses iconic registration to reduce for in-plane artifacts in long-axis-view image stacks and in-plane and out-of-plane motion artifacts in sort-axis-view image stack. Four similarity measures were evaluated: the normalized correlation, the normalized mutual information, the sum of absolute voxel di erences and the Slomka metric proposed by Slomka et al. The qualitative evaluation assessed the misalignment of di erent anatomical structures of the left ventricle as follows: the misalignment of the interventricular septum and the lateral wall for short-axis-view acquisitions and the misalignment between the short-axis-view image and long-axis-view images. Results showed the correction using the normalized correlation as the most appropriated with an 80% of success.

Interpolator for numerically controlled machine tools

DOEpatents

Bowers, Gary L.; Davenport, Clyde M.; Stephens, Albert E.

1976-01-01

A digital differential analyzer circuit is provided that depending on the embodiment chosen can carry out linear, parabolic, circular or cubic interpolation. In the embodiment for parabolic interpolations, the circuit provides pulse trains for the X and Y slide motors of a two-axis machine to effect tool motion along a parabolic path. The pulse trains are generated by the circuit in such a way that parabolic tool motion is obtained from information contained in only one block of binary input data. A part contour may be approximated by one or more parabolic arcs. Acceleration and initial velocity values from a data block are set in fixed bit size registers for each axis separately but simultaneously and the values are integrated to obtain the movement along the respective axis as a function of time. Integration is performed by continual addition at a specified rate of an integrand value stored in one register to the remainder temporarily stored in another identical size register. Overflows from the addition process are indicative of the integral. The overflow output pulses from the second integration may be applied to motors which position the respective machine slides according to a parabolic motion in time to produce a parabolic machine tool motion in space. An additional register for each axis is provided in the circuit to allow "floating" of the radix points of the integrand registers and the velocity increment to improve position accuracy and to reduce errors encountered when the acceleration integrand magnitudes are small when compared to the velocity integrands. A divider circuit is provided in the output of the circuit to smooth the output pulse spacing and prevent motor stall, because the overflow pulses produced in the binary addition process are spaced unevenly in time. The divider has the effect of passing only every nth motor drive pulse, with n being specifiable. The circuit inputs (integrands, rates, etc.) are scaled to give exactly n times the desired number of pulses out, in order to compensate for the divider.

Estimation of the axis of a screw motion from noisy data--a new method based on Plücker lines.

PubMed

Kiat Teu, Koon; Kim, Wangdo

2006-01-01

The problems of estimating the motion and orientation parameters of a body segment from two n point-set patterns are analyzed using the Plücker coordinates of a line (Plücker lines). The aim is to find algorithms less complex than those in conventional use, and thus facilitating more accurate computation of the unknown parameters. All conventional techniques use point transformation to calculate the screw axis. In this paper, we present a novel technique that directly estimates the axis of a screw motion as a Plücker line. The Plücker line can be transformed via the dual-number coordinate transformation matrix. This method is compared with Schwartz and Rozumalski [2005. A new method for estimating joint parameters from motion data. Journal of Biomechanics 38, 107-116] in simulations of random measurement errors and systematic skin movements. Simulation results indicate that the methods based on Plücker lines (Plücker line method) are superior in terms of extremely good results in the determination of the screw axis direction and position as well as a concise derivation of mathematical statements. This investigation yielded practical results, which can be used to locate the axis of a screw motion in a noisy environment. Developing the dual transformation matrix (DTM) from noisy data and determining the screw axis from a given DTM is done in a manner analogous to that for handling simple rotations. A more robust approach to solve for the dual vector associated with DTM is also addressed by using the eigenvector and the singular value decomposition.

Learning Dynamic Control of Body Roll Orientation

PubMed Central

Vimal, Vivekanand Pandey; Lackner, James R.; DiZio, Paul

2016-01-01

Our objective was to examine how the control of orientation is learned in a task involving dynamically balancing about an unstable equilibrium point, the gravitational vertical, in the absence of leg reflexes and muscle stiffness. Subjects (n=10) used a joystick to set themselves to the gravitational vertical while seated in a multi-axis rotation system device (MARS) programmed with inverted pendulum dynamics. The MARS is driven by powerful servomotors and can faithfully follow joystick commands up to 2.5 Hz with a 30 ms latency. To make the task extremely difficult, the pendulum constant was set to 600°/sec2. Each subject participated in 5 blocks of 4 trials, with a trial ending after a cumulative 100 s of balancing, excluding reset times when a subject lost control. To characterize performance and learning, we used metrics derived from joystick movements, phase portraits (joystick deflections vs MARS position and MARS velocity vs angular position), and stabilogram diffusion functions. We found that as subjects improved their balancing performance they did so by making fewer destabilizing joystick movements and reducing the number and duration of joystick commands. The control strategy they acquired involved making more persistent short-term joystick movements, waiting longer before making changes to ongoing motion, and only intervening intermittently. PMID:26525709

[Basic laws of blood screw motion in human common carotid arteries].

PubMed

Kulikov, V P; Kirsanov, R I

2008-08-01

The basic laws of blood screw motion in common carotid arteries in people were determined by means of modern ultrasound techniques for the first time. 92 healthy adults, aged 18-30, were examined. The blood flow in the middle one-third of common carotid arteries was registered by means of Color Doppler Imaging and impulse Doppler with the help of ultrasound Medison 8000EX scanner by linear transducer of 5-9 MHz. The steady registration of blood screw motion in both common carotid arteries in Color Doppler Imaging regimen was observed in 54.3 % of cases. The direction of screw stream rotation in most cases (54%) was multi-directed: in the right common carotid artery it was right, in the left common carotid artery--left (48%), and in 6% of cases it was reverse. For 46% of cases blood rotation in both common carotid arteries was one-directed (26%--right, 20%--left). The velocity parameters of rotation component of blood motion were determined, maximum velocity being 19.68 +/- 5.84 cm/sec, minimum--4.57 +/- 2.89 cm/sec, average--7.48 +/- 2.49 cm/sec, angular--10.7 +/- 2.49 sec(-1). The rated velocity of blood cells motion in screw motion with regard of screw current lines to the vessel vertical axis makes up from 158.67 +/- 32.79 to 224.39 +/- 46.37 cm/sec.

Trunk motion and gait characteristics of pregnant women when walking: report of a longitudinal study with a control group

PubMed Central

2013-01-01

Background A longitudinal repeated measures design over pregnancy and post-birth, with a control group would provide insight into the mechanical adaptations of the body under conditions of changing load during a common female human lifespan condition, while minimizing the influences of inter human differences. The objective was to investigate systematic changes in the range of motion for the pelvic and thoracic segments of the spine, the motion between these segments (thoracolumbar spine) and temporospatial characteristics of step width, stride length and velocity during walking as pregnancy progresses and post-birth. Methods Nine pregnant women were investigated when walking along a walkway at a self-selected velocity using an 8 camera motion analysis system on four occasions throughout pregnancy and once post birth. A control group of twelve non-pregnant nulliparous women were tested on three occasions over the same time period. The existence of linear trends for change was investigated. Results As pregnancy progresses there was a significant linear trend for increase in step width (p = 0.05) and a significant linear trend for decrease in stride length (p = 0.05). Concurrently there was a significant linear trend for decrease in the range of motion of the pelvic segment (p = 0.03) and thoracolumbar spine (p = 0.01) about a vertical axis (side to side rotation), and the pelvic segment (p = 0.04) range of motion around an anterio-posterior axis (side tilt). Post-birth, step width readapted whereas pelvic (p = 0.02) and thoracic (p < 0.001) segment flexion-extension range of motion decreased and increased respectively. The magnitude of all changes was greater than that accounted for with natural variability with re testing. Conclusions As pregnancy progressed and post-birth there were significant linear trends seen in biomechanical changes when walking at a self-determined natural speed that were greater than that accounted for by natural variability with repeated testing. Not all adaptations were resolved by eight weeks post birth. PMID:23514204

Validation of a new method for finding the rotational axes of the knee using both marker-based roentgen stereophotogrammetric analysis and 3D video-based motion analysis for kinematic measurements.

PubMed

Roland, Michelle; Hull, M L; Howell, S M

2011-05-01

In a previous paper, we reported the virtual axis finder, which is a new method for finding the rotational axes of the knee. The virtual axis finder was validated through simulations that were subject to limitations. Hence, the objective of the present study was to perform a mechanical validation with two measurement modalities: 3D video-based motion analysis and marker-based roentgen stereophotogrammetric analysis (RSA). A two rotational axis mechanism was developed, which simulated internal-external (or longitudinal) and flexion-extension (FE) rotations. The actual axes of rotation were known with respect to motion analysis and RSA markers within ± 0.0006 deg and ± 0.036 mm and ± 0.0001 deg and ± 0.016 mm, respectively. The orientation and position root mean squared errors for identifying the longitudinal rotation (LR) and FE axes with video-based motion analysis (0.26 deg, 0.28 m, 0.36 deg, and 0.25 mm, respectively) were smaller than with RSA (1.04 deg, 0.84 mm, 0.82 deg, and 0.32 mm, respectively). The random error or precision in the orientation and position was significantly better (p=0.01 and p=0.02, respectively) in identifying the LR axis with video-based motion analysis (0.23 deg and 0.24 mm) than with RSA (0.95 deg and 0.76 mm). There was no significant difference in the bias errors between measurement modalities. In comparing the mechanical validations to virtual validations, the virtual validations produced comparable errors to those of the mechanical validation. The only significant difference between the errors of the mechanical and virtual validations was the precision in the position of the LR axis while simulating video-based motion analysis (0.24 mm and 0.78 mm, p=0.019). These results indicate that video-based motion analysis with the equipment used in this study is the superior measurement modality for use with the virtual axis finder but both measurement modalities produce satisfactory results. The lack of significant differences between validation techniques suggests that the virtual sensitivity analysis previously performed was appropriately modeled. Thus, the virtual axis finder can be applied with a thorough understanding of its errors in a variety of test conditions.

Fast susceptibility-weighted imaging with three-dimensional short-axis propeller (SAP)-echo-planar imaging.

PubMed

Holdsworth, Samantha J; Yeom, Kristen W; Moseley, Michael E; Skare, S

2015-05-01

Susceptibility-weighted imaging (SWI) in neuroimaging can be challenging due to long scan times of three-dimensional (3D) gradient recalled echo (GRE), while faster techniques such as 3D interleaved echo-planar imaging (iEPI) are prone to motion artifacts. Here we outline and implement a 3D short-axis propeller echo-planar imaging (SAP-EPI) trajectory as a faster, motion-correctable approach for SWI. Experiments were conducted on a 3T MRI system. The 3D SAP-EPI, 3D iEPI, and 3D GRE SWI scans were acquired on two volunteers. Controlled motion experiments were conducted to test the motion-correction capability of 3D SAP-EPI. The 3D SAP-EPI SWI data were acquired on two pediatric patients as a potential alternative to 2D GRE used clinically. The 3D GRE images had a better target resolution (0.47 × 0.94 × 2 mm, scan time = 5 min), iEPI and SAP-EPI images (resolution = 0.94 × 0.94 × 2 mm) were acquired in a faster scan time (1:52 min) with twice the brain coverage. SAP-EPI showed motion-correction capability and some immunity to undersampling from rejected data. While 3D SAP-EPI suffers from some geometric distortion, its short scan time and motion-correction capability suggest that SAP-EPI may be a useful alternative to GRE and iEPI for use in SWI, particularly in uncooperative patients. © 2014 Wiley Periodicals, Inc.

The potential of multi-slice computed tomography based volumetry for demonstrating reverse remodeling induced by cardiac resynchronization therapy.

PubMed

Langer, Christoph; Schroeder, Janina; Peterschroeder, Andreas; Vaske, Bernhard; Faber, Lothar; Welge, Dirk; Niethammer, Matthias; Lamp, Barbara; Butz, Thomas; Bitter, Thomas; Oldenburg, Olaf; Horstkotte, Dieter

2010-07-01

Multi-slice computed tomography (MSCT) was proved to provide precise cardiac volumetric assessment. Cardiac resynchronization therapy (CRT) is an effective treatment for selected patients with heart failure and reduced ejection fraction (HFREF). In HFREF patients we investigated the potential of MSCT based wall motion analysis in order to demonstrate CRT-induced reversed remodeling. Besides six patients with normal cardiac pump function serving as control group seven HFREF patients underwent contrast enhanced MSCT before and after CRT. Short cardiac axis views of the left ventricle (LV) in end-diastole (ED) and end-systole (ES) served for planimetry. Pre- and post-CRT MSCT based volumetry was compared with 2D echo. To demonstrate CRT-induced reverse remodeling, MSCT based multi-segment color-coded polar maps were introduced. With regard to the HFREF patients pre-CRT MSCT based volumetry correlated with 2D echo data for LV-EDV (MSCT 278.3+/-75.0mL vs. echo 274.4+/-85.6mL) r=0.380, p=0.401, LV-ESV (MSCT 226.7+/-75.4mL vs. echo 220.1+/-74.0mL) r=0.323, p=0.479 and LV-EF (MSCT 20.2+/-8.8% vs. echo 20.0+/-11.9%) r=0.617, p=0.143. Post-CRT MSCT correlated well with 2D echo: LV-EDV (MSCT 218.9+/-106.4mL vs. echo 188.7+/-93.1mL) r=0.87, p=0.011, LV-ESV (MSCT 145+/-71.5mL vs. echo 125.6+/-78mL) r=0.84, p=0.018 and LV-EF (MSCT 29.6+/-11.3mL vs. echo 38.6+/-14.6mL) r=0.89, p=0.007. There was a significant increase of the mid-ventricular septum in terms of absolute LV wall thickening of the responders (pre 0.9+/-2.1mm vs. post 3.3+/-2.2mm; p<0.0005). MSCT based volumetry involving multi-segment color-coded polar maps offers wall motion analysis to demonstrate CRT-induced reverse remodeling which needs to be further validated. 2010 Elsevier Ltd. All rights reserved.

Computer simulation of aircraft motions and propulsion system dynamics for the YF-12 aircraft at supersonic cruise conditions

NASA Technical Reports Server (NTRS)

Brown, S. C.

1973-01-01

A computer simulation of the YF-12 aircraft motions and propulsion system dynamics is presented. The propulsion system was represented in sufficient detail so that interactions between aircraft motions and the propulsion system dynamics could be investigated. Six degree-of-freedom aircraft motions together with the three-axis stability augmentation system were represented. The mixed compression inlets and their controls were represented in the started mode for a range of flow conditions up to the inlet unstart boundary. Effects of inlet moving geometry on aircraft forces and movements as well as effects of aircraft motions on the inlet behavior were simulated. The engines, which are straight subjects, were represented in the afterburning mode, with effects of changes in aircraft flight conditions included. The simulation was capable of operating in real time.

Accurate free and forced rotational motions of rigid Venus

NASA Astrophysics Data System (ADS)

Cottereau, L.; Souchay, J.; Aljbaae, S.

2010-06-01

Context. The precise and accurate modelling of a terrestrial planet like Venus is an exciting and challenging topic, all the more interesting because it can be compared with that of Earth for which such a modelling has already been achieved at the milli-arcsecond level. Aims: We aim to complete a previous study, by determining the polhody at the milli-arcsecond level, i.e. the torque-free motion of the angular momentum axis of a rigid Venus in a body-fixed frame, as well as the nutation of its third axis of figure in space, which is fundamental from an observational point of view. Methods: We use the same theoretical framework as Kinoshita (1977, Celest. Mech., 15, 277) did to determine the precession-nutation motion of a rigid Earth. It is based on a representation of the rotation of a rigid Venus, with the help of Andoyer variables and a set of canonical equations in Hamiltonian formalism. Results: In a first part we computed the polhody, we showed that this motion is highly elliptical, with a very long period of 525 cy compared with 430 d for the Earth. This is due to the very small dynamical flattening of Venus in comparison with our planet. In a second part we precisely computed the Oppolzer terms, which allow us to represent the motion in space of the third Venus figure axis with respect to the Venus angular momentum axis under the influence of the solar gravitational torque. We determined the corresponding tables of the nutation coefficients of the third figure axis both in longitude and in obliquity due to the Sun, which are of the same order of amplitude as for the Earth. We showed that the nutation coefficients for the third figure axis are significantly different from those of the angular momentum axis on the contrary of the Earth. Our analytical results have been validated by a numerical integration, which revealed the indirect planetary effects.

Study on robot motion control for intelligent welding processes based on the laser tracking sensor

NASA Astrophysics Data System (ADS)

Zhang, Bin; Wang, Qian; Tang, Chen; Wang, Ju

2017-06-01

A robot motion control method is presented for intelligent welding processes of complex spatial free-form curve seams based on the laser tracking sensor. First, calculate the tip position of the welding torch according to the velocity of the torch and the seam trajectory detected by the sensor. Then, search the optimal pose of the torch under constraints using genetic algorithms. As a result, the intersection point of the weld seam and the laser plane of the sensor is within the detectable range of the sensor. Meanwhile, the angle between the axis of the welding torch and the tangent of the weld seam meets the requirements. The feasibility of the control method is proved by simulation.

Multi-Axis Space Inertia Test Facility inside the Altitude Wind Tunnel

NASA Image and Video Library

1960-04-21

The Multi-Axis Space Test Inertial Facility (MASTIF) in the Altitude Wind Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. Although the Mercury astronaut training and mission planning were handled by the Space Task Group at Langley Research Center, NASA Lewis played an important role in the program, beginning with the Big Joe launch. Big Joe was a singular attempt early in the program to use a full-scale Atlas booster and simulate the reentry of a mockup Mercury capsule without actually placing it in orbit. A unique three-axis gimbal rig was built inside Lewis’ Altitude Wind Tunnel to test Big Joe’s attitude controls. The control system was vital since the capsule would burn up on reentry if it were not positioned correctly. The mission was intended to assess the performance of the Atlas booster, the reliability of the capsule’s attitude control system and beryllium heat shield, and the capsule recovery process. The September 9, 1959 launch was a success for the control system and heatshield. Only a problem with the Atlas booster kept the mission from being a perfect success. The MASTIF was modified in late 1959 to train Project Mercury pilots to bring a spinning spacecraft under control. An astronaut was secured in a foam couch in the center of the rig. The rig then spun on three axes from 2 to 50 rotations per minute. Small nitrogen gas thrusters were used by the astronauts to bring the MASTIF under control.

Mechatronic Development and Vision Feedback Control of a Nanorobotics Manipulation System inside SEM for Nanodevice Assembly

PubMed Central

Yang, Zhan; Wang, Yaqiong; Yang, Bin; Li, Guanghui; Chen, Tao; Nakajima, Masahiro; Sun, Lining; Fukuda, Toshio

2016-01-01

Carbon nanotubes (CNT) have been developed in recent decades for nanodevices such as nanoradios, nanogenerators, carbon nanotube field effect transistors (CNTFETs) and so on, indicating that the application of CNTs for nanoscale electronics may play a key role in the development of nanotechnology. Nanorobotics manipulation systems are a promising method for nanodevice construction and assembly. For the purpose of constructing three-dimensional CNTFETs, a nanorobotics manipulation system with 16 DOFs was developed for nanomanipulation of nanometer-scale objects inside the specimen chamber of a scanning electron microscope (SEM). Nanorobotics manipulators are assembled into four units with four DOFs (X-Y-Z-θ) individually. The rotational one is actuated by a picomotor. That means a manipulator has four DOFs including three linear motions in the X, Y, Z directions and a 360-degree rotational one (X-Y-Z-θ stage, θ is along the direction rotating with X or Y axis). Manipulators are actuated by picomotors with better than 30 nm linear resolution and <1 micro-rad rotary resolution. Four vertically installed AFM cantilevers (the axis of the cantilever tip is vertical to the axis of electronic beam of SEM) served as the end-effectors to facilitate the real-time observation of the operations. A series of kinematic derivations of these four manipulators based on the Denavit-Hartenberg (D-H) notation were established. The common working space of the end-effectors is 2.78 mm by 4.39 mm by 6 mm. The manipulation strategy and vision feedback control for multi-manipulators operating inside the SEM chamber were been discussed. Finally, application of the designed nanorobotics manipulation system by successfully testing of the pickup-and-place manipulation of an individual CNT onto four probes was described. The experimental results have shown that carbon nanotubes can be successfully picked up with this nanorobotics manipulation system. PMID:27649180

Mechatronic Development and Vision Feedback Control of a Nanorobotics Manipulation System inside SEM for Nanodevice Assembly.

PubMed

Yang, Zhan; Wang, Yaqiong; Yang, Bin; Li, Guanghui; Chen, Tao; Nakajima, Masahiro; Sun, Lining; Fukuda, Toshio

2016-09-14

Carbon nanotubes (CNT) have been developed in recent decades for nanodevices such as nanoradios, nanogenerators, carbon nanotube field effect transistors (CNTFETs) and so on, indicating that the application of CNTs for nanoscale electronics may play a key role in the development of nanotechnology. Nanorobotics manipulation systems are a promising method for nanodevice construction and assembly. For the purpose of constructing three-dimensional CNTFETs, a nanorobotics manipulation system with 16 DOFs was developed for nanomanipulation of nanometer-scale objects inside the specimen chamber of a scanning electron microscope (SEM). Nanorobotics manipulators are assembled into four units with four DOFs (X-Y-Z-θ) individually. The rotational one is actuated by a picomotor. That means a manipulator has four DOFs including three linear motions in the X, Y, Z directions and a 360-degree rotational one (X-Y-Z-θ stage, θ is along the direction rotating with X or Y axis). Manipulators are actuated by picomotors with better than 30 nm linear resolution and <1 micro-rad rotary resolution. Four vertically installed AFM cantilevers (the axis of the cantilever tip is vertical to the axis of electronic beam of SEM) served as the end-effectors to facilitate the real-time observation of the operations. A series of kinematic derivations of these four manipulators based on the Denavit-Hartenberg (D-H) notation were established. The common working space of the end-effectors is 2.78 mm by 4.39 mm by 6 mm. The manipulation strategy and vision feedback control for multi-manipulators operating inside the SEM chamber were been discussed. Finally, application of the designed nanorobotics manipulation system by successfully testing of the pickup-and-place manipulation of an individual CNT onto four probes was described. The experimental results have shown that carbon nanotubes can be successfully picked up with this nanorobotics manipulation system.

Sequence-dependent rotation axis changes and interaction torque use in overarm throwing.

PubMed

Hansen, Clint; Rezzoug, Nasser; Gorce, Philippe; Venture, Gentiane; Isableu, Brice

2016-01-01

We examined the role of rotation axes during an overarm throwing task. Participants performed such task and were asked to throw a ball at maximal velocity at a target. The purpose of this study was to examine whether the minimum inertia axis would be exploited during the throwing phases, a time when internal-external rotations of the shoulder are particularly important. A motion capture system was used to evaluate the performance and to compute the potential axes of rotation (minimum inertia axis, shoulder-centre of mass axis and the shoulder-elbow axis). More specifically, we investigated whether a velocity-dependent change in rotational axes can be observed in the different throwing phases and whether the control obeys the principle of minimum inertia resistance. Our results showed that the limbs' rotational axis mainly coincides with the minimum inertia axis during the cocking phase and with the shoulder-elbow axis during the acceleration phase. Besides these rotation axes changes, the use of interaction torque is also sequence-dependent. The sequence-dependent rotation axes changes associated with the use of interaction torque during the acceleration phase could be a key factor in the production of hand velocity at ball release.

Comparison of individual pitch and smart rotor control strategies for load reduction

NASA Astrophysics Data System (ADS)

Plumley, C.; Leithead, W.; Jamieson, P.; Bossanyi, E.; Graham, M.

2014-06-01

Load reduction is increasingly seen as an essential part of controller and wind turbine design. On large multi-MW wind turbines that experience high levels of wind shear and turbulence across the rotor, individual pitch control and smart rotor control are being considered. While individual pitch control involves adjusting the pitch of each blade individually to reduce the cyclic loadings on the rotor, smart rotor control involves activating control devices distributed along the blades to alter the local aerodynamics of the blades. Here we investigate the effectiveness of using a DQ-axis control and a distributed (independent) control for both individual pitch and trailing edge flap smart rotor control. While load reductions are similar amongst the four strategies across a wide range of variables, including blade root bending moments, yaw bearing and shaft, the pitch actuator requirements vary. The smart rotor pitch actuator has reduced travel, rates, accelerations and power requirements than that of the individual pitch controlled wind turbines. This benefit alone however would be hard to justify the added design complexities of using a smart rotor, which can be seen as an alternative to upgrading the pitch actuator and bearing. In addition, it is found that the independent control strategy is apt at roles that the collective pitch usually targets, such as tower motion and speed control, and it is perhaps here, in supplementing other systems, that the future of the smart rotor lies.

Voyager Saturn encounter attitude and articulation control experience

NASA Technical Reports Server (NTRS)

Carlisle, G.; Hill, M.

1981-01-01

The Voyager attitude and articulation control system is designed for a three-axis stabilized spacecraft; it uses a biasable sun sensor and a Canopus Star Tracker (CST) for celestial control, as well as a dry inertial reference unit, comprised of three dual-axis dry gryos, for inertial control. A series of complex maneuvers was required during the first of two Voyager spacecraft encounters with Saturn (November 13, 1980); these maneuvers involved rotating the spacecraft simultaneously about two or three axes while maintaining accurate pointing of the scan platform. Titan and Saturn earth occulation experiments and a ring scattering experiment are described. Target motion compensation and the effects of celestial sensor interference are also considered. Failure of the CST, which required an extensive reevaluation of the star reference and attitude control mode strategy, is discussed. Results analyzed thus far show that the system performed with high accuracy, gathering data deeper into Saturn's atmosphere than on any previous planetary encounter.

Modeling human vestibular responses during eccentric rotation and off vertical axis rotation

NASA Technical Reports Server (NTRS)

Merfeld, D. M.; Paloski, W. H. (Principal Investigator)

1995-01-01

A mathematical model has been developed to help explain human multi-sensory interactions. The most important constituent of the model is the hypothesis that the nervous system incorporates knowledge of sensory dynamics into an "internal model" of these dynamics. This internal model allows the nervous system to integrate the sensory information from many different sensors into a coherent estimate of self-motion. The essence of the model is unchanged from a previously published model of monkey eye movement responses; only a few variables have been adjusted to yield the prediction of human responses. During eccentric rotation, the model predicts that the axis of eye rotation shifts slightly toward alignment with gravito-inertial force. The model also predicts that the time course of the perception of tilt following the acceleration phase of eccentric rotation is much slower than that during deceleration. During off vertical axis rotation (OVAR) the model predicts a small horizontal bias along with small horizontal, vertical, and torsional oscillations. Following OVAR stimulation, when stopped right- or left-side down, a small vertical component is predicted that decays with the horizontal post-rotatory response. All of the predictions are consistent with measurements of human responses.

HARV ANSER Flight Test Data Retrieval and Processing Procedures

NASA Technical Reports Server (NTRS)

Yeager, Jessie C.

1997-01-01

Under the NASA High-Alpha Technology Program the High Alpha Research Vehicle (HARV) was used to conduct flight tests of advanced control effectors, advanced control laws, and high-alpha design guidelines for future super-maneuverable fighters. The High-Alpha Research Vehicle is a pre-production F/A-18 airplane modified with a multi-axis thrust-vectoring system for augmented pitch and yaw control power and Actuated Nose Strakes for Enhanced Rolling (ANSER) to augment body-axis yaw control power. Flight testing at the Dryden Flight Research Center (DFRC) began in July 1995 and continued until May 1996. Flight data will be utilized to evaluate control law performance and aircraft dynamics, determine aircraft control and stability derivatives using parameter identification techniques, and validate design guidelines. To accomplish these purposes, essential flight data parameters were retrieved from the DFRC data system and stored on the Dynamics and Control Branch (DCB) computer complex at Langley. This report describes the multi-step task used to retrieve and process this data and documents the results of these tasks. Documentation includes software listings, flight information, maneuver information, time intervals for which data were retrieved, lists of data parameters and definitions, and example data plots.

Models for the Effects of G-seat Cuing on Roll-axis Tracking Performance

NASA Technical Reports Server (NTRS)

Levison, W. H.; Mcmillan, G. R.; Martin, E. A.

1984-01-01

Including whole-body motion in a flight simulator improves performance for a variety of tasks requiring a pilot to compensate for the effects of unexpected disturbances. A possible mechanism for this improvement is that whole-body motion provides high derivative vehicle state information whic allows the pilot to generate more lead in responding to the external disturbances. During development of motion simulating algorithms for an advanced g-cuing system it was discovered that an algorithm based on aircraft roll acceleration producted little or no performance improvement. On the other hand, algorithms based on roll position or roll velocity produced performance equivalent to whole-body motion. The analysis and modeling conducted at both the sensory system and manual control performance levels to explain the above results are described.

High speed, precision motion strategies for lightweight structures

NASA Technical Reports Server (NTRS)

Book, Wayne J.

1987-01-01

Abstracts of published papers and dissertations generated during the reporting period are compiled. Work on fine motion control was completed. Specifically, real time control of flexible manipulator vibrations were experimentally investigated. A linear model based on the application of Lagrangian dynamics to a rigid body mode and a series of separable flexible modes was examined with respect to model order requirements, and modal candidate selection. State feedback control laws were implemented based upon linear quadratic regulator design. Specification of the closed loop poles in the regulator design process was obtained by inclusion of a prescribed degree of stability in the manipulator model. Work on gross motion planning and control is also summarized. A systematic method to symbolically derive the full nonlinear dynamic equations of motion of multi-link flexible manipulators was developed.

Attitude motion of a non-attitude-controlled cylindrical satellite

NASA Technical Reports Server (NTRS)

Wilkinson, C. K.

1988-01-01

In 1985, two non-attitude-controlled satellites were each placed in a low earth orbit by the Scout Launch Vehicle. The satellites were cylindrical in shape and contained reservoirs of hydrazine fuel. Three-axis magnetometer measurements, telemetered in real time, were used to derive the attitude motion of each satellite. Algorithms are generated to deduce possible orientations (and magnitudes) of each vehicle's angular momentum for each telemetry contact. To resolve ambiguities at each contact, a force model was derived to simulate the significant long-term effects of magnetic, gravity gradient, and aerodynamic torques on the angular momentum of the vehicles. The histories of the orientation and magnitude of the angular momentum are illustrated.

Two-point motional Stark effect diagnostic for Madison Symmetric Torus

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

Ko, J.; Den Hartog, D. J.; Caspary, K. J.

2010-10-15

A high-precision spectral motional Stark effect (MSE) diagnostic provides internal magnetic field measurements for Madison Symmetric Torus (MST) plasmas. Currently, MST uses two spatial views - on the magnetic axis and on the midminor (off-axis) radius, the latter added recently. A new analysis scheme has been developed to infer both the pitch angle and the magnitude of the magnetic field from MSE spectra. Systematic errors are reduced by using atomic data from atomic data and analysis structure in the fit. Reconstructed current density and safety factor profiles are more strongly and globally constrained with the addition of the off-axis radiusmore » measurement than with the on-axis one only.« less

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.

Fuzzy logic control of an AGV

NASA Astrophysics Data System (ADS)

Kelkar, Nikhal; Samu, Tayib; Hall, Ernest L.

1997-09-01

Automated guided vehicles (AGVs) have many potential applications in manufacturing, medicine, space and defense. The purpose of this paper is to describe exploratory research on the design of a modular autonomous mobile robot controller. The controller incorporates a fuzzy logic approach for steering and speed control, a neuro-fuzzy approach for ultrasound sensing (not discussed in this paper) and an overall expert system. The advantages of a modular system are related to portability and transportability, i.e. any vehicle can become autonomous with minimal modifications. A mobile robot test-bed has been constructed using a golf cart base. This cart has full speed control with guidance provided by a vision system and obstacle avoidance using ultrasonic sensors. The speed and steering fuzzy logic controller is supervised by a 486 computer through a multi-axis motion controller. The obstacle avoidance system is based on a micro-controller interfaced with six ultrasonic transducers. This micro- controller independently handles all timing and distance calculations and sends a steering angle correction back to the computer via the serial line. This design yields a portable independent system in which high speed computer communication is not necessary. Vision guidance is accomplished with a CCD camera with a zoom lens. The data is collected by a vision tracking device that transmits the X, Y coordinates of the lane marker to the control computer. Simulation and testing of these systems yielded promising results. This design, in its modularity, creates a portable autonomous fuzzy logic controller applicable to any mobile vehicle with only minor adaptations.

Motion-free hybrid design laser beam propagation analyzer using a digital micromirror device and a variable focus liquid lens.

PubMed

Sheikh, Mumtaz; Riza, Nabeel A

2010-06-01

To the best of our knowledge, we propose the first motion-free laser beam propagation analyzer with a hybrid design using a digital micromirror device (DMD) and a liquid electronically controlled variable focus lens (ECVFL). Unlike prior analyzers that require profiling the beam at multiple locations along the light propagation axis, the proposed analyzer profiles the beam at the same plane for multiple values of the ECVFL focal length, thus eliminating beam profiler assembly motion. In addition to measuring standard Gaussian beam parameters, the analyzer can also be used to measure the M(2) beam propagation parameter of a multimode beam. Proof-of-concept beam parameter measurements with the proposed analyzer are successfully conducted for a 633 nm laser beam. Given the all-digital nature of the DMD-based profiling and all-analog motion-free nature of the ECVFL beam focus control, the proposed analyzer versus prior art promises better repeatability, speed, and reliability.

Flow Behavior Around a Fast-Starting Robotic Fish

NASA Astrophysics Data System (ADS)

Ma, Ganzhong; Currier, Todd; Modarres-Sadeghi, Yahya

2017-11-01

A robotic fish is used to study the flow behavior around the body of a fast-starting fish as it experiences a fast-start. The robotic fish is designed and built emulating a Northern Pike, Esox Lucius, which can accelerate at up to 245 m/s2. In previous studies, we had focused on the flow around the tail during the fast-start, by using a tail which acted flexibly in the preparatory stage and rigidly in the propulsive stage. We have extended that study by including the fish body in the experimental setup, where the body can bend into a C-shape, so that the influence of the body motion on the resulting flow around the structure can be understood as well. In the tests, the fish can rotate about a vertical axis, where a multi-axis force sensor measures flow forces acting on the body. Synchronized with the force measurement, flow visualizations using bubble image velocimetry are conducted, and the observed shed vortices are related to the peak forces observed during the maneuver.

Advanced Multi-Axis Spine Testing: Clinical Relevance and Research Recommendations

PubMed Central

Holsgrove, Timothy P.; Nayak, Nikhil R.; Welch, William C.

2015-01-01

Back pain and spinal degeneration affect a large proportion of the general population. The economic burden of spinal degeneration is significant, and the treatment of spinal degeneration represents a large proportion of healthcare costs. However, spinal surgery does not always provide improved clinical outcomes compared to non-surgical alternatives, and modern interventions, such as total disc replacement, may not offer clinically relevant improvements over more established procedures. Although psychological and socioeconomic factors play an important role in the development and response to back pain, the variation in clinical success is also related to the complexity of the spine, and the multi-faceted manner by which spinal degeneration often occurs. The successful surgical treatment of degenerative spinal conditions requires collaboration between surgeons, engineers, and scientists in order to provide a multi-disciplinary approach to managing the complete condition. In this review, we provide relevant background from both the clinical and the basic research perspectives, which is synthesized into several examples and recommendations for consideration in increasing translational research between communities with the goal of providing improved knowledge and care. Current clinical imaging, and multi-axis testing machines, offer great promise for future research by combining invivo kinematics and loading with in-vitro testing in six degrees of freedom to offer more accurate predictions of the performance of new spinal instrumentation. Upon synthesis of the literature, it is recommended that in-vitro tests strive to recreate as many aspects of the in-vivo environment as possible, and that a physiological preload is a critical factor in assessing spinal biomechanics in the laboratory. A greater link between surgical procedures, and the outcomes in all three anatomical planes should be considered in both the in-vivo and in-vitro settings, to provide data relevant to quality of motion, and stability. PMID:26273552

Dual-mode disturbance-accommodating pointing controller for Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Addington, Stewart I.; Johnson, C. D.

1995-03-01

Cyclic thermal expansions and mechanical stiction effects in the solar arrays on the Hubble Space Telescope (HST) are triggering repeated occurrences of damped, relaxation-type flex-body vibrations of the solar arrays. Those solar array vibrations are, in turn, causing unwanted deviations of the telescope from its specified pointing direction. In this paper we propose two strategies one can adopt in designing a telescope-pointing controller to cope with the aforementioned disturbances: 1) a total isolation (TI) control strategy whereby the HST controller torques are designed to adaptively counteract and cancel out the persistent disturbing torques that are causing the unwanted telescope motions and 2) an array damping (AD) control strategy whereby the HST controller torques are used to actively augment the natural dampening of the solar array vibrations and the attendant telescope motions, between triggerings of the stiction-related flex-body relaxation oscillations. Using the principles of disturbance accommodation control theory, a dual-mode controller for a generic, planar-motion (single-axis) model of the HST is proposed. This controller incorporates both the TI and AD modes of disturbance accommodation. Simulation studies of the closed-loop system using generic parameter values clearly indicate, qualitatively, the enhanced pointing performance such a controller can achieve.

A mechanical simulator of cardiac wall kinematics.

PubMed

Cutrì, Elena; Bagnoli, Paola; Marcelli, Emanuela; Biondi, Federico; Cercenelli, Laura; Costantino, Maria Laura; Plicchi, Gianni; Fumero, Roberto

2010-01-01

Aim of this study is to develop a mechanical simulator (MS) reproducing cardiac wall kinematics [i.e., radial (R), longitudinal (L) and rotational (RT) motions] to test piezoelectric gyroscopic sensors (GS) that are able to measure cardiac torsion that has proved to be a sensitive index of cardiac performance. The MS consists of three brushless motors controlled by a dedicated software either separately or simultaneously reproducing the three main cardiac wall movements (R, L, RT) obtained by implementing different physiologic or pathologic velocity profiles derived from in vivo data. GS accuracy (max % error) was experimentally tested by connecting it to the MS driven in velocity in different working conditions [i.e., cardiac period (515-1030 ms), RT angle (4-16 degrees), GS axis inclination (0-90 degrees) with respect to the cardiac rotation axis]. The MS reproduced the tested velocity profiles well. The GS showed high accuracy in measuring both physiologic and pathologic RT velocity profiles, whereas they proved insensitive to R and L motions. GS axis inclination influenced measurements; however, it was possible to correct this taking the inclination angle cosine into account. The MS proved to be a useful tool to study cardiac wall kinematics and test GS reliability with a view to in vivo application.

Analysis multi-agent with precense of the leader

NASA Astrophysics Data System (ADS)

Achmadi, Sentot; Marjono, Miswanto

2017-12-01

The phenomenon of swarm is a natural phenomenon that is often done by a collection of living things in the form of motion from one place to another. By clustering, a group of animals can increase their effectiveness in food search and avoid predators. A group of geese also performs a swarm phenomenon when flying and forms an inverted V-formation with one of the geese acting as a leader. Each flying track of members of the geese group always follows the leader's path at a certain distance. This article discusses the mathematical modeling of the swarm phenomenon, which is the optimal tracking control for multi-agent model with the influence of the leader in the 2-dimensional space. The leader in this model is intended to track the specified path. Firstly, the leader's motion control is to follow the predetermined path using the Tracking Error Dynamic method. Then, the path from the leader is used to design the motion control of each agent to track the leader's path at a certain distance. The result of numerical simulation shows that the leader trajectory can track the specified path. Similarly, the motion of each agent can trace and follow the leader's path.

Effects of multi-directional vibrotactile feedback on vestibular-deficient postural performance during continuous multi-directional support surface perturbations.

PubMed

Sienko, K H; Balkwill, M D; Oddsson, L I E; Wall, C

2008-01-01

Single-axis vibrotactile feedback of trunk tilt provided in real-time has previously been shown to significantly reduce the root-mean-square (RMS) trunk sway in subjects with vestibular loss during single-axis perturbation. This research examines the effect of multi-directional vibrotactile feedback on postural sway during continuous multi-directional surface perturbations when the subjects' eyes are closed. Eight subjects with vestibular loss donned a multi-axis feedback device that mapped body tilt estimates onto their torsos with a 3-row by 16-column array of tactile actuators (tactors). Tactor row indicated tilt magnitude and tactor column indicated tilt direction. Root-mean-square trunk tilt, elliptical fits to trunk sway trajectory areas, percentage of time spent outside a no vibrotactile feedback zone, RMS center of pressure, and anchoring index parameters indicating intersegmental coordination were used to assess the efficacy of the multi-directional vibrotactile balance aid. Four tactor display configurations in addition to the tactors off configuration were evaluated. Subjects had significantly reduced RMS trunk sway, significantly smaller elliptical fits of the trajectory area, and spent significantly less time outside of the no feedback zone in the tactors on versus the tactors off configuration. Among the displays evaluated in this study, there was not an optimal tactor column configuration for standing tasks involving continuous surface perturbations. Furthermore, subjects performed worse when erroneous information was displayed. Therefore, a spatial resolution of 90 degrees (4 columns) seems to be as effective as a spatial resolution of 22.5 degrees (16 columns) for control of standing.

Relative-Motion Sensors and Actuators for Two Optical Tables

NASA Technical Reports Server (NTRS)

Gursel, Yekta; McKenney, Elizabeth

2004-01-01

Optoelectronic sensors and magnetic actuators have been developed as parts of a system for controlling the relative position and attitude of two massive optical tables that float on separate standard air suspensions that attenuate ground vibrations. In the specific application for which these sensors and actuators were developed, one of the optical tables holds an optical system that mimics distant stars, while the other optical table holds a test article that simulates a spaceborne stellar interferometer that would be used to observe the stars. The control system is designed to suppress relative motion of the tables or, on demand, to impose controlled relative motion between the tables. The control system includes a sensor system that detects relative motion of the tables in six independent degrees of freedom and a drive system that can apply force to the star-simulator table in the six degrees of freedom. The sensor system includes (1) a set of laser heterodyne gauges and (2) a set of four diode lasers on the star-simulator table, each aimed at one of four quadrant photodiodes at nominal corresponding positions on the test-article table. The heterodyne gauges are used to measure relative displacements along the x axis.

Numerical investigation of flow motion and performance of a horizontal axis tidal turbine subjected to a steady current

NASA Astrophysics Data System (ADS)

Li, Lin-juan; Zheng, Jin-hai; Peng, Yu-xuan; Zhang, Ji-sheng; Wu, Xiu-guang

2015-04-01

Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k- ɛ model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.

Automatic control in multidrive electrotechnical complexes with semiconductor converters

NASA Astrophysics Data System (ADS)

Vasilev, B. U.; Mardashov, D. V.

2017-01-01

The frequency convertor and the automatic control system, which can be used in the multi-drive electromechanical system with a few induction motions, are considered. The paper presents the structure of existing modern multi-drive electric drives inverters, namely, electric drives with a total frequency converter and few electric motions, and an electric drive, in which the converter is used for power supply and control of the independent frequency. It was shown that such technical solutions of frequency converters possess a number of drawbacks. The drawbacks are given. It was shown that the control of technological processes using the electric drive of this structure may be provided under very limited conditions, as the energy efficiency and the level of electromagnetic compatibility of electric drives is low. The authors proposed using a multi-inverter structure with an active rectifier in multidrive electric drives with induction motors frequency converters. The application of such frequency converter may solve the problem of electromagnetic compatibility, namely, consumption of sinusoidal currents from the network and the maintenance of a sinusoidal voltage and energy compatibility, namely, consumption of practically active energy from the network. Also, the paper proposes the use of the automatic control system, which by means of a multi-inverter frequency converter provides separate control of drive machines and flexible regulation of technological processes. The authors present oscillograms, which confirm the described characteristics of the developed electrical drive. The possible subsequent ways to improve the multi-motor drives are also described.

Control of an automated mobile manipulator using artificial immune system

NASA Astrophysics Data System (ADS)

Deepak, B. B. V. L.; Parhi, Dayal R.

2016-03-01

This paper addresses the coordination and control of a wheeled mobile manipulator (WMM) using artificial immune system. The aim of the developed methodology is to navigate the system autonomously and transport jobs and tools in manufacturing environments. This study integrates the kinematic structures of a four-axis manipulator and a differential wheeled mobile platform. The motion of the developed WMM is controlled by the complete system of parametric equation in terms of joint velocities and makes the robot to follow desired trajectories by the manipulator and platform within its workspace. The developed robot system performs its action intelligently according to the sensed environmental criteria within its search space. To verify the effectiveness of the proposed immune-based motion planner for WMM, simulations as well as experimental results are presented in various unknown environments.

ZAG-Otolith: Modification of Otolith-Ocular Reflexes, Motion Perception and Manual Control during Variable Radius Centrifugation Following Space Flight

NASA Technical Reports Server (NTRS)

Wood, S. J.; Clarke, A. H.; Rupert, A. H.; Harm, D. L.; Clement, G. R.

2009-01-01

Two joint ESA-NASA studies are examining changes in otolith-ocular reflexes and motion perception following short duration space flights, and the operational implications of post-flight tilt-translation ambiguity for manual control performance. Vibrotactile feedback of tilt orientation is also being evaluated as a countermeasure to improve performance during a closed-loop nulling task. METHODS. Data is currently being collected on astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation is utilized to elicit otolith reflexes in the lateral plane without concordant roll canal cues. Unilateral centrifugation (400 deg/s, 3.5 cm radius) stimulates one otolith positioned off-axis while the opposite side is centered over the axis of rotation. During this paradigm, roll-tilt perception is measured using a subjective visual vertical task and ocular counter-rolling is obtained using binocular video-oculography. During a second paradigm (216 deg/s, <20 cm radius), the effects of stimulus frequency (0.15 - 0.6 Hz) are examined on eye movements and motion perception. A closed-loop nulling task is also performed with and without vibrotactile display feedback of chair radial position. PRELIMINARY RESULTS. Data collection is currently ongoing. Results to date suggest there is a trend for perceived tilt and translation amplitudes to be increased at the low and medium frequencies on landing day compared to pre-flight. Manual control performance is improved with vibrotactile feedback. DISCUSSION. One result of this study will be to characterize the variability (gain, asymmetry) in both otolithocular responses and motion perception during variable radius centrifugation, and measure the time course of postflight recovery. This study will also address how adaptive changes in otolith-mediated reflexes correspond to one's ability to perform closed-loop nulling tasks following G-transitions, and whether manual control performance can be improved with vibrotactile feedback of orientation.

Modification of Otolith-Ocular Reflexes, Motion Perception and Manual Control During Variable Radius Centrifugation Following Space Flight

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Clarke, A. H.; Rupert, A. H.; Harm, D. L.; Clement, G. R.

2009-01-01

Two joint ESA-NASA studies are examining changes in otolith-ocular reflexes and motion perception following short duration space flights, and the operational implications of post-flight tilt-translation ambiguity for manual control performance. Vibrotactile feedback of tilt orientation is also being evaluated as a countermeasure to improve performance during a closed-loop nulling task. Data is currently being collected on astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation is utilized to elicit otolith reflexes in the lateral plane without concordant roll canal cues. Unilateral centrifugation (400 deg/s, 3.5 cm radius) stimulates one otolith positioned off-axis while the opposite side is centered over the axis of rotation. During this paradigm, roll-tilt perception is measured using a subjective visual vertical task and ocular counter-rolling is obtained using binocular video-oculography. During a second paradigm (216 deg/s, less than 20 cm radius), the effects of stimulus frequency (0.15 - 0.6 Hz) are examined on eye movements and motion perception. A closed-loop nulling task is also performed with and without vibrotactile display feedback of chair radial position. Data collection is currently ongoing. Results to date suggest there is a trend for perceived tilt and translation amplitudes to be increased at the low and medium frequencies on landing day compared to pre-flight. Manual control performance is improved with vibrotactile feedback. One result of this study will be to characterize the variability (gain, asymmetry) in both otolith-ocular responses and motion perception during variable radius centrifugation, and measure the time course of post-flight recovery. This study will also address how adaptive changes in otolith-mediated reflexes correspond to one's ability to perform closed-loop nulling tasks following G-transitions, and whether manual control performance can be improved with vibrotactile feedback of orientation.

Electromagnetic variable degrees of freedom actuator systems and methods

DOEpatents

Montesanti, Richard C [Pleasanton, CA; Trumper, David L [Plaistow, NH; Kirtley, Jr., James L.

2009-02-17

The present invention provides a variable reluctance actuator system and method that can be adapted for simultaneous rotation and translation of a moving element by applying a normal-direction magnetic flux on the moving element. In a beneficial example arrangement, the moving element includes a swing arm that carries a cutting tool at a set radius from an axis of rotation so as to produce a rotary fast tool servo that provides a tool motion in a direction substantially parallel to the surface-normal of a workpiece at the point of contact between the cutting tool and workpiece. An actuator rotates a swing arm such that a cutting tool moves toward and away from a mounted rotating workpiece in a controlled manner in order to machine the workpiece. Position sensors provide rotation and displacement information for a swing arm to a control system. A control system commands and coordinates motion of the fast tool servo with the motion of a spindle, rotating table, cross-feed slide, and in feed slide of a precision lathe.

Manual control of yaw motion with combined visual and vestibular cues

NASA Technical Reports Server (NTRS)

Zacharias, G. L.; Young, L. R.

1977-01-01

Measurements are made of manual control performance in the closed-loop task of nulling perceived self-rotation velocity about an earth-vertical axis. Self-velocity estimation was modelled as a function of the simultaneous presentation of vestibular and peripheral visual field motion cues. Based on measured low-frequency operator behavior in three visual field environments, a parallel channel linear model is proposed which has separate visual and vestibular pathways summing in a complementary manner. A correction to the frequency responses is provided by a separate measurement of manual control performance in an analogous visual pursuit nulling task. The resulting dual-input describing function for motion perception dependence on combined cue presentation supports the complementary model, in which vestibular cues dominate sensation at frequencies above 0.05 Hz. The describing function model is extended by the proposal of a non-linear cue conflict model, in which cue weighting depends on the level of agreement between visual and vestibular cues.

Locomotor Adaptation Improves Balance Control, Multitasking Ability and Reduces the Metabolic Cost of Postural Instability

NASA Technical Reports Server (NTRS)

Bloomberg, J. J.; Peters, B. T.; Mulavara, A. P.; Brady, R. A.; Batson, C. D.; Miller, C. A.; Ploutz-Snyder, R. J.; Guined, J. R.; Buxton, R. E.; Cohen, H. S.

2011-01-01

During exploration-class missions, sensorimotor disturbances may lead to disruption in the ability to ambulate and perform functional tasks during the initial introduction to a novel gravitational environment following a landing on a planetary surface. The overall goal of our current project is to develop a sensorimotor adaptability training program to facilitate rapid adaptation to these environments. We have developed a unique training system comprised of a treadmill placed on a motion-base facing a virtual visual scene. It provides an unstable walking surface combined with incongruent visual flow designed to enhance sensorimotor adaptability. Greater metabolic cost incurred during balance instability means more physical work is required during adaptation to new environments possibly affecting crewmembers? ability to perform mission critical tasks during early surface operations on planetary expeditions. The goal of this study was to characterize adaptation to a discordant sensory challenge across a number of performance modalities including locomotor stability, multi-tasking ability and metabolic cost. METHODS: Subjects (n=15) walked (4.0 km/h) on a treadmill for an 8 -minute baseline walking period followed by 20-minutes of walking (4.0 km/h) with support surface motion (0.3 Hz, sinusoidal lateral motion, peak amplitude 25.4 cm) provided by the treadmill/motion-base system. Stride frequency and auditory reaction time were collected as measures of locomotor stability and multi-tasking ability, respectively. Metabolic data (VO2) were collected via a portable metabolic gas analysis system. RESULTS: At the onset of lateral support surface motion, subj ects walking on our treadmill showed an increase in stride frequency and auditory reaction time indicating initial balance and multi-tasking disturbances. During the 20-minute adaptation period, balance control and multi-tasking performance improved. Similarly, throughout the 20-minute adaptation period, VO2 gradually decreased following an initial increase after the onset of support surface motion. DISCUSSION: Resu lts confirmed that walking in discordant conditions not only compromises locomotor stability and the ability to multi-task, but comes at a quantifiable metabolic cost. Importantly, like locomotor stability and multi-tasking ability, metabolic expenditure while walking in discordant sensory conditions improved during adaptation. This confirms that sensorimotor adaptability training can benefit multiple performance parameters central to the successful completion of critical mission tasks.

Response analysis of curved bridge with unseating failure control system under near-fault ground motions

NASA Astrophysics Data System (ADS)

Zuo, Ye; Sun, Guangjun; Li, Hongjing

2018-01-01

Under the action of near-fault ground motions, curved bridges are prone to pounding, local damage of bridge components and even unseating. A multi-scale fine finite element model of a typical three-span curved bridge is established by considering the elastic-plastic behavior of piers and pounding effect of adjacent girders. The nonlinear time-history method is used to study the seismic response of the curved bridge equipped with unseating failure control system under the action of near-fault ground motion. An in-depth analysis is carried to evaluate the control effect of the proposed unseating failure control system. The research results indicate that under the near-fault ground motion, the seismic response of the curved bridge is strong. The unseating failure control system perform effectively to reduce the pounding force of the adjacent girders and the probability of deck unseating.

Graphene/elastomer composite-based photo-thermal nanopositioners

PubMed Central

Loomis, James; Fan, Xiaoming; Khosravi, Farhad; Xu, Peng; Fletcher, Micah; Cohn, Robert W.; Panchapakesan, Balaji

2013-01-01

The addition of nanomaterials to polymers can result not only in significant material property improvements, but also assist in creating entirely new composite functionalities. By dispersing graphene nanoplatelets (GNPs) within a polydimethylsiloxane matrix, we show that efficient light absorption by GNPs and subsequent energy transduction to the polymeric chains can be used to controllably produce significant amounts of motion through entropic elasticity of the pre-strained composite. Using dual actuators, a two-axis sub-micron resolution stage was developed, and allowed for two-axis photo-thermal positioning (~100 μm per axis) with 120 nm resolution (feedback sensor limitation), and ~5 μm/s actuation speeds. A PID control loop automatically stabilizes the stage against thermal drift, as well as random thermal-induced position fluctuations (up to the bandwidth of the feedback and position sensor). Maximum actuator efficiency values of ~0.03% were measured, approximately 1000 times greater than recently reported for light-driven polymer systems. PMID:23712601

The Multi-Axis Space Test Inertia Facility in the Altitude Wind Tunnel

NASA Image and Video Library

1959-12-21

National Aeronautics and Space Administration (NASA) pilot Joe Algranti tests the Multi-Axis Space Test Inertia Facility (MASTIF) inside the Altitude Wind Tunnel while researcher Robert Miller looks on. The MASTIF was a three-axis rig with a pilot’s chair mounted in the center to train Project Mercury pilots to bring a spinning spacecraft under control. An astronaut was secured in a foam couch in the center of the rig. The rig then spun on three axes from 2 to 50 rotations per minute. Small nitrogen gas thrusters were used by the astronauts to bring the MASTIF under control. The device was originally designed in early 1959 without the chair and controllers. It was used by Lewis researchers to determine if the Lewis-designed autopilot system could rectify the capsule’s attitude following separation. If the control system failed to work properly, the heatshield would be out of place and the spacecraft would burn up during reentry. The system was flight tested during the September 1959 launch of the Lewis-assembled Big Joe capsule. The MASTIF was adapted in late 1959 for the astronaut training. NASA engineers added a pilot’s chair, a hand controller, and an instrument display to the MASTIF in order familiarize the astronauts with the sensations of an out-of-control spacecraft. NASA Lewis researcher James Useller and Algranti perfected and calibrated the MASTIF in the fall of 1959. In February and March 1960, the seven Project Mercury astronauts traveled to Cleveland to train on the MASTIF.

Motion of a pendulum with damping and vibrating axis of suspension at unconventional values of parameters

NASA Astrophysics Data System (ADS)

Demidov, Ivan; Sorokin, Vladislav

2018-05-01

Motion of a pendulum with damping and vibrating axis of suspension is considered at unconventional values of parameters. Case when the frequency of external loading and the natural frequency of the pendulum in the absence of this loading are of the same order is studied. Vibration intensity is assumed to be relatively low. In this case, the corresponding equation of the pendulum's motions doesn't involve an explicit small parameter. To solve the equation a new modification of the method of direct separation of motions is used. As the result, stability conditions of the pendulum inverted position are determined. Effects of damping on these conditions are discussed.

Pixel-wise deblurring imaging system based on active vision for structural health monitoring at a speed of 100 km/h

NASA Astrophysics Data System (ADS)

Hayakawa, Tomohiko; Moko, Yushi; Morishita, Kenta; Ishikawa, Masatoshi

2018-04-01

In this paper, we propose a pixel-wise deblurring imaging (PDI) system based on active vision for compensation of the blur caused by high-speed one-dimensional motion between a camera and a target. The optical axis is controlled by back-and-forth motion of a galvanometer mirror to compensate the motion. High-spatial-resolution image captured by our system in high-speed motion is useful for efficient and precise visual inspection, such as visually judging abnormal parts of a tunnel surface to prevent accidents; hence, we applied the PDI system for structural health monitoring. By mounting the system onto a vehicle in a tunnel, we confirmed significant improvement in image quality for submillimeter black-and-white stripes and real tunnel-surface cracks at a speed of 100 km/h.

Large-area Overhead Manipulator for Access of Fields

USDA-ARS?s Scientific Manuscript database

Multi-axis, cable-driven manipulators have evolved over many years providing large area suspended platform access, programmability, relatively rigid and flexibly-positioned platform control and full six degree of freedom (DOF) manipulation of sensors and tools. We describe innovations for a new six...

Direct Imaging Search for Extrasolar Planets in the Pleiades

NASA Technical Reports Server (NTRS)

Yamamoto, Kodai; Matsuo, Taro; Shibai, Hiroshi; Itoh, Yoichi; Konishi, Mihokko; Sudo, Jun; Tanii, Ryoko; Fukagawa, Misato; Sumi, Takahiro; Kudo, Tomoyuki;

Inflight redesign of the IUE attitude control system

NASA Technical Reports Server (NTRS)

Femiano, M. D.

1986-01-01

The one- and two-gyro system designs of the International Ultraviolet Explorer (IUE) attitude control system (ACS) are examined. The inertial reference assembly that provides the primary attitude reference for IUE consists of six rate sensors which are single-axis rate integrating gyros. The gyros operate in a pulse rebalanced mode that produces an output pulse for 0.01 arcsec of motion about the input axis. The functions of the fine error sensor, fine sun sensor (FSS), the IUE reaction wheels, the onboard computer, and the hold/slew algorithm are described. The use of the hold/slew algorithm to compute the control voltage for the ACS based on the Kalman filter is studied. A two-gyro system was incorporated into IUE following gyro failure. The procedures for establishing attitude control with the two-gyro design based on the FSS is analyzed. The performance of the two-gyro system is evaluated; it is observed that the pitch and yaw gyro control is 0.24 arcsec and the control is sufficient to permit extended periods of observation.

Zero-gyro control of the International Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

O'Donnell, James R., Jr.; Hoffman, Henry C.

1993-01-01

The IUE was built for an anticipated lifespan of three years with a goal of five. It has been operating for over 15 years, even though it has had only two working gyros since August 17, 1985, through the use of a two-gyro attitude control system that uses information from IUE's fine sun sensor (FSS) and the two remaining gyros to provide three-axis control. A one-gyro control system that uses an additional axis of information from the FSS has been developed and tested on-orbit. The purpose of this paper is to discuss the work in progress towards the development of a zero-gyro control law for IUE. Motion about the sunline, which cannot be measured by the FSS, is measured and controlled in the zero-gyro system by applying a momentum bias perpendicular to the sunline and measuring the transfer of this momentum between the spacecraft reaction wheels, while the spacecraft is held in the other two axes using position and derived-rate information from the FSS.

Modelling resonances of the standing body exposed to vertical whole-body vibration: Effects of posture

NASA Astrophysics Data System (ADS)

Subashi, G. H. M. J.; Matsumoto, Y.; Griffin, M. J.

2008-10-01

Lumped parameter mathematical models representing anatomical parts of the human body have been developed to represent body motions associated with resonances of the vertical apparent mass and the fore-and-aft cross-axis apparent mass of the human body standing in five different postures: 'upright', 'lordotic', 'anterior lean', 'knees bent', and 'knees more bent'. The inertial and geometric parameters of the models were determined from published anthropometric data. Stiffness and damping parameters were obtained by comparing model responses with experimental data obtained previously. The principal resonance of the vertical apparent mass, and the first peak in the fore-and-aft cross-axis apparent mass, of the standing body in an upright posture (at 5-6 Hz) corresponded to vertical motion of the viscera in phase with the vertical motion of the entire body due to deformation of the tissues at the soles of the feet, with pitch motion of the pelvis out of phase with pitch motion of the upper body above the pelvis. Upward motion of the body was in phase with the forward pitch motion of the pelvis. Changing the posture of the upper body had minor effects on the mode associated with the principal resonances of the apparent mass and cross-axis apparent mass, but the mode changed significantly with bending of the legs. In legs-bent postures, the principal resonance (at about 3 Hz) was attributed to bending of the legs coupled with pitch motion of the pelvis in phase with pitch motion of the upper body. In this mode, extension of the legs was in phase with the forward pitch motion of the upper body and the upward vertical motion of the viscera.

Dynamic modulation of ocular orientation during visually guided saccades and smooth-pursuit eye movements

NASA Technical Reports Server (NTRS)

Hess, Bernhard J M.; Angelaki, Dora E.

2003-01-01

Rotational disturbances of the head about an off-vertical yaw axis induce a complex vestibuloocular reflex pattern that reflects the brain's estimate of head angular velocity as well as its estimate of instantaneous head orientation (at a reduced scale) in space coordinates. We show that semicircular canal and otolith inputs modulate torsional and, to a certain extent, also vertical ocular orientation of visually guided saccades and smooth-pursuit eye movements in a similar manner as during off-vertical axis rotations in complete darkness. It is suggested that this graviceptive control of eye orientation facilitates rapid visual spatial orientation during motion.

A dynamic model of the human postural control system

NASA Technical Reports Server (NTRS)

Hill, J. C.

1972-01-01

A digital simulation of the pitch axis dynamics of a stick man of figures is described. Difficulties encountered in linearizing the equations of motion are discussed; the conclusion reached is that a completely linear simulation is of such restricted validity that only a nonlinear simulation is of any practical use. Typical simulation results obtained from the full nonlinear model are presented.

A dynamic model of the human postural control system.

NASA Technical Reports Server (NTRS)

Hill, J. C.

1971-01-01

Description of a digital simulation of the pitch axis dynamics of a stick man. The difficulties encountered in linearizing the equations of motion are discussed; the conclusion reached is that a completely linear simulation is of such restricted validity that only a nonlinear simulation is of any practical use. Typical simulation results obtained from the full nonlinear model are illustrated.

Overcoming Robot-Arm Joint Singularities

NASA Technical Reports Server (NTRS)

Barker, L. K.; Houck, J. A.

1986-01-01

Kinematic equations allow arm to pass smoothly through singular region. Report discusses mathematical singularities in equations of robotarm control. Operator commands robot arm to move in direction relative to its own axis system by specifying velocity in that direction. Velocity command then resolved into individual-joint rotational velocities in robot arm to effect motion. However, usual resolved-rate equations become singular when robot arm is straightened.

Susceptibility of the squirrel monkey to different motion conditions

NASA Technical Reports Server (NTRS)

Fox, Robert A.; Daunton, Nancy G.; Coleman, J.

1991-01-01

The exact stimulus eliciting vomiting in animal studies of motion sickness is difficult to specify because the vestibular stimulation produced by many motion conditions is confounded by voluntary movements with animals. This is an important problem because experiments with animal models of motion sickness can provide useful information about antimotion sickness drugs or the role of neural mechanisms, only when animals are exposed to the same motion stimuli in each experimental session. A series of tests were conducted to determine the susceptibility of 15 adult squirrel monkeys to motion sickness in freely moving and restrained test conditions. Canal stimulation was varied by exposing the monkey in freely moving conditions to varying degrees of angular velocity (60, 90, 120, 150 deg/sec), and in restrained conditions to one angular velocity (150 deg/sec) and to cross-coupling effects of whole-body roll movements during rotation. Otolith stimulation was investigated by using sinusoidal vertical linear acceleration during free movement conditions, and off-vertical rotation and earth-horizontal (BBQ) rotation while restrained. The percentage of freely moving animal vomiting during vertical axis rotation was 27, 93, 86, and 92 for the angular velocities of 60, 90, 120, and 150 deg/sec respectively. None of the monkeys vomited during vertical axis rotation or cross-coupled rotation when restrained. Otolith stimulation appears to be a less provocative stimulus for the squirrel monkey as the percentage of animals vomiting were 13, 0, and 7 for the conditions of free movement during oscillation, restraint during off-vertical, and BBQ rotation respectively. Motion sickness to the point of vomiting occurred regularly only in conditions where self-motion was possible. Such effects could occur because voluntary movement during motion augments vestibular effects by producing self-inflicted cross-coupling, but the failure to elicit vomiting with experimenter-coupling cross-coupling argues against this interpretation. Alternatively, these results might imply that feedback from movement control mechanisms may play an important role in sensory conflict as suggested by Oman's sensory-motor conflict theory.

Quality control procedures for dynamic treatment delivery techniques involving couch motion.

PubMed

Yu, Victoria Y; Fahimian, Benjamin P; Xing, Lei; Hristov, Dimitre H

2014-08-01

In this study, the authors introduce and demonstrate quality control procedures for evaluating the geometric and dosimetric fidelity of dynamic treatment delivery techniques involving treatment couch motion synchronous with gantry and multileaf collimator (MLC). Tests were designed to evaluate positional accuracy, velocity constancy and accuracy for dynamic couch motion under a realistic weight load. A test evaluating the geometric accuracy of the system in delivering treatments over complex dynamic trajectories was also devised. Custom XML scripts that control the Varian TrueBeam™ STx (Serial #3) axes in Developer Mode were written to implement the delivery sequences for the tests. Delivered dose patterns were captured with radiographic film or the electronic portal imaging device. The couch translational accuracy in dynamic treatment mode was 0.01 cm. Rotational accuracy was within 0.3°, with 0.04 cm displacement of the rotational axis. Dose intensity profiles capturing the velocity constancy and accuracy for translations and rotation exhibited standard deviation and maximum deviations below 3%. For complex delivery involving MLC and couch motions, the overall translational accuracy for reproducing programmed patterns was within 0.06 cm. The authors conclude that in Developer Mode, TrueBeam™ is capable of delivering dynamic treatment delivery techniques involving couch motion with good geometric and dosimetric fidelity.

Maneuver simulations of flexible spacecraft by solving TPBVP

NASA Technical Reports Server (NTRS)

Bainum, Peter M.; Li, Feiyue

1991-01-01

The optimal control of large angle rapid maneuvers and vibrations of a Shuttle mast reflector system is considered. The nonlinear equations of motion are formulated by using Lagrange's formula, with the mast modeled as a continuous beam. The nonlinear terms in the equations come from the coupling between the angular velocities, the modal coordinates, and the modal rates. Pontryagin's Maximum Principle is applied to the slewing problem, to derive the necessary conditions for the optimal controls, which are bounded by given saturation levels. The resulting two point boundary value problem (TPBVP) is then solved by using the quasilinearization algorithm and the method of particular solutions. In the numerical simulations, the structural parameters and the control limits from the Spacecraft Control Lab Experiment (SCOLE) are used. In the 2-D case, only the motion in the plane of an Earth orbit or the single axis slewing motion is discussed. In the 3-D slewing, the mast is modeled as a continuous beam subjected to 3-D deformations. The numerical results for both the linearized system and the nonlinear system are presented to compare the differences in their time response.

Free polar motion of a triaxial and elastic body in Hamiltonian formalism: Application to the Earth and Mars

NASA Astrophysics Data System (ADS)

Folgueira, M.; Souchay, J.

2005-03-01

The purpose of this paper is to show how to solve in Hamiltonian formalism the equations of the polar motion of any arbitrarily shaped elastic celestial body, i.e. the motion of its rotation axis (or angular momentum) with respect to its figure axis. With this aim, we deduce from canonical equations related to the rotational Hamiltonian of the body, the analytical solution for its free polar motion which depends both on the elasticity and on its moments of inertia. In particular, we study the influence of the phase angle δ, responsible for the dissipation, on the damping of the polar motion. In order to validate our analytical equations, we show that, to first order, they are in complete agreement with those obtained from the classical Liouville equations. Then we adapt our calculations to the real data obtained from the polar motion of the Earth (polhody). For that purpose, we characterize precisely the differences in radius J-χ and in angle l-θ between the polar coordinates (χ,θ) and (J,l) representing respectively the motion of the axis of rotation of the Earth and the motion of its angular momentum axis, with respect to an Earth-fixed reference frame, after showing the influence of the choice of the origin on these coordinates, and on the determination of the Chandler period as well. Then we show that the phase lag δ responsible for the damping for the selected time interval, between Feb. 1982 and Apr. 1990, might be of the order of δ ≈ 6 °, according to a numerical integration starting from our analytical equations. Moreover, we emphasize the presence in our calculations for both χ and θ, of an oscillation with a period TChandler/2, due to the triaxial shape of our planet, and generally not taken into account. In a last step, we apply our analytical formulation to the polar motion of Mars, thus showing the high dependence of its damping on the poorly known value of its Love number k. Moreover we emphasize the large oscillations of Mars' polar motion due to the triaxiality of this planet.

Free Body Dynamics of a Spinning Cylinder With Planar Restraint (a.k.a. Barrel of Fun)

NASA Technical Reports Server (NTRS)

Moraru, Laurentiu; Dimofte, Florin; Hendricks, Robert C.

2006-01-01

The dynamic motion of a cylinder on a floor or hard surface is both entertaining and instructive. With maintenance torques, motion can be sustained and controlled as illustrated in a video clip that can be viewed in the PDF file of this document. The analysis of such a cylinder with and without end caps is burned on rotation about its center of mass and restrained by a plane normal to the axis passing through its center of mass at an angle alpha. For small values of alpha, the governing equations are simplified, and for symmetric bodies, stability requires rotation greater than [2 square root of(JWL*)]/J(sub X), where J is the transverse mass moment of inertia, W is the weight of the cylinder, L* is the cylinder length from the base to the center of mass, and JX is the mass moment of inertia about the longitudinal axis OX of the barrel. Comparisons to data are made and some applications are discussed.

Hybrid suboptimal control of multi-rate multi-loop sampled-data systems

NASA Technical Reports Server (NTRS)

Shieh, Leang S.; Chen, Gwangchywan; Tsai, Jason S. H.

1992-01-01

A hybrid state-space controller is developed for suboptimal digital control of multirate multiloop multivariable continuous-time systems. First, an LQR is designed for a continuous-time subsystem which has a large bandwidth and is connnected in the inner loop of the overall system. The designed LQR would optimally place the eigenvalues of a closed-loop subsystem in the common region of an open sector bounded by sector angles + or - pi/2k for k = 2 or 3 from the negative real axis and the left-hand side of a vertical line on the negative real axis in the s-plane. Then, the developed continuous-time state-feedback gain is converted into an equivalent fast-rate discrete-time state-feedback gain via a digital redesign technique (Tsai et al. 1989, Shieh et al. 1990) reviewed here. A real state reconstructor is redeveloped utilizing the fast-rate input-output data of the system of interest. The design procedure of multiloop multivariable systems using multirate samplers is shown, and a terminal homing missile system example is used to demonstrate the effectiveness of the proposed method.

Locations of stationary/periodic solutions in mean motion resonances according to the properties of dust grains

NASA Astrophysics Data System (ADS)

Pástor, P.

2016-07-01

The equations of secular evolution for dust grains in mean motion resonances with a planet are solved for stationary points. Non-gravitational effects caused by stellar radiation (the Poynting-Robertson effect and the stellar wind) are taken into account. The solutions are stationary in the semimajor axis, eccentricity and resonant angle, but allow the pericentre to advance. The semimajor axis of stationary solutions can be slightly shifted from the exact resonant value. The periodicity of the stationary solutions in a reference frame orbiting with the planet is proved analytically. The existence of periodic solutions in mean motion resonances means that analytical theory enables infinitely long capture times for dust particles. The stationary solutions are periodic motions to which the eccentricity asymptotically approaches and around which the libration occurs. Initial conditions corresponding to the stationary solutions are successfully found by numerically integrating the equation of motion. Numerically and analytically determined shifts of the semimajor axis from the exact resonance for the stationary solutions are in excellent agreement. The stationary solutions can be plotted by the locations of pericentres in the reference frame orbiting with the planet. The pericentres are distributed in space according to the properties of the dust particles.

Simulation results of corkscrew motion in DARHT-II

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

Chan, K. D.; Ekdahl, C. A.; Chen, Y. J.

2003-01-01

DARHT-II, the second axis of the Dual-Axis Radiographic Hydrodynamics Test Facility, is being commissioned. DARHT-II is a linear induction accelerator producing 2-microsecond electron beam pulses at 20 MeV and 2 kA. These 2-microsecond pulses will be chopped into four short pulses to produce time resolved x-ray images. Radiographic application requires the DARHT-II beam to have excellent beam quality, and it is important to study various beam effects that may cause quality degradation of a DARHT-II beam. One of the beam dynamic effects under study is 'corkscrew' motion. For corkscrew motion, the beam centroid is deflected off axis due to misalignmentsmore » of the solenoid magnets. The deflection depends on the beam energy variation, which is expected to vary by {+-}0.5% during the 'flat-top' part of a beam pulse. Such chromatic aberration will result in broadening of beam spot size. In this paper, we will report simulation results of our study of corkscrew motion in DARHT-II. Sensitivities of beam spot size to various accelerator parameters and the strategy for minimizing corkscrew motion will be described. Measured magnet misalignment is used in the simulation.« less

Control Parameters Optimization Based on Co-Simulation of a Mechatronic System for an UA-Based Two-Axis Inertially Stabilized Platform.

PubMed

Zhou, Xiangyang; Zhao, Beilei; Gong, Guohao

2015-08-14

This paper presents a method based on co-simulation of a mechatronic system to optimize the control parameters of a two-axis inertially stabilized platform system (ISP) applied in an unmanned airship (UA), by which high control performance and reliability of the ISP system are achieved. First, a three-dimensional structural model of the ISP is built by using the three-dimensional parametric CAD software SOLIDWORKS(®); then, to analyze the system's kinematic and dynamic characteristics under operating conditions, dynamics modeling is conducted by using the multi-body dynamics software ADAMS™, thus the main dynamic parameters such as displacement, velocity, acceleration and reaction curve are obtained, respectively, through simulation analysis. Then, those dynamic parameters were input into the established MATLAB(®) SIMULINK(®) controller to simulate and test the performance of the control system. By these means, the ISP control parameters are optimized. To verify the methods, experiments were carried out by applying the optimized parameters to the control system of a two-axis ISP. The results show that the co-simulation by using virtual prototyping (VP) is effective to obtain optimized ISP control parameters, eventually leading to high ISP control performance.

Control Parameters Optimization Based on Co-Simulation of a Mechatronic System for an UA-Based Two-Axis Inertially Stabilized Platform

PubMed Central

Zhou, Xiangyang; Zhao, Beilei; Gong, Guohao

2015-01-01

This paper presents a method based on co-simulation of a mechatronic system to optimize the control parameters of a two-axis inertially stabilized platform system (ISP) applied in an unmanned airship (UA), by which high control performance and reliability of the ISP system are achieved. First, a three-dimensional structural model of the ISP is built by using the three-dimensional parametric CAD software SOLIDWORKS®; then, to analyze the system’s kinematic and dynamic characteristics under operating conditions, dynamics modeling is conducted by using the multi-body dynamics software ADAMS™, thus the main dynamic parameters such as displacement, velocity, acceleration and reaction curve are obtained, respectively, through simulation analysis. Then, those dynamic parameters were input into the established MATLAB® SIMULINK® controller to simulate and test the performance of the control system. By these means, the ISP control parameters are optimized. To verify the methods, experiments were carried out by applying the optimized parameters to the control system of a two-axis ISP. The results show that the co-simulation by using virtual prototyping (VP) is effective to obtain optimized ISP control parameters, eventually leading to high ISP control performance. PMID:26287210

VO2 estimation using 6-axis motion sensor with sports activity classification.

PubMed

Nagata, Takashi; Nakamura, Naoteru; Miyatake, Masato; Yuuki, Akira; Yomo, Hiroyuki; Kawabata, Takashi; Hara, Shinsuke

2016-08-01

In this paper, we focus on oxygen consumption (VO2) estimation using 6-axis motion sensor (3-axis accelerometer and 3-axis gyroscope) for people playing sports with diverse intensities. The VO2 estimated with a small motion sensor can be used to calculate the energy expenditure, however, its accuracy depends on the intensities of various types of activities. In order to achieve high accuracy over a wide range of intensities, we employ an estimation framework that first classifies activities with a simple machine-learning based classification algorithm. We prepare different coefficients of linear regression model for different types of activities, which are determined with training data obtained by experiments. The best-suited model is used for each type of activity when VO2 is estimated. The accuracy of the employed framework depends on the trade-off between the degradation due to classification errors and improvement brought by applying separate, optimum model to VO2 estimation. Taking this trade-off into account, we evaluate the accuracy of the employed estimation framework by using a set of experimental data consisting of VO2 and motion data of people with a wide range of intensities of exercises, which were measured by a VO2 meter and motion sensor, respectively. Our numerical results show that the employed framework can improve the estimation accuracy in comparison to a reference method that uses a common regression model for all types of activities.

Conceptual design of a novel multi-DoF manual instrument for laparoscopic surgery.

PubMed

Wang, Xiaofei; Wang, Shuxin; Li, Jianmin; Zhang, Guokai; Wu, Zhiliang

2013-03-01

Laparoscopic surgery is becoming increasingly popular throughout the world. But the conventional instruments used in many surgeries are not flexible enough to be operated. Challenging tasks, such as suturing and knot-tying tasks are difficult to complete using conventional instruments with limited degrees of freedom (DoFs). In the paper, a novel cable-driven multi-DoF manual instrument is presented with a simple structure but strong functionality. The proposed instrument has been developed with a wristlike operation end (OE), a wristlike end effector (EE), and the transmission system. It can be operated intuitively. The orientation and the position of the EE are directly controlled by surgeons due to the one-to-one motion mapping structure. The clamp structure and tension device are reasonably designed. The pitch, yaw, and the open and close motion are actuated by cables. Based on the optimization index Global Condition Index (GCI), four cables are used to actuate the pitch and yaw motions, while other two are used for the open and close motion. The layout of the cables is also determined by the GCI. Experiments carried out with a prototype show that tasks such as suturing and knot-tying can be completed comfortably. Due to the intuitive control and multi-DoFs, surgeons can use the prototype to finish the tasks with ease. The instrument developed herein with intuitive control and dexterity can be used alone or together with a robotic system to accomplish some challenging tasks that are difficult for conventional instruments. Copyright © 2012 John Wiley & Sons, Ltd.

Multi-segment foot kinematics after total ankle replacement and ankle arthrodesis during relatively long-distance gait.

PubMed

Rouhani, H; Favre, J; Aminian, K; Crevoisier, X

2012-07-01

This study aimed to investigate the influence of ankle osteoarthritis (AOA) treatments, i.e., ankle arthrodesis (AA) and total ankle replacement (TAR), on the kinematics of multi-segment foot and ankle complex during relatively long-distance gait. Forty-five subjects in four groups (AOA, AA, TAR, and control) were equipped with a wearable system consisting of inertial sensors installed on the tibia, calcaneus, and medial metatarsals. The subjects walked 50-m twice while the system measured the kinematic parameters of their multi-segment foot: the range of motion of joints between tibia, calcaneus, and medial metatarsals in three anatomical planes, and the peaks of angular velocity of these segments in the sagittal plane. These parameters were then compared among the four groups. It was observed that the range of motion and peak of angular velocities generally improved after TAR and were similar to the control subjects. However, unlike AOA and TAR, AA imposed impairments in the range of motion in the coronal plane for both the tibia-calcaneus and tibia-metatarsals joints. In general, the kinematic parameters showed significant correlation with established clinical scales (FFI and AOFAS), which shows their convergent validity. Based on the kinematic parameters of multi-segment foot during 50-m gait, this study showed significant improvements in foot mobility after TAR, but several significant impairments remained after AA. Copyright © 2012 Elsevier B.V. All rights reserved.

Multi-Axis Force Sensor for Human-Robot Interaction Sensing in a Rehabilitation Robotic Device.

PubMed

Grosu, Victor; Grosu, Svetlana; Vanderborght, Bram; Lefeber, Dirk; Rodriguez-Guerrero, Carlos

2017-06-05

Human-robot interaction sensing is a compulsory feature in modern robotic systems where direct contact or close collaboration is desired. Rehabilitation and assistive robotics are fields where interaction forces are required for both safety and increased control performance of the device with a more comfortable experience for the user. In order to provide an efficient interaction feedback between the user and rehabilitation device, high performance sensing units are demanded. This work introduces a novel design of a multi-axis force sensor dedicated for measuring pelvis interaction forces in a rehabilitation exoskeleton device. The sensor is conceived such that it has different sensitivity characteristics for the three axes of interest having also movable parts in order to allow free rotations and limit crosstalk errors. Integrated sensor electronics make it easy to acquire and process data for a real-time distributed system architecture. Two of the developed sensors are integrated and tested in a complex gait rehabilitation device for safe and compliant control.

Design and implementation of self-balancing coaxial two wheel robot based on HSIC

NASA Astrophysics Data System (ADS)

Hu, Tianlian; Zhang, Hua; Dai, Xin; Xia, Xianfeng; Liu, Ran; Qiu, Bo

2007-12-01

This thesis has studied the control problem concerning position and orientation control of self-balancing coaxial two wheel robot based on the human simulated intelligent control (HSIC) theory. Adopting Lagrange equation, the dynamic model of self-balancing coaxial two-wheel Robot is built up, and the Sensory-motor Intelligent Schemas (SMIS) of HSIC controller for the robot is designed by analyzing its movement and simulating the human controller. In robot's motion process, by perceiving position and orientation of the robot and using multi-mode control strategy based on characteristic identification, the HSIC controller enables the robot to control posture. Utilizing Matlab/Simulink, a simulation platform is established and a motion controller is designed and realized based on RT-Linux real-time operating system, employing high speed ARM9 processor S3C2440 as kernel of the motion controller. The effectiveness of the new design is testified by the experiment.

Detection of system failures in multi-axes tasks. [pilot monitored instrument approach

NASA Technical Reports Server (NTRS)

Ephrath, A. R.

1975-01-01

The effects of the pilot's participation mode in the control task on his workload level and failure detection performance were examined considering a low visibility landing approach. It is found that the participation mode had a strong effect on the pilot's workload, the induced workload being lowest when the pilot acted as a monitoring element during a coupled approach and highest when the pilot was an active element in the control loop. The effects of workload and participation mode on failure detection were separated. The participation mode was shown to have a dominant effect on the failure detection performance, with a failure in a monitored (coupled) axis being detected significantly faster than a comparable failure in a manually controlled axis.

Speed control system for an access gate

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

Bzorgi, Fariborz M

2012-03-20

An access control apparatus for an access gate. The access gate typically has a rotator that is configured to rotate around a rotator axis at a first variable speed in a forward direction. The access control apparatus may include a transmission that typically has an input element that is operatively connected to the rotator. The input element is generally configured to rotate at an input speed that is proportional to the first variable speed. The transmission typically also has an output element that has an output speed that is higher than the input speed. The input element and the outputmore » element may rotate around a common transmission axis. A retardation mechanism may be employed. The retardation mechanism is typically configured to rotate around a retardation mechanism axis. Generally the retardation mechanism is operatively connected to the output element of the transmission and is configured to retard motion of the access gate in the forward direction when the first variable speed is above a control-limit speed. In many embodiments the transmission axis and the retardation mechanism axis are substantially co-axial. Some embodiments include a freewheel/catch mechanism that has an input connection that is operatively connected to the rotator. The input connection may be configured to engage an output connection when the rotator is rotated at the first variable speed in a forward direction and configured for substantially unrestricted rotation when the rotator is rotated in a reverse direction opposite the forward direction. The input element of the transmission is typically operatively connected to the output connection of the freewheel/catch mechanism.« less

A Novel Model-Based Driving Behavior Recognition System Using Motion Sensors.

PubMed

Wu, Minglin; Zhang, Sheng; Dong, Yuhan

2016-10-20

In this article, a novel driving behavior recognition system based on a specific physical model and motion sensory data is developed to promote traffic safety. Based on the theory of rigid body kinematics, we build a specific physical model to reveal the data change rule during the vehicle moving process. In this work, we adopt a nine-axis motion sensor including a three-axis accelerometer, a three-axis gyroscope and a three-axis magnetometer, and apply a Kalman filter for noise elimination and an adaptive time window for data extraction. Based on the feature extraction guided by the built physical model, various classifiers are accomplished to recognize different driving behaviors. Leveraging the system, normal driving behaviors (such as accelerating, braking, lane changing and turning with caution) and aggressive driving behaviors (such as accelerating, braking, lane changing and turning with a sudden) can be classified with a high accuracy of 93.25%. Compared with traditional driving behavior recognition methods using machine learning only, the proposed system possesses a solid theoretical basis, performs better and has good prospects.

A Novel Model-Based Driving Behavior Recognition System Using Motion Sensors

PubMed Central

Wu, Minglin; Zhang, Sheng; Dong, Yuhan

2016-01-01

In this article, a novel driving behavior recognition system based on a specific physical model and motion sensory data is developed to promote traffic safety. Based on the theory of rigid body kinematics, we build a specific physical model to reveal the data change rule during the vehicle moving process. In this work, we adopt a nine-axis motion sensor including a three-axis accelerometer, a three-axis gyroscope and a three-axis magnetometer, and apply a Kalman filter for noise elimination and an adaptive time window for data extraction. Based on the feature extraction guided by the built physical model, various classifiers are accomplished to recognize different driving behaviors. Leveraging the system, normal driving behaviors (such as accelerating, braking, lane changing and turning with caution) and aggressive driving behaviors (such as accelerating, braking, lane changing and turning with a sudden) can be classified with a high accuracy of 93.25%. Compared with traditional driving behavior recognition methods using machine learning only, the proposed system possesses a solid theoretical basis, performs better and has good prospects. PMID:27775625

Modular hybrid plasma reactor and related systems and methods

DOEpatents

Kong, Peter C.; Grandy, Jon D.; Detering, Brent A.

2010-06-22

A device, method and system for generating a plasma is disclosed wherein an electrical arc is established and the movement of the electrical arc is selectively controlled. In one example, modular units are coupled to one another to collectively define a chamber. Each modular unit may include an electrode and a cathode spaced apart and configured to generate an arc therebetween. A device, such as a magnetic or electromagnetic device, may be used to selectively control the movement of the arc about a longitudinal axis of the chamber. The arcs of individual modules may be individually controlled so as to exhibit similar or dissimilar motions about the longitudinal axis of the chamber. In another embodiment, an inlet structure may be used to selectively define the flow path of matter introduced into the chamber such that it travels in a substantially circular or helical path within the chamber.

Enhanced spin transfer torque effect for transverse domain walls in cylindrical nanowires

NASA Astrophysics Data System (ADS)

Franchin, Matteo; Knittel, Andreas; Albert, Maximilian; Chernyshenko, Dmitri S.; Fischbacher, Thomas; Prabhakar, Anil; Fangohr, Hans

2011-09-01

Recent studies have predicted extraordinary properties for transverse domain walls in cylindrical nanowires: zero depinning current, the absence of the Walker breakdown, and applications as domain wall oscillators. In order to reliably control the domain wall motion, it is important to understand how they interact with pinning centers, which may be engineered, for example, through modulations in the nanowire geometry (such as notches or extrusions) or in the magnetic properties of the material. In this paper we study the motion and depinning of transverse domain walls through pinning centers in ferromagnetic cylindrical nanowires. We use (i) magnetic fields and (ii) spin-polarized currents to drive the domain walls along the wire. The pinning centers are modelled as a section of the nanowire which exhibits a uniaxial crystal anisotropy where the anisotropy easy axis and the wire axis enclose a variable angle θP. Using (i) magnetic fields, we find that the minimum and the maximum fields required to push the domain wall through the pinning center differ by 30%. On the contrary, using (ii) spin-polarized currents, we find variations of a factor 130 between the minimum value of the depinning current density (observed for θP=0∘, i.e., anisotropy axis pointing parallel to the wire axis) and the maximum value (for θP=90∘, i.e., anisotropy axis perpendicular to the wire axis). We study the depinning current density as a function of the height of the energy barrier of the pinning center using numerical and analytical methods. We find that for an industry standard energy barrier of 40kBT, a depinning current of about 5μA (corresponding to a current density of 6×1010A/m2 in a nanowire of 10nm diameter) is sufficient to depin the domain wall. We reveal and explain the mechanism that leads to these unusually low depinning currents. One requirement for this depinning mechanism is for the domain wall to be able to rotate around its own axis. With the right barrier design, the spin torque transfer term is acting exactly against the damping in the micromagnetic system, and thus the low current density is sufficient to accumulate enough energy quickly. These key insights may be crucial in furthering the development of novel memory technologies, such as the racetrack memory, that can be controlled through low current densities.

Effects of off-axis elliptical training on reducing pain and improving knee function in individuals with patellofemoral pain

PubMed Central

Tsai, Liang-Ching; Lee, Song Joo; Yang, Aaron J.; Ren, Yupeng; Press, Joel M.; Zhang, Li-Qun

2014-01-01

Objective To examine whether an off-axis elliptical training program reduces pain and improves knee function in individuals with patellofemoral pain (PFP). Design Controlled laboratory study, pre-test-post-test. Setting University rehabilitation center. Participants Twelve adult subjects with PFP. Interventions Subjects with PFP completed an exercise program consisting of 18 sessions of lower extremity off-axis training using a custom-made elliptical trainer that allows frontal-plane sliding and transverse-plane pivoting of the footplates. Main Outcome Measures Changes in knee pain and function post-training and 6 weeks following training were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) scores. Lower extremity off-axis control was assessed by pivoting and sliding instability, calculated as the root mean square (RMS) of the footplate pivoting angle and sliding distance during elliptical exercise. Subjects’ single-leg hop distance and proprioception in detecting lower extremity pivoting motion were also evaluated. Results Subjects reported significantly greater KOOS and IKDC scores (increased by 12–18 points) and hop distance (increased by 0.2 m) following training. A significant decrease in the pivoting and sliding RMS was also observed following training. Additionally, subjects with PFP demonstrated improved pivoting proprioception when tested under a minimum-weight-bearing position. Conclusions An off-axis elliptical training program was effective in enhancing lower extremity neuromuscular control on the frontal and transverse planes, reducing pain and improving knee function in persons with PFP. PMID:25591131

A dual-mode disturbance-accommodating controller for the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Addington, Stewart; Johnson, C. D.

Cyclic thermal expansions and mechanical stiction effects in the Solar Arrays on the Hubble Space Telescope (HST) are triggering repeated occurrences of damped, relaxation-type flex-body vibrations of the solar arrays. Those solar array vibrations are, in turn, causing unwanted, oscillating disturbance torques on the HST main body, which cause unwanted deviations of the telescope from its specified pointing direction. In this paper we propose two strategies one can adopt in designing a telescope-pointing controller to cope with the aforementioned disturbances: (1) a `total isolation' (TI) control strategy whereby the HST controller torques are designed to adaptively counteract and cancel-out the persistent disturbing torques that are causing the unwanted telescope motions, and (2) an `array damping' (AD) control strategy whereby the HST controller torques are used to actively augment the natural dampening of the solar array vibrations and the attendant telescope motions, between triggerings of the stiction-related flex-body relaxation oscillations. Using the principles of Disturbance-Accommodating Control (DAC) Theory a dual-mode controller for a generic, planar-motion (single-axis) model of the HST is proposed. This controller incorporates both the TI and AD modes of disturbance-accommodation. Simulation studies of the closed-loop system using generic parameter values clearly indicate, qualitatively, the enhanced pointing-performance such a controller can achieve.

High performance MRI simulations of motion on multi-GPU systems.

PubMed

Xanthis, Christos G; Venetis, Ioannis E; Aletras, Anthony H

2014-07-04

MRI physics simulators have been developed in the past for optimizing imaging protocols and for training purposes. However, these simulators have only addressed motion within a limited scope. The purpose of this study was the incorporation of realistic motion, such as cardiac motion, respiratory motion and flow, within MRI simulations in a high performance multi-GPU environment. Three different motion models were introduced in the Magnetic Resonance Imaging SIMULator (MRISIMUL) of this study: cardiac motion, respiratory motion and flow. Simulation of a simple Gradient Echo pulse sequence and a CINE pulse sequence on the corresponding anatomical model was performed. Myocardial tagging was also investigated. In pulse sequence design, software crushers were introduced to accommodate the long execution times in order to avoid spurious echoes formation. The displacement of the anatomical model isochromats was calculated within the Graphics Processing Unit (GPU) kernel for every timestep of the pulse sequence. Experiments that would allow simulation of custom anatomical and motion models were also performed. Last, simulations of motion with MRISIMUL on single-node and multi-node multi-GPU systems were examined. Gradient Echo and CINE images of the three motion models were produced and motion-related artifacts were demonstrated. The temporal evolution of the contractility of the heart was presented through the application of myocardial tagging. Better simulation performance and image quality were presented through the introduction of software crushers without the need to further increase the computational load and GPU resources. Last, MRISIMUL demonstrated an almost linear scalable performance with the increasing number of available GPU cards, in both single-node and multi-node multi-GPU computer systems. MRISIMUL is the first MR physics simulator to have implemented motion with a 3D large computational load on a single computer multi-GPU configuration. The incorporation of realistic motion models, such as cardiac motion, respiratory motion and flow may benefit the design and optimization of existing or new MR pulse sequences, protocols and algorithms, which examine motion related MR applications.

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.

Extreme-UV scanning wafer and reticle stages

DOEpatents

Williams, Mark E.

2002-01-01

A stage for precise positioning of a chuck in three orthogonal linear axes and in three orthogonal rotation axes that includes first and second subassemblies. The a first subassembly includes (i) a monolithic mirror that supports the chuck wherein the monolithic mirror has at least two polished orthogonal faces for interferometric determination of the X, Y, and .THETA.z positions; (ii) a plurality of electromagnetic actuators that control fine positioning in all six axes and coarse positioning in one axis; (iii) a position sensor for measuring the vertical Z position of the monolithic mirror; and (iv) a Lorentz actuator, that includes magnet array, for effecting motion in the Y axis. The a second subassembly comprising a stepping axis beam over which the first subassembly is suspended, wherein the stepping axis beam includes a drive coil array for the Lorentz actuator. T the stage can also include a cable stage subassembly that is positioned a fixed distance away from the monolithic mirror and/or a mechanical zero reference for the first subassembly.

Digital active material processing platform effort (DAMPER), SBIR phase 2

NASA Technical Reports Server (NTRS)

Blackburn, John; Smith, Dennis

1992-01-01

Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

Digital active material processing platform effort (DAMPER), SBIR phase 2

NASA Astrophysics Data System (ADS)

Blackburn, John; Smith, Dennis

1992-11-01

Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

Development of modular control software for construction 3D-printer

NASA Astrophysics Data System (ADS)

Bazhanov, A.; Yudin, D.; Porkhalo, V.

2018-03-01

This article discusses the approach to developing modular software for real-time control of an industrial construction 3D printer. The proposed structure of a two-level software solution is implemented for a robotic system that moves in a Cartesian coordinate system with multi-axis interpolation. An algorithm for the formation and analysis of a path is considered to enable the most effective control of printing through dynamic programming.

Determining the maximum diameter for holes in the shoe without compromising shoe integrity when using a multi-segment foot model.

PubMed

Shultz, Rebecca; Jenkyn, Thomas

2012-01-01

Measuring individual foot joint motions requires a multi-segment foot model, even when the subject is wearing a shoe. Each foot segment must be tracked with at least three skin-mounted markers, but for these markers to be visible to an optical motion capture system holes or 'windows' must be cut into the structure of the shoe. The holes must be sufficiently large avoiding interfering with the markers, but small enough that they do not compromise the shoe's structural integrity. The objective of this study was to determine the maximum size of hole that could be cut into a running shoe upper without significantly compromising its structural integrity or changing the kinematics of the foot within the shoe. Three shoe designs were tested: (1) neutral cushioning, (2) motion control and (3) stability shoes. Holes were cut progressively larger, with four sizes tested in all. Foot joint motions were measured: (1) hindfoot with respect to midfoot in the frontal plane, (2) forefoot twist with respect to midfoot in the frontal plane, (3) the height-to-length ratio of the medial longitudinal arch and (4) the hallux angle with respect to first metatarsal in the sagittal plane. A single subject performed level walking at her preferred pace in each of the three shoes with ten repetitions for each hole size. The largest hole that did not disrupt shoe integrity was an oval of 1.7cm×2.5cm. The smallest shoe deformations were seen with the motion control shoe. The least change in foot joint motion was forefoot twist in both the neutral shoe and stability shoe for any size hole. This study demonstrates that for a hole smaller than this size, optical motion capture with a cluster-based multi-segment foot model is feasible for measure foot in shoe kinematics in vivo. Copyright © 2011. Published by Elsevier Ltd.

The multi-axis vibration environment and man.

PubMed

Lovesey, E J

1970-12-01

Many investigations into the effects of vibration on man have been performed since Mallock's first study of London Underground vibrations in 1902. The vibration research has tended to be confined to the vertical (heave) axis, yet recent experiments have indicated that low frequency vibration along the lateral (sway) axis has a greater adverse effect upon comfort and performance. Measurements of the vibration environments in current forms of transport including motor vehicles, hovercraft and aircraft etc have shown that appreciable quantities of vibration along all three axes exist. Further vibration research should consider the effects of multi-axis vibrations upon man rather than limit tests to single axis vibration.

Novel Expressions of Equations of Relative Motion and Control in Keplerian Orbits

DTIC Science & Technology

2009-04-01

Control, and Dynamics, Vol. 29, No. 2, March– April 2006, pp. 495–499. doi:10.2514/1.19148 [12] Singla, P., Subbarao , K ., and Junkins, J. L...negative orbit normal, and thex axis is defined as i j k , where i; j and k are the basis vector of the LVLH frame. Thus, in a circular orbit, the x...a. REPORT unclassified b . ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

Electrically Controlled Valve With Small Motor

NASA Technical Reports Server (NTRS)

Reinicke, Robert H.; Mohtar, Rafic; Nelson, Richard O.

1992-01-01

Design of electrically controlled valve exploits force-multiplying principle to overcome large back-pressure force resisting initial opening. Design makes possible to open valve by use of relatively small motor adequate for rest of valve motion, but otherwise not large enough to open valve. In simple linear lifting, small horizontal forces applied to pair of taut cables to lift large weight through short distance. In rotary lifting, similar effect achieved by rotating, about an axis, disk to which initially axial cables attached.

Estimating non-circular motions in barred galaxies using numerical N-body simulations

NASA Astrophysics Data System (ADS)

Randriamampandry, T. H.; Combes, F.; Carignan, C.; Deg, N.

2015-12-01

The observed velocities of the gas in barred galaxies are a combination of the azimuthally averaged circular velocity and non-circular motions, primarily caused by gas streaming along the bar. These non-circular flows must be accounted for before the observed velocities can be used in mass modelling. In this work, we examine the performance of the tilted-ring method and the DISKFIT algorithm for transforming velocity maps of barred spiral galaxies into rotation curves (RCs) using simulated data. We find that the tilted-ring method, which does not account for streaming motions, under-/overestimates the circular motions when the bar is parallel/perpendicular to the projected major axis. DISKFIT, which does include streaming motions, is limited to orientations where the bar is not aligned with either the major or minor axis of the image. Therefore, we propose a method of correcting RCs based on numerical simulations of galaxies. We correct the RC derived from the tilted-ring method based on a numerical simulation of a galaxy with similar properties and projections as the observed galaxy. Using observations of NGC 3319, which has a bar aligned with the major axis, as a test case, we show that the inferred mass models from the uncorrected and corrected RCs are significantly different. These results show the importance of correcting for the non-circular motions and demonstrate that new methods of accounting for these motions are necessary as current methods fail for specific bar alignments.

Programmable Positioner For Spot Welding

NASA Technical Reports Server (NTRS)

Roden, William A.

1989-01-01

Welding station mechanized by installing preset indexing system and gear drive. Mechanism includes a low-cost, versatile, single-axis motion control and motor drive to provide fully-automatic weld sequencing and spot-to-spot spacing. Welding station relieves operator of some difficult, tedious tasks and increases both productivity and quality of welds. Results in welds of higher quality and greater accuracy, fewer weld defects, and faster welding operation.

The relation of motion sickness to the spatial-temporal properties of velocity storage

NASA Technical Reports Server (NTRS)

Dai, Mingjia; Kunin, Mikhail; Raphan, Theodore; Cohen, Bernard; Young, L. R. (Principal Investigator)

2003-01-01

Tilting the head in roll to or from the upright while rotating at a constant velocity (roll while rotating, RWR) alters the position of the semicircular canals relative to the axis of rotation. This produces vertical and horizontal nystagmus, disorientation, vertigo, and nausea. With recurrent exposure, subjects habituate and can make more head movements before experiencing overpowering motion sickness. We questioned whether promethazine lessened the vertigo or delayed the habituation, whether habituation of the vertigo was related to the central vestibular time constant, i.e., to the time constant of velocity storage, and whether the severity of the motion sickness was related to deviation of the axis of eye velocity from gravity. Sixteen subjects received promethazine and placebo in a double-blind, crossover study in two consecutive 4-day test series 1 month apart, termed series I and II. Horizontal and vertical eye movements were recorded with video-oculography while subjects performed roll head movements of approx. 45 degrees over 2 s to and from the upright position while being rotated at 138 degrees /s around a vertical axis. Motion sickness was scaled from 1 (no sickness) to an endpoint of 20, at which time the subject was too sick to continue or was about to vomit. Habituation was determined by the number of head movements that subjects made before reaching the maximum motion sickness score of 20. Head movements increased steadily in each session with repeated testing, and there was no difference between the number of head movements made by the promethazine and placebo groups. Horizontal and vertical angular vestibulo-ocular reflex (aVOR) time constants declined in each test, with the declines being closely correlated to the increase in the number of head movements. The strength of vertiginous sensation was associated with the amount of deviation of the axis of eye velocity from gravity; the larger the deviation of the eye velocity axis from gravity, the more severe the motion sickness. Thus, promethazine neither reduced the nausea associated with RWR, nor retarded or hastened habituation. The inverse relationship between the aVOR time constants and number of head movements to motion sickness, and the association of the severity of motion sickness with the extent, strength, and time of deviation of eye velocity from gravity supports the postulate that the spatiotemporal properties of velocity storage, which are processed between the nodulus and uvula of the vestibulocerebellum and the vestibular nuclei, are likely to represent the source of the conflict responsible for producing motion sickness.

Bipartite flocking for multi-agent systems

NASA Astrophysics Data System (ADS)

Fan, Ming-Can; Zhang, Hai-Tao; Wang, Miaomiao

2014-09-01

This paper addresses the bipartite flock control problem where a multi-agent system splits into two clusters upon internal or external excitations. Using structurally balanced signed graph theory, LaSalle's invariance principle and Barbalat's Lemma, we prove that the proposed algorithm guarantees a bipartite flocking behavior. In each of the two disjoint clusters, all individuals move with the same direction. Meanwhile, every pair of agents in different clusters moves with opposite directions. Moreover, all agents in the two separated clusters approach a common velocity magnitude, and collision avoidance among all agents is ensured as well. Finally, the proposed bipartite flock control method is examined by numerical simulations. The bipartite flocking motion addressed by this paper has its references in both natural collective motions and human group behaviors such as predator-prey and panic escaping scenarios.

GN/C translation and rotation control parameters for AR/C (category 2)

NASA Technical Reports Server (NTRS)

Henderson, David M.

1991-01-01

Detailed analysis of the Automatic Rendezvous and Capture problem indicate a need for three different regions of mathematical description for the GN&C algorithms: (1) multi-vehicle orbital mechanics to the rendezvous interface point, i.e., within 100 n.; (2) relative motion solutions (such as Clohessy-Wiltshire type) from the far-field to the near-field interface, i.e., within 1 nm; and (3) close proximity motion, the nearfield motion where the relative differences in the gravitational and orbit inertial accelerations can be neglected from the equations of motion. This paper defines the reference coordinate frames and control parameters necessary to model the relative motion and attitude of spacecraft in the close proximity of another space system (Region 2 and 3) during the Automatic Rendezvous and Capture phase of an orbit operation.

The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

NASA Technical Reports Server (NTRS)

Merfeld, D. M.; Young, L. R.

1995-01-01

The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These results are consistent with the hypothesis that the measurement of gravito-inertial force by the otolith organs is resolved into central estimates of linear acceleration and gravity, such that the central estimate of gravitational force minus the central estimate of linear acceleration approximately equals the otolith measurement of gravito-inertial force.

Communication Dependent Control of Multi-Vehicle Formations

DTIC Science & Technology

2016-05-11

On Maximizing the Second Smallest Eigen- value of a State-Dependent Graph Laplacian,” IEEE Transactions on Au- tomatic Control, vol. 51, no. 1, pp...Collective Motion With Limited Communication,” IEEE Transactions on Au- tomatic Control, vol. 53, no. 3, pp. 706–719, 2008. [Online]. Available: http

Development of support system to handle ultrasound probe by coordinated motion with medical robot.

PubMed

Masuda, Kohji; Takachi, Yuuki; Urayama, Yasuhiro; Yoshinaga, Takashi

2011-01-01

We have developed a support system using our ultrasound diagnosis robot, which is able to support manual handling of ultrasound probe in echography to alleviate fatigue of examiner. This system realizes a coordinated motion according to the motion of the probe, which is hold by the robot and is moved by an examiner. We have established four kinds of situations, which are initial fixation, coordinate motions with/without contact on the body surface, and automatic chase motion of an internal organ. The system recognizes when the examiner grasps the ultrasound probe by 6-axis force sensor and touches it on body surface by processing echograms. Not only unskilled examiners but also a professional sonographer have evaluated the performance of the system after elucidating multiple parameters for compliance control and self-weight and moment compensation of the probe. As the results, this system has the potential to be able to support advanced diagnosis for conventional echography.

A 17 degree of freedom anthropomorphic manipulator

NASA Technical Reports Server (NTRS)

Vold, Havard I.; Karlen, James P.; Thompson, Jack M., Jr.; Farrell, James D.; Eismann, Paul H.

1989-01-01

A 17 axis anthropomorphic manipulator, providing coordinated control of two seven degree of freedom arms mounted on a three degree of freedom torso-waist assembly, is presented. This massively redundant telerobot, designated the Robotics Research K/B-2017 Dexterous Manipulator, employs a modular mechanism design with joint-mounted actuators based on brushless motors and harmonic drive gear reducers. Direct joint torque control at the servo level causes these high-output joint drives to behave like direct-drive actuators, facilitating the implementation of an effective impedance control scheme. The redundant, but conservative motion control system models the manipulator as a spring-loaded linkage with viscous damping and rotary inertia at each joint. This approach allows for real time, sensor-driven control of manipulator pose using a hierarchy of competing rules, or objective functions, to avoid unplanned collisions with objects in the workplace, to produce energy-efficient, graceful motion, to increase leverage, to control effective impedance at the tool or to favor overloaded joints.

Nonlinear Dynamics of a Multistage Gear Transmission System with Multi-Clearance

NASA Astrophysics Data System (ADS)

Xiang, Ling; Zhang, Yue; Gao, Nan; Hu, Aijun; Xing, Jingtang

The nonlinear torsional model of a multistage gear transmission system which consists of a planetary gear and two parallel gear stages is established with time-varying meshing stiffness, comprehensive gear error and multi-clearance. The nonlinear dynamic responses are analyzed by applying the reference of backlash bifurcation parameters. The motions of the system on the change of backlash are identified through global bifurcation diagram, largest Lyapunov exponent (LLE), FFT spectra, Poincaré maps, the phase diagrams and time series. The numerical results demonstrate that the system exhibits rich features of nonlinear dynamics such as the periodic motion, nonperiodic states and chaotic states. It is found that the sun-planet backlash has more complex effect on the system than the ring-planet backlash. The motions of the system with backlash of parallel gear are diverse including some different multi-periodic motions. Furthermore, the state of the system can change from chaos into quasi-periodic behavior, which means that the dynamic behavior of the system is composed of more stable components with the increase of the backlash. Correspondingly, the parameters of the system should be designed properly and controlled timely for better operation and enhancing the life of the system.

Analysis on the multi-dimensional spectrum of the thrust force for the linear motor feed drive system in machine tools

NASA Astrophysics Data System (ADS)

Yang, Xiaojun; Lu, Dun; Ma, Chengfang; Zhang, Jun; Zhao, Wanhua

2017-01-01

The motor thrust force has lots of harmonic components due to the nonlinearity of drive circuit and motor itself in the linear motor feed drive system. What is more, in the motion process, these thrust force harmonics may vary with the position, velocity, acceleration and load, which affects the displacement fluctuation of the feed drive system. Therefore, in this paper, on the basis of the thrust force spectrum obtained by the Maxwell equation and the electromagnetic energy method, the multi-dimensional variation of each thrust harmonic is analyzed under different motion parameters. Then the model of the servo system is established oriented to the dynamic precision. The influence of the variation of the thrust force spectrum on the displacement fluctuation is discussed. At last the experiments are carried out to verify the theoretical analysis above. It can be found that the thrust harmonics show multi-dimensional spectrum characteristics under different motion parameters and loads, which should be considered to choose the motion parameters and optimize the servo control parameters in the high-speed and high-precision machine tools equipped with the linear motor feed drive system.

CHARGED DUST GRAIN DYNAMICS SUBJECT TO SOLAR WIND, POYNTING–ROBERTSON DRAG, AND THE INTERPLANETARY MAGNETIC FIELD

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

Lhotka, Christoph; Bourdin, Philippe; Narita, Yasuhito, E-mail: christoph.lhotka@oeaw.ac.at, E-mail: philippe.bourdin@oeaw.ac.at, E-mail: yasuhito.narita@oeaw.ac.at

We investigate the combined effect of solar wind, Poynting–Robertson drag, and the frozen-in interplanetary magnetic field on the motion of charged dust grains in our solar system. For this reason, we derive a secular theory of motion by the means of an averaging method and validate it with numerical simulations of the unaveraged equations of motions. The theory predicts that the secular motion of charged particles is mainly affected by the z -component of the solar magnetic axis, or the normal component of the interplanetary magnetic field. The normal component of the interplanetary magnetic field leads to an increase ormore » decrease of semimajor axis depending on its functional form and sign of charge of the dust grain. It is generally accepted that the combined effects of solar wind and photon absorption and re-emmision (Poynting–Robertson drag) lead to a decrease in semimajor axis on secular timescales. On the contrary, we demonstrate that the interplanetary magnetic field may counteract these drag forces under certain circumstances. We derive a simple relation between the parameters of the magnetic field, the physical properties of the dust grain, as well as the shape and orientation of the orbital ellipse of the particle, which is a necessary conditions for the stabilization in semimajor axis.« less

Suppression of flutter

NASA Technical Reports Server (NTRS)

Nissim, E. (Inventor)

1973-01-01

An active aerodynamic control system to control flutter over a large range of oscillatory frequencies is described. The system is not affected by mass, stiffness, elastic axis, or center of gravity location of the system, mode of vibration, or Mach number. The system consists of one or more pairs of leading edge and trailing edge hinged or deformable control surfaces, each pair operated in concert by a stability augmentation system. Torsion and bending motions are sensed and converted by the stability augmentation system into leading and trailing edge control surface deflections which produce lift forces and pitching moments to suppress flutter.

Dynamic motion analysis of dart throwers motion visualized through computerized tomography and calculation of the axis of rotation.

PubMed

Edirisinghe, Y; Troupis, J M; Patel, M; Smith, J; Crossett, M

2014-05-01

We used a dynamic three-dimensional (3D) mapping method to model the wrist in dynamic unrestricted dart throwers motion in three men and four women. With the aid of precision landmark identification, a 3D coordinate system was applied to the distal radius and the movement of the carpus was described. Subsequently, with dynamic 3D reconstructions and freedom to position the camera viewpoint anywhere in space, we observed the motion pathways of all carpal bones in dart throwers motion and calculated its axis of rotation. This was calculated to lie in 27° of anteversion from the coronal plane and 44° of varus angulation relative to the transverse plane. This technique is a safe and a feasible carpal imaging method to gain key information for decision making in future hand surgical and rehabilitative practices.

Fidelity of the ensemble code for visual motion in primate retina.

PubMed

Frechette, E S; Sher, A; Grivich, M I; Petrusca, D; Litke, A M; Chichilnisky, E J

2005-07-01

Sensory experience typically depends on the ensemble activity of hundreds or thousands of neurons, but little is known about how populations of neurons faithfully encode behaviorally important sensory information. We examined how precisely speed of movement is encoded in the population activity of magnocellular-projecting parasol retinal ganglion cells (RGCs) in macaque monkey retina. Multi-electrode recordings were used to measure the activity of approximately 100 parasol RGCs simultaneously in isolated retinas stimulated with moving bars. To examine how faithfully the retina signals motion, stimulus speed was estimated directly from recorded RGC responses using an optimized algorithm that resembles models of motion sensing in the brain. RGC population activity encoded speed with a precision of approximately 1%. The elementary motion signal was conveyed in approximately 10 ms, comparable to the interspike interval. Temporal structure in spike trains provided more precise speed estimates than time-varying firing rates. Correlated activity between RGCs had little effect on speed estimates. The spatial dispersion of RGC receptive fields along the axis of motion influenced speed estimates more strongly than along the orthogonal direction, as predicted by a simple model based on RGC response time variability and optimal pooling. on and off cells encoded speed with similar and statistically independent variability. Simulation of downstream speed estimation using populations of speed-tuned units showed that peak (winner take all) readout provided more precise speed estimates than centroid (vector average) readout. These findings reveal how faithfully the retinal population code conveys information about stimulus speed and the consequences for motion sensing in the brain.

Plane of vertebral movement eliciting muscle lengthening history in the low back influences the decrease in muscle spindle responsiveness of the cat

PubMed Central

Ge, Weiqing; Cao, Dong-Yuan; Long, Cynthia R.

2011-01-01

Proprioceptive feedback is thought to play a significant role in controlling both lumbopelvic and intervertebral orientations. In the lumbar spine, a vertebra's positional history along the dorsal-ventral axis has been shown to alter the position, movement, and velocity sensitivity of muscle spindles in the multifidus and longissimus muscles. These effects appear due to muscle history. Because spinal motion segments have up to 6 degrees of freedom for movement, we were interested in whether the axis along which the history is applied differentially affects paraspinal muscle spindles. We tested the null hypothesis that the loading axis, which creates a vertebra's positional history, has no effect on a lumbar muscle spindle's subsequent response to vertebral position or movement. Identical displacements were applied along three orthogonal axes directly at the L6 spinous process using a feedback motor system under displacement control. Single-unit nerve activity was recorded from 60 muscle spindle afferents in teased filaments from L6 dorsal rootlets innervating intact longissimus or multifidus muscles of deeply anesthetized cats. Muscle lengthening histories along the caudal-cranial and dorsal-ventral axis, compared with the left-right axis, produced significantly greater reductions in spindle responses to vertebral position and movement. The spinal anatomy suggested that the effect of a lengthening history is greatest when that history had occurred along an axis lying within the anatomical plane of the facet joint. Speculation is made that the interaction between normal spinal mechanics and the inherent thixotropic property of muscle spindles poses a challenge for feedback and feedforward motor control of the lumbar spine. PMID:21960662

The Multi-Scale Environment of RS Cnc from CO and HI Observations

NASA Astrophysics Data System (ADS)

Hoai, D. T.; Matthews, L. D.; Winters, J. M.; Nhung, P. T.; Gérard, E.; Libert, Y.; Le Bertre, T.

2015-08-01

We present a detailed study of the circumstellar gas distribution and kinematics of the semi-regular variable star RS Cnc on spatial scales ranging from ˜1″ (˜150 AU) to ˜6' (˜0.24 pc). The close environment of RS Cnc (from 1 to 20″) can be described with a model in which the density and velocity vary smoothly from the equatorial plane to the polar axis. In this model the mass loss rate is higher along the polar directions than in the equatorial plane, which does not favor current models invoking stellar rotation or a magnetic field as the cause of the axi-symmetry. Outside this region, the study of which is limited by the photo-dissociation of CO, HI data at 21 cm show that the flow is slowed down at a typical distance of 1' (˜0.04 pc). Further away (1 to 6', or 0.04 to 0.24 pc), the flow is distorted by the relative motion of the star with respect to the interstellar medium.

A dynamic motion simulator for future European docking systems

NASA Technical Reports Server (NTRS)

Brondino, G.; Marchal, PH.; Grimbert, D.; Noirault, P.

1990-01-01

Europe's first confrontation with docking in space will require extensive testing to verify design and performance and to qualify hardware. For this purpose, a Docking Dynamics Test Facility (DDTF) was developed. It allows reproduction on the ground of the same impact loads and relative motion dynamics which would occur in space during docking. It uses a 9 degree of freedom, servo-motion system, controlled by a real time computer, which simulates the docking spacecraft in a zero-g environment. The test technique involves and active loop based on six axis force and torque detection, a mathematical simulation of individual spacecraft dynamics, and a 9 degree of freedom servomotion of which 3 DOFs allow extension of the kinematic range to 5 m. The configuration was checked out by closed loop tests involving spacecraft control models and real sensor hardware. The test facility at present has an extensive configuration that allows evaluation of both proximity control and docking systems. It provides a versatile tool to verify system design, hardware items and performance capabilities in the ongoing HERMES and COLUMBUS programs. The test system is described and its capabilities are summarized.

Flower tracking in hawkmoths: behavior and energetics.

PubMed

Sprayberry, Jordanna D H; Daniel, Thomas L

2007-01-01

As hovering feeders, hawkmoths cope with flower motions by tracking those motions to maintain contact with the nectary. This study examined the tracking, feeding and energetic performance of Manduca sexta feeding from flowers moving at varied frequencies and in different directions. In general we found that tracking performance decreased as frequency increased; M. sexta tracked flowers moving at 1 Hz best. While feeding rates were highest for stationary flowers, they remained relatively constant for all tested frequencies of flower motion. Calculations of net energy gain showed that energy expenditure to track flowers is minimal compared to energy intake; therefore, patterns of net energy gain mimicked patterns of feeding rate. The direction effects of flower motion were greater than the frequency effects. While M. sexta appeared equally capable of tracking flowers moving in the horizontal and vertical motion axes, they demonstrated poor ability to track flowers moving in the looming axis. Additionally, both feeding rates and net energy gain were lower for looming axis flower motions.

Study of the transverse beam motion in the DARHT Phase II accelerator

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

Chen, Yu-Jiuan; Fawley, W M; Houck, T L

1998-08-20

The accelerator for the second-axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT) facility will accelerate a 4-kA, 3-MeV, 2--µs long electron current pulse to 20 MeV. The energy variation of the beam within the flat-top portion of the current pulse is (plus or equal to) 0.5%. The performance of the DARHT Phase II radiographic machine requires the transverse beam motion to be much less than the beam spot size which is about 1.5 mm diameter on the x-ray converter. In general, the leading causes of the transverse beam motion in an accelerator are the beam breakup instability (BBU) andmore » the corkscrew motion. We have modeled the transverse beam motion in the DARHT Phase II accelerator with various magnetic tunes and accelerator cell configurations by using the BREAKUP code. The predicted sensitivity of corkscrew motion and BBU growth to different tuning algorithms will be presented.« less

Pseudo Dynamic Testing and Seismic Rehabilitation of Iraqi Brick, Bearing and Shear Walls

DTIC Science & Technology

2008-04-01

R es ea rc h L ab or at or y Approved for public release; distribution is unlimited. ERDC/CERL TR-08-6 April 2008 Pseudo Dynamic Testing and...Model 307-50 and one Satec 100 kip servo-hydraulic actuator controlled by closed-loop servo controllers and an Instron 8800 multi-axis controller and RS...Plus testing software.* The Satec actuator was operated in displacement control mode, and the 50 kip CGS actuators were operated in modal control

Nonlinear Aeroelastic Equations of Motion of Twisted, Nonuniform, Flexible Horizontal-Axis Wind Turbine Blades

NASA Technical Reports Server (NTRS)

Kaza, K. R. V.

1980-01-01

The second-degree nonlinear equations of motion for a flexible, twisted, nonuniform, horizontal axis wind turbine blade were developed using Hamilton's principle. A mathematical ordering scheme which was consistent with the assumption of a slender beam was used to discard some higher-order elastic and inertial terms in the second-degree nonlinear equations. The blade aerodynamic loading which was employed accounted for both wind shear and tower shadow and was obtained from strip theory based on a quasi-steady approximation of two-dimensional, incompressible, unsteady, airfoil theory. The resulting equations had periodic coefficients and were suitable for determining the aeroelastic stability and response of large horizontal-axis wind turbine blades.

Factors determining the spin axis of a pitched fastball in baseball.

PubMed

Jinji, Tsutomu; Sakurai, Shinji; Hirano, Yuichi

2011-04-01

In this study, we wished to investigate the factors that determine the direction of the spin axis of a pitched baseball. Nineteen male baseball pitchers were recruited to pitch fastballs. The pitching motion was recorded with a three-dimensional motion analysis system (1000 Hz), and the orientations of the hand segment in a global coordinate system were calculated using Euler rotation angles. Reflective markers were attached to the ball, and the direction of the spin axis was calculated on the basis of their positional changes. The spin axis directions were significantly correlated with the orientations of the hand just before ball release. The ball is released from the fingertip and rotates on a plane that is formed by the palm and fingers; the spin axis of the ball is parallel to this plane. The lift force of the pitched baseball is largest when the angular and translational velocity vectors are mutually perpendicular. Furthermore, to increase the lift forces for the fastballs, the palm must face home plate.

Parallel controller construction for a multi-DOF hand rehabilitation equipment

NASA Astrophysics Data System (ADS)

Ito, Satoshi; Ueki, Satoshi; Ishihara, Koji; Miura, Masayuki; Kawasaki, Haruhisa; Ishigure, Yasuhiko; Nishimoto, Yutakai

2007-12-01

This paper describes the development of a hand rehabilitation system for stroke patients. Our aim is to provide fine motion exercise for a hand and fingers. Thus, a hand rehabilitation device that assists patients' finger movements was developed. Because this device has 18 degrees of freedom of motion, it is diffcult for disabled patients to use it by themselves. Therefore, an appropriate control strategy and control system are required to allow its safe and effective use. In light of this requirement, a control system was constructed which is comprised of four separated controllers. This paper presents the structure of the control system and introduces the control protocols used in our hand rehabilitation system.

Modeling and experiment of three-degree-of-freedom actuators using piezoelectric buzzers

NASA Astrophysics Data System (ADS)

Chen, W. M.; Liu, T. S.

2013-10-01

This study presents innovative three-degree-of-freedom piezoelectric actuators. Under the piezoelectric force and dry friction, the piezoelectric actuators not only can move in the Z-axis direction, but also rotate around the Y-axis and Z-axis. The Z-axis displacement can reach 62 mm and the rotation angle around the Y-axis and Z-axis can reach 270° and 360°, respectively. Compared with the literature, this innovative actuator design achieves one-degree-of-freedom translation and two-degree-of-freedom rotation. Equations of motion are derived based on the piezoelectric properties and Newton’s law. Two types of actuators are created in this study. In the first type, the centers of four piezoelectric buzzers are attached to an arm while in the other type each rim of the four piezoelectric buzzers is attached to the arm. Experimental results are compared with theoretical results. According to the experimental results, the present actuator can accomplish a translational velocity of 11 mm s-1, a Y-axis angular velocity of 8.96 rad s-1, a Z-axis angular velocity of 2.63 rad s-1, and a force of 2.49 mN. By using four piezoelectric buzzers, this study creates piezoelectric actuators capable of both translational and rotational motions.

Regional cardiac wall motion from gated myocardial perfusion SPECT studies

NASA Astrophysics Data System (ADS)

Smith, M. F.; Brigger, P.; Ferrand, S. K.; Dilsizian, V.; Bacharach, S. L.

1999-06-01

A method for estimating regional epicardial and endocardial wall motion from gated myocardial perfusion SPECT studies has been developed. The method uses epicardial and endocardial boundaries determined from four long-axis slices at each gate of the cardiac cycle. The epicardial and endocardial wall position at each time gate is computed with respect to stationary reference ellipsoids, and wall motion is measured along lines normal to these ellipsoids. An initial quantitative evaluation of the method was made using the beating heart from the dynamic mathematical cardiac torso (MCAT) phantom, with and without a 1.5-cm FWHM Gaussian blurring filter. Epicardial wall motion was generally well-estimated within a fraction of a 3.56-mm voxel, although apical motion was overestimated with the Gaussian filter. Endocardial wall motion was underestimated by about two voxels with and without the Gaussian filter. The MCAT heart phantom was modified to model hypokinetic and dyskinetic wall motion. The wall motion analysis method enabled this abnormal motion to be differentiated from normal motion. Regional cardiac wall motion also was analyzed for /sup 201/Tl patient studies. Estimated wall motion was consistent with a nuclear medicine physician's visual assessment of motion from gated long-axis slices for male and female study examples. Additional research is required for a comprehensive evaluation of the applicability of the method to patient studies with normal and abnormal wall motion.

High performance MRI simulations of motion on multi-GPU systems

PubMed Central

2014-01-01

Background MRI physics simulators have been developed in the past for optimizing imaging protocols and for training purposes. However, these simulators have only addressed motion within a limited scope. The purpose of this study was the incorporation of realistic motion, such as cardiac motion, respiratory motion and flow, within MRI simulations in a high performance multi-GPU environment. Methods Three different motion models were introduced in the Magnetic Resonance Imaging SIMULator (MRISIMUL) of this study: cardiac motion, respiratory motion and flow. Simulation of a simple Gradient Echo pulse sequence and a CINE pulse sequence on the corresponding anatomical model was performed. Myocardial tagging was also investigated. In pulse sequence design, software crushers were introduced to accommodate the long execution times in order to avoid spurious echoes formation. The displacement of the anatomical model isochromats was calculated within the Graphics Processing Unit (GPU) kernel for every timestep of the pulse sequence. Experiments that would allow simulation of custom anatomical and motion models were also performed. Last, simulations of motion with MRISIMUL on single-node and multi-node multi-GPU systems were examined. Results Gradient Echo and CINE images of the three motion models were produced and motion-related artifacts were demonstrated. The temporal evolution of the contractility of the heart was presented through the application of myocardial tagging. Better simulation performance and image quality were presented through the introduction of software crushers without the need to further increase the computational load and GPU resources. Last, MRISIMUL demonstrated an almost linear scalable performance with the increasing number of available GPU cards, in both single-node and multi-node multi-GPU computer systems. Conclusions MRISIMUL is the first MR physics simulator to have implemented motion with a 3D large computational load on a single computer multi-GPU configuration. The incorporation of realistic motion models, such as cardiac motion, respiratory motion and flow may benefit the design and optimization of existing or new MR pulse sequences, protocols and algorithms, which examine motion related MR applications. PMID:24996972

Parabrachial nucleus neuronal responses to off-vertical axis rotation in macaques

PubMed Central

McCandless, Cyrus H.; Balaban, Carey D.

2010-01-01

The caudal aspect of the parabrachial nucleus (PBN) contains neurons responsive to whole body, periodic rotational stimulation in alert monkeys. This study characterizes the angular and linear motion-sensitive response properties of PBN unit responses during off-vertical axis rotation (OVAR) and position trapezoid stimulation. The OVAR responses displayed a constant firing component which varied from the firing rate at rest. Nearly two-thirds of the units also modulated their discharges with respect to head orientation (re: gravity) during constant velocity OVAR stimulation. The modulated response magnitudes were equal during ipsilateral and contralateral OVARs, indicative of a one-dimensional accelerometer. These response orientations during OVAR divided the units into three spatially tuned populations, with peak modulation responses centered in the ipsilateral ear down, contralateral anterior semicircular canal down, and occiput down orientations. Because the orientation of the OVAR modulation response was opposite in polarity to the orientation of the static tilt component of responses to position trapezoids for the majority of units, the linear acceleration responses were divided into colinear dynamic linear and static tilt components. The orientations of these unit responses formed two distinct population response axes: (1) units with an interaural linear response axis and (2) units with an ipsilateral anterior semicircular canal-contralateral posterior semicircular canal plane linear response axis. The angular rotation sensitivity of these units is in a head-vertical plane that either contains the linear acceleration response axis or is perpendicular to the linear acceleration axis. Hence, these units behave like head-based (‘strap-down’) inertial guidance sensors. Because the PBN contributes to sensory and interoceptive processing, it is suggested that vestibulo-recipient caudal PBN units may detect potentially dangerous anomalies in control of postural stability during locomotion. In particular, these signals may contribute to the range of affective and emotional responses that include panic associated with falling, malaise associated with motion sickness and mal-de-debarquement, and comorbid balance and anxiety disorders. PMID:20039027

A multi-channel opto-electronic sensor to accurately monitor heart rate against motion artefact during exercise.

PubMed

Alzahrani, Abdullah; Hu, Sijung; Azorin-Peris, Vicente; Barrett, Laura; Esliger, Dale; Hayes, Matthew; Akbare, Shafique; Achart, Jérôme; Kuoch, Sylvain

2015-10-12

This study presents the use of a multi-channel opto-electronic sensor (OEPS) to effectively monitor critical physiological parameters whilst preventing motion artefact as increasingly demanded by personal healthcare. The aim of this work was to study how to capture the heart rate (HR) efficiently through a well-constructed OEPS and a 3-axis accelerometer with wireless communication. A protocol was designed to incorporate sitting, standing, walking, running and cycling. The datasets collected from these activities were processed to elaborate sport physiological effects. t-test, Bland-Altman Agreement (BAA), and correlation to evaluate the performance of the OEPS were used against Polar and Mio-Alpha HR monitors. No differences in the HR were found between OEPS, and either Polar or Mio-Alpha (both p > 0.05); a strong correlation was found between Polar and OEPS (r: 0.96, p < 0.001); the bias of BAA 0.85 bpm, the standard deviation (SD) 9.20 bpm, and the limits of agreement (LOA) from -17.18 bpm to +18.88 bpm. For the Mio-Alpha and OEPS, a strong correlation was found (r: 0.96, p < 0.001); the bias of BAA 1.63 bpm, SD 8.62 bpm, LOA from -15.27 bpm to +18.58 bpm. These results demonstrate the OEPS to be capable of carrying out real time and remote monitoring of heart rate.

Contribution of intravestibular sensory conflict to motion sickness and dizziness in migraine disorders.

PubMed

Wang, Joanne; Lewis, Richard F

2016-10-01

Migraine is associated with enhanced motion sickness susceptibility and can cause episodic vertigo [vestibular migraine (VM)], but the mechanisms relating migraine to these vestibular symptoms remain uncertain. We tested the hypothesis that the central integration of rotational cues (from the semicircular canals) and gravitational cues (from the otolith organs) is abnormal in migraine patients. A postrotational tilt paradigm generated a conflict between canal cues (which indicate the head is rotating) and otolith cues (which indicate the head is tilted and stationary), and eye movements were measured to quantify two behaviors that are thought to minimize this conflict: suppression and reorientation of the central angular velocity signal, evidenced by attenuation ("dumping") of the vestibuloocular reflex and shifting of the rotational axis of the vestibuloocular reflex toward the earth vertical. We found that normal and migraine subjects, but not VM patients, displayed an inverse correlation between the extent of dumping and the size of the axis shift such that the net "conflict resolution" mediated through these two mechanisms approached an optimal value and that the residual sensory conflict in VM patients (but not migraine or normal subjects) correlated with motion sickness susceptibility. Our findings suggest that the brain normally controls the dynamic and spatial characteristics of central vestibular signals to minimize intravestibular sensory conflict and that this process is disrupted in VM, which may be responsible for the enhance motion intolerance and episodic vertigo that characterize this disorder. Copyright © 2016 the American Physiological Society.

Experimental study at low supersonic speeds of a missile concept having opposing wraparound tails

NASA Technical Reports Server (NTRS)

Allen, Jerry M.; Watson, Carolyn B.

1994-01-01

A wind-tunnel investigation has been performed at low supersonic speeds (at Mach numbers of 1.60, and 2.16) to evaluate the aerodynamic characteristics of a missile concept capable of being tube launched and controlled with a simple one-axis canard controller. This concept, which features an axisymmetric body with two planar canards and four wraparound tail fins arranged in opposing pairs, must be in rolling motion to be controllable in any radial plane with the planar canards. Thus, producing a constant rolling moment that is invariant with speed and attitude to provide the motion is desirable. Two tail-fin shaping designs, one shaved and one beveled, were evaluated for their efficiency in producing the needed rolling moments, and the results showed that the shaved fins were much more desirable for this task than the beveled fins.

Development of X-Y servo pneumatic-piezoelectric hybrid actuators for position control with high response, large stroke and nanometer accuracy.

PubMed

Chiang, Mao-Hsiung

2010-01-01

This study aims to develop a X-Y dual-axial intelligent servo pneumatic-piezoelectric hybrid actuator for position control with high response, large stroke (250 mm, 200 mm) and nanometer accuracy (20 nm). In each axis, the rodless pneumatic actuator serves to position in coarse stroke and the piezoelectric actuator compensates in fine stroke. Thus, the overall control systems of the single axis become a dual-input single-output (DISO) system. Although the rodless pneumatic actuator has relatively larger friction force, it has the advantage of mechanism for multi-axial development. Thus, the X-Y dual-axial positioning system is developed based on the servo pneumatic-piezoelectric hybrid actuator. In addition, the decoupling self-organizing fuzzy sliding mode control is developed as the intelligent control strategies. Finally, the proposed novel intelligent X-Y dual-axial servo pneumatic-piezoelectric hybrid actuators are implemented and verified experimentally.

Development of X-Y Servo Pneumatic-Piezoelectric Hybrid Actuators for Position Control with High Response, Large Stroke and Nanometer Accuracy

PubMed Central

Chiang, Mao-Hsiung

2010-01-01

This study aims to develop a X-Y dual-axial intelligent servo pneumatic-piezoelectric hybrid actuator for position control with high response, large stroke (250 mm, 200 mm) and nanometer accuracy (20 nm). In each axis, the rodless pneumatic actuator serves to position in coarse stroke and the piezoelectric actuator compensates in fine stroke. Thus, the overall control systems of the single axis become a dual-input single-output (DISO) system. Although the rodless pneumatic actuator has relatively larger friction force, it has the advantage of mechanism for multi-axial development. Thus, the X-Y dual-axial positioning system is developed based on the servo pneumatic-piezoelectric hybrid actuator. In addition, the decoupling self-organizing fuzzy sliding mode control is developed as the intelligent control strategies. Finally, the proposed novel intelligent X-Y dual-axial servo pneumatic-piezoelectric hybrid actuators are implemented and verified experimentally. PMID:22319266

Three-Axis Time-Optimal Attitude Maneuvers of a Rigid-Body

NASA Astrophysics Data System (ADS)

Wang, Xijing; Li, Jisheng

With the development trends for modern satellites towards macro-scale and micro-scale, new demands are requested for its attitude adjustment. Precise pointing control and rapid maneuvering capabilities have long been part of many space missions. While the development of computer technology enables new optimal algorithms being used continuously, a powerful tool for solving problem is provided. Many papers about attitude adjustment have been published, the configurations of the spacecraft are considered rigid body with flexible parts or gyrostate-type systems. The object function always include minimum time or minimum fuel. During earlier satellite missions, the attitude acquisition was achieved by using the momentum ex change devices, performed by a sequential single-axis slewing strategy. Recently, the simultaneous three-axis minimum-time maneuver(reorientation) problems have been studied by many researchers. It is important to research the minimum-time maneuver of a rigid spacecraft within onboard power limits, because of potential space application such as surveying multiple targets in space and academic value. The minimum-time maneuver of a rigid spacecraft is a basic problem because the solutions for maneuvering flexible spacecraft are based on the solution to the rigid body slew problem. A new method for the open-loop solution for a rigid spacecraft maneuver is presented. Having neglected all perturbation torque, the necessary conditions of spacecraft from one state to another state can be determined. There is difference between single-axis with multi-axis. For single- axis analytical solution is possible and the switching line passing through the state-space origin belongs to parabolic. For multi-axis, it is impossible to get analytical solution due to the dynamic coupling between the axes and must be solved numerically. Proved by modern research, Euler axis rotations are quasi-time-optimal in general. On the basis of minimum value principles, a research for reorienting an inertial syrnmetric spacecraft with time cost function from an initial state of rest to a final state of rest is deduced. And the solution to it is stated below: Firstly, the essential condition for solving the problem is deduced with the minimum value principle. The necessary conditions for optimality yield a two point boundary-value problem (TPBVP), which, when solved, produces the control history that minimize time performance index. In the nonsingular control, the solution is the' bang-bang maneuver. The control profile is characterized by Saturated controls for the entire maneuver. The singular control maybe existed. It is only singular in mathematics. According to physical principle, the bigger the mode of the control torque is, the shorter the time is. So saturated controls are used in singular control. Secondly, the control parameters are always in maximum, so the key problem is to determine switch point thus original problem is changed to find the changing time. By the use of adjusting the switch on/off time, the genetic algorithm, which is a new robust method is optimized to determine the switch features without the gyroscopic coupling. There is improvement upon the traditional GA in this research. The homotopy method to find the nonlinear algebra is based on rigorous topology continuum theory. Based on the idea of the homotopy, the relaxation parameters are introduced, and the switch point is figured out with simulated annealing. Computer simulation results using a rigid body show that the new method is feasible and efficient. A practical method of computing approximate solutions to the time-optimal control- switch times for rigid body reorientation has been developed.

Injuries of the atlas and axis. A follow-up study of 85 axis and 10 atlas fractures.

PubMed

Ersmark, H; Kalen, R

1987-04-01

In a follow-up study of ten atlas and 85 axis fractures, 12% had residual symptoms in the form of local and radiating cervical pain. The residual symptoms were interpreted as a sign of a mild demyelinating process initiated by the trauma of the medulla. At least 22% of the accidents occurred while the person was under the influence of drugs or alcohol. Therefore, a wide range of residual symptoms (progressive or nonprogressive) could be attributed in part to abuse of drugs and alcohol. A permanent measurable loss of motion occurred following injury to the atlas or axis, irrespective of the modality of treatment. Cervical fusion created the greatest loss of motion and collar immobilization the least. Skull traction and a halo-vest were intermediate in patients with loss of motion, and the degree of loss of range was essentially equal. Residual symptoms, including pain, were found in 20% of those treated with a collar, 40% of those treated with surgical methods, 5% of those treated with traction, and 5% of those treated with a Halo-vest. Residual symptoms did not correlate at all with degree of displacement of the original fracture.

Multi-Axis Thrust Measurements of the EO-1 Pulsed Plasma Thruster

NASA Technical Reports Server (NTRS)

Arrington, Lynn A.; Haag, Thomas W.

1999-01-01

Pulsed plasma thrusters are low thrust propulsive devices which have a high specific impulse at low power. A pulsed plasma thruster is currently scheduled to fly as an experiment on NASA's Earth Observing-1 satellite mission. The pulsed plasma thruster will be used to replace one of the reaction wheels. As part of the qualification testing of the thruster it is necessary to determine the nominal thrust as a function of charge energy. These data will be used to determine control algorithms. Testing was first completed on a breadboard pulsed plasma thruster to determine nominal or primary axis thrust and associated propellant mass consumption as a function of energy and then later to determine if any significant off-axis thrust component existed. On conclusion that there was a significant off-axis thrust component with the bread-board in the direction of the anode electrode, the test matrix was expanded on the flight hardware to include thrust measurements along all three orthogonal axes. Similar off-axis components were found with the flight unit.

An analytic model of the in-line and cross-axis apparent mass of the seated human body exposed to vertical vibration with and without a backrest

NASA Astrophysics Data System (ADS)

Zheng, Guangtai; Qiu, Yi; Griffin, Michael J.

2011-12-01

During vertical excitation of the seated human body there are vertical and fore-and-aft forces at the seat that are influenced by contact with a backrest, so it is desirable to take into account the effect of a backrest when developing models of the seated human body. Initially, a seven degree-of-freedom multi-body dynamic model was developed for the human body sitting with an upright posture unsupported by a backrest and exposed to vertical vibration. The model was optimized to fit the vertical apparent mass and the fore-and-aft cross-axis apparent mass measured on a seat. The model was then extended by the addition of vertical and fore-and-aft reaction forces to the upper lumbar spine to model the interaction between the human body and a backrest. By minimizing the least square error between experimental data and the analytical solution of the apparent masses on the seat and at the back, the human body model was able to represent both the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and at the back. Parameter sensitivity studies showed that the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and the backrest were all highly sensitive to the axial stiffness of the tissue beneath the pelvis. Pitch motion of the upper-body contributed to the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat. The apparent mass at the back was more sensitive to the stiffness and damping of the lower back than the properties of the upper back.

Computer numerically controlled (CNC) aspheric shaping with toroidal Wheels (Abstract Only)

NASA Astrophysics Data System (ADS)

Ketelsen, D.; Kittrell, W. C.; Kuhn, W. M.; Parks, R. E.; Lamb, George L.; Baker, Lynn

1987-01-01

Contouring with computer numerically controlled (CNC) machines can be accomplished with several different tool geometries and coordinated machine axes. To minimize the number of coordinated axes for nonsymmetric work to three, it is common practice to use a spherically shaped tool such as a ball-end mill. However, to minimize grooving due to the feed and ball radius, it is desirable to use a long ball radius, but there is clearly a practical limit to ball diameter with the spherical tool. We have found that the use of commercially available toroidal wheels permits long effective cutting radii, which in turn improve finish and minimize grooving for a set feed. In addition, toroidal wheels are easier than spherical wheels to center accurately. Cutting parameters are also easier to control because the feed rate past the tool does not change as the slope of the work changes. The drawback to the toroidal wheel is the more complex calculation of the tool path. Of course, once the algorithm is worked out, the tool path is as easily calculated as for a spherical tool. We have performed two experiments with the Large Optical Generator (LOG) that were ideally suited to three-axis contouring--surfaces that have no axis of rotational symmetry. By oscillating the cutting head horizontally or vertically (in addition to the motions required to generate the power of the surface) , and carefully coordinating those motions with table rotation, the mostly astigmatic departure for these surfaces is produced. The first experiment was a pair of reflector molds that together correct the spherical aberration of the Arecibo radio telescope. The larger of these was 5 m in diameter and had a 12 cm departure from the best-fit sphere. The second experiment was the generation of a purely astigmatic surface to demonstrate the feasibility of producing axially symmetric asphe.rics while mounted and rotated about any off-axis point. Measurements of the latter (the first experiment had relatively loose tolerances) indicate an accuracy only 3 or 4 times that achieved by conventional two-axis contouring (10 AM as opposed to 3 pm rms) The successful completion of these projects demonstrates the successful application of three-axis contouring with the LOG. Toroidal cutters have also solved many of the drawbacks of spherical wheels. Work remains to be done in improving machine response and decreasing the contribution of backlash errors.

Three-dimensional organization of vestibular-related eye movements to off-vertical axis rotation and linear translation in pigeons

NASA Technical Reports Server (NTRS)

Dickman, J. D.; Angelaki, D. E.

1999-01-01

During linear accelerations, compensatory reflexes should continually occur in order to maintain objects of visual interest as stable images on the retina. In the present study, the three-dimensional organization of the vestibulo-ocular reflex in pigeons was quantitatively examined during linear accelerations produced by constant velocity off-vertical axis yaw rotations and translational motion in darkness. With off-vertical axis rotations, sinusoidally modulated eye-position and velocity responses were observed in all three components, with the vertical and torsional eye movements predominating the response. Peak torsional and vertical eye positions occurred when the head was oriented with the lateral visual axis of the right eye directed orthogonal to or aligned with the gravity vector, respectively. No steady-state horizontal nystagmus was obtained with any of the rotational velocities (8-58 degrees /s) tested. During translational motion, delivered along or perpendicular to the lateral visual axis, vertical and torsional eye movements were elicited. No significant horizontal eye movements were observed during lateral translation at frequencies up to 3 Hz. These responses suggest that, in pigeons, all linear accelerations generate eye movements that are compensatory to the direction of actual or perceived tilt of the head relative to gravity. In contrast, no translational horizontal eye movements, which are known to be compensatory to lateral translational motion in primates, were observed under the present experimental conditions.

Multivariable control theory applied to hierarchial attitude control for planetary spacecraft

NASA Technical Reports Server (NTRS)

Boland, J. S., III; Russell, D. W.

1972-01-01

Multivariable control theory is applied to the design of a hierarchial attitude control system for the CARD space vehicle. The system selected uses reaction control jets (RCJ) and control moment gyros (CMG). The RCJ system uses linear signal mixing and a no-fire region similar to that used on the Skylab program; the y-axis and z-axis systems which are coupled use a sum and difference feedback scheme. The CMG system uses the optimum steering law and the same feedback signals as the RCJ system. When both systems are active the design is such that the torques from each system are never in opposition. A state-space analysis was made of the CMG system to determine the general structure of the input matrices (steering law) and feedback matrices that will decouple the axes. It is shown that the optimum steering law and proportional-plus-rate feedback are special cases. A derivation of the disturbing torques on the space vehicle due to the motion of the on-board television camera is presented. A procedure for computing an upper bound on these torques (given the system parameters) is included.

A multi-directional in vitro investigation into friction, damage and wear of innovative chondroplasty materials against articular cartilage.

PubMed

Northwood, Ewen; Fisher, John

2007-08-01

The wear of the biomaterial/cartilage interface is vital for the development of innovative chondroplasty therapies. The aim of this study was to investigate potential chondroplasty biomaterials when sliding against natural articular cartilage under uniaxial reciprocating and multi-directional rotation/reciprocating motions. Three biphasic hydrogels were compared to articular cartilage (negative control) and stainless steel (positive control). Friction was measured by means of a simple geometry friction and wear simulator. All tests were completed in 25% bovine serum at 20 degrees C. Mechanical alterations to the surface structure were quantified using surface topography. Articular cartilage produced a constant friction value of 0.05 (confidence interval=0.015) with and without rotation. Stainless steel against articular cartilage produced an increase in friction over time resulting in a peak value of 0.7 (confidence interval=0.02) without rotation, increasing to 0.88 (confidence interval=0.03) with rotation. All biphasic hydrogels produced peak friction values lower than the positive control and demonstrated no difference between uni- and multi-directional motion. Degradation of the opposing cartilage surface showed a significant difference between the positive and negative controls, with the greater cartilage damage when sliding against stainless steel under uni-directional motion. The lower friction and reduction of opposing cartilage surface degradation with the potential chondroplasty biomaterials can be attributed to their biphasic properties. This study illustrated the importance of biphasic properties within the tribology of cartilage substitution materials and future work will focus on the optimisation of biphasic properties such that materials more closely mimic natural cartilage.

Spatial Map of Synthesized Criteria for the Redundancy Resolution of Human Arm Movements.

PubMed

Li, Zhi; Milutinovic, Dejan; Rosen, Jacob

2015-11-01

The kinematic redundancy of the human arm enables the elbow position to rotate about the axis going through the shoulder and wrist, which results in infinite possible arm postures when the arm reaches to a target in a 3-D workspace. To infer the control strategy the human motor system uses to resolve redundancy in reaching movements, this paper compares five redundancy resolution criteria and evaluates their arm posture prediction performance using data on healthy human motion. Two synthesized criteria are developed to provide better real-time arm posture prediction than the five individual criteria. Of these two, the criterion synthesized using an exponential method predicts the arm posture more accurately than that using a least squares approach, and therefore is preferable for inferring the contributions of the individual criteria to motor control during reaching movements. As a methodology contribution, this paper proposes a framework to compare and evaluate redundancy resolution criteria for arm motion control. A cluster analysis which associates criterion contributions with regions of the workspace provides a guideline for designing a real-time motion control system applicable to upper-limb exoskeletons for stroke rehabilitation.

Seismic Motion Stability, Measurement and Precision Control.

DTIC Science & Technology

1979-12-01

tiltmeter . Tilt was corrected by changing air pressure in one bank of isolators to maintain the reference tiltmeter at null well within the 0.1 arcsecond...frequency rotations (0-0.1 Hz), a high quality, two-axis tiltmeter is used. The azimuth orientation angle could be measured with a four-position gyro...compassing system with considerably less accuracy than the tiltmeters . However, it would provide a continuous automatic azimuth determination update every

Effect of Acceleration Frequency on Spatial Orientation Mechanisms

DTIC Science & Technology

2010-09-30

by aircraft, ground vehicle, and ship motion. Method. With controlled laboratory off-vertical axis rotation (OVAR), gaze reflexes respond to low...finding that vestibular gaze reflexes become altered at the same frequency where OVAR becomes most sickening will have important implications for...the collected data, a revised crossover rate of 0.42 Hz was extrapolated as the most probable spin frequency for inducing gaze reflex changes with the

Description and theory of operation of the computer by-pass system for the NASA F-8 digital fly-by-wire control system

NASA Technical Reports Server (NTRS)

1978-01-01

A triplex digital flight control system was installed in a NASA F-8C airplane to provide fail operate, full authority control. The triplex digital computers and interface circuitry process the pilot commands and aircraft motion feedback parameters according to the selected control laws, and they output the surface commands as an analog signal to the servoelectronics for position control of the aircraft's power actuators. The system and theory of operation of the computer by pass and servoelectronics are described and an automated ground test for each axis is included.

Newton-Euler Dynamic Equations of Motion for a Multi-body Spacecraft

NASA Technical Reports Server (NTRS)

Stoneking, Eric

2007-01-01

The Magnetospheric MultiScale (MMS) mission employs a formation of spinning spacecraft with several flexible appendages and thruster-based control. To understand the complex dynamic interaction of thruster actuation, appendage motion, and spin dynamics, each spacecraft is modeled as a tree of rigid bodies connected by spherical or gimballed joints. The method presented facilitates assembling by inspection the exact, nonlinear dynamic equations of motion for a multibody spacecraft suitable for solution by numerical integration. The building block equations are derived by applying Newton's and Euler's equations of motion to an "element" consisting of two bodies and one joint (spherical and gimballed joints are considered separately). Patterns in the "mass" and L'force" matrices guide assembly by inspection of a general N-body tree-topology system. Straightforward linear algebra operations are employed to eliminate extraneous constraint equations, resulting in a minimum-dimension system of equations to solve. This method thus combines a straightforward, easily-extendable, easily-mechanized formulation with an efficient computer implementation.

SU-E-I-24: Design and Fabrication of a Multi-Functional Neck and Thyroid Phantom for Medical Dosimetry and Calibration

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

Mehdizadeh, S; Sina, S; Karimipourfard, M

Purpose: The purpose of this study is the design and fabrication of a multipurpose anthropomorphic neck and thyroid phantom for use in medical applications (i.e. quality control of images in nuclear medicine, and dosimetry). Methods: The designed neck phantom is composed of seven elliptic cylindrical slices with semi-major axis of 14 and semi-minor axis of 12.5 cm, each having the thickness of 2cm. Thyroid gland, bony part of the neck, and the wind pipe were also built inside the neck phantom. Results: The phantom contains some removable plugs,inside and at its surface to accommodate the TLD chips with different shapesmore » and dimensions, (i.e. rod, cylindrical and cubical TLD chips)for the purpose of medical dosimetry (i.e. in radiology, radiotherapy, and nuclear medicine). For the purpose of quality control of images in nuclear medicine, the removable thyroid gland was built to accommodate the radioactive iodine. The female and male thyroid glands were built in two sizes separately. Conclusion: The designed phantom is a multi-functional phantom which is applicable for dosimetry in diagnostic radiology, radiotherapy, and quality control of images in nuclear medicine.« less

Motion of Optically Heated Spheres at the Water-Air Interface.

PubMed

Girot, A; Danné, N; Würger, A; Bickel, T; Ren, F; Loudet, J C; Pouligny, B

2016-03-22

A micrometer-sized spherical particle classically equilibrates at the water-air interface in partial wetting configuration, causing about no deformation to the interface. In condition of thermal equilibrium, the particle just undergoes faint Brownian motion, well visible under a microscope. We report experimental observations when the particle is made of a light-absorbing material and is heated up by a vertical laser beam. We show that, at small laser power, the particle is trapped in on-axis configuration, similarly to 2-dimensional trapping of a transparent sphere by optical forces. Conversely, on-axis trapping becomes unstable at higher power. The particle escapes off the laser axis and starts orbiting around the axis. We show that the laser-heated particle behaves as a microswimmer with velocities on the order of several 100 μm/s with just a few milliwatts of laser power.

The Role of Mean-motion Resonances in Semimajor Axis Mobility of Asteroids

NASA Astrophysics Data System (ADS)

Milić Žitnik, Ivana; Novaković, Bojan

2016-01-01

Here, we report our findings about the effect of 11 two-body mean-motion resonances (MMRs) with Jupiter, on the mobility of an asteroid’s semimajor axis caused by the Yarkovsky effect. This study is accomplished using numerical integrations of test particles. The obtained results reveal that MMRs could either speed up or slow down the drift in the semimajor axis. Moreover, this allows us to determine the distribution that represents the best data obtained for time delays dtr caused by the resonances on the mobility of an asteroid. We also found a certain functional relationship that describes dependence of the average time lead/lag < {dtr}> on the strength of the resonance SR and the semimajor axis drift speed da/dt. As the Yarkovsky effect scales as 1/D, an important consequence of this relationship is that average time lead/lag < {dtr}> is directly proportional to the diameter D of an asteroid.

The influence of orbit selection on the accuracy of the Stanford Relativity gyroscope experiment

NASA Technical Reports Server (NTRS)

Vassar, R.; Everitt, C. W. F.; Vanpatten, R. A.; Breakwell, J. V.

1980-01-01

This paper discusses an error analysis for the Stanford Relativity experiment, designed to measure the precession of a gyroscope's spin-axis predicted by general relativity. Measurements will be made of the spin-axis orientations of 4 superconducting spherical gyroscopes carried by an earth-satellite. Two relativistic precessions are predicted: a 'geodetic' precession associated with the satellite's orbital motion and a 'motional' precession due to the earth's rotation. Using a Kalman filter covariance analysis with a realistic error model we have computed the error in determining the relativistic precession rates. Studies show that a slightly off-polar orbit is better than a polar orbit for determining the 'motional' drift.

High Precision Motion Control System for the Two-Stage Light Gas Gun at the Dynamic Compression Sector

NASA Astrophysics Data System (ADS)

Zdanowicz, E.; Guarino, V.; Konrad, C.; Williams, B.; Capatina, D.; D'Amico, K.; Arganbright, N.; Zimmerman, K.; Turneaure, S.; Gupta, Y. M.

2017-06-01

The Dynamic Compression Sector (DCS) at the Advanced Photon Source (APS), located at Argonne National Laboratory (ANL), has a diverse set of dynamic compression drivers to obtain time resolved x-ray data in single event, dynamic compression experiments. Because the APS x-ray beam direction is fixed, each driver at DCS must have the capability to move through a large range of linear and angular motions with high precision to accommodate a wide variety of scientific needs. Particularly challenging was the design and implementation of the motion control system for the two-stage light gas gun, which rests on a 26' long structure and weighs over 2 tons. The target must be precisely positioned in the x-ray beam while remaining perpendicular to the gun barrel axis to ensure one-dimensional loading of samples. To accommodate these requirements, the entire structure can pivot through 60° of angular motion and move 10's of inches along four independent linear directions with 0.01° and 10 μm resolution, respectively. This presentation will provide details of how this system was constructed, how it is controlled, and provide examples of the wide range of x-ray/sample geometries that can be accommodated. Work supported by DOE/NNSA.

Neural Action Fields for Optic Flow Based Navigation: A Simulation Study of the Fly Lobula Plate Network

PubMed Central

Borst, Alexander; Weber, Franz

2011-01-01

Optic flow based navigation is a fundamental way of visual course control described in many different species including man. In the fly, an essential part of optic flow analysis is performed in the lobula plate, a retinotopic map of motion in the environment. There, the so-called lobula plate tangential cells possess large receptive fields with different preferred directions in different parts of the visual field. Previous studies demonstrated an extensive connectivity between different tangential cells, providing, in principle, the structural basis for their large and complex receptive fields. We present a network simulation of the tangential cells, comprising most of the neurons studied so far (22 on each hemisphere) with all the known connectivity between them. On their dendrite, model neurons receive input from a retinotopic array of Reichardt-type motion detectors. Model neurons exhibit receptive fields much like their natural counterparts, demonstrating that the connectivity between the lobula plate tangential cells indeed can account for their complex receptive field structure. We describe the tuning of a model neuron to particular types of ego-motion (rotation as well as translation around/along a given body axis) by its ‘action field’. As we show for model neurons of the vertical system (VS-cells), each of them displays a different type of action field, i.e., responds maximally when the fly is rotating around a particular body axis. However, the tuning width of the rotational action fields is relatively broad, comparable to the one with dendritic input only. The additional intra-lobula-plate connectivity mainly reduces their translational action field amplitude, i.e., their sensitivity to translational movements along any body axis of the fly. PMID:21305019

Dynamics of colloidal particles in electrohydrodynamic convection of nematic liquid crystal.

PubMed

Takahashi, Kentaro; Kimura, Yasuyuki

2014-07-01

We have studied the dynamics of micrometer-sized colloidal particles in electrohydrodynamic convection of nematic liquid crystal. Above the onset voltage of electroconvection, the parallel array of convection rolls appears to be perpendicular to the nematic field at first. The particles are forced to rotate by convection flow and are trapped within a single roll in this voltage regime. A slow glide motion along the roll axis is also observed. The frequency of rotational motion and the glide velocity increase with the applied voltage. Under a much larger voltage where the roll axis temporally fluctuates, the particles occasionally hop to the neighbor rolls. In this voltage regime, the motion of the particles becomes two-dimensional. The motion perpendicular to the roll axis exhibits diffusion behavior at a long time period. The effective diffusion constant is 10(3)-10(4) times larger than the molecular one. The observed behavior is compared with the result obtained by a simple stochastic model for the transport of the particles in convection. The enhancement of diffusion can be quantitatively described well by the rotation frequency in a roll, the width of the roll, and the hopping probability to the neighbor rolls.

Optics for multimode lasers with elongated depth of field

NASA Astrophysics Data System (ADS)

Laskin, Alexander; Laskin, Vadim; Ostrun, Aleksei

2017-02-01

Modern multimode high-power lasers are widely used in industrial applications and control of their radiation, especially by focusing, is of great importance. Because of relatively low optical quality, characterized by high values of specifications Beam Parameter Product (BPP) or M², the depth of field by focusing of multimode laser radiation is narrow. At the same time laser technologies like deep penetration welding, cutting of thick metal sheets get benefits from elongated depth of field in area of focal plane, therefore increasing of zone along optical axis with minimized spot size is important technical task. As a solution it is suggested to apply refractive optical systems splitting an initial laser beam into several beamlets, which are focused in different foci separated along optical axis with providing reliable control of energy portions in each separate focus, independently of beam size or mode structure. With the multi-focus optics, the length of zone of material processing along optical axis is defined rather by distances between separate foci, which are determined by optical design of the optics and can be chosen according to requirements of a particular laser technology. Due to stability of the distances between foci there is provided stability of a technology process. This paper describes some design features of refractive multi-focus optics, examples of real implementations and experimental results will be presented as well.

Assessment of the rotation motion at the papillary muscle short-axis plane with normal subjects by two-dimensional speckle tracking imaging: a basic clinical study.

PubMed

Ni, Xian-Da; Huang, Jun; Hu, Yuan-Ping; Xu, Rui; Yang, Wei-Yu; Zhou, Li-Ming

2013-01-01

The aim of this study was to observe the rotation patterns at the papillary muscle plane in the Left Ventricle(LV) with normal subjects using two-dimensional speckle tracking imaging(2D-STI). We acquired standard of the basal, the papillary muscle and the apical short-axis images of the LV in 64 subjects to estimate the LV rotation motion by 2D-STI. The rotational degrees at the papillary muscle short-axis plane were measured at 15 different time points in the analysis of two heart cycles. There were counterclockwise rotation, clockwise rotation, and counterclockwise to clockwise rotation at the papillary muscle plane in the LV with normal subjects, respectively. The ROC analysis of the rotational degrees was performed at the papillary muscle short-axis plane at the peak LV torsion for predicting whether the turnaround point of twist to untwist motion pattern was located at the papillary muscle level. Sensitivity and specificity were 97% and 67%, respectively, with a cut-off value of 0.34°, and an area under the ROC curve of 0.8. At the peak LV torsion, there was no correlation between the rotational degrees at the papillary muscle short-axis plane and the LVEF in the normal subjects(r = 0.000, p = 0.998). In the study, we conclude that there were three rotation patterns at the papillary muscle short-axis levels, and the transition from basal clockwise rotation to apical counterclockwise rotation is located at the papillary muscle level.

Absolute plate motions and true polar wander in the absence of hotspot tracks.

PubMed

Steinberger, Bernhard; Torsvik, Trond H

2008-04-03

The motion of continents relative to the Earth's spin axis may be due either to rotation of the entire Earth relative to its spin axis--true polar wander--or to the motion of individual plates. In order to distinguish between these over the past 320 Myr (since the formation of the Pangaea supercontinent), we present here computations of the global average of continental motion and rotation through time in a palaeomagnetic reference frame. Two components are identified: a steady northward motion and, during certain time intervals, clockwise and anticlockwise rotations, interpreted as evidence for true polar wander. We find approximately 18 degrees anticlockwise rotation about 250-220 Myr ago and the same amount of clockwise rotation about 195-145 Myr ago. In both cases the rotation axis is located at about 10-20 degrees W, 0 degrees N, near the site that became the North American-South American-African triple junction at the break-up of Pangaea. This was followed by approximately 10 degrees clockwise rotation about 145-135 Myr ago, followed again by the same amount of anticlockwise rotation about 110-100 Myr ago, with a rotation axis in both cases approximately 25-50 degrees E in the reconstructed area of North Africa and Arabia. These rotation axes mark the maxima of the degree-two non-hydrostatic geoid during those time intervals, and the fact that the overall net rotation since 320 Myr ago is nearly zero is an indication of long-term stability of the degree-two geoid and related mantle structure. We propose a new reference frame, based on palaeomagnetism, but corrected for the true polar wander identified in this study, appropriate for relating surface to deep mantle processes from 320 Myr ago until hotspot tracks can be used (about 130 Myr ago).

Unifying model of carpal mechanics based on computationally derived isometric constraints and rules-based motion - the stable central column theory.

PubMed

Sandow, M J; Fisher, T J; Howard, C Q; Papas, S

2014-05-01

This study was part of a larger project to develop a (kinetic) theory of carpal motion based on computationally derived isometric constraints. Three-dimensional models were created from computed tomography scans of the wrists of ten normal subjects and carpal spatial relationships at physiological motion extremes were assessed. Specific points on the surface of the various carpal bones and the radius that remained isometric through range of movement were identified. Analysis of the isometric constraints and intercarpal motion suggests that the carpus functions as a stable central column (lunate-capitate-hamate-trapezoid-trapezium) with a supporting lateral column (scaphoid), which behaves as a 'two gear four bar linkage'. The triquetrum functions as an ulnar translation restraint, as well as controlling lunate flexion. The 'trapezoid'-shaped trapezoid places the trapezium anterior to the transverse plane of the radius and ulna, and thus rotates the principal axis of the central column to correspond to that used in the 'dart thrower's motion'. This study presents a forward kinematic analysis of the carpus that provides the basis for the development of a unifying kinetic theory of wrist motion based on isometric constraints and rules-based motion.

Simulation analysis of adaptive cruise prediction control

NASA Astrophysics Data System (ADS)

Zhang, Li; Cui, Sheng Min

2017-09-01

Predictive control is suitable for multi-variable and multi-constraint system control.In order to discuss the effect of predictive control on the vehicle longitudinal motion, this paper establishes the expected spacing model by combining variable pitch spacing and the of safety distance strategy. The model predictive control theory and the optimization method based on secondary planning are designed to obtain and track the best expected acceleration trajectory quickly. Simulation models are established including predictive and adaptive fuzzy control. Simulation results show that predictive control can realize the basic function of the system while ensuring the safety. The application of predictive and fuzzy adaptive algorithm in cruise condition indicates that the predictive control effect is better.

Thrust vector control of upper stage with a gimbaled thruster during orbit transfer

NASA Astrophysics Data System (ADS)

Wang, Zhaohui; Jia, Yinghong; Jin, Lei; Duan, Jiajia

2016-10-01

In launching Multi-Satellite with One-Vehicle, the main thruster provided by the upper stage is mounted on a two-axis gimbal. During orbit transfer, the thrust vector of this gimbaled thruster (GT) should theoretically pass through the mass center of the upper stage and align with the command direction to provide orbit transfer impetus. However, it is hard to be implemented from the viewpoint of the engineering mission. The deviations of the thrust vector from the command direction would result in large velocity errors. Moreover, the deviations of the thrust vector from the upper stage mass center would produce large disturbance torques. This paper discusses the thrust vector control (TVC) of the upper stage during its orbit transfer. Firstly, the accurate nonlinear coupled kinematic and dynamic equations of the upper stage body, the two-axis gimbal and the GT are derived by taking the upper stage as a multi-body system. Then, a thrust vector control system consisting of the special attitude control of the upper stage and the gimbal rotation of the gimbaled thruster is proposed. The special attitude control defined by the desired attitude that draws the thrust vector to align with the command direction when the gimbal control makes the thrust vector passes through the upper stage mass center. Finally, the validity of the proposed method is verified through numerical simulations.

Ion kinematics in a plasma focus.

NASA Technical Reports Server (NTRS)

Gary, S. P.; Hohl, F.

1973-01-01

The results of numerical integrations of three-dimensional equations of motion of ions subject to given electric and magnetic fields are presented. The fields represent those which may exist in the pinch phase of the plasma focus, although here they depend only on the radial coordinate. The ions initially have Maxwellian velocity distributions, and their trajectories are interpreted in terms of single-particle constants of the motion. Two models of the axial electric field Ez are considered. For strong Ez away from the axis, there is a cyclotron acceleration which leads to ion heating. For positive Ez on the axis, ions within a Larmor radius of the axis undergo very efficient acceleration; the results for this new model are in general agreement with experimental results.

Hobby-Eberly Telescope: commissioning experience and observing plans

NASA Astrophysics Data System (ADS)

Glaspey, John W.; Adams, M. T.; Booth, John A.; Cornell, Mark E.; Fowler, James R.; Krabbendam, Victor L.; Ramsey, Lawrence W.; Ray, Frank B.; Ricklefs, Randall L.; Spiesman, W. J.

1998-07-01

Experience in bringing into operation the 91-segment primary mirror alignment and control system, the focal plane tracker system, and other critical subsystems of the HET will be described. Particular attention is given to the tracker, which utilizes three linear and three rotational degrees of freedom to follow sidereal targets. Coarse time-dependent functions for each axis are downloaded to autonomous PMAC controllers that provide the precise motion drives to the two linear stages and the hexapod system. Experience gained in aligning the sperate mirrors and then maintaining image quality in a variable thermal environments will also be described. Because of the fixed elevation of the primary optical axis, only a limited amount of time is available for observing objects in the 12 degrees wide observing band. With a small core HET team working with McDonald Observatory staff, efficient, reliable, uncomplicated methodologies are required in all aspects of the observing operations.

Robotic real-time translational and rotational head motion correction during frameless stereotactic radiosurgery

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

Liu, Xinmin; Belcher, Andrew H.; Grelewicz, Zachary

Purpose: To develop a control system to correct both translational and rotational head motion deviations in real-time during frameless stereotactic radiosurgery (SRS). Methods: A novel feedback control with a feed-forward algorithm was utilized to correct for the coupling of translation and rotation present in serial kinematic robotic systems. Input parameters for the algorithm include the real-time 6DOF target position, the frame pitch pivot point to target distance constant, and the translational and angular Linac beam off (gating) tolerance constants for patient safety. Testing of the algorithm was done using a 4D (XY Z + pitch) robotic stage, an infrared headmore » position sensing unit and a control computer. The measured head position signal was processed and a resulting command was sent to the interface of a four-axis motor controller, through which four stepper motors were driven to perform motion compensation. Results: The control of the translation of a brain target was decoupled with the control of the rotation. For a phantom study, the corrected position was within a translational displacement of 0.35 mm and a pitch displacement of 0.15° 100% of the time. For a volunteer study, the corrected position was within displacements of 0.4 mm and 0.2° over 98.5% of the time, while it was 10.7% without correction. Conclusions: The authors report a control design approach for both translational and rotational head motion correction. The experiments demonstrated that control performance of the 4D robotic stage meets the submillimeter and subdegree accuracy required by SRS.« less

Brain-machine interface control of a manipulator using small-world neural network and shared control strategy.

PubMed

Li, Ting; Hong, Jun; Zhang, Jinhua; Guo, Feng

2014-03-15

The improvement of the resolution of brain signal and the ability to control external device has been the most important goal in BMI research field. This paper describes a non-invasive brain-actuated manipulator experiment, which defined a paradigm for the motion control of a serial manipulator based on motor imagery and shared control. The techniques of component selection, spatial filtering and classification of motor imagery were involved. Small-world neural network (SWNN) was used to classify five brain states. To verify the effectiveness of the proposed classifier, we replace the SWNN classifier by a radial basis function (RBF) networks neural network, a standard multi-layered feed-forward backpropagation network (SMN) and a multi-SVM classifier, with the same features for the classification. The results also indicate that the proposed classifier achieves a 3.83% improvement over the best results of other classifiers. We proposed a shared control method consisting of two control patterns to expand the control of BMI from the software angle. The job of path building for reaching the 'end' point was designated as an assessment task. We recorded all paths contributed by subjects and picked up relevant parameters as evaluation coefficients. With the assistance of two control patterns and series of machine learning algorithms, the proposed BMI originally achieved the motion control of a manipulator in the whole workspace. According to experimental results, we confirmed the feasibility of the proposed BMI method for 3D motion control of a manipulator using EEG during motor imagery. Copyright © 2013 Elsevier B.V. All rights reserved.

Motion Path of the Instant Center of Rotation in the Cervical Spine During In Vivo Dynamic Flexion-Extension: Implications for Artificial Disc Design and Evaluation of Motion Quality Following Arthrodesis

PubMed Central

Anderst, William; Baillargeon, Emma; Donaldson, William; Lee, Joon; Kang, James

2013-01-01

Study Design Case-control. Objective To characterize the motion path of the instant center of rotation (ICR) at each cervical motion segment from C2 to C7 during dynamic flexion-extension in asymptomatic subjects. To compare asymptomatic and single-level arthrodesis patient ICR paths. Summary of Background Data The ICR has been proposed as an alternative to range of motion (ROM) for evaluating the quality of spine movement and for identifying abnormal midrange kinematics. The motion path of the ICR during dynamic motion has not been reported. Methods 20 asymptomatic controls, 12 C5/C6 and 5 C6/C7 arthrodesis patients performed full ROM flexion-extension while biplane radiographs were collected at 30 Hz. A previously validated tracking process determined three-dimensional vertebral position with sub-millimeter accuracy. The finite helical axis method was used to calculate the ICR between adjacent vertebrae. A linear mixed-model analysis identified differences in the ICR path among motion segments and between controls and arthrodesis patients. Results From C2/C3 to C6/C7, the mean ICR location moved superior for each successive motion segment (p < .001). The AP change in ICR location per degree of flexion-extension decreased from the C2/C3 motion segment to the C6/C7 motion segment (p < .001). Asymptomatic subject variability (95% CI) in the ICR location averaged ±1.2 mm in the SI direction and ±1.9 mm in the AP direction over all motion segments and flexion-extension angles. Asymptomatic and arthrodesis groups were not significantly different in terms of average ICR position (all p ≥ .091) or in terms of the change in ICR location per degree of flexion-extension (all p ≥ .249). Conclusions To replicate asymptomatic in vivo cervical motion, disc replacements should account for level-specific differences in the location and motion path of ICR. Single-level anterior arthrodesis does not appear to affect cervical motion quality during flexion-extension. PMID:23429677

An immediate effect of axial neck rotation training with real time visual feedback using a smartphone inclinometer on improvement in axial neck rotation function.

PubMed

Park, Kyue-Nam; Kwon, Oh-Yun; Kim, Si-Hyun; Jeon, In-Cheol

2017-03-01

The purpose of this study was to compare the immediate effects of axial neck rotation training (Axi-NRT) with and without real-time visual feedback (VF) using a smartphone inclinometer on the range of motion (ROM) for axial neck rotation and the onset of compensatory neck lateral bending and extension during active neck rotation. Twenty participants with restricted ROM for neck rotation but no neck pain (21.1 ± 1.6 years and 8 males, 12 females) were recruited for Axi-NRT with VF, and twenty age- and gender-matched participants with restricted ROM for neck rotation were recruited for Axi-NRT without VF. Changes in ROM for neck rotation and the onset time of compensatory neck movement during active neck rotation were measured using an electromagnetic tracking system. Axi-NRT with VF was more effective in increasing ROM for neck rotation and decreasing and delaying the onset of compensatory neck movements during active neck rotation compared with Axi-NRT without VF. Repeated Axi-NRT using VF is useful to educate participants in maintaining the axis of the cervical spine and to increase ROM for axial neck rotation with less compensatory neck motion in participants with a restricted range of neck rotations.

Welding technology transfer task/laser based weld joint tracking system for compressor girth welds

NASA Technical Reports Server (NTRS)

Looney, Alan

1991-01-01

Sensors to control and monitor welding operations are currently being developed at Marshall Space Flight Center. The laser based weld bead profiler/torch rotation sensor was modified to provide a weld joint tracking system for compressor girth welds. The tracking system features a precision laser based vision sensor, automated two-axis machine motion, and an industrial PC controller. The system benefits are elimination of weld repairs caused by joint tracking errors which reduces manufacturing costs and increases production output, simplification of tooling, and free costly manufacturing floor space.

Effect of direction of head movement on motion sickness caused by Coriolis stimulation.

PubMed

Woodman, P D; Griffin, M J

1997-02-01

During constant speed rotation of the body, head rotation about an axis other than the axis of rotation of the body (i.e., Coriolis is stimulation) induces motion sickness. The position of the body relative to the center of rotation will influence the sickness caused by Coriolis stimulation; the direction of head movement will not affect the sickness caused by Coriolis stimulation. There were 24 seated subjects (12 male, 12 female) who made 30 degrees pitch motions of the head every 30 s while rotating about a vertical axis at 10 r.p.m. on a turntable at two separate locations: a) at the center of rotation; and b) 0.75 m from the center of rotation. After each head movement the subjects gave ratings of motion illness. There was no significant difference between illness 0.75 m from the center of rotation and illness at the center of rotation, or between the illness ratings from male and female subjects. Moving the head up from the horizontal caused significantly fewer increases in ratings of motion illness than moving the head back down to the horizontal. Precise location of the body at the center of rotation is not critical during Coriolis stimulation, but the direction of head movement has a large effect on nausea. An influence of somatosensory information on sickness caused by Coriolis stimulation is suggested.

Mass center estimation of a drag-free satellite

NASA Technical Reports Server (NTRS)

Sanz Fernandez De Cordova, S.; Debra, D. B.

1975-01-01

The mass center location of a spinning drag-free satellite can be estimated because there is control required to accelerate the mass center along the axis of spin as long as there is some nutation in the spinning motion. Linear and nonlinear models are compared and observability discussed. Online estimation fails when nutation is damped so an offline mechanization is proposed. A new sensor has been designed to permit greater relative motion than was possible on the drag-free satellite flown in 1972 (JH-1). Experimental laboratory results using a spinning vehicle with the new sensor mounted 30 cm from a spherical air bearing support are presented which confirm earlier simulation results.

Nonlinear Dynamics of a Spring-Supported Piston in a Vibrated Liquid-Filled Housing: II. Experiments

NASA Astrophysics Data System (ADS)

O'Hern, T. J.; Torczynski, J. R.; Clausen, J. R.

2016-11-01

The nonlinear dynamics of a piston supported by a spring in a vibrated liquid-filled housing is investigated experimentally. The housing containing the piston and the liquid is subjected to vibrations along its axis. A post fixed to the housing penetrates a hole through the piston and produces a flow resistance that depends on piston position. Flexible bellows attached to the housing ends enable the piston, liquid, and bellows to execute a collective motion that forces little liquid through the flow resistance. The low damping of this motion leads to a resonance, at which the flow-resistance nonlinearity produces a net force on the piston that can cause it to compress its spring. Experiments are performed to investigate the nonlinear dynamics of this system, and these results are compared to theoretical and numerical results. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Positional reference system for ultraprecision machining

DOEpatents

Arnold, Jones B.; Burleson, Robert R.; Pardue, Robert M.

1982-01-01

A stable positional reference system for use in improving the cutting tool-to-part contour position in numerical controlled-multiaxis metal turning machines is provided. The reference system employs a plurality of interferometers referenced to orthogonally disposed metering bars which are substantially isolated from machine strain induced position errors for monitoring the part and tool positions relative to the metering bars. A microprocessor-based control system is employed in conjunction with the plurality of position interferometers and part contour description data inputs to calculate error components for each axis of movement and output them to corresponding axis drives with appropriate scaling and error compensation. Real-time position control, operating in combination with the reference system, makes possible the positioning of the cutting points of a tool along a part locus with a substantially greater degree of accuracy than has been attained previously in the art by referencing and then monitoring only the tool motion relative to a reference position located on the machine base.

Positional reference system for ultraprecision machining

DOEpatents

Arnold, J.B.; Burleson, R.R.; Pardue, R.M.

1980-09-12

A stable positional reference system for use in improving the cutting tool-to-part contour position in numerical controlled-multiaxis metal turning machines is provided. The reference system employs a plurality of interferometers referenced to orthogonally disposed metering bars which are substantially isolated from machine strain induced position errors for monitoring the part and tool positions relative to the metering bars. A microprocessor-based control system is employed in conjunction with the plurality of positions interferometers and part contour description data input to calculate error components for each axis of movement and output them to corresponding axis driven with appropriate scaling and error compensation. Real-time position control, operating in combination with the reference system, makes possible the positioning of the cutting points of a tool along a part locus with a substantially greater degree of accuracy than has been attained previously in the art by referencing and then monitoring only the tool motion relative to a reference position located on the machine base.

EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

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

Napolitano, Arthur Soriano; Vogel, Sven C.

2017-08-03

Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, themore » collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.« less

Study on pixel matching method of the multi-angle observation from airborne AMPR measurements

NASA Astrophysics Data System (ADS)

Hou, Weizhen; Qie, Lili; Li, Zhengqiang; Sun, Xiaobing; Hong, Jin; Chen, Xingfeng; Xu, Hua; Sun, Bin; Wang, Han

2015-10-01

For the along-track scanning mode, the same place along the ground track could be detected by the Advanced Multi-angular Polarized Radiometer (AMPR) with several different scanning angles from -55 to 55 degree, which provides a possible means to get the multi-angular detection for some nearby pixels. However, due to the ground sample spacing and spatial footprint of the detection, the different sizes of footprints cannot guarantee the spatial matching of some partly overlap pixels, which turn into a bottleneck for the effective use of the multi-angular detected information of AMPR to study the aerosol and surface polarized properties. Based on our definition and calculation of t he pixel coincidence rate for the multi-angular detection, an effective multi-angle observation's pixel matching method is presented to solve the spatial matching problem for airborne AMPR. Assuming the shape of AMPR's each pixel is an ellipse, and the major axis and minor axis depends on the flying attitude and each scanning angle. By the definition of coordinate system and origin of coordinate, the latitude and longitude could be transformed into the Euclidian distance, and the pixel coincidence rate of two nearby ellipses could be calculated. Via the traversal of each ground pixel, those pixels with high coincidence rate could be selected and merged, and with the further quality control of observation data, thus the ground pixels dataset with multi-angular detection could be obtained and analyzed, providing the support for the multi-angular and polarized retrieval algorithm research in t he next study.

Development of a four-axis moving phantom for patient-specific QA of surrogate signal-based tracking IMRT.

PubMed

Mukumoto, Nobutaka; Nakamura, Mitsuhiro; Yamada, Masahiro; Takahashi, Kunio; Akimoto, Mami; Miyabe, Yuki; Yokota, Kenji; Kaneko, Shuji; Nakamura, Akira; Itasaka, Satoshi; Matsuo, Yukinori; Mizowaki, Takashi; Kokubo, Masaki; Hiraoka, Masahiro

2016-12-01

The purposes of this study were two-fold: first, to develop a four-axis moving phantom for patient-specific quality assurance (QA) in surrogate signal-based dynamic tumor-tracking intensity-modulated radiotherapy (DTT-IMRT), and second, to evaluate the accuracy of the moving phantom and perform patient-specific dosimetric QA of the surrogate signal-based DTT-IMRT. The four-axis moving phantom comprised three orthogonal linear actuators for target motion and a fourth one for surrogate motion. The positional accuracy was verified using four laser displacement gauges under static conditions (±40 mm displacements along each axis) and moving conditions [eight regular sinusoidal and fourth-power-of-sinusoidal patterns with peak-to-peak motion ranges (H) of 10-80 mm and a breathing period (T) of 4 s, and three irregular respiratory patterns with H of 1.4-2.5 mm in the left-right, 7.7-11.6 mm in the superior-inferior, and 3.1-4.2 mm in the anterior-posterior directions for the target motion, and 4.8-14.5 mm in the anterior-posterior direction for the surrogate motion, and T of 3.9-4.9 s]. Furthermore, perpendicularity, defined as the vector angle between any two axes, was measured using an optical measurement system. The reproducibility of the uncertainties in DTT-IMRT was then evaluated. Respiratory motions from 20 patients acquired in advance were reproduced and compared three-dimensionally with the originals. Furthermore, patient-specific dosimetric QAs of DTT-IMRT were performed for ten pancreatic cancer patients. The doses delivered to Gafchromic films under tracking and moving conditions were compared with those delivered under static conditions without dose normalization. Positional errors of the moving phantom under static and moving conditions were within 0.05 mm. The perpendicularity of the moving phantom was within 0.2° of 90°. The differences in prediction errors between the original and reproduced respiratory motions were -0.1 ± 0.1 mm for the lateral direction, -0.1 ± 0.2 mm for the superior-inferior direction, and -0.1 ± 0.1 mm for the anterior-posterior direction. The dosimetric accuracy showed significant improvements, of 92.9% ± 4.0% with tracking versus 69.8% ± 7.4% without tracking, in the passing rates of γ with the criterion of 3%/1 mm (p < 0.001). Although the dosimetric accuracy of IMRT without tracking showed a significant negative correlation with the 3D motion range of the target (r = - 0.59, p < 0.05), there was no significant correlation for DTT-IMRT (r = 0.03, p = 0.464). The developed four-axis moving phantom had sufficient accuracy to reproduce patient respiratory motions, allowing patient-specific QA of the surrogate signal-based DTT-IMRT under realistic conditions. Although IMRT without tracking decreased the dosimetric accuracy as the target motion increased, the DTT-IMRT achieved high dosimetric accuracy.

On the Long-Term "Hesitation Waltz" Between the Earth's Figure and Rotation Axes

NASA Astrophysics Data System (ADS)

Couhert, A.; Mercier, F.; Bizouard, C.

2017-12-01

The principal figure axis of the Earth refers to its axis of maximum inertia. In the absence of external torques, the latter should closely coincide with the rotation pole, when averaged over many years. However, because of tidal and non-tidal mass redistributions within the Earth system, the rotational axis executes a circular motion around the figure axis essentially at seasonal time scales. In between, it is not clear what happens at decadal time spans and how well the two axes are aligned. The long record of accurate Satellite Laser Ranging (SLR) observations to Lageos makes possible to directly measure the long time displacement of the figure axis with respect to the crust, through the determination of the degree 2 order 1 geopotential coefficients for the 34-year period 1983-2017. On the other hand, the pole coordinate time series (mainly from GNSS and VLBI data) yield the motion of the rotation pole with even a greater accuracy. This study is focused on the analysis of the long-term behavior of the two time series, as well as the derivation of possible explanations for their discrepancies.

A study of electrostatic spring softening for dual-axis micromirror

NASA Astrophysics Data System (ADS)

Zhao, Yi; E H Tay, Francis; Zhou, Guangya; Siong Chau, Fook

2006-08-01

Electrostatic spring softening is an important characteristic of electrostatically actuated dual-axis micromirror, since it lowers the resonant frequencies. This paper presents an approach based on approximating the electrostatic forces by the first-order Taylor's series expansion to investigate this characteristic. The dual-axis micromirror studied in this paper has three motion modes, two torsional (about x- and y-axis, respectively) and one translational (about z-axis). The stiffnesses of all these modes are softened by a DC bias voltage applied to the mirror plate. The resonant frequencies are lowered with the increment of the bias voltage. The relationship of the bias voltage and the resonant frequencies of all the motion modes is derived. The analytical results show that the resonant frequency curves are affected by the capacitor geometries, i.e. the gap between the mirror plate and the electrodes and the electrodes size. The lowering curves drop slowly when the bias voltage is small. While for large bias voltage, the lowering curves drop rapidly. The experiment results are consistent with those obtained by the analytical approach.

A recursive approach to the equations of motion for the maneuvering and control of flexible multi-body systems

NASA Technical Reports Server (NTRS)

Kwak, Moon K.; Meirovitch, Leonard

1991-01-01

Interest lies in a mathematical formulation capable of accommodating the problem of maneuvering a space structure consisting of a chain of articulated flexible substructures. Simultaneously, any perturbations from the 'rigid body' maneuvering and any elastic vibration must be suppressed. The equations of motion for flexible bodies undergoing rigid body motions and elastic vibrations can be obtained conveniently by means of Lagrange's equations in terms of quasi-coordinates. The advantage of this approach is that it yields equations in terms of body axes, which are the same axes that are used to express the control forces and torques. The equations of motion are nonlinear hybrid differential quations. The partial differential equations can be discretized (in space) by means of the finite element method or the classical Rayleigh-Ritz method. The result is a set of nonlinear ordinary differential equations of high order. The nonlinearity can be traced to the rigid body motions and the high order to the elastic vibration. Elastic motions tend to be small when compared with rigid body motions.

Enhancement of absorption and resistance of motion utilizing a multi-channel opto-electronic sensor to effectively monitor physiological signs during sport exercise

NASA Astrophysics Data System (ADS)

Alzahrani, Abdullah; Hu, Sijung; Azorin-Peris, Vicente; Barrett, Laura; Esliger, Dale; Hayes, Matthew; Akbare, Shafique; Achart, Jérôme; Kuoch, Sylvain

2015-03-01

This study presents an effective engineering approach for human vital signs monitoring as increasingly demanded by personal healthcare. The aim of this work is to study how to capture critical physiological parameters efficiently through a well-constructed electronic system and a robust multi-channel opto-electronic patch sensor (OEPS), together with a wireless communication. A unique design comprising multi-wavelength illumination sources and a rapid response photo sensor with a 3-axis accelerometer enables to recover pulsatile features, compensate motion and increase signal-to-noise ratio. An approved protocol with designated tests was implemented at Loughborough University a UK leader in sport and exercise assessment. The results of sport physiological effects were extracted from the datasets of physical movements, i.e. sitting, standing, waking, running and cycling. t-test, Bland-Altman and correlation analysis were applied to evaluate the performance of the OEPS system against Acti-Graph and Mio-Alpha.There was no difference in heart rate measured using OEPS and both Acti-Graph and Mio-Alpha (both p<0.05). Strong correlations were observed between HR measured from the OEPS and both the Acti-graph and Mio-Alpha (r = 0.96, p<0.001). Bland-Altman analysis for the Acti-Graph and OEPS found the bias 0.85 bpm, the standard deviation 9.20 bpm, and the limits of agreement (LOA) -17.18 bpm to +18.88 bpm for lower and upper limits of agreement respectively, for the Mio-Alpha and OEPS the bias is 1.63 bpm, standard deviation SD8.62 bpm, lower and upper limits of agreement, - 15.27 bpm and +18.58 bpm respectively. The OEPS demonstrates a real time, robust and remote monitoring of cardiovascular function.

A separation of antiferromagnetic spin motion modes in the training effect of exchange biased Co/CoO film with in-plane anisotropy

NASA Astrophysics Data System (ADS)

Wu, R.; Yun, C.; Ding, S. L.; Wen, X.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Du, H. L.; Yang, J. B.

2016-08-01

The motion of antiferromagnetic interfacial spins is investigated through the temperature evolution of training effect in a Co/CoO film with in-plane biaxial anisotropy. Significant differences in the training effect and its temperature dependence are observed in the magnetic easy axis and hard axis (HA) and ascribed to the different motion modes of antiferromagnetic interfacial spins, the collective spin cluster rotation (CSR) and the single spin reversal (SSR), caused by different magnetization reversal modes of ferromagnetic layer. These motion modes of antiferromagnetic spins are successfully separated using a combination of an exponential function and a classic n-1/2 function. A larger CSR to SSR ratio and a shorter lifetime of CSR found in the HA indicates that the domain rotation in the ferromagnetic layer tends to activate and accelerate a CSR mode in the antiferromagnetic spins.

Conflicting motion perspective simulating sinultaneous clockwise and counterclockwise rotation in depth.

PubMed

Hershberger, W A; Stewart, M R; Laughlin, N K

1976-05-01

Motion projections (pictures) simulating a horizontal array of vertical lines rotating in depth about its central vertical line were observed by 24 college students who rotated a crank handle in the direction of apparent rotation. All displays incorporated contradictory motion perspective: Whereas the perspective transformation in the vertical (y) dimension stimulated one direction of rotation, the transformation in the horizontal (x) dimension simulated the opposite direction. The amount of perspective in each dimension was varied independently of the other by varying the projection ratio used for each dimension. We used the same five ratios for each dimension, combining them factorially to generate the 25 displays. Analysis of variance of the duration of crank turning which agreed with y-axis information yielded main effects of both x and y projection ratios but no interaction, revealing that x- and y-axis motion perspectives mediate kinetic depth effects which are functionally independent.

The image evaluation of iterative motion correction reconstruction algorithm PROPELLER T2-weighted imaging compared with MultiVane T2-weighted imaging

NASA Astrophysics Data System (ADS)

Lee, Suk-Jun; Yu, Seung-Man

2017-08-01

The purpose of this study was to evaluate the usefulness and clinical applications of MultiVaneXD which was applying iterative motion correction reconstruction algorithm T2-weighted images compared with MultiVane images taken with a 3T MRI. A total of 20 patients with suspected pathologies of the liver and pancreatic-biliary system based on clinical and laboratory findings underwent upper abdominal MRI, acquired using the MultiVane and MultiVaneXD techniques. Two reviewers analyzed the MultiVane and MultiVaneXD T2-weighted images qualitatively and quantitatively. Each reviewer evaluated vessel conspicuity by observing motion artifacts and the sharpness of the portal vein, hepatic vein, and upper organs. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated by one reviewer for quantitative analysis. The interclass correlation coefficient was evaluated to measure inter-observer reliability. There were significant differences between MultiVane and MultiVaneXD in motion artifact evaluation. Furthermore, MultiVane was given a better score than MultiVaneXD in abdominal organ sharpness and vessel conspicuity, but the difference was insignificant. The reliability coefficient values were over 0.8 in every evaluation. MultiVaneXD (2.12) showed a higher value than did MultiVane (1.98), but the difference was insignificant ( p = 0.135). MultiVaneXD is a motion correction method that is more advanced than MultiVane, and it produced an increased SNR, resulting in a greater ability to detect focal abdominal lesions.

Motion of glossy objects does not promote separation of lighting and surface colour

PubMed Central

2017-01-01

The surface properties of an object, such as texture, glossiness or colour, provide important cues to its identity. However, the actual visual stimulus received by the eye is determined by both the properties of the object and the illumination. We tested whether operational colour constancy for glossy objects (the ability to distinguish changes in spectral reflectance of the object, from changes in the spectrum of the illumination) was affected by rotational motion of either the object or the light source. The different chromatic and geometric properties of the specular and diffuse reflections provide the basis for this discrimination, and we systematically varied specularity to control the available information. Observers viewed animations of isolated objects undergoing either lighting or surface-based spectral transformations accompanied by motion. By varying the axis of rotation, and surface patterning or geometry, we manipulated: (i) motion-related information about the scene, (ii) relative motion between the surface patterning and the specular reflection of the lighting, and (iii) image disruption caused by this motion. Despite large individual differences in performance with static stimuli, motion manipulations neither improved nor degraded performance. As motion significantly disrupts frame-by-frame low-level image statistics, we infer that operational constancy depends on a high-level scene interpretation, which is maintained in all conditions. PMID:29291113

Initial Satellite Formation Flight Results from the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Farahmand, Mitra

2016-01-01

This paper will describe the results that have been obtained to date concerning MMS formation flying. The MMS spacecraft spin at a rate of 3.1 RPM, with spin axis roughly aligned with Ecliptic North. Several booms are used to deploy instruments: two 5 m magnetometer booms in the spin plane, two rigid booms of length 12.5 m along the positive and negative spin axes, and four flexible wire booms of length 60 m in the spin plane. Minimizing flexible motion of the wire booms requires that reorientation of the spacecraft spin axis be kept to a minimum: this is limited to attitude maneuvers to counteract the effects of gravity-gradient and apparent solar motion. Orbital maneuvers must therefore be carried out in essentially the nominal science attitude. These burns make use of a set of monopropellant hydrazine thrusters: two (of thrust 4.5 N) along the spin axis in each direction, and eight (of thrust 18 N) in the spin plane; the latter are pulsed at the spin rate to produce a net delta-v. An on-board accelerometer-based controller is used to accurately generate a commanded delta-v. Navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the MOC Flight Dynamics Operations Area (FDOA) for maneuver design. These commands are then uplinked to the spacecraft and executed autonomously using the controller, with the ground monitoring the burns in real time.

Modes of uncontrolled rotational motion of the Progress M-29M spacecraft

NASA Astrophysics Data System (ADS)

Belyaev, M. Yu.; Matveeva, T. V.; Monakhov, M. I.; Rulev, D. N.; Sazonov, V. V.

2018-01-01

We have reconstructed the uncontrolled rotational motion of the Progress M-29M transport cargo spacecraft in the single-axis solar orientation mode (the so-called sunward spin) and in the mode of the gravitational orientation of a rotating satellite. The modes were implemented on April 3-7, 2016 as a part of preparation for experiments with the DAKON convection sensor onboard the Progress spacecraft. The reconstruction was performed by integral statistical techniques using the measurements of the spacecraft's angular velocity and electric current from its solar arrays. The measurement data obtained in a certain time interval have been jointly processed using the least-squares method by integrating the equations of the spacecraft's motion relative to the center of mass. As a result of processing, the initial conditions of motion and parameters of the mathematical model have been estimated. The motion in the sunward spin mode is the rotation of the spacecraft with an angular velocity of 2.2 deg/s about the normal to the plane of solar arrays; the normal is oriented toward the Sun or forms a small angle with this direction. The duration of the mode is several orbit passes. The reconstruction has been performed over time intervals of up to 1 h. As a result, the actual rotational motion of the spacecraft relative to the Earth-Sun direction was obtained. In the gravitational orientation mode, the spacecraft was rotated about its longitudinal axis with an angular velocity of 0.1-0.2 deg/s; the longitudinal axis executed small oscillated relative to the local vertical. The reconstruction of motion relative to the orbital coordinate system was performed in time intervals of up to 7 h using only the angularvelocity measurements. The measurements of the electric current from solar arrays were used for verification.

A novel soft biomimetic microrobot with two motion attitudes.

PubMed

Shi, Liwei; Guo, Shuxiang; Li, Maoxun; Mao, Shilian; Xiao, Nan; Gao, Baofeng; Song, Zhibin; Asaka, Kinji

2012-12-06

 A variety of microrobots have commonly been used in the fields of biomedical engineering and underwater operations during the last few years. Thanks to their compact structure, low driving power, and simple control systems, microrobots can complete a variety of underwater tasks, even in limited spaces. To accomplish our objectives, we previously designed several bio-inspired underwater microrobots with compact structure, flexibility, and multi-functionality, using ionic polymer metal composite (IPMC) actuators. To implement high-position precision for IPMC legs, in the present research, we proposed an electromechanical model of an IPMC actuator and analysed the deformation and actuating force of an equivalent IPMC cantilever beam, which could be used to design biomimetic legs, fingers, or fins for an underwater microrobot. We then evaluated the tip displacement of an IPMC actuator experimentally. The experimental deflections fit the theoretical values very well when the driving frequency was larger than 1 Hz. To realise the necessary multi-functionality for adapting to complex underwater environments, we introduced a walking biomimetic microrobot with two kinds of motion attitudes: a lying state and a standing state. The microrobot uses eleven IPMC actuators to move and two shape memory alloy (SMA) actuators to change its motion attitude. In the lying state, the microrobot implements stick-insect-inspired walking/rotating motion, fish-like swimming motion, horizontal grasping motion, and floating motion. In the standing state, it implements inchworm-inspired crawling motion in two horizontal directions and grasping motion in the vertical direction. We constructed a prototype of this biomimetic microrobot and evaluated its walking, rotating, and floating speeds experimentally. The experimental results indicated that the robot could attain a maximum walking speed of 3.6 mm/s, a maximum rotational speed of 9°/s, and a maximum floating speed of 7.14 mm/s. Obstacle-avoidance and swimming experiments were also carried out to demonstrate its multi-functionality.

First metatarsophalangeal joint motion in Homo sapiens: theoretical association of two-axis kinematics and specific morphometrics.

PubMed

Durrant, Michael N; McElroy, Tucker; Durrant, Lara

2012-01-01

The metatarsal head and proximal phalanx exhibit considerable asymmetry in their shape and geometry, but there is little documentation in the literature regarding the prevalence of structural characteristics that occur in a given population. Although there is a considerable volume of in vivo and in vitro experiments demonstrating first metatarsal inversion around its longitudinal axis with dorsiflexion, little is known regarding the applicability of specific morphometrics to these motions. Nine distinctive osseous characteristics in the metatarsal head and phalanx were selected based on their location, geometry, and perceived functional relationship to previous studies describing metatarsal motion as inversion with dorsiflexion. The prevalences of the chosen characteristics were determined in a cohort of 21 randomly selected skeletal specimens, 19 of which were provided by the anatomical preparation office at the University of California, San Diego, and two of which were in the possession of one of us (M.D.). The frequency of occurrence of each selected morphological characteristic in this sample and the relevant summary statistics confirm a strong association between the selected features and a conceptual two-axis kinematic model of the metatarsophalangeal joint. The selected morphometrics are consistent with inversion of the metatarsal around its longitudinal axis as it dorsiflexes.

Friction measurement in a hip wear simulator.

PubMed

Saikko, Vesa

2016-05-01

A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated. © IMechE 2016.

Ambiguous Tilt and Translation Motion Cues in Astronauts after Space Flight

NASA Technical Reports Server (NTRS)

Clement, G.; Harm, D. L.; Rupert, A. H.; Beaton, K. H.; Wood, S. J.

2008-01-01

Adaptive changes during space flight in how the brain integrates vestibular cues with visual, proprioceptive, and somatosensory information can lead to impaired movement coordination, vertigo, spatial disorientation, and perceptual illusions following transitions between gravity levels. This joint ESA-NASA pre- and post-flight experiment is designed to examine both the physiological basis and operational implications for disorientation and tilt-translation disturbances in astronauts following short-duration space flights. The first specific aim is to examine the effects of stimulus frequency on adaptive changes in eye movements and motion perception during independent tilt and translation motion profiles. Roll motion is provided by a variable radius centrifuge. Pitch motion is provided by NASA's Tilt-Translation Sled in which the resultant gravitoinertial vector remains aligned with the body longitudinal axis during tilt motion (referred to as the Z-axis gravitoinertial or ZAG paradigm). We hypothesize that the adaptation of otolith-mediated responses to these stimuli will have specific frequency characteristics, being greatest in the mid-frequency range where there is a crossover of tilt and translation. The second specific aim is to employ a closed-loop nulling task in which subjects are tasked to use a joystick to null-out tilt motion disturbances on these two devices. The stimuli consist of random steps or sum-of-sinusoids stimuli, including the ZAG profiles on the Tilt-Translation Sled. We hypothesize that the ability to control tilt orientation will be compromised following space flight, with increased control errors corresponding to changes in self-motion perception. The third specific aim is to evaluate how sensory substitution aids can be used to improve manual control performance. During the closed-loop nulling task on both devices, small tactors placed around the torso vibrate according to the actual body tilt angle relative to gravity. We hypothesize that performance on the closed-loop tilt control task will be improved with this tactile display feedback of tilt orientation. The current plans include testing on eight crewmembers following Space Shuttle missions or short stay onboard the International Space Station. Measurements are obtained pre-flight at L-120 (plus or minus 30), L-90 (plus or minus 30), and L-30, (plus or minus 10) days and post-flight at R+0, R+1, R+2 or 3, R+4 or 5, and R+8 days. Pre-and post-flight testing (from R+1 on) is performed in the Neuroscience Laboratory at the NASA Johnson Space Center on both the Tilt-Translation Device and a variable radius centrifuge. A second variable radius centrifuge, provided by DLR for another joint ESA-NASA project, has been installed at the Baseline Data Collection Facility at Kennedy Space Center to collect data immediately after landing. ZAG was initiated with STS-122/1E and the first post-flight testing will take place after STS-123/1JA landing.

Multi-spacecraft Observations of the Rotation and Nonradial Motion of a CME Flux Rope Causing an Intense Geomagnetic Storm

NASA Astrophysics Data System (ADS)

Liu, Yi A.; Liu, Ying D.; Hu, Huidong; Wang, Rui; Zhao, Xiaowei

2018-02-01

We present an investigation of the rotation and nonradial motion of a coronal mass ejection (CME) from AR 12468 on 2015 December 16 using observations from SDO, SOHO, STEREO A, and Wind. The EUV and HMI observations of the source region show that the associated magnetic flux rope (MFR) axis pointed to the east before the eruption. We use a nonlinear force-free field (NLFFF) extrapolation to determine the configuration of the coronal magnetic field and calculate the magnetic energy density distributions at different heights. The distribution of the magnetic energy density shows a strong gradient toward the northeast. The propagation direction of the CME from a Graduated Cylindrical Shell (GCS) modeling deviates from the radial direction of the source region by about 45° in longitude and about 30° in latitude, which is consistent with the gradient of the magnetic energy distribution around the AR. The MFR axis determined by the GCS modeling points southward, which has rotated counterclockwise by about 95° compared with the orientation of the MFR in the low corona. The MFR reconstructed by a Grad–Shafranov (GS) method at 1 au has almost the same orientation as the MFR from the GCS modeling, which indicates that the MFR rotation occurred in the low corona. It is the rotation of the MFR that caused the intense geomagnetic storm with the minimum D st of ‑155 nT. These results suggest that the coronal magnetic field surrounding the MFR plays a crucial role in the MFR rotation and propagation direction.

The feasibility of a modified shoe for multi-segment foot motion analysis: a preliminary study.

PubMed

Halstead, J; Keenan, A M; Chapman, G J; Redmond, A C

2016-01-01

The majority of multi-segment kinematic foot studies have been limited to barefoot conditions, because shod conditions have the potential for confounding surface-mounted markers. The aim of this study was to investigate whether a shoe modified with a webbed upper can accommodate multi-segment foot marker sets without compromising kinematic measurements under barefoot and shod conditions. Thirty participants (15 controls and 15 participants with midfoot pain) underwent gait analysis in two conditions; barefoot and wearing a shoe (shod) in a random order. The shod condition employed a modified shoe (rubber plimsoll) with a webbed upper, allowing skin mounted reflective markers to be visualised through slits in the webbed material. Three dimensional foot kinematics were captured using the Oxford multi-segment foot model whilst participants walked at a self-selected speed. The foot pain group showed greater hindfoot eversion and less hindfoot dorsiflexion than controls in the barefoot condition and these differences were maintained when measured in the shod condition. Differences between the foot pain and control participants were also observed for walking speed in the barefoot and in the shod conditions. No significant differences between foot pain and control groups were demonstrated at the forefoot in either condition. Subtle differences between pain and control groups, which were found during barefoot walking are retained when wearing the modified shoe. The novel properties of the modified shoe offers a potential solution for the use of passive infrared based motion analysis for shod applications, for instance to investigate the kinematic effect of foot orthoses.

Electrostatic Model Applied to ISS Charged Water Droplet Experiment

NASA Technical Reports Server (NTRS)

Stevenson, Daan; Schaub, Hanspeter; Pettit, Donald R.

2015-01-01

The electrostatic force can be used to create novel relative motion between charged bodies if it can be isolated from the stronger gravitational and dissipative forces. Recently, Coulomb orbital motion was demonstrated on the International Space Station by releasing charged water droplets in the vicinity of a charged knitting needle. In this investigation, the Multi-Sphere Method, an electrostatic model developed to study active spacecraft position control by Coulomb charging, is used to simulate the complex orbital motion of the droplets. When atmospheric drag is introduced, the simulated motion closely mimics that seen in the video footage of the experiment. The electrostatic force's inverse dependency on separation distance near the center of the needle lends itself to analytic predictions of the radial motion.

Measurement of nanoparticle size, suspension polydispersity, and stability using near-field optical trapping and light scattering (Conference Presentation)

NASA Astrophysics Data System (ADS)

Schein, Perry; O'Dell, Dakota; Erickson, David

2017-02-01

Nanoparticles are becoming ubiquitous in applications including diagnostic assays, drug delivery and therapeutics. However, there remain challenges in the quality control of these products. Here we present methods for the orthogonal measurement of these parameters by tracking the motion of the nanoparticle in all three special dimensions as it interacts with an optical waveguide. These simultaneous measurements from a single particle basis address some of the gaps left by current measurement technologies such as nanoparticle tracking analysis, ζ-potential measurements, and absorption spectroscopy. As nanoparticles suspended in a microfluidic channel interact with the evanescent field of an optical waveguide, they experience forces and resulting motion in three dimensions: along the propagation axis of the waveguide (x-direction) they are propelled by the optical forces, parallel to the plane of the waveguide and perpendicular to the optical propagation axis (y-direction) they experience an optical gradient force generated from the waveguide mode profile which confines them in a harmonic potential well, and normal to the surface of the waveguide they experience an exponential downward optical force balanced by the surface interactions that confines the particle in an asymmetric well. Building on our Nanophotonic Force Microscopy technique, in this talk we will explain how to simultaneously use the motion in the y-direction to estimate the size of the particle, the comparative velocity in the x-direction to measure the polydispersity of a particle population, and the motion in the z-direction to measure the potential energy landscape of the interaction, providing insight into the colloidal stability.

Effect of Rotation on Scaffold Motion and Cell Growth in Rotating Bioreactors.

PubMed

Varley, Mark C; Markaki, Athina E; Brooks, Roger A

2017-06-01

Efficient use of different bioreactor designs to improve cell growth in three-dimensional scaffolds requires an understanding of their mechanism of action. To address this for rotating wall vessel bioreactors, fluid and scaffold motion were investigated experimentally at different rotation speeds and vessel fill volumes. Low cost bioreactors with single and dual axis rotation were developed to investigate the effect of these systems on human osteoblast proliferation in free floating and constrained collagen-glycosaminoglycan porous scaffolds. A range of scaffold motions (free fall, periodic oscillation, and orbital motion) were observed at the rotation speeds and vessel fluid/air ratios used, with 85% fluid fill and an outer vessel wall velocity of ∼14 mm s -1 producing a scaffold in a free fall state. The cell proliferation results showed that after 14 and 21 days of culture, this combination of fluid fill and speed of rotation produced significantly greater cell numbers in the scaffolds than when lower or higher rotation speeds (p < 0.002) or when the chamber was 60% or 100% full (p < 0.01). The fluid flow and scaffold motion experiments show that biaxial rotation would not improve the mass transfer of medium into the scaffold as the second axis of rotation can only transition the scaffold toward oscillatory or orbital motion and, hence, reduce mass transport to the scaffold. The cell culture results confirmed that there was no benefit to the second axis of rotation with no significant difference in cell proliferation either when the scaffolds were free floating or constrained (p > 0.05).

Effect of Rotation on Scaffold Motion and Cell Growth in Rotating Bioreactors

PubMed Central

Varley, Mark C.; Markaki, Athina E.

2017-01-01

Efficient use of different bioreactor designs to improve cell growth in three-dimensional scaffolds requires an understanding of their mechanism of action. To address this for rotating wall vessel bioreactors, fluid and scaffold motion were investigated experimentally at different rotation speeds and vessel fill volumes. Low cost bioreactors with single and dual axis rotation were developed to investigate the effect of these systems on human osteoblast proliferation in free floating and constrained collagen-glycosaminoglycan porous scaffolds. A range of scaffold motions (free fall, periodic oscillation, and orbital motion) were observed at the rotation speeds and vessel fluid/air ratios used, with 85% fluid fill and an outer vessel wall velocity of ∼14 mm s−1 producing a scaffold in a free fall state. The cell proliferation results showed that after 14 and 21 days of culture, this combination of fluid fill and speed of rotation produced significantly greater cell numbers in the scaffolds than when lower or higher rotation speeds (p < 0.002) or when the chamber was 60% or 100% full (p < 0.01). The fluid flow and scaffold motion experiments show that biaxial rotation would not improve the mass transfer of medium into the scaffold as the second axis of rotation can only transition the scaffold toward oscillatory or orbital motion and, hence, reduce mass transport to the scaffold. The cell culture results confirmed that there was no benefit to the second axis of rotation with no significant difference in cell proliferation either when the scaffolds were free floating or constrained (p > 0.05). PMID:28125920

Helical Axis Data Visualization and Analysis of the Knee Joint Articulation.

PubMed

Millán Vaquero, Ricardo Manuel; Vais, Alexander; Dean Lynch, Sean; Rzepecki, Jan; Friese, Karl-Ingo; Hurschler, Christof; Wolter, Franz-Erich

2016-09-01

We present processing methods and visualization techniques for accurately characterizing and interpreting kinematical data of flexion-extension motion of the knee joint based on helical axes. We make use of the Lie group of rigid body motions and particularly its Lie algebra for a natural representation of motion sequences. This allows to analyze and compute the finite helical axis (FHA) and instantaneous helical axis (IHA) in a unified way without redundant degrees of freedom or singularities. A polynomial fitting based on Legendre polynomials within the Lie algebra is applied to provide a smooth description of a given discrete knee motion sequence which is essential for obtaining stable instantaneous helical axes for further analysis. Moreover, this allows for an efficient overall similarity comparison across several motion sequences in order to differentiate among several cases. Our approach combines a specifically designed patient-specific three-dimensional visualization basing on the processed helical axes information and incorporating computed tomography (CT) scans for an intuitive interpretation of the axes and their geometrical relation with respect to the knee joint anatomy. In addition, in the context of the study of diseases affecting the musculoskeletal articulation, we propose to integrate the above tools into a multiscale framework for exploring related data sets distributed across multiple spatial scales. We demonstrate the utility of our methods, exemplarily processing a collection of motion sequences acquired from experimental data involving several surgery techniques. Our approach enables an accurate analysis, visualization and comparison of knee joint articulation, contributing to the evaluation and diagnosis in medical applications.

Multi-Level Risk Factors for Suicidal Ideation Among at-Risk Adolescent Females: The Role of Hypothalamic-Pituitary-Adrenal Axis Responses to Stress

PubMed Central

Calhoun, Casey D.; Hastings, Paul D.; Rudolph, Karen D.; Nock, Matthew K.; Prinstein, Mitchell J.

2014-01-01

Adopting a multi-level approach, this study examined risk factors for adolescent suicidal ideation, with specific attention to (a) hypothalamic-pituitary-adrenal (HPA) axis stress responses and (b) the interplay between HPA-axis and other risk factors from multiple domains (i.e., psychological, interpersonal and biological). Participants were 138 adolescent females (Mage=14.13 years, SD=1.40) at risk for suicidal behaviors. At baseline, lifetime suicidal ideation and a number of risk factors were assessed (i.e., depressive symptoms, impulsiveness, pubertal status and peer stress). Participants were exposed to a psychosocial stress task and HPA-axis responses were assessed by measuring cortisol levels pre- and post-stressor. At 3 months post-baseline, suicidal ideation again was assessed. Using group-based trajectory modeling, three groups of cortisol stress-response patterns were identified (i.e., hyporesponsive, normative, and hyperresponsive). As compared to females in the normative and hyporesponsive group, females in the hyperresponsive group were more likely to report a lifetime history of suicidal ideation at baseline, above and beyond the effects of the other predictors. Moreover, as compared to females in the normative group, females in the hyperresponsive group were at increased risk for reporting suicidal ideation 3 months later, after controlling for prior ideation. No interactions between cortisol group and the other risk factors were significant, with the exception of a non-significant trend between impulsiveness and cortisol group on lifetime suicidal ideation. Findings highlight the importance of HPA-axis responses to acute stressors as a risk factor for suicidal ideation among adolescents. PMID:24958308

Assessment of the Rotation Motion at the Papillary Muscle Short-Axis Plane with Normal Subjects by Two-Dimensional Speckle Tracking Imaging: A Basic Clinical Study

PubMed Central

Ni, Xian-Da; Huang, Jun; Hu, Yuan-Ping; Xu, Rui; Yang, Wei-Yu; Zhou, Li-Ming

2013-01-01

Background The aim of this study was to observe the rotation patterns at the papillary muscle plane in the Left Ventricle(LV) with normal subjects using two-dimensional speckle tracking imaging(2D-STI). Methods We acquired standard of the basal, the papillary muscle and the apical short-axis images of the LV in 64 subjects to estimate the LV rotation motion by 2D-STI. The rotational degrees at the papillary muscle short-axis plane were measured at 15 different time points in the analysis of two heart cycles. Results There were counterclockwise rotation, clockwise rotation, and counterclockwise to clockwise rotation at the papillary muscle plane in the LV with normal subjects, respectively. The ROC analysis of the rotational degrees was performed at the papillary muscle short-axis plane at the peak LV torsion for predicting whether the turnaround point of twist to untwist motion pattern was located at the papillary muscle level. Sensitivity and specificity were 97% and 67%, respectively, with a cut-off value of 0.34°, and an area under the ROC curve of 0.8. At the peak LV torsion, there was no correlation between the rotational degrees at the papillary muscle short-axis plane and the LVEF in the normal subjects(r = 0.000, p = 0.998). Conclusions In the study, we conclude that there were three rotation patterns at the papillary muscle short-axis levels, and the transition from basal clockwise rotation to apical counterclockwise rotation is located at the papillary muscle level. PMID:24376634

Effect of Long-Period Ocean Tides on the Earth's Polar Motion

NASA Technical Reports Server (NTRS)

Gross, R. S.; Chao, B. F.; Desai, S. D.

1997-01-01

The second-degree zonal tide raising potential is symmetric about the polar axis and hence can excite the Earth's polar motion only through its action upon nonaxisymmetric features of the Earth such as the oceans.

Effects of angular acceleration on man - Choice reaction time using visual and rotary motion information

NASA Technical Reports Server (NTRS)

Clark, B.; Stewart, J. D.

1974-01-01

This experiment was concerned with the effects of rotary acceleration on choice reaction time (RTc) to the motion of a luminous line on a cathode-ray tube. Specifically, it compared the (RTc) to rotary acceleration alone, visual acceleration alone, and simultaneous, double stimulation by both rotary and visual acceleration. Thirteen airline pilots were rotated about an earth-vertical axis in a precision rotation device while they observed a vertical line. The stimuli were 7 rotary and visual accelerations which were matched for rise time. The pilot responded as quickly as possible by displacing a vertical controller to the right or left. The results showed a decreasing (RTc) with increasing acceleration for all conditions, while the (RTc) to rotary motion alone was substantially longer than for all other conditions. The (RTc) to the double stimulation was significantly longer than that for visual acceleration alone.

Microwave fields driven domain wall motions in antiferromagnetic nanowires

NASA Astrophysics Data System (ADS)

Chen, Z. Y.; Yan, Z. R.; Zhang, Y. L.; Qin, M. H.; Fan, Z.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

2018-06-01

In this work, we study the microwave field driven domain wall (DW) motion in an antiferromagnetic nanowire, using the numerical calculations based on a classical Heisenberg spin model with the biaxial magnetic anisotropy. We show that a proper combination of a static magnetic field plus an oscillating field perpendicular to the nanowire axis is sufficient to drive the DW propagation along the nanowire. More importantly, the drift velocity at the resonance frequency is comparable to that induced by temperature gradients, suggesting that microwave field can be a very promising tool to control DW motions in antiferromagnetic nanostructures. The dependences of resonance frequency and drift velocity on the static and oscillating fields, the axial anisotropy, and the damping constant are discussed in details. Furthermore, the optimal orientations of the field are also numerically determined and explained. This work provides useful information for the spin dynamics in antiferromagnetic nanostructures for spintronics applications.

Hybrid PD and effective multi-mode positive position feedback control for slewing and vibration suppression of a smart flexible manipulator

NASA Astrophysics Data System (ADS)

Lou, Jun-qiang; Wei, Yan-ding; Yang, Yi-ling; Xie, Feng-ran

2015-03-01

A hybrid control strategy for slewing and vibration suppression of a smart flexible manipulator is presented in this paper. It consists of a proportional derivative controller to realize motion control, and an effective multi-mode positive position feedback (EMPPF) controller to suppress the multi-mode vibration. Rather than treat each mode equally as the standard multi-mode PPF, the essence of the EMPPF is that control forces of different modes are applied according to the mode parameters of the respective modes, so the vibration modes with less vibration energy receive fewer control forces. Stability conditions for the close loop system are established through stability analysis. Optimal parameters of the EMPPF controller are obtained using the method of root locus analysis. The performance of the proposed strategy is demonstrated by simulation and experiments. Experimental results show that the first two vibration modes of the manipulator are effectively suppressed. The setting time of the setup descends approximately 55%, reaching 3.12 s from 5.67 s.

Differences in knee adduction moment between healthy subjects and patients with osteoarthritis depend on the knee axis definition.

PubMed

Meireles, S; De Groote, F; Van Rossom, S; Verschueren, S; Jonkers, I

2017-03-01

This study, firstly, investigates the effect of using an anatomical versus a functional axis of rotation (FAR) on knee adduction moment (KAM) in healthy subjects and patients with knee osteoarthritis (KOA). Secondly, this study reports KAM for models with FAR calculated using weight-bearing and non-weight-bearing motion. Three musculoskeletal models were created using OpenSim with different knee axis of rotation (AR): transepicondylar axis (TEA); FAR calculated based on SARA algorithm using a weight-bearing motion (wFAR) and a non-weight-bearing motion (nwFAR). KAM were calculated during gait in fifty-nine subjects (n=20 healthy, n=16 early OA, n=23 established OA) for all models and groups. Significant differences between the three groups in the first peak KAM were found when TEA was used (p=0.038). However, these differences were no longer present when using FAR. In subjects with established OA, KAMs were significantly reduced when using nwFAR compared to TEA models but also compared to wFAR models. The presence of excessive KAM in subjects with established KOA showed to be dependent on the definition of the AR: anatomical versus functional. Therefore, caution should be accounted when comparing KAM in different studies on KOA patients. In patients with end-stage knee OA where increased passive knee laxity is likely to exist, the use of weight-bearing motions should be considered to avoid increased variability in the location and orientation of a FAR obtained from activities with only limited joint loading. Copyright © 2017 Elsevier B.V. All rights reserved.

OJ287: Deciphering the "Rosetta stone of blazars★"

NASA Astrophysics Data System (ADS)

Britzen, S.; Fendt, C.; Witzel, G.; Qian, S.-J.; Pashchenko, I. N.; Kurtanidze, O.; Zajacek, M.; Martinez, G.; Karas, V.; Aller, M.; Aller, H.; Eckart, A.; Nilsson, K.; Arévalo, P.; Cuadra, J.; Subroweit, M.; Witzel, A.

2018-04-01

OJ287 is the best candidate Active Galactic Nucleus (AGN) for hosting a supermassive binary black hole (SMBBH) at very close separation. We present 120 Very Long Baseline Array (VLBA) observations (at 15 GHz) covering the time between Apr. 1995 and Apr. 2017. We find that the OJ287 radio jet is precessing on a timescale of ˜ 22 yr. In addition, our data are consistent with a jet-axis rotation on a yearly timescale. We model the precession (24±2 yr) and combined motion of jet precession and jet-axis rotation. The jet motion explains the variability of the total radio flux-density via viewing angle changes and Doppler beaming. Half of the jet-precession timescale is of the order of the dominant optical periodicity timescale. We suggest that the optical emission is synchrotron emission and related to the jet radiation. The jet dynamics and flux-density light curves can be understood in terms of geometrical effects. Disturbances of an accretion disc caused by a plunging black hole do not seem necessary to explain the observed variability. Although the SMBBH model does not seem necessary to explain the observed variability, a SMBBH or Lense-Thirring precession (disc aSround single black hole) seem to be required to explain the timescale of the precessing motion. Besides jet rotation also nutation of the jet axis could explain the observed motion of the jet axis. We find a strikingly similar scaling for the timescales for precession and nutation as indicated for SS433 with a factor of roughly 50 times longer in OJ287.

Pure visual imagery as a potential approach to achieve three classes of control for implementation of BCI in non-motor disorders

NASA Astrophysics Data System (ADS)

Sousa, Teresa; Amaral, Carlos; Andrade, João; Pires, Gabriel; Nunes, Urbano J.; Castelo-Branco, Miguel

2017-08-01

Objective. The achievement of multiple instances of control with the same type of mental strategy represents a way to improve flexibility of brain-computer interface (BCI) systems. Here we test the hypothesis that pure visual motion imagery of an external actuator can be used as a tool to achieve three classes of electroencephalographic (EEG) based control, which might be useful in attention disorders. Approach. We hypothesize that different numbers of imagined motion alternations lead to distinctive signals, as predicted by distinct motion patterns. Accordingly, a distinct number of alternating sensory/perceptual signals would lead to distinct neural responses as previously demonstrated using functional magnetic resonance imaging (fMRI). We anticipate that differential modulations should also be observed in the EEG domain. EEG recordings were obtained from twelve participants using three imagery tasks: imagery of a static dot, imagery of a dot with two opposing motions in the vertical axis (two motion directions) and imagery of a dot with four opposing motions in vertical or horizontal axes (four directions). The data were analysed offline. Main results. An increase of alpha-band power was found in frontal and central channels as a result of visual motion imagery tasks when compared with static dot imagery, in contrast with the expected posterior alpha decreases found during simple visual stimulation. The successful classification and discrimination between the three imagery tasks confirmed that three different classes of control based on visual motion imagery can be achieved. The classification approach was based on a support vector machine (SVM) and on the alpha-band relative spectral power of a small group of six frontal and central channels. Patterns of alpha activity, as captured by single-trial SVM closely reflected imagery properties, in particular the number of imagined motion alternations. Significance. We found a new mental task based on visual motion imagery with potential for the implementation of multiclass (3) BCIs. Our results are consistent with the notion that frontal alpha synchronization is related with high internal processing demands, changing with the number of alternation levels during imagery. Together, these findings suggest the feasibility of pure visual motion imagery tasks as a strategy to achieve multiclass control systems with potential for BCI and in particular, neurofeedback applications in non-motor (attentional) disorders.

Elevation scanning laser/multi-sensor hazard detection system controller and mirror/mast speed control components. [roving vehicle electromechanical devices

NASA Technical Reports Server (NTRS)

Craig, J.; Yerazunis, S. W.

1978-01-01

The electro-mechanical and electronic systems involved with pointing a laser beam from a roving vehicle along a desired vector are described. A rotating 8 sided mirror, driven by a phase-locked dc motor servo system, and monitored by a precision optical shaft encoder is used. This upper assembly is then rotated about an orthogonal axis to allow scanning into all 360 deg around the vehicle. This axis is also driven by a phase locked dc motor servo-system, and monitored with an optical shaft encoder. The electronics are realized in standard TTL integrated circuits with UV-erasable proms used to store desired coordinates of laser fire. Related topics such as the interface to the existing test vehicle are discussed.

Time Frequency Analysis of Spacecraft Propellant Tank Spinning Slosh

NASA Technical Reports Server (NTRS)

Green, Steven T.; Burkey, Russell C.; Sudermann, James

2010-01-01

Many spacecraft are designed to spin about an axis along the flight path as a means of stabilizing the attitude of the spacecraft via gyroscopic stiffness. Because of the assembly requirements of the spacecraft and the launch vehicle, these spacecraft often spin about an axis corresponding to a minor moment of inertia. In such a case, any perturbation of the spin axis will cause sloshing motions in the liquid propellant tanks that will eventually dissipate enough kinetic energy to cause the spin axis nutation (wobble) to grow further. This spinning slosh and resultant nutation growth is a primary design problem of spinning spacecraft and one that is not easily solved by analysis or simulation only. Testing remains the surest way to address spacecraft nutation growth. This paper describes a test method and data analysis technique that reveal the resonant frequency and damping behavior of liquid motions in a spinning tank. Slosh resonant frequency and damping characteristics are necessary inputs to any accurate numerical dynamic simulation of the spacecraft.

Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm.

PubMed

Liang, Lihua; Yuan, Jia; Zhang, Songtao; Zhao, Peng

2018-01-01

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller.

Design a software real-time operation platform for wave piercing catamarans motion control using linear quadratic regulator based genetic algorithm

PubMed Central

Liang, Lihua; Zhang, Songtao; Zhao, Peng

2018-01-01

This work presents optimal linear quadratic regulator (LQR) based on genetic algorithm (GA) to solve the two degrees of freedom (2 DoF) motion control problem in head seas for wave piercing catamarans (WPC). The proposed LQR based GA control strategy is to select optimal weighting matrices (Q and R). The seakeeping performance of WPC based on proposed algorithm is challenged because of multi-input multi-output (MIMO) system of uncertain coefficient problems. Besides the kinematical constraint problems of WPC, the external conditions must be considered, like the sea disturbance and the actuators (a T-foil and two flaps) control. Moreover, this paper describes the MATLAB and LabVIEW software plats to simulate the reduction effects of WPC. Finally, the real-time (RT) NI CompactRIO embedded controller is selected to test the effectiveness of the actuators based on proposed techniques. In conclusion, simulation and experimental results prove the correctness of the proposed algorithm. The percentage of heave and pitch reductions are more than 18% in different high speeds and bad sea conditions. And the results also verify the feasibility of NI CompactRIO embedded controller. PMID:29709008

A two-degrees-of-freedom miniature manipulator actuated by antagonistic shape memory alloys

NASA Astrophysics Data System (ADS)

Lai, Chih-Ming; Chu, Cheng-Yu; Lan, Chao-Chieh

2013-08-01

This paper presents a miniature manipulator that can provide rotations around two perpendicularly intersecting axes. Each axis is actuated by a pair of shape memory alloy (SMA) wires. SMA wire actuators are known for their large energy density and ease of actuation. These advantages make them ideal for applications that have stringent size and weight constraints. SMA actuators can be temperature-controlled to contract and relax like muscles. When correctly designed, antagonistic SMA actuators have a faster response and larger range of motion than bias-type SMA actuators. This paper proposes an antagonistic actuation model to determine the manipulator parameters that are required to generate sufficient workspace. Effects of SMA prestrain and spring stiffness on the manipulator are investigated. Taking advantage of proper prestrain, the actuator size can be made much smaller while maintaining the same motion. The use of springs in series with SMA can effectively reduce actuator stress. A controller and an anti-slack algorithm are developed to ensure fast and accurate motion. Speed, stress, and loading experiments are conducted to demonstrate the performance of the manipulator.

Automated Slicing for a Multi-Axis Metal Deposition System (Preprint)

DTIC Science & Technology

2006-09-01

experimented with different materials like H13 tool steel to build the part. Following the same slicing and scanning toolpath result, there is a geometric...and analysis tool -centroidal axis. Similar to medial axis, it contains geometry and topological information but is significantly computationally...geometry reasoning and analysis tool -centroidal axis. Similar to medial axis, it contains geometry and topological information but is significantly

A study on validating KinectV2 in comparison of Vicon system as a motion capture system for using in Health Engineering in industry

NASA Astrophysics Data System (ADS)

Jebeli, Mahvash; Bilesan, Alireza; Arshi, Ahmadreza

2017-06-01

The currently available commercial motion capture systems are constrained by space requirement and thus pose difficulties when used in developing kinematic description of human movements within the existing manufacturing and production cells. The Kinect sensor does not share similar limitations but it is not as accurate. The proposition made in this article is to adopt the Kinect sensor in to facilitate implementation of Health Engineering concepts to industrial environments. This article is an evaluation of the Kinect sensor accuracy when providing three dimensional kinematic data. The sensor is thus utilized to assist in modeling and simulation of worker performance within an industrial cell. For this purpose, Kinect 3D data was compared to that of Vicon motion capture system in a gait analysis laboratory. Results indicated that the Kinect sensor exhibited a coefficient of determination of 0.9996 on the depth axis and 0.9849 along the horizontal axis and 0.2767 on vertical axis. The results prove the competency of the Kinect sensor to be used in the industrial environments.

A new measuring method for motion accuracy of 3-axis NC equipments based on composite trajectory of circle and non-circle

NASA Astrophysics Data System (ADS)

Yang, Fan; Du, Zhengchun; Yang, Jiangguo; Hong, Maisheng

2011-12-01

Geometric motion error measurement has been considered as an important task for accuracy enhancement and quality assurance of NC machine tools and CMMs. In consideration of the disadvantages of traditional measuring methods,a new measuring method for motion accuracy of 3-axis NC equipments based on composite trajectory including circle and non-circle(straight line and/or polygonal line) is proposed. The principles and techniques of the new measuring method are discussed in detail. 8 feasible measuring strategies based on different measuring groupings are summarized and optimized. The experiment of the most preferable strategy is carried out on the 3-axis CNC vertical machining center Cincinnati 750 Arrow by using cross grid encoder. The whole measuring time of 21 error components of the new method is cut down to 1-2 h because of easy installation, adjustment, operation and the characteristics of non-contact measurement. Result shows that the new method is suitable for `on machine" measurement and has good prospects of wide application.

SU-G-BRA-17: Tracking Multiple Targets with Independent Motion in Real-Time Using a Multi-Leaf Collimator

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

Ge, Y; Keall, P; Poulsen, P

Purpose: Multiple targets with large intrafraction independent motion are often involved in advanced prostate, lung, abdominal, and head and neck cancer radiotherapy. Current standard of care treats these with the originally planned fields, jeopardizing the treatment outcomes. A real-time multi-leaf collimator (MLC) tracking method has been developed to address this problem for the first time. This study evaluates the geometric uncertainty of the multi-target tracking method. Methods: Four treatment scenarios are simulated based on a prostate IMAT plan to treat a moving prostate target and static pelvic node target: 1) real-time multi-target MLC tracking; 2) real-time prostate-only MLC tracking; 3)more » correcting for prostate interfraction motion at setup only; and 4) no motion correction. The geometric uncertainty of the treatment is assessed by the sum of the erroneously underexposed target area and overexposed healthy tissue areas for each individual target. Two patient-measured prostate trajectories of average 2 and 5 mm motion magnitude are used for simulations. Results: Real-time multi-target tracking accumulates the least uncertainty overall. As expected, it covers the static nodes similarly well as no motion correction treatment and covers the moving prostate similarly well as the real-time prostate-only tracking. Multi-target tracking reduces >90% of uncertainty for the static nodal target compared to the real-time prostate-only tracking or interfraction motion correction. For prostate target, depending on the motion trajectory which affects the uncertainty due to leaf-fitting, multi-target tracking may or may not perform better than correcting for interfraction prostate motion by shifting patient at setup, but it reduces ∼50% of uncertainty compared to no motion correction. Conclusion: The developed real-time multi-target MLC tracking can adapt for the independently moving targets better than other available treatment adaptations. This will enable PTV margin reduction to minimize health tissue toxicity while remain tumor coverage when treating advanced disease with independently moving targets involved. The authors acknowledge funding support from the Australian NHMRC Australia Fellowship and NHMRC Project Grant No. APP1042375.« less

Instant axis of rotation of L4-5 motion segment--a biomechanical study on cadaver lumbar spine.

PubMed

Sengupta, Dilip K; Demetropoulos, Constantine K; Herkowitz, Harry N

2011-06-01

The instant axis of rotation (IAR) is an important kinematic property to characterise of lumbar spine motion. The goal of this biomechanical study on cadaver lumbar spine was to determine the excursion of the IAR for flexion (FE), lateral bending (LB) and axial rotation (AR) motion at L4-5 segment. Ten cadaver lumbar spine specimens were tested in a 6 degrees-of-freedom spine tester with continuous clyclical loading using pure moment and follower pre-load, to produce physiological motion. The specimens were x-rayed and CT scanned prior to testing to identify marker position. Continuous motion tracking was done by Optotrak motion capture device. A continuous tracking of the IAR excursion was calculated from the continuous motions capturedata using a computer programme. IAR translates forward in flexion and backwards in extension with mean excursion of 26.5 mm (+/- 5.6 SD). During LB motion, IAR translates laterally in the same direction, and the mean excursion was 15.35 mm (+/- 8.75 SD). During axial rotation the IAR translates in the horizontal plane in a semicircular arc, around the centre of the vertebral body, but the IAR translates in the opposite direction of rotation. The IAR excursion was faster and larger during neutral zone motion in FE and LB, but uniform for AR motion. This is the first published data on the continuous excursion of IAR of a lumbar motion segment. The methodology is accurate and precise, but not practicable for in vivo testing.

Analysis of accelerated motion in the theory of relativity

NASA Technical Reports Server (NTRS)

Jones, R. T.

1976-01-01

Conventional treatments of accelerated motion in the theory of relativity have led to certain difficulties of interpretation. Certain reversals in the apparent gravitational field of an accelerated body may be avoided by simpler analysis based on the use of restricted conformal transformations. In the conformal theory the velocity of light remains constant even for experimenters in accelerated motion. The problem considered is that of rectilinear motion with a variable velocity. The motion takes place along the x or x' axis of two coordinate systems.

Ranging Apparatus and Method Implementing Stereo Vision System

NASA Technical Reports Server (NTRS)

Li, Larry C. (Inventor); Cox, Brian J. (Inventor)

1997-01-01

A laser-directed ranging system for use in telerobotics applications and other applications involving physically handicapped individuals. The ranging system includes a left and right video camera mounted on a camera platform, and a remotely positioned operator. The position of the camera platform is controlled by three servo motors to orient the roll axis, pitch axis and yaw axis of the video cameras, based upon an operator input such as head motion. A laser is provided between the left and right video camera and is directed by the user to point to a target device. The images produced by the left and right video cameras are processed to eliminate all background images except for the spot created by the laser. This processing is performed by creating a digital image of the target prior to illumination by the laser, and then eliminating common pixels from the subsequent digital image which includes the laser spot. The horizontal disparity between the two processed images is calculated for use in a stereometric ranging analysis from which range is determined.

Model reference adaptive control (MRAC)-based parameter identification applied to surface-mounted permanent magnet synchronous motor

NASA Astrophysics Data System (ADS)

Zhong, Chongquan; Lin, Yaoyao

2017-11-01

In this work, a model reference adaptive control-based estimated algorithm is proposed for online multi-parameter identification of surface-mounted permanent magnet synchronous machines. By taking the dq-axis equations of a practical motor as the reference model and the dq-axis estimation equations as the adjustable model, a standard model-reference-adaptive-system-based estimator was established. Additionally, the Popov hyperstability principle was used in the design of the adaptive law to guarantee accurate convergence. In order to reduce the oscillation of identification result, this work introduces a first-order low-pass digital filter to improve precision regarding the parameter estimation. The proposed scheme was then applied to an SPM synchronous motor control system without any additional circuits and implemented using a DSP TMS320LF2812. For analysis, the experimental results reveal the effectiveness of the proposed method.

Robotic Compliant Motion Control for Aircraft Refueling Applications

DTIC Science & Technology

1988-12-01

J. DUVALL 29 SEP 88 C-26 SUBROUTINE IMPCONST(CONST,MINV, BMAT ) Abstract: This subroutine calculates the 25 constants used by the Fortran subroutine...mass with center of gravity along the joint 6 axis. The desired mass and the damping ( BMAT ) matrices are assumed to be diagonal. Joints angles 4,5...constants. MINV -- A 2x2 matrix containing the elements of the inverse desired mass matrix (diagonal). BMAT -- A 2x2 matrix of damping coefficents (diagonal

Comparison study on disturbance estimation techniques in precise slow motion control

NASA Astrophysics Data System (ADS)

Fan, S.; Nagamune, R.; Altintas, Y.; Fan, D.; Zhang, Z.

2010-08-01

Precise low speed motion control is important for the industrial applications of both micro-milling machine tool feed drives and electro-optical tracking servo systems. It calls for precise position and instantaneous velocity measurement and disturbance, which involves direct drive motor force ripple, guide way friction and cutting force etc., estimation. This paper presents a comparison study on dynamic response and noise rejection performance of three existing disturbance estimation techniques, including the time-delayed estimators, the state augmented Kalman Filters and the conventional disturbance observers. The design technique essentials of these three disturbance estimators are introduced. For designing time-delayed estimators, it is proposed to substitute Kalman Filter for Luenberger state observer to improve noise suppression performance. The results show that the noise rejection performances of the state augmented Kalman Filters and the time-delayed estimators are much better than the conventional disturbance observers. These two estimators can give not only the estimation of the disturbance but also the low noise level estimations of position and instantaneous velocity. The bandwidth of the state augmented Kalman Filters is wider than the time-delayed estimators. In addition, the state augmented Kalman Filters can give unbiased estimations of the slow varying disturbance and the instantaneous velocity, while the time-delayed estimators can not. The simulation and experiment conducted on X axis of a 2.5-axis prototype micro milling machine are provided.

Principal components of wrist circumduction from electromagnetic surgical tracking.

PubMed

Rasquinha, Brian J; Rainbow, Michael J; Zec, Michelle L; Pichora, David R; Ellis, Randy E

2017-02-01

An electromagnetic (EM) surgical tracking system was used for a functionally calibrated kinematic analysis of wrist motion. Circumduction motions were tested for differences in subject gender and for differences in the sense of the circumduction as clockwise or counter-clockwise motion. Twenty subjects were instrumented for EM tracking. Flexion-extension motion was used to identify the functional axis. Subjects performed unconstrained wrist circumduction in a clockwise and counter-clockwise sense. Data were decomposed into orthogonal flexion-extension motions and radial-ulnar deviation motions. PCA was used to concisely represent motions. Nonparametric Wilcoxon tests were used to distinguish the groups. Flexion-extension motions were projected onto a direction axis with a root-mean-square error of [Formula: see text]. Using the first three principal components, there was no statistically significant difference in gender (all [Formula: see text]). For motion sense, radial-ulnar deviation distinguished the sense of circumduction in the first principal component ([Formula: see text]) and in the third principal component ([Formula: see text]); flexion-extension distinguished the sense in the second principal component ([Formula: see text]). The clockwise sense of circumduction could be distinguished by a multifactorial combination of components; there were no gender differences in this small population. These data constitute a baseline for normal wrist circumduction. The multifactorial PCA findings suggest that a higher-dimensional method, such as manifold analysis, may be a more concise way of representing circumduction in human joints.

Ankle-foot orthosis bending axis influences running mechanics.

PubMed

Russell Esposito, Elizabeth; Ranz, Ellyn C; Schmidtbauer, Kelly A; Neptune, Richard R; Wilken, Jason M

2017-07-01

Passive-dynamic ankle-foot orthoses (AFOs) are commonly prescribed to improve locomotion for people with lower limb musculoskeletal weakness. The clinical prescription and design process are typically qualitative and based on observational assessment and experience. Prior work examining the effect of AFO design characteristics generally excludes higher impact activities such as running, providing clinicians and researchers limited information to guide the development of objective prescription guidelines. The proximal location of the bending axis may directly influence energy storage and return and resulting running mechanics. The purpose of this study was to determine if the location of an AFO's bending axis influences running mechanics. Marker and force data were recorded as 12 participants with lower extremity weakness ran overground while wearing a passive-dynamic AFO with posterior struts manufactured with central (middle) and off-centered (high and low) bending axes. Lower extremity joint angles, moments, powers, and ground reaction forces were calculated and compared between limbs and across bending axis conditions. Bending axis produced relatively small but significant changes. Ankle range of motion increased as the bending axis shifted distally (p<0.003). Peak ankle power absorption was greater in the low axis than high (p=0.013), and peak power generation was greater in the low condition than middle or high conditions (p<0.009). Half of the participants preferred the middle bending axis, four preferred low and two preferred high. Overall, if greater ankle range of motion is tolerated, a low bending axis provides power and propulsive benefits during running, although individual preference and physical ability should also be considered. Published by Elsevier B.V.

New Tests of the Fixed Hotspot Approximation

NASA Astrophysics Data System (ADS)

Gordon, R. G.; Andrews, D. L.; Horner-Johnson, B. C.; Kumar, R. R.

2005-05-01

We present new methods for estimating uncertainties in plate reconstructions relative to the hotspots and new tests of the fixed hotspot approximation. We find no significant motion between Pacific hotspots, on the one hand, and Indo-Atlantic hotspots, on the other, for the past ~ 50 Myr, but large and significant apparent motion before 50 Ma. Whether this motion is truly due to motion between hotspots or alternatively due to flaws in the global plate motion circuit can be tested with paleomagnetic data. These tests give results consistent with the fixed hotspot approximation and indicate significant misfits when a relative plate motion circuit through Antarctica is employed for times before 50 Ma. If all of the misfit to the global plate motion circuit is due to motion between East and West Antarctica, then that motion is 800 ± 500 km near the Ross Sea Embayment and progressively less along the Trans-Antarctic Mountains toward the Weddell Sea. Further paleomagnetic tests of the fixed hotspot approximation can be made. Cenozoic and Cretaceous paleomagnetic data from the Pacific plate, along with reconstructions of the Pacific plate relative to the hotspots, can be used to estimate an apparent polar wander (APW) path of Pacific hotspots. An APW path of Indo-Atlantic hotspots can be similarly estimated (e.g. Besse & Courtillot 2002). If both paths diverge in similar ways from the north pole of the hotspot reference frame, it would indicate that the hotspots have moved in unison relative to the spin axis, which may be attributed to true polar wander. If the two paths diverge from one another, motion between Pacific hotspots and Indo-Atlantic hotspots would be indicated. The general agreement of the two paths shows that the former is more important than the latter. The data require little or no motion between groups of hotspots, but up to ~10 mm/yr of motion is allowed within uncertainties. The results disagree, in particular, with the recent extreme interpretation of Tarduno et al. [2003], who assume (1) that motion of the Indo-Atlantic hotspots relative to the spin axis can be ignored during the past 85 Myr, and (2) that the Hawaiian hotspot has been fixed relative to the spin axis since the age of the Hawaiian-Emperor bend. Our results indicate that both assumptions are false.

A microprocessor application to a strapdown laser gyro navigator

NASA Technical Reports Server (NTRS)

Giardina, C.; Luxford, E.

1980-01-01

The replacement of analog circuit control loops for laser gyros (path length control, cross axis temperature compensation loops, dither servo and current regulators) with digital filters residing in microcomputers is addressed. In addition to the control loops, a discussion is given on applying the microprocessor hardware to compensation for coning and skulling motion where simple algorithms are processed at high speeds to compensate component output data (digital pulses) for linear and angular vibration motions. Highlights are given on the methodology and system approaches used in replacing differential equations describing the analog system in terms of the mechanized difference equations of the microprocessor. Standard one for one frequency domain techniques are employed in replacing analog transfer functions by their transform counterparts. Direct digital design techniques are also discussed along with their associated benefits. Time and memory loading analyses are also summarized, as well as signal and microprocessor architecture. Trade offs in algorithm, mechanization, time/memory loading, accuracy, and microprocessor architecture are also given.

Artifact Noise Removal Techniques on Seismocardiogram Using Two Tri-Axial Accelerometers

PubMed Central

Luu, Loc; Dinh, Anh

2018-01-01

The aim of this study is on the investigation of motion noise removal techniques using two-accelerometer sensor system and various placements of the sensors on gentle movement and walking of the patients. A Wi-Fi based data acquisition system and a framework on Matlab are developed to collect and process data while the subjects are in motion. The tests include eight volunteers who have no record of heart disease. The walking and running data on the subjects are analyzed to find the minimal-noise bandwidth of the SCG signal. This bandwidth is used to design filters in the motion noise removal techniques and peak signal detection. There are two main techniques of combining signals from the two sensors to mitigate the motion artifact: analog processing and digital processing. The analog processing comprises analog circuits performing adding or subtracting functions and bandpass filter to remove artifact noises before entering the data acquisition system. The digital processing processes all the data using combinations of total acceleration and z-axis only acceleration. The two techniques are tested on three placements of accelerometer sensors including horizontal, vertical, and diagonal on gentle motion and walking. In general, the total acceleration and z-axis acceleration are the best techniques to deal with gentle motion on all sensor placements which improve average systolic signal-noise-ratio (SNR) around 2 times and average diastolic SNR around 3 times comparing to traditional methods using only one accelerometer. With walking motion, ADDER and z-axis acceleration are the best techniques on all placements of the sensors on the body which enhance about 7 times of average systolic SNR and about 11 times of average diastolic SNR comparing to only one accelerometer method. Among the sensor placements, the performance of horizontal placement of the sensors is outstanding comparing with other positions on all motions. PMID:29614821

From reaching to reach-to-grasp: the arm posture difference and its implications on human motion control strategy.

PubMed

Li, Zhi; Milutinović, Dejan; Rosen, Jacob

2017-05-01

Reach-to-grasp arm postures differ from those in pure reaching because they are affected by grasp position/orientation, rather than simple transport to a position during a reaching motion. This paper investigates this difference via an analysis of experimental  data collected on reaching and reach-to-grasp motions. A seven-degree-of-freedom (DOFs) kinematic arm model with the swivel angle is used for the motion analysis. Compared to a widely used anatomical arm model, this model distinguishes clearly the four grasping-relevant DOFs (GR-DOFs) that are affected by positions and orientations of the objects to be grasped. These four GR-DOFs include the swivel angle that measures the elbow rotation about the shoulder-wrist axis, and three wrist joint angles. For each GR-DOF, we quantify position vs orientation task-relevance bias that measures how much the DOF is affected by the grasping position vs orientation. The swivel angle and forearm supination have similar bias, and the analysis of their motion suggests two hypotheses regarding the synergistic coordination of the macro- and micro-structures of the human arm (1) DOFs with similar task-relevance are synergistically coordinated; and (2) such synergy breaks when a task-relevant DOF is close to its joint limit without necessarily reaching the limit. This study provides a motion analysis method to reduce the control complexity for reach-to-grasp tasks, and suggests using dynamic coupling to coordinate the hand and arm of upper-limb exoskeletons.

Design of a dynamic test platform for autonomous robot vision systems

NASA Technical Reports Server (NTRS)

Rich, G. C.

1980-01-01

The concept and design of a dynamic test platform for development and evluation of a robot vision system is discussed. The platform is to serve as a diagnostic and developmental tool for future work with the RPI Mars Rover's multi laser/multi detector vision system. The platform allows testing of the vision system while its attitude is varied, statically or periodically. The vision system is mounted on the test platform. It can then be subjected to a wide variety of simulated can thus be examined in a controlled, quantitative fashion. Defining and modeling Rover motions and designing the platform to emulate these motions are also discussed. Individual aspects of the design process are treated separately, as structural, driving linkages, and motors and transmissions.

[A simulation study with finite element model on the unequal loss of peripheral vision caused by acceleration].

PubMed

Geng, Xiaoqi; Liu, Xiaoyu; Liu, Songyang; Xu, Yan; Zhao, Xianliang; Wang, Jie; Fan, Yubo

2017-04-01

An unequal loss of peripheral vision may happen with high sustaining multi-axis acceleration, leading to a great potential flight safety hazard. In the present research, finite element method was used to study the mechanism of unequal loss of peripheral vision. Firstly, a 3D geometric model of skull was developed based on the adult computer tomography (CT) images. The model of double eyes was created by mirroring with the previous right eye model. Then, the double-eye model was matched to the skull model, and fat was filled between eyeballs and skull. Acceleration loads of head-to-foot (G z ), right-to-left (G y ), chest-to-back (G x ) and multi-axis directions were applied to the current model to simulate dynamic response of retina by explicit dynamics solution. The results showed that the relative strain of double eyes was 25.7% under multi-axis acceleration load. Moreover, the strain distributions showed a significant difference among acceleration loaded in different directions. It indicated that a finite element model of double eyes was an effective means to study the mechanism of an unequal loss of peripheral vision at sustaining high multi-axis acceleration.

A pelvic motion driven electrical stimulator for drop-foot treatment.

PubMed

Chen, Shih-Wei; Chen, Shih-Ching; Chen, Chiun-Fan; Lai, Jin-Shin; Kuo, Te-Son

2009-01-01

Foot switches operating with force sensitive resistors placed in the shoe sole were considered as an effective way for driving FES assisted walking systems in gait restoration. However, the reliability and durability of the foot switches run down after a certain number of steps. As an alternative for foot switches, a simple, portable, and easy to handle motion driven electrical stimulator (ES) is provided for drop foot treatment. The device is equipped with a single tri-axis accelerometer worn on the pelvis, a commercial dual channel electrical stimulator, and a controller unit. By monitoring the pelvic rotation and acceleration during a walking cycle, the events including heel strike and toe off of each step is thereby predicted by a post-processing neural network model.

DEVICE FOR CONVEYING AND ROTATING OBJECTS

DOEpatents

Frantz, C.E.; Roslund, J.

1958-01-21

A device is described for conveying cylindrical material with a combined rotary and axial motion. The material rides on a series of balls which are retained in a guide plate and rotated by bearing against a rotating drum. The drum has a series of conical sections or grooves cut in its outer surface on which the balls ride. The grooves and balls match in such a way that all the balls are caused to rotate about an axis at an angle to the drum axis. This skewed rotation of the ball imparts a longitudinal as well as a rotary motion to the cylinders being conveyed.

Cervical helical axis characteristics and its center of rotation during active head and upper arm movements-comparisons of whiplash-associated disorders, non-specific neck pain and asymptomatic individuals.

PubMed

Grip, Helena; Sundelin, Gunnevi; Gerdle, Björn; Stefan Karlsson, J

2008-09-18

The helical axis model can be used to describe translation and rotation of spine segments. The aim of this study was to investigate the cervical helical axis and its center of rotation during fast head movements (side rotation and flexion/extension) and ball catching in patients with non-specific neck pain or pain due to whiplash injury as compared with matched controls. The aim was also to investigate correlations with neck pain intensity. A finite helical axis model with a time-varying window was used. The intersection point of the axis during different movement conditions was calculated. A repeated-measures ANOVA model was used to investigate the cervical helical axis and its rotation center for consecutive levels of 15 degrees during head movement. Irregularities in axis movement were derived using a zero-crossing approach. In addition, head, arm and upper body range of motion and velocity were observed. A general increase of axis irregularity that correlated to pain intensity was observed in the whiplash group. The rotation center was superiorly displaced in the non-specific neck pain group during side rotation, with the same tendency for the whiplash group. During ball catching, an anterior displacement (and a tendency to an inferior displacement) of the center of rotation and slower and more restricted upper body movements implied a changed movement strategy in neck pain patients, possibly as an attempt to stabilize the cervical spine during head movement.

Adaptive nonlinear control for autonomous ground vehicles

NASA Astrophysics Data System (ADS)

Black, William S.

We present the background and motivation for ground vehicle autonomy, and focus on uses for space-exploration. Using a simple design example of an autonomous ground vehicle we derive the equations of motion. After providing the mathematical background for nonlinear systems and control we present two common methods for exactly linearizing nonlinear systems, feedback linearization and backstepping. We use these in combination with three adaptive control methods: model reference adaptive control, adaptive sliding mode control, and extremum-seeking model reference adaptive control. We show the performances of each combination through several simulation results. We then consider disturbances in the system, and design nonlinear disturbance observers for both single-input-single-output and multi-input-multi-output systems. Finally, we show the performance of these observers with simulation results.

Magnetic steering control of multi-cellular bio-hybrid microswimmers.

PubMed

Carlsen, Rika Wright; Edwards, Matthew R; Zhuang, Jiang; Pacoret, Cecile; Sitti, Metin

2014-10-07

Bio-hybrid devices, which integrate biological cells with synthetic components, have opened a new path in miniaturized systems with the potential to provide actuation and control for systems down to a few microns in size. Here, we address the challenge of remotely controlling bio-hybrid microswimmers propelled by multiple bacterial cells. These devices have been proposed as a viable method for targeted drug delivery but have also been shown to exhibit stochastic motion. We demonstrate a method of remote magnetic control that significantly reduces the stochasticity of the motion, enabling steering control. The demonstrated microswimmers consist of multiple Serratia marcescens (S. marcescens) bacteria attached to a 6 μm-diameter superparamagnetic bead. We characterize their motion and define the parameters governing their controllability. We show that the microswimmers can be controlled along two-dimensional (2-D) trajectories using weak magnetic fields (≤10 mT) and can achieve 2-D swimming speeds up to 7.3 μm s(-1). This magnetic steering approach can be integrated with sensory-based steering in future work, enabling new control strategies for bio-hybrid microsystems.

Effects of motion and b-matrix correction for high resolution DTI with short-axis PROPELLER-EPI

PubMed Central

Aksoy, Murat; Skare, Stefan; Holdsworth, Samantha; Bammer, Roland

2010-01-01

Short-axis PROPELLER-EPI (SAP-EPI) has been proven to be very effective in providing high-resolution diffusion-weighted and diffusion tensor data. The self-navigation capabilities of SAP-EPI allow one to correct for motion, phase errors, and geometric distortion. However, in the presence of patient motion, the change in the effective diffusion-encoding direction (i.e. the b-matrix) between successive PROPELLER ‘blades’ can decrease the accuracy of the estimated diffusion tensors, which might result in erroneous reconstruction of white matter tracts in the brain. In this study, we investigate the effects of alterations in the b-matrix as a result of patient motion on the example of SAP-EPI DTI and eliminate these effects by incorporating our novel single-step non-linear diffusion tensor estimation scheme into the SAP-EPI post-processing procedure. Our simulations and in-vivo studies showed that, in the presence of patient motion, correcting the b-matrix is necessary in order to get more accurate diffusion tensor and white matter pathway reconstructions. PMID:20222149

Inertial sensor-based smoother for gait analysis.

PubMed

Suh, Young Soo

2014-12-17

An off-line smoother algorithm is proposed to estimate foot motion using an inertial sensor unit (three-axis gyroscopes and accelerometers) attached to a shoe. The smoother gives more accurate foot motion estimation than filter-based algorithms by using all of the sensor data instead of using the current sensor data. The algorithm consists of two parts. In the first part, a Kalman filter is used to obtain initial foot motion estimation. In the second part, the error in the initial estimation is compensated using a smoother, where the problem is formulated in the quadratic optimization problem. An efficient solution of the quadratic optimization problem is given using the sparse structure. Through experiments, it is shown that the proposed algorithm can estimate foot motion more accurately than a filter-based algorithm with reasonable computation time. In particular, there is significant improvement in the foot motion estimation when the foot is moving off the floor: the z-axis position error squared sum (total time: 3.47 s) when the foot is in the air is 0.0807 m2 (Kalman filter) and 0.0020 m2 (the proposed smoother).

Human joint motion estimation for electromyography (EMG)-based dynamic motion control.

PubMed

Zhang, Qin; Hosoda, Ryo; Venture, Gentiane

2013-01-01

This study aims to investigate a joint motion estimation method from Electromyography (EMG) signals during dynamic movement. In most EMG-based humanoid or prosthetics control systems, EMG features were directly or indirectly used to trigger intended motions. However, both physiological and nonphysiological factors can influence EMG characteristics during dynamic movements, resulting in subject-specific, non-stationary and crosstalk problems. Particularly, when motion velocity and/or joint torque are not constrained, joint motion estimation from EMG signals are more challenging. In this paper, we propose a joint motion estimation method based on muscle activation recorded from a pair of agonist and antagonist muscles of the joint. A linear state-space model with multi input single output is proposed to map the muscle activity to joint motion. An adaptive estimation method is proposed to train the model. The estimation performance is evaluated in performing a single elbow flexion-extension movement in two subjects. All the results in two subjects at two load levels indicate the feasibility and suitability of the proposed method in joint motion estimation. The estimation root-mean-square error is within 8.3% ∼ 10.6%, which is lower than that being reported in several previous studies. Moreover, this method is able to overcome subject-specific problem and compensate non-stationary EMG properties.

Period Doubling, Tripling, and Quintupling in the Break-up of a Liquid Jet Driven Transversely to Axis of Motion

NASA Astrophysics Data System (ADS)

Hussein, Salome; Bradley, Stuart; Willmott, Geoff

2017-11-01

The Rayleigh-Plateau instability has been the subject of study for over a century. Many modern technologies now actively take advantage of this phenomenon, from ink-jet printing to fuel injection systems. In pursuit of a precision fluid delivery system, we aimed to design a monodisperse droplet generator. One approach used a piezoelectric element to oscillate the jet transversely to the axis of motion. While at certain frequencies (approx. 1.0kHz) we observed the expected and desired jet breakup behavior, lower frequencies yielded a serpentine profile along the jet, with a node and anti-node, before breaking up. In addition, within a range of driving frequencies, we observed the jet splitting into multiple discrete drop trajectories, intermittently converging back into one in between those instances, then finally entering the region where the RP instability dominated. While initially considered an undesirable aspect of the design, we will demonstrate that these regions are predictable and robust enough to offer a much finer degree of control over spray coverage - as opposed to a binary choice between the pinpoint precision of a monodisperse stream and an imprecise conventional spray. New Zealand Ministry of Business, Innovation, and Employment.

Motion immune diffusion imaging using augmented MUSE (AMUSE) for high-resolution multi-shot EPI

PubMed Central

Guhaniyogi, Shayan; Chu, Mei-Lan; Chang, Hing-Chiu; Song, Allen W.; Chen, Nan-kuei

2015-01-01

Purpose To develop new techniques for reducing the effects of microscopic and macroscopic patient motion in diffusion imaging acquired with high-resolution multi-shot EPI. Theory The previously reported Multiplexed Sensitivity Encoding (MUSE) algorithm is extended to account for macroscopic pixel misregistrations as well as motion-induced phase errors in a technique called Augmented MUSE (AMUSE). Furthermore, to obtain more accurate quantitative DTI measures in the presence of subject motion, we also account for the altered diffusion encoding among shots arising from macroscopic motion. Methods MUSE and AMUSE were evaluated on simulated and in vivo motion-corrupted multi-shot diffusion data. Evaluations were made both on the resulting imaging quality and estimated diffusion tensor metrics. Results AMUSE was found to reduce image blurring resulting from macroscopic subject motion compared to MUSE, but yielded inaccurate tensor estimations when neglecting the altered diffusion encoding. Including the altered diffusion encoding in AMUSE produced better estimations of diffusion tensors. Conclusion The use of AMUSE allows for improved image quality and diffusion tensor accuracy in the presence of macroscopic subject motion during multi-shot diffusion imaging. These techniques should facilitate future high-resolution diffusion imaging. PMID:25762216

Multi-component ground motion response spectra for coupled horizontal, vertical, angular accelerations, and tilt

USGS Publications Warehouse

Kalkan, E.; Graizer, V.

2007-01-01

Rotational and vertical components of ground motion are almost always ignored in design or in the assessment of structures despite the fact that vertical motion can be twice as much as the horizontal motion and may exceed 2g level, and rotational excitation may reach few degrees in the proximity of fault rupture. Coupling of different components of ground excitation may significantly amplify the seismic demand by introducing additional lateral forces and enhanced P-?? effects. In this paper, a governing equation of motion is postulated to compute the response of a SDOF oscillator under a multi-component excitation. The expanded equation includes secondary P-?? components associated with the combined impacts of tilt and vertical excitations in addition to the inertial forcing terms due to the angular and translational accelerations. The elastic and inelastic spectral ordinates traditionally generated considering the uniaxial input motion are compared at the end with the multi-component response spectra of coupled horizontal, vertical and tilting motions. The proposed multi-component response spectrum reflects kinematic characteristics of the ground motion that are not identifiable by the conventional spectrum itself, at least for the near-fault region where high intensity vertical shaking and rotational excitation are likely to occur.

A simple 5-DoF MR-compatible motion signal measurement system.

PubMed

Chung, Soon-Cheol; Kim, Hyung-Sik; Yang, Jae-Woong; Lee, Su-Jeong; Choi, Mi-Hyun; Kim, Ji-Hye; Yeon, Hong-Won; Park, Jang-Yeon; Yi, Jeong-Han; Tack, Gye-Rae

2011-09-01

The purpose of this study was to develop a simple motion measurement system with magnetic resonance (MR) compatibility and safety. The motion measurement system proposed here can measure 5-DoF motion signals without deteriorating the MR images, and it has no effect on the intense and homogeneous main magnetic field, the temporal-gradient magnetic field (which varies rapidly with time), the transceiver radio frequency (RF) coil, and the RF pulse during MR data acquisition. A three-axis accelerometer and a two-axis gyroscope were used to measure 5-DoF motion signals, and Velcro was used to attach a sensor module to a finger or wrist. To minimize the interference between the MR imaging system and the motion measurement system, nonmagnetic materials were used for all electric circuit components in an MR shield room. To remove the effect of RF pulse, an amplifier, modulation circuit, and power supply were located in a shielded case, which was made of copper and aluminum. The motion signal was modulated to an optic signal using pulse width modulation, and the modulated optic signal was transmitted outside the MR shield room using a high-intensity light-emitting diode and an optic cable. The motion signal was recorded on a PC by demodulating the transmitted optic signal into an electric signal. Various kinematic variables, such as angle, acceleration, velocity, and jerk, can be measured or calculated by using the motion measurement system developed here. This system also enables motion tracking by extracting the position information from the motion signals. It was verified that MR images and motion signals could reliably be measured simultaneously.

Role of orientation reference selection in motion sickness

NASA Technical Reports Server (NTRS)

Peterka, Robert J.; Black, F. Owen

1992-01-01

The overall objective of this proposal is to understand the relationship between human orientation control and motion sickness susceptibility. Three areas related to orientation control will be investigated. These three areas are (1) reflexes associated with the control of eye movements and posture, (2) the perception of body rotation and position with respect to gravity, and (3) the strategies used to resolve sensory conflict situations which arise when different sensory systems provide orientation cues which are not consistent with one another or with previous experience. Of particular interest is the possibility that a subject may be able to ignore an inaccurate sensory modality in favor of one or more other sensory modalities which do provide accurate orientation reference information. We refer to this process as sensory selection. This proposal will attempt to quantify subjects' sensory selection abilities and determine if this ability confers some immunity to the development of motion sickness symptoms. Measurements of reflexes, motion perception, sensory selection abilities, and motion sickness susceptibility will concentrate on pitch and roll motions since these seem most relevant to the space motion sickness problem. Vestibulo-ocular (VOR) and oculomotor reflexes will be measured using a unique two-axis rotation device developed in our laboratory over the last seven years. Posture control reflexes will be measured using a movable posture platform capable of independently altering proprioceptive and visual orientation cues. Motion perception will be quantified using closed loop feedback technique developed by Zacharias and Young (Exp Brain Res, 1981). This technique requires a subject to null out motions induced by the experimenter while being exposed to various confounding sensory orientation cues. A subject's sensory selection abilities will be measured by the magnitude and timing of his reactions to changes in sensory environments. Motion sickness susceptibility will be measured by the time required to induce characteristic changes in the pattern of electrogastrogram recordings while exposed to various sensory environments during posture and motion perception tests. The results of this work are relevant to NASA's interest in understanding the etiology of space motion sickness. If any of the reflex, perceptual, or sensory selection abilities of subjects are found to correlate with motion sickness susceptibility, this work may be an important step in suggesting a method of predicting motion sickness susceptibility. If sensory selection can provide a means to avoid sensory conflict, then further work may lead to training programs which could enhance a subject's sensory selection ability and therefore minimize motion sickness susceptibility.

Shot H3837: Darht's first dual-axis explosive experiment

NASA Astrophysics Data System (ADS)

Harsh, James F.; Hull, Lawrence; Mendez, Jacob; McNeil, Wendy Vogan

2012-03-01

Test H3837 was the first explosive shot performed in front of both flash x-ray axes at the Los Alamos Dual Axis Radiographic Hydrodynamic Test (DARHT) facility. Executed in November 2009, the shot was an explosively-driven metal flyer plate in a series of experiments designed to explore equation-of-state properties of shocked materials. Imaging the initial shock wave traveling through the flyer plate, DARHT Axis II captured the range of motion from the shock front emergence in the flyer to breakout at the free surface; the Axis I pulse provided a perpendicular perspective of the shot at a time coinciding with the third pulse of Axis II.

Studies of the Interactions Between Vestibular Function and Tactual Orientation Display Systems

NASA Technical Reports Server (NTRS)

Cholewiak, Roger W.; Reschke, Millard F.

1997-01-01

When humans experience conditions in which internal vestibular cues to movement or spatial location are challenged or contradicted by external visual information, the result can be spatial disorientation, often leading to motion sickness. Spatial disorientation can occur in any situation in which the individual is passively moved in the environment, but is most common in automotive, aircraft, or undersea travel. Significantly, the incidence of motion sickness in space travel is great: The majority of individuals in Shuttle operations suffer from the syndrome. Even after the space-sickness-producing influences of spatial disorientation dissipate, usually within several days, there are other situations in which, because of the absence of reliable or familiar vestibular cues, individuals in space still experience disorientation, resulting in a reliance on the already preoccupied sense of vision. One possible technique to minimize the deleterious effects of spatial disorientation might be to present attitude information (including orientation, direction, and motion) through another less-used sensory modality - the sense of touch. Data from experiences with deaf and blind persons indicate that this channel can provide useful communication and mobility information on a real-time basis. More recently, technologies have developed to present effective attitude information to pilots in situations in which dangerously ambiguous and conflicting visual and vestibular sensations occur. This summers project at NASA-Johnson Space Center will evaluate the influence of motion-based spatial disorientation on the perception of tactual stimuli representing veridical position and orientation information, presented by new dynamic vibrotactile array display technologies. In addition, the possibility will be explored that tactile presentations of motion and direction from this alternative modality might be useful in mitigating or alleviating spatial disorientation produced by multi-axis rotatory systems, monitored by physiological recording techniques developed at JSC.

Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions

NASA Astrophysics Data System (ADS)

Varshney, Kapil; Chang, Song; Wang, Z. Jane

2013-05-01

Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

Unsteady aerodynamic forces and torques on falling parallelograms in coupled tumbling-helical motions.

PubMed

Varshney, Kapil; Chang, Song; Wang, Z Jane

2013-05-01

Falling parallelograms exhibit coupled motion of autogyration and tumbling, similar to the motion of falling tulip seeds, unlike maple seeds which autogyrate but do not tumble, or rectangular cards which tumble but do not gyrate. This coupled tumbling and autogyrating motion are robust, when card parameters, such as aspect ratio, internal angle, and mass density, are varied. We measure the three-dimensional (3D) falling kinematics of the parallelograms and quantify their descending speed, azimuthal rotation, tumbling rotation, and cone angle in each falling. The cone angle is insensitive to the variation of the card parameters, and the card tumbling axis does not overlap with but is close to the diagonal axis. In addition to this connection to the dynamics of falling seeds, these trajectories provide an ideal set of data to analyze 3D aerodynamic force and torque at an intermediate range of Reynolds numbers, and the results will be useful for constructing 3D aerodynamic force and torque models. Tracking these free falling trajectories gives us a nonintrusive method for deducing instantaneous aerodynamic forces. We determine the 3D aerodynamic forces and torques based on Newton-Euler equations. The dynamical analysis reveals that, although the angle of attack changes dramatically during tumbling, the aerodynamic forces have a weak dependence on the angle of attack. The aerodynamic lift is dominated by the coupling of translational and rotational velocities. The aerodynamic torque has an unexpectedly large component perpendicular to the card. The analysis of the Euler equation suggests that this large torque is related to the deviation of the tumbling axis from the principle axis of the card.

Domain wall kinetics of lithium niobate single crystals near the hexagonal corner

NASA Astrophysics Data System (ADS)

Choi, Ju Won; Ko, Do-Kyeong; Yu, Nan Ei; Kitamura, Kenji; Ro, Jung Hoon

2015-03-01

A mesospheric approach based on a simple microscopic 2D Ising model in a hexagonal lattice plane is proposed to explain macroscopic "asymmetric in-out domain wall motion" observation in the (0001) plane of MgO-doped stoichiometric lithium niobate. Under application of an electric field that was higher than the conventional coercive field (Ec) to the ferroelectric crystal, a natural hexagonal domain was obtained with walls that were parallel to the Y-axis of the crystal. When a fraction of the coercive field of around 0.1Ec is applied in the reverse direction, this hexagonal domain is shrunk (moved inward) from the corner site into a shape with a corner angle of around 150° and 15° wall slopes to the Y-axis. A flipped electric field of 0.15Ec is then applied to recover the natural hexagonal shape, and the 150° corner shape changes into a flat wall with 30° slope (moved outward). The differences in corner domain shapes between inward and outward domain motion were analyzed theoretically in terms of corner and wall site energies, which are described using the domain corner angle and wall slope with respect to the crystal Y-axis, respectively. In the inward domain wall motion case, the energy levels of the evolving 150° domain corner and 15° slope walls are most competitive, and could co-exist. In the outward case, the energy levels of corners with angles >180° are highly stable when compared with the possible domain walls; only a flat wall with 30° slope to the Y-axis is possible during outward motion.

[Evaluation of echocardiographic left ventricular wall motion analysis supported by internet picture viewing system].

PubMed

Hirano, Yutaka; Ikuta, Shin-Ichiro; Nakano, Manabu; Akiyama, Seita; Nakamura, Hajime; Nasu, Masataka; Saito, Futoshi; Nakagawa, Junichi; Matsuzaki, Masashi; Miyazaki, Shunichi

2007-02-01

Assessment of deterioration of regional wall motion by echocardiography is not only subjective but also features difficulties with interobserver agreement. Progress in digital communication technology has made it possible to send video images from a distant location via the Internet. The possibility of evaluating left ventricular wall motion using video images sent via the Internet to distant institutions was evaluated. Twenty-two subjects were randomly selected. Four sets of video images (parasternal long-axis view, parasternal short-axis view, apical four-chamber view, and apical two-chamber view) were taken for one cardiac cycle. The images were sent via the Internet to two institutions (observer C in facility A and observers D and E in facility B) for evaluation. Great care was taken to prevent disclosure of patient information to these observers. Parasternal long-axis images were divided into four segments, and the parasternal short-axis view, apical four-chamber view, and apical two-chamber view were divided into six segments. One of the following assessments, normokinesis, hypokinesis, akinesis, or dyskinesis, was assigned to each segment. The interobserver rates of agreement in judgments between observers C and D, observers C and E, and intraobserver agreement rate (for observer D) were calculated. The rate of interobserver agreement was 85.7% (394/460 segments; Kappa = 0.65) between observers C and D, 76.7% (353/460 segments; Kappa = 0.39) between observers D and E, and 76.3% (351/460 segments; Kappa = 0.36)between observers C and E, and intraobserver agreement was 94.3% (434/460; Kappa = 0.86). Segments of difference judgments between observers C and D were normokinesis-hypokinesis; 62.1%, hypokinesis-akinesis; 33.3%, akinesis-dyskinesis; 3.0%, and normokinesis-akinesis; 1.5%. Wall motion can be evaluated at remote institutions via the Internet.

Three-dimensional ballistocardiography and respiratory motion in sustained microgravity

NASA Technical Reports Server (NTRS)

Prisk, G. K.; Verhaeghe, S.; Padeken, D.; Hamacher, H.; Paiva, M.; West, J. B. (Principal Investigator)

2001-01-01

BACKGROUND: We measured the three-dimensional ballistocardiogram (BCG) in a free-floating subject in sustained microgravity during spaceflight to test the usefulness of such measurements for future non-invasive monitoring of cardiac function, and to examine the effects of respiratory movement on the BCG in three axes. METHODS: Acceleration was measured using a three-axis accelerometer fastened to the lumbar region of the subject while simultaneous recordings of ECG, and respiratory motion via impedance plethysmography were also made. Data were recorded during a 146-s period of inactivity on the part of the subject during which time there was no contact with the spacecraft. RESULTS: Total body motion due to respiratory activity was consistent with that calculated from the known action of the diaphragm and conservation of momentum. The accelerations due to cardiac activity, ensemble averaged over the R-R interval, were greatest along the head-to-foot axis. Maximum amplitude of the HIJK complex of the BCG generated by ventricular ejection was greatest in the head to foot axis (approximately 70 x 10(-3) m x s(-2)), but there were also substantial accelerations along the dorsoventral axis of up to 43 10(-3) m x s(-2), that are not measured interrestrial two-dimensional studies. The amplitude of the BCG was strongly affected by lung volume, with accelerations being reduced 50 to 70% between end-inspiration and end-expiration. CONCLUSIONS: These data suggest a greatly reduced transmission of the cardiac motion to the body at end-expiration (FRC) than at higher lung volumes. The BCG might be further developed as a non-invasive means of monitoring parameters such as stroke volume in microgravity.

Compressive Video Recovery Using Block Match Multi-Frame Motion Estimation Based on Single Pixel Cameras

PubMed Central

Bi, Sheng; Zeng, Xiao; Tang, Xin; Qin, Shujia; Lai, King Wai Chiu

2016-01-01

Compressive sensing (CS) theory has opened up new paths for the development of signal processing applications. Based on this theory, a novel single pixel camera architecture has been introduced to overcome the current limitations and challenges of traditional focal plane arrays. However, video quality based on this method is limited by existing acquisition and recovery methods, and the method also suffers from being time-consuming. In this paper, a multi-frame motion estimation algorithm is proposed in CS video to enhance the video quality. The proposed algorithm uses multiple frames to implement motion estimation. Experimental results show that using multi-frame motion estimation can improve the quality of recovered videos. To further reduce the motion estimation time, a block match algorithm is used to process motion estimation. Experiments demonstrate that using the block match algorithm can reduce motion estimation time by 30%. PMID:26950127

A separation of antiferromagnetic spin motion modes in the training effect of exchange biased Co/CoO film with in-plane anisotropy

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

Wu, R.; Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS; Yun, C.

2016-08-07

The motion of antiferromagnetic interfacial spins is investigated through the temperature evolution of training effect in a Co/CoO film with in-plane biaxial anisotropy. Significant differences in the training effect and its temperature dependence are observed in the magnetic easy axis and hard axis (HA) and ascribed to the different motion modes of antiferromagnetic interfacial spins, the collective spin cluster rotation (CSR) and the single spin reversal (SSR), caused by different magnetization reversal modes of ferromagnetic layer. These motion modes of antiferromagnetic spins are successfully separated using a combination of an exponential function and a classic n{sup −1/2} function. A largermore » CSR to SSR ratio and a shorter lifetime of CSR found in the HA indicates that the domain rotation in the ferromagnetic layer tends to activate and accelerate a CSR mode in the antiferromagnetic spins.« less

Application of dragonfly algorithm for optimal performance analysis of process parameters in turn-mill operations- A case study

NASA Astrophysics Data System (ADS)

Vikram, K. Arun; Ratnam, Ch; Lakshmi, VVK; Kumar, A. Sunny; Ramakanth, RT

2018-02-01

Meta-heuristic multi-response optimization methods are widely in use to solve multi-objective problems to obtain Pareto optimal solutions during optimization. This work focuses on optimal multi-response evaluation of process parameters in generating responses like surface roughness (Ra), surface hardness (H) and tool vibration displacement amplitude (Vib) while performing operations like tangential and orthogonal turn-mill processes on A-axis Computer Numerical Control vertical milling center. Process parameters like tool speed, feed rate and depth of cut are considered as process parameters machined over brass material under dry condition with high speed steel end milling cutters using Taguchi design of experiments (DOE). Meta-heuristic like Dragonfly algorithm is used to optimize the multi-objectives like ‘Ra’, ‘H’ and ‘Vib’ to identify the optimal multi-response process parameters combination. Later, the results thus obtained from multi-objective dragonfly algorithm (MODA) are compared with another multi-response optimization technique Viz. Grey relational analysis (GRA).

Customization, control, and characterization of a commercial haptic device for high-fidelity rendering of weak forces.

PubMed

Gurari, Netta; Baud-Bovy, Gabriel

2014-09-30

The emergence of commercial haptic devices offers new research opportunities to enhance our understanding of the human sensory-motor system. Yet, commercial device capabilities have limitations which need to be addressed. This paper describes the customization of a commercial force feedback device for displaying forces with a precision that exceeds the human force perception threshold. The device was outfitted with a multi-axis force sensor and closed-loop controlled to improve its transparency. Additionally, two force sensing resistors were attached to the device to measure grip force. Force errors were modeled in the frequency- and time-domain to identify contributions from the mass, viscous friction, and Coulomb friction during open- and closed-loop control. The effect of user interaction on system stability was assessed in the context of a user study which aimed to measure force perceptual thresholds. Findings based on 15 participants demonstrate that the system maintains stability when rendering forces ranging from 0-0.20 N, with an average maximum absolute force error of 0.041 ± 0.013 N. Modeling the force errors revealed that Coulomb friction and inertia were the main contributors to force distortions during respectively slow and fast motions. Existing commercial force feedback devices cannot render forces with the required precision for certain testing scenarios. Building on existing robotics work, this paper shows how a device can be customized to make it reliable for studying the perception of weak forces. The customized and closed-loop controlled device is suitable for measuring force perceptual thresholds. Copyright © 2014 Elsevier B.V. All rights reserved.

Control theory analysis of a three-axis VTOL flight director. M.S. Thesis - Pennsylvania State Univ.

NASA Technical Reports Server (NTRS)

Niessen, F. R.

1971-01-01

A control theory analysis of a VTOL flight director and the results of a fixed-based simulator evaluation of the flight-director commands are discussed. The VTOL configuration selected for this study is a helicopter-type VTOL which controls the direction of the thrust vector by means of vehicle-attitude changes and, furthermore, employs high-gain attitude stabilization. This configuration is the same as one which was simulated in actual instrument flight tests with a variable stability helicopter. Stability analyses are made for each of the flight-director commands, assuming a single input-output, multi-loop system model for each control axis. The analyses proceed from the inner-loops to the outer-loops, using an analytical pilot model selected on the basis of the innermost-loop dynamics. The time response of the analytical model of the system is primarily used to adjust system gains, while root locus plots are used to identify dominant modes and mode interactions.

A Multi-wavelength Study of an Isolated MSP Bow Shock

NASA Astrophysics Data System (ADS)

Romani, Roger W.; Slane, Patrick; Green, Andrew

2017-08-01

PSR J2124-3358 is the only single MSP known to sport an Halpha bow shock. This shock, now also seen in the UV, encloses an unusual X-ray pulsar wind nebula (PWN) with a long off-axis trail. Combining the X-ray and UV images with AAT/KOALA integral field spectroscopy of the Halpha emission, we have an unusually complete picture of the pulsar's (101 km/s transverse) motion and the latitudinal distribution of its wind flux. These images reveal the 3-D orientation of a hard-spectrum PWN jet and a softer equatorial outflow. Within the context of a thin shock model, we can constrain the total energy output of the pulsar and the neutron star moment of inertia. The IFU spectra show extreme Balmer dominance, which also constrains the nature of the UV shock emission.

Design and control of a multi-DOF micromanipulator dedicated to multiscale micromanipulation

NASA Astrophysics Data System (ADS)

Yang, Yi-Ling; Wei, Yan-Ding; Lou, Jun-Qiang; Fu, Lei; Fang, Sheng

2017-11-01

This paper presents the design, implementation and control of a new piezoelectrically actuated compliant micromanipulator dedicated to multiscale, precision and reliable operations. To begin with, the manipulator is devised to obtain multi degrees of freedom and large workspace ranges. Two-stage amplification mechanisms (consists of the leverage and the rocker mechanisms) and composite parallelogram mechanisms are combined to construct the lower microstage. Meanwhile, the structure design of the upper dual-driven microgripper is based on the bridge-type mechanism and the unilateral parallelogram mechanism. Through finite-element analysis, the structural parameters of the micromanipulator are optimized and the structural interaction performances are examined. Moreover, a cooperative control strategy is proposed to achieve the synchronous control of the motion trajectory, the gripper position and the contact force. Precision motion control in terms of the hysteresis phenomenon and system disturbances is ensured by using an adaptive sliding mode control (SMC). In particular, an improved nonsymmetrical Bouc-Wen model and a fuzzy regulator are proposed in the SMC. Several experimental investigations are conducted to validate the effectiveness of the developed micromanipulator by performing transferring operations of a micro-object. Experimental results demonstrate that the micromanipulator presents good characteristics, and precision and robust operation can be acquired using the cooperative controller.

Tilt-rotor flutter control in cruise flight

NASA Technical Reports Server (NTRS)

Nasu, Ken-Ichi

1986-01-01

Tilt-rotor flutter control under cruising operation is analyzed. The rotor model consists of a straight fixed wing, a pylon attached to the wingtip, and a three-blade rotor. The wing is cantilevered to the fuselage and is allowed to bend forward and upward. It also has a torsional degree of freedom about the elastic axis. Each rotor blade has two bending degrees of freedom. Feedback of wingtip velocity and acceleration to cyclic pitch is investigated for flutter control, using strip theory and linearized equations of motion. To determine the feedback gain, an eigenvalue analysis is performed. A second, independent, timewise calculation is conducted to evaluate the control law while employing more sophisticated aerodynamics. The effectiveness of flutter control by cyclic pitch change was confirmed.

Modeling and tachometer feedback in the control of an experimental single link flexible structure

NASA Technical Reports Server (NTRS)

Garcia, Ephrahim; Inman, Daniel J.

1990-01-01

In this work a formulation for the modeling of a single link flexible structure will be introduced that includes the effects of dynamic interaction between the actuator and structure. These effects are the rotational modal participation factors for the structure's vibratory motion that occurs at the slewing axis. It will be shown, both theoretically and experimentally, that this dynamic interaction can be advantageous for vibration suppression of the flexible modes of the system during slewing positioning maneuvers.

Strong Motion Seismograph Based On MEMS Accelerometer

NASA Astrophysics Data System (ADS)

Teng, Y.; Hu, X.

2013-12-01

The MEMS strong motion seismograph we developed used the modularization method to design its software and hardware.It can fit various needs in different application situation.The hardware of the instrument is composed of a MEMS accelerometer,a control processor system,a data-storage system,a wired real-time data transmission system by IP network,a wireless data transmission module by 3G broadband,a GPS calibration module and power supply system with a large-volumn lithium battery in it. Among it,the seismograph's sensor adopted a three-axis with 14-bit high resolution and digital output MEMS accelerometer.Its noise level just reach about 99μg/√Hz and ×2g to ×8g dynamically selectable full-scale.Its output data rates from 1.56Hz to 800Hz. Its maximum current consumption is merely 165μA,and the device is so small that it is available in a 3mm×3mm×1mm QFN package. Furthermore,there is access to both low pass filtered data as well as high pass filtered data,which minimizes the data analysis required for earthquake signal detection. So,the data post-processing can be simplified. Controlling process system adopts a 32-bit low power consumption embedded ARM9 processor-S3C2440 and is based on the Linux operation system.The processor's operating clock at 400MHz.The controlling system's main memory is a 64MB SDRAM with a 256MB flash-memory.Besides,an external high-capacity SD card data memory can be easily added.So the system can meet the requirements for data acquisition,data processing,data transmission,data storage,and so on. Both wired and wireless network can satisfy remote real-time monitoring, data transmission,system maintenance,status monitoring or updating software.Linux was embedded and multi-layer designed conception was used.The code, including sensor hardware driver,the data acquisition,earthquake setting out and so on,was written on medium layer.The hardware driver consist of IIC-Bus interface driver, IO driver and asynchronous notification driver. The application program layer mainly concludes: earthquake parameter module, local database managing module, data transmission module, remote monitoring, FTP service and so on. The application layer adopted multi-thread process. The whole strong motion seismograph was encapsulated in a small aluminum box, which size is 80mm×120mm×55mm. The inner battery can work continuesly more than 24 hours. The MEMS accelerograph uses modular design for its software part and hardware part. It has remote software update function and can meet the following needs: a) Auto picking up the earthquake event; saving the data on wave-event files and hours files; It may be used for monitoring strong earthquake, explosion, bridge and house health. b) Auto calculate the earthquake parameters, and transferring those parameters by 3G wireless broadband network. This kind of seismograph has characteristics of low cost, easy installation. They can be concentrated in the urban region or areas need to specially care. We can set up a ground motion parameters quick report sensor network while large earthquake break out. Then high-resolution-fine shake-map can be easily produced for the need of emergency rescue. c) By loading P-wave detection program modules, it can be used for earthquake early warning for large earthquakes; d) Can easily construct a high-density layout seismic monitoring network owning remote control and modern intelligent earthquake sensor.

Adaptive metalenses with simultaneous electrical control of focal length, astigmatism, and shift.

PubMed

She, Alan; Zhang, Shuyan; Shian, Samuel; Clarke, David R; Capasso, Federico

2018-02-01

Focal adjustment and zooming are universal features of cameras and advanced optical systems. Such tuning is usually performed longitudinally along the optical axis by mechanical or electrical control of focal length. However, the recent advent of ultrathin planar lenses based on metasurfaces (metalenses), which opens the door to future drastic miniaturization of mobile devices such as cell phones and wearable displays, mandates fundamentally different forms of tuning based on lateral motion rather than longitudinal motion. Theory shows that the strain field of a metalens substrate can be directly mapped into the outgoing optical wavefront to achieve large diffraction-limited focal length tuning and control of aberrations. We demonstrate electrically tunable large-area metalenses controlled by artificial muscles capable of simultaneously performing focal length tuning (>100%) as well as on-the-fly astigmatism and image shift corrections, which until now were only possible in electron optics. The device thickness is only 30 μm. Our results demonstrate the possibility of future optical microscopes that fully operate electronically, as well as compact optical systems that use the principles of adaptive optics to correct many orders of aberrations simultaneously.

A method to determine the orientation of the upper arm about its longitudinal axis during dynamic motions.

PubMed

Gordon, Brian J; Dapena, Jesús

2013-01-04

Inaccuracy in determining the orientation of the upper arm about its longitudinal axis (twist orientation) has been a pervasive problem in sport biomechanics research. The purpose of this study was to develop a method to improve the calculation of the upper arm twist orientation in dynamic sports activities. The twist orientation of the upper arm is defined by the orientation of its mediolateral axis. The basis for the new method is that at any angle in the flexion/extension range of an individual's elbow, it is possible to define a true mediolateral axis and also a surrogate mediolateral axis perpendicular to the plane containing the shoulder, elbow and wrist joints. The difference between the twist orientations indicated by these two versions of the mediolateral axis will vary from one elbow angle to another, but if the elbow joint deforms equally in different activities, for any given subject the difference should be constant at any given value of the elbow angle. Application of the new method required individuals to execute sedate elbow extension trials prior to the dynamic trials. Three-dimensional motion analysis of the sedate extension trials allowed quantification of the difference between the true and surrogate mediolateral axes for all angles in the entire flexion/extension range of an individual's elbow. This made it possible to calculate in any dynamic trial the twist orientation defined by the true mediolateral axis from the twist orientation defined by the surrogate mediolateral axis. The method was tested on a wooden model of the arm. Copyright © 2012 Elsevier Ltd. All rights reserved.

An investigation into the vertical axis control power requirements for landing VTOL type aircraft onboard nonaviation ships in various sea states

NASA Technical Reports Server (NTRS)

Stevens, M. E.; Roskam, J.

1985-01-01

The problem of determining the vertical axis control requirements for landing a VTOL aircraft on a moving ship deck in various sea states is examined. Both a fixed-base piloted simulation and a nonpiloted simulation were used to determine the landing performance as influenced by thrust-to-weight ratio, vertical damping, and engine lags. The piloted simulation was run using a fixed-based simulator at Ames Research center. Simplified versions of an existing AV-8A Harrier model and an existing head-up display format were used. The ship model used was that of a DD963 class destroyer. Simplified linear models of the pilot, aircraft, ship motion, and ship air-wake turbulence were developed for the nonpiloted simulation. A unique aspect of the nonpiloted simulation was the development of a model of the piloting strategy used for shipboard landing. This model was refined during the piloted simulation until it provided a reasonably good representation of observed pilot behavior.

Two-degrees-of-freedom piezo-driven fast steering mirror with cross-axis decoupling capability

NASA Astrophysics Data System (ADS)

Shao, Shubao; Tian, Zheng; Song, Siyang; Xu, Minglong

2018-05-01

Because mechanical cross coupling between its axes would lead to degradation of the scanning precision of a piezo-driven fast steering mirror (PFSM), a two-degrees-of-freedom (2-DoF) PFSM with a cross-axis decoupling capability, in which 2-DoF flexure hinges are used, is proposed in this work. The overall structure of the proposed PFSM is first introduced and then both static and dynamic models are established analytically; in addition, the decoupling mechanism is described in detail and the low dynamic cross coupling ratios that occur between the two DoFs are shown. Because of the decoupling property of the PFSM, the 2-DoF motion is treated as a combination of two independent one-degree-of-freedom (1-DoF) motions and two independent proportional-integral-derivative controllers are thus used separately in the control of the two DoFs. Based on this control strategy, experiments involving both 1-DoF trajectory tracking and 2-DoF trajectory tracking are implemented. The test results show that the proposed PFSM can achieve the tilt range of ±7 mrad for both axes with the low coupling ratios that are less than 2% (-34 dB), and the bandwidths of both axes are higher than 810 Hz; in addition, the maximal tracking full scale range errors for 1-DoF trajectory tracking and 2-DoF trajectory tracking are less than 0.2% and 1%, respectively, where the larger error of 2-DoF trajectory tracking is mainly caused by the remaining cross coupling between axes.

Remote control for motor vehicle

NASA Technical Reports Server (NTRS)

Johnson, Dale R. (Inventor); Ciciora, John A. (Inventor)

1984-01-01

A remote controller is disclosed for controlling the throttle, brake and steering mechanism of a conventional motor vehicle, with the remote controller being particularly advantageous for use by severely handicapped individuals. The controller includes a remote manipulator which controls a plurality of actuators through interfacing electronics. The remote manipulator is a two-axis joystick which controls a pair of linear actuators and a rotary actuator, with the actuators being powered by electric motors to effect throttle, brake and steering control of a motor vehicle adapted to include the controller. The controller enables the driver to control the adapted vehicle from anywhere in the vehicle with one hand with minimal control force and range of motion. In addition, even though a conventional vehicle is adapted for use with the remote controller, the vehicle may still be operated in the normal manner.

Relationship between selected orientation rest frame, circular vection and space motion sickness

NASA Technical Reports Server (NTRS)

Harm, D. L.; Parker, D. E.; Reschke, M. F.; Skinner, N. C.

1998-01-01

Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration.

Motion state analysis of space target based on optical cross section

NASA Astrophysics Data System (ADS)

Tian, Qichen; Li, Zhi; Xu, Can; Liu, Chenghao

2017-10-01

In order to solve the problem that the movement state analysis method of the space target based on OCS is not related to the real motion state. This paper proposes a method based on OCS for analyzing the state of space target motion. This paper first establish a three-dimensional model of real STSS satellite, then change the satellite's surface into element, and assign material to each panel according to the actual conditions of the satellite. This paper set up a motion scene according to the orbit parameters of STSS satellite in STK, and the motion states are set to three axis steady state and slowly rotating unstable state respectively. In these two states, the occlusion condition of the surface element is firstly determined, and the effective face element is selected. Then, the coordinates of the observation station and the solar coordinates in the satellite body coordinate system are input into the OCS calculation program, and the OCS variation curves of the three axis steady state and the slow rotating unstable state STSS satellite are obtained. Combining the satellite surface structure and the load situation, the OCS change curve of the three axis stabilized satellite is analyzed, and the conclude that the OCS curve fluctuates up and down when the sunlight is irradiated to the load area; By using Spectral analysis method, autocorrelation analysis and the cross residual method, the rotation speed of OCS satellite in slow rotating unstable state is analyzed, and the rotation speed of satellite is successfully reversed. By comparing the three methods, it is found that the cross residual method is more accurate.

Fabrication of micro-lens array on convex surface by meaning of micro-milling

NASA Astrophysics Data System (ADS)

Zhang, Peng; Du, Yunlong; Wang, Bo; Shan, Debin

2014-08-01

In order to develop the application of the micro-milling technology, and to fabricate ultra-precision optical surface with complex microstructure, in this paper, the primary experimental research on micro-milling complex microstructure array is carried out. A complex microstructure array surface with vary parameters is designed, and the mathematic model of the surface is set up and simulated. For the fabrication of the designed microstructure array surface, a micro three-axis ultra-precision milling machine tool is developed, aerostatic guideway drove directly by linear motor is adopted in order to guarantee the enough stiffness of the machine, and novel numerical control strategy with linear encoders of 5nm resolution used as the feedback of the control system is employed to ensure the extremely high motion control accuracy. With the help of CAD/CAM technology, convex micro lens array on convex spherical surface with different scales on material of polyvinyl chloride (PVC) and pure copper is fabricated using micro tungsten carbide ball end milling tool based on the ultra-precision micro-milling machine. Excellent nanometer-level micro-movement performance of the axis is proved by motion control experiment. The fabrication is nearly as the same as the design, the characteristic scale of the microstructure is less than 200μm and the accuracy is better than 1μm. It prove that ultra-precision micro-milling technology based on micro ultra-precision machine tool is a suitable and optional method for micro manufacture of microstructure array surface on different kinds of materials, and with the development of micro milling cutter, ultraprecision micro-milling complex microstructure surface will be achieved in future.

Inertial acceleration as a measure of linear vection: An alternative to magnitude estimation. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Carpenter-Smith, Theodore R.; Futamura, Robert G.; Parker, Donald E.

1995-01-01

The present study focused on the development of a procedure to assess perceived self-motion induced by visual surround motion - vection. Using an apparatus that permitted independent control of visual and inertial stimuli, prone observers were translated along their head x-axis (fore/aft). The observers' task was to report the direction of self-motion during passive forward and backward translations of their bodies coupled with exposure to various visual surround conditions. The proportion of 'forward' responses was used to calculate each observer's point of subjective equality (PSE) for each surround condition. The results showed that the moving visual stimulus produced a significant shift in the PSE when data from the moving surround condition were compared with the stationary surround and no-vision condition. Further, the results indicated that vection increased monotonically with surround velocities between 4 and 40/s. It was concluded that linear vection can be measured in terms of changes in the amplitude of whole-body inertial acceleration required to elicit equivalent numbers of 'forward' and 'backward' self-motion reports.

Influence of Vibrotactile Feedback on Controlling Tilt Motion After Spaceflight

NASA Technical Reports Server (NTRS)

Wood, S. J.; Rupert, A. H.; Vanya, R. D.; Esteves, J. T.; Clement, G.

2011-01-01

We hypothesize that adaptive changes in how inertial cues from the vestibular system are integrated with other sensory information leads to perceptual disturbances and impaired manual control following transitions between gravity environments. The primary goals of this ongoing post-flight investigation are to quantify decrements in manual control of tilt motion following short-duration spaceflight and to evaluate vibrotactile feedback of tilt as a sensorimotor countermeasure. METHODS. Data is currently being collected on 9 astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation (216 deg/s, <20 cm radius) in a darkened room is utilized to elicit otolith reflexes in the lateral plane without concordant canal or visual cues. A Tilt-Translation Sled (TTS) is capable of synchronizing pitch tilt with fore-aft translation to align the resultant gravitoinertial vector with the longitudinal body axis, thereby eliciting canal reflexes without concordant otolith or visual cues. A simple 4 tactor system was implemented to provide feedback when tilt position exceeded predetermined levels in either device. Closed-loop nulling tasks are performed during random tilt steps or sum-of-sines (TTS only) with and without vibrotactile feedback of chair position. RESULTS. On landing day the manual control performance without vibrotactile feedback was reduced by >30% based on the gain or the amount of tilt disturbance successfully nulled. Manual control performance tended to return to baseline levels within 1-2 days following landing. Root-mean-square position error and tilt velocity were significantly reduced with vibrotactile feedback. CONCLUSIONS. These preliminary results are consistent with our hypothesis that adaptive changes in vestibular processing corresponds to reduced manual control performance following G-transitions. A simple vibrotactile prosthesis improves the ability to null out tilt motion within a limited range of motion disturbances.

A multilevel control system for the large space telescope. [numerical analysis/optimal control

NASA Technical Reports Server (NTRS)

Siljak, D. D.; Sundareshan, S. K.; Vukcevic, M. B.

1975-01-01

A multilevel scheme was proposed for control of Large Space Telescope (LST) modeled by a three-axis-six-order nonlinear equation. Local controllers were used on the subsystem level to stabilize motions corresponding to the three axes. Global controllers were applied to reduce (and sometimes nullify) the interactions among the subsystems. A multilevel optimization method was developed whereby local quadratic optimizations were performed on the subsystem level, and global control was again used to reduce (nullify) the effect of interactions. The multilevel stabilization and optimization methods are presented as general tools for design and then used in the design of the LST Control System. The methods are entirely computerized, so that they can accommodate higher order LST models with both conceptual and numerical advantages over standard straightforward design techniques.

A study of numerical methods of solution of the equations of motion of a controlled satellite under the influence of gravity gradient torque

NASA Technical Reports Server (NTRS)

Thompson, J. F.; Mcwhorter, J. C.; Siddiqi, S. A.; Shanks, S. P.

1973-01-01

Numerical methods of integration of the equations of motion of a controlled satellite under the influence of gravity-gradient torque are considered. The results of computer experimentation using a number of Runge-Kutta, multi-step, and extrapolation methods for the numerical integration of this differential system are presented, and particularly efficient methods are noted. A large bibliography of numerical methods for initial value problems for ordinary differential equations is presented, and a compilation of Runge-Kutta and multistep formulas is given. Less common numerical integration techniques from the literature are noted for further consideration.

On a model of the processes of maintaining a technological area by a manipulator

NASA Astrophysics Data System (ADS)

Ghukasyan, A. A.; Ordyan, A. Ya

2018-04-01

The research refers to the results of mathematical modeling of the process of maintaining a technological area which consists of unstable or fixed objects (targets) and a controlled multi-link manipulator [1–9]. It is assumed that, in the maintenance process, the dynamic characteristics and the phase vector of the manipulator state can change at certain finite times depending on the mass of the cargo or instrument [10, 11]. Some controllability problems are investigated in the case where the manipulator motion on each maintenance interval is described by linear differential equations with constant coefficients and the motions of the objects are given.

State Derivation of a 12-Axis Gyroscope-Free Inertial Measurement Unit

PubMed Central

Lu, Jau-Ching; Lin, Pei-Chun

2011-01-01

The derivation of linear acceleration, angular acceleration, and angular velocity states from a 12-axis gyroscope-free inertial measurement unit that utilizes four 3-axis accelerometer measurements at four distinct locations is reported. Particularly, a new algorithm which derives the angular velocity from its quadratic form and derivative form based on the context-based interacting multiple model is demonstrated. The performance of the system was evaluated under arbitrary 3-dimensional motion. PMID:22163791

Human otolith-ocular reflexes during off-vertical axis rotation: effect of frequency on tilt-translation ambiguity and motion sickness

NASA Technical Reports Server (NTRS)

Wood, Scott J.; Paloski, W. H. (Principal Investigator)

2002-01-01

The purpose of this study was to examine how the modulation of tilt and translation otolith-ocular responses during constant velocity off-vertical axis rotation varies as a function of stimulus frequency. Eighteen human subjects were rotated in darkness about their longitudinal axis 30 degrees off-vertical at stimulus frequencies between 0.05 and 0.8 Hz. The modulation of torsion decreased while the modulation of horizontal slow phase velocity (SPV) increased with increasing frequency. It is inferred that the ambiguity of otolith afferent information is greatest in the frequency region where tilt (torsion) and translational (horizontal SPV) otolith-ocular responses crossover. It is postulated that the previously demonstrated peak in motion sickness susceptibility during linear accelerations around 0.3 Hz is the result of frequency segregation of ambiguous otolith information being inadequate to distinguish between tilt and translation.

Erosion in radial inflow turbines. Volume 2: Balance of centrifugal and radial drag forces on erosive particles

NASA Technical Reports Server (NTRS)

Clevenger, W. B., Jr.; Tabakoff, W.

1974-01-01

The particle motion in two-dimensional free and forced inward flowing vortices is considered. A particle in such a flow field experiences a balance between the aerodynamic drag forces that tend to drive erosive particles toward the axis, and centrifugal forces that prevent these particles from traveling toward the axis. Results predict that certain sizes of particles will achieve a stable orbit about the turbine axis in the inward flowing free vortex. In this condition, the radial drag force is equal to the centrifugal force. The sizes of particles that will achieve a stable orbit is shown to be related to the gas flow velocity diagram at a particular radius. A second analysis yields a description of particle sizes that will experience a centrifugal force that is greater than the radial component of the aerodynamic drag force for a more general type of particle motion.

Accelerating Large Data Analysis By Exploiting Regularities

NASA Technical Reports Server (NTRS)

Moran, Patrick J.; Ellsworth, David

2003-01-01

We present techniques for discovering and exploiting regularity in large curvilinear data sets. The data can be based on a single mesh or a mesh composed of multiple submeshes (also known as zones). Multi-zone data are typical to Computational Fluid Dynamics (CFD) simulations. Regularities include axis-aligned rectilinear and cylindrical meshes as well as cases where one zone is equivalent to a rigid-body transformation of another. Our algorithms can also discover rigid-body motion of meshes in time-series data. Next, we describe a data model where we can utilize the results from the discovery process in order to accelerate large data visualizations. Where possible, we replace general curvilinear zones with rectilinear or cylindrical zones. In rigid-body motion cases we replace a time-series of meshes with a transformed mesh object where a reference mesh is dynamically transformed based on a given time value in order to satisfy geometry requests, on demand. The data model enables us to make these substitutions and dynamic transformations transparently with respect to the visualization algorithms. We present results with large data sets where we combine our mesh replacement and transformation techniques with out-of-core paging in order to achieve significant speed-ups in analysis.

EPICS-based control and data acquisition for the APS slope profiler (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sullivan, Joseph; Assoufid, Lahsen; Qian, Jun; Jemian, Peter R.; Mooney, Tim; Rivers, Mark L.; Goetze, Kurt; Sluiter, Ronald L.; Lang, Keenan

2016-09-01

The motion control, data acquisition and analysis system for APS Slope Measuring Profiler was implemented using the Experimental Physics and Industrial Control System (EPICS). EPICS was designed as a framework with software tools and applications that provide a software infrastructure used in building distributed control systems to operate devices such as particle accelerators, large experiments and major telescopes. EPICS was chosen to implement the APS Slope Measuring Profiler because it is also applicable to single purpose systems. The control and data handling capability available in the EPICS framework provides the basic functionality needed for high precision X-ray mirror measurement. Those built in capabilities include hardware integration of high-performance motion control systems (3-axis gantry and tip-tilt stages), mirror measurement devices (autocollimator, laser spot camera) and temperature sensors. Scanning the mirror and taking measurements was accomplished with an EPICS feature (the sscan record) which synchronizes motor positioning with measurement triggers and data storage. Various mirror scanning modes were automatically configured using EPICS built-in scripting. EPICS tools also provide low-level image processing (areaDetector). Operation screens were created using EPICS-aware GUI screen development tools.

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.

Roll and Yaw of Paramecium swimming in a viscous fluid

NASA Astrophysics Data System (ADS)

Jung, Sunghwan; Jana, Saikat; Giarra, Matt; Vlachos, Pavlos

2012-11-01

Many free-swimming microorganisms like ciliates, flagellates, and invertebrates exhibit helical trajectories. In particular, the Paramecium spirally swims along its anterior direction by the beating of cilia. Due to the oblique beating stroke of cilia, the Paramecium rotates along its long axis as it swims forward. Simultaneously, this long axis turns toward the oral groove side. Combined roll and yaw motions of Paramecium result in swimming along a spiral course. Using Particle Image Velocimetry, we measure and quantify the flow field and fluid stress around Paramecium. We will discuss how the non-uniform stress distribution around the body induces this yaw motion.

Multi-muscle FES force control of the human arm for arbitrary goals.

PubMed

Schearer, Eric M; Liao, Yu-Wei; Perreault, Eric J; Tresch, Matthew C; Memberg, William D; Kirsch, Robert F; Lynch, Kevin M

2014-05-01

We present a method for controlling a neuroprosthesis for a paralyzed human arm using functional electrical stimulation (FES) and characterize the errors of the controller. The subject has surgically implanted electrodes for stimulating muscles in her shoulder and arm. Using input/output data, a model mapping muscle stimulations to isometric endpoint forces measured at the subject's hand was identified. We inverted the model of this redundant and coupled multiple-input multiple-output system by minimizing muscle activations and used this inverse for feedforward control. The magnitude of the total root mean square error over a grid in the volume of achievable isometric endpoint force targets was 11% of the total range of achievable forces. Major sources of error were random error due to trial-to-trial variability and model bias due to nonstationary system properties. Because the muscles working collectively are the actuators of the skeletal system, the quantification of errors in force control guides designs of motion controllers for multi-joint, multi-muscle FES systems that can achieve arbitrary goals.

High-contrast imaging in multi-star systems: progress in technology development and lab results

NASA Astrophysics Data System (ADS)

Belikov, Ruslan; Pluzhnik, Eugene; Bendek, Eduardo; Sirbu, Dan

2017-09-01

We present the continued progress and laboratory results advancing the technology readiness of Multi-Star Wavefront Control (MSWC), a method to directly image planets and disks in multi-star systems such as Alpha Centauri. This method works with almost any coronagraph (or external occulter with a DM) and requires little or no change to existing and mature hardware. In particular, it works with single-star coronagraphs and does not require the off-axis star(s) to be coronagraphically suppressed. Because of the ubiquity of multistar systems, this method increases the science yield of many missions and concepts such as WFIRST, Exo-C/S, HabEx, LUVOIR, and potentially enables the detection of Earthlike planets (if they exist) around our nearest neighbor star, Alpha Centauri, with a small and low-cost space telescope such as ACESat. Our lab demonstrations were conducted at the Ames Coronagraph Experiment (ACE) laboratory and show both the feasibility as well as the trade-offs involved in using MSWC. We show several simulations and laboratory tests at roughly TRL-3 corresponding to representative targets and missions, including Alpha Centauri with WFIRST. In particular, we demonstrate MSWC in Super-Nyquist mode, where the distance between the desired dark zone and the off-axis star is larger than the conventional (sub-Nyquist) control range of the DM. Our laboratory tests did not yet include a coronagraph, but did demonstrate significant speckle suppression from two independent light sources at sub- as well as super-Nyquist separations.

Multi-application controls: Robust nonlinear multivariable aerospace controls applications

NASA Technical Reports Server (NTRS)

Enns, Dale F.; Bugajski, Daniel J.; Carter, John; Antoniewicz, Bob

1994-01-01

This viewgraph presentation describes the general methodology used to apply Honywell's Multi-Application Control (MACH) and the specific application to the F-18 High Angle-of-Attack Research Vehicle (HARV) including piloted simulation handling qualities evaluation. The general steps include insertion of modeling data for geometry and mass properties, aerodynamics, propulsion data and assumptions, requirements and specifications, e.g. definition of control variables, handling qualities, stability margins and statements for bandwidth, control power, priorities, position and rate limits. The specific steps include choice of independent variables for least squares fits to aerodynamic and propulsion data, modifications to the management of the controls with regard to integrator windup and actuation limiting and priorities, e.g. pitch priority over roll, and command limiting to prevent departures and/or undesirable inertial coupling or inability to recover to a stable trim condition. The HARV control problem is characterized by significant nonlinearities and multivariable interactions in the low speed, high angle-of-attack, high angular rate flight regime. Systematic approaches to the control of vehicle motions modeled with coupled nonlinear equations of motion have been developed. This paper will discuss the dynamic inversion approach which explicity accounts for nonlinearities in the control design. Multiple control effectors (including aerodynamic control surfaces and thrust vectoring control) and sensors are used to control the motions of the vehicles in several degrees-of-freedom. Several maneuvers will be used to illustrate performance of MACH in the high angle-of-attack flight regime. Analytical methods for assessing the robust performance of the multivariable control system in the presence of math modeling uncertainty, disturbances, and commands have reached a high level of maturity. The structured singular value (mu) frequency response methodology is presented as a method for analyzing robust performance and the mu-synthesis method will be presented as a method for synthesizing a robust control system. The paper concludes with the author's expectations regarding future applications of robust nonlinear multivariable controls.

IECON '87: Industrial applications of control and simulation; Proceedings of the 1987 International Conference on Industrial Electronics, Control, and Instrumentation, Cambridge, MA, Nov. 3, 4, 1987

NASA Technical Reports Server (NTRS)

Hartley, Tom T. (Editor)

1987-01-01

Recent advances in control-system design and simulation are discussed in reviews and reports. Among the topics considered are fast algorithms for generating near-optimal binary decision programs, trajectory control of robot manipulators with compensation of load effects via a six-axis force sensor, matrix integrators for real-time simulation, a high-level control language for an autonomous land vehicle, and a practical engineering design method for stable model-reference adaptive systems. Also addressed are the identification and control of flexible-limb robots with unknown loads, adaptive control and robust adaptive control for manipulators with feedforward compensation, adaptive pole-placement controllers with predictive action, variable-structure strategies for motion control, and digital signal-processor-based variable-structure controls.

On Motion Planning and Control of Multi-Link Lightweight Robotic Manipulators

NASA Technical Reports Server (NTRS)

Cetinkunt, Sabri

1987-01-01

A general gross and fine motion planning and control strategy is needed for lightweight robotic manipulator applications such as painting, welding, material handling, surface finishing, and spacecraft servicing. The control problem of lightweight manipulators is to perform fast, accurate, and robust motions despite the payload variations, structural flexibility, and other environmental disturbances. Performance of the rigid manipulator model based computed torque and decoupled joint control methods are determined and simulated for the counterpart flexible manipulators. A counterpart flexible manipulator is defined as a manipulator which has structural flexibility, in addition to having the same inertial, geometric, and actuation properties of a given rigid manipulator. An adaptive model following control (AMFC) algorithm is developed to improve the performance in speed, accuracy, and robustness. It is found that the AMFC improves the speed performance by a factor of two over the conventional non-adaptive control methods for given accuracy requirements while proving to be more robust with respect to payload variations. Yet there are clear limitations on the performance of AMFC alone as well, which are imposed by the arm flexibility. In the search to further improve speed performance while providing a desired accuracy and robustness, a combined control strategy is developed. Furthermore, the problem of switching from one control structure to another during the motion and implementation aspects of combined control are discussed.

Coherent electronic wave packet motion in C(60) controlled by the waveform and polarization of few-cycle laser fields.

PubMed

Li, H; Mignolet, B; Wachter, G; Skruszewicz, S; Zherebtsov, S; Süssmann, F; Kessel, A; Trushin, S A; Kling, Nora G; Kübel, M; Ahn, B; Kim, D; Ben-Itzhak, I; Cocke, C L; Fennel, T; Tiggesbäumker, J; Meiwes-Broer, K-H; Lemell, C; Burgdörfer, J; Levine, R D; Remacle, F; Kling, M F

2015-03-27

Strong laser fields can be used to trigger an ultrafast molecular response that involves electronic excitation and ionization dynamics. Here, we report on the experimental control of the spatial localization of the electronic excitation in the C_{60} fullerene exerted by an intense few-cycle (4 fs) pulse at 720 nm. The control is achieved by tailoring the carrier-envelope phase and the polarization of the laser pulse. We find that the maxima and minima of the photoemission-asymmetry parameter along the laser-polarization axis are synchronized with the localization of the coherent electronic wave packet at around the time of ionization.

Analytical study of the effects of soft tissue artefacts on functional techniques to define axes of rotation.

PubMed

De Rosario, Helios; Page, Álvaro; Besa, Antonio

2017-09-06

The accurate location of the main axes of rotation (AoR) is a crucial step in many applications of human movement analysis. There are different formal methods to determine the direction and position of the AoR, whose performance varies across studies, depending on the pose and the source of errors. Most methods are based on minimizing squared differences between observed and modelled marker positions or rigid motion parameters, implicitly assuming independent and uncorrelated errors, but the largest error usually results from soft tissue artefacts (STA), which do not have such statistical properties and are not effectively cancelled out by such methods. However, with adequate methods it is possible to assume that STA only account for a small fraction of the observed motion and to obtain explicit formulas through differential analysis that relate STA components to the resulting errors in AoR parameters. In this paper such formulas are derived for three different functional calibration techniques (Geometric Fitting, mean Finite Helical Axis, and SARA), to explain why each technique behaves differently from the others, and to propose strategies to compensate for those errors. These techniques were tested with published data from a sit-to-stand activity, where the true axis was defined using bi-planar fluoroscopy. All the methods were able to estimate the direction of the AoR with an error of less than 5°, whereas there were errors in the location of the axis of 30-40mm. Such location errors could be reduced to less than 17mm by the methods based on equations that use rigid motion parameters (mean Finite Helical Axis, SARA) when the translation component was calculated using the three markers nearest to the axis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptive Registration of Varying Contrast-Weighted Images for Improved Tissue Characterization (ARCTIC): Application to T1 Mapping

PubMed Central

Roujol, Sébastien; Foppa, Murilo; Weingartner, Sebastian; Manning, Warren J.; Nezafat, Reza

2014-01-01

Purpose To propose and evaluate a novel non-rigid image registration approach for improved myocardial T1 mapping. Methods Myocardial motion is estimated as global affine motion refined by a novel local non-rigid motion estimation algorithm. A variational framework is proposed, which simultaneously estimates motion field and intensity variations, and uses an additional regularization term to constrain the deformation field using automatic feature tracking. The method was evaluated in 29 patients by measuring the DICE similarity coefficient (DSC) and the myocardial boundary error (MBE) in short axis and four chamber data. Each image series was visually assessed as “no motion” or “with motion”. Overall T1 map quality and motion artifacts were assessed in the 85 T1 maps acquired in short axis view using a 4-point scale (1-non diagnostic/severe motion artifact, 4-excellent/no motion artifact). Results Increased DSC (0.78±0.14 to 0.87±0.03, p<0.001), reduced MBE (1.29±0.72mm to 0.84±0.20mm, p<0.001), improved overall T1 map quality (2.86±1.04 to 3.49±0.77, p<0.001), and reduced T1 map motion artifacts (2.51±0.84 to 3.61±0.64, p<0.001) were obtained after motion correction of “with motion” data (~56% of data). Conclusion The proposed non-rigid registration approach reduces the respiratory-induced motion that occurs during breath-hold T1 mapping, and significantly improves T1 map quality. PMID:24798588

One-Dimensional Spacecraft Formation Flight Testbed for Terrestrial Charged Relative Motion Experiments

NASA Astrophysics Data System (ADS)

Seubert, Carl R.

Spacecraft operating in a desired formation offers an abundance of attractive mission capabilities. One proposed method of controlling a close formation of spacecraft is with Coulomb (electrostatic) forces. The Coulomb formation flight idea utilizes charge emission to drive the spacecraft to kilovolt-level potentials and generate adjustable, micronewton- to millinewton-level Coulomb forces for relative position control. In order to advance the prospects of the Coulomb formation flight concept, this dissertation presents the design and implementation of a unique one-dimensional testbed. The disturbances of the testbed are identified and reduced below 1 mN. This noise level offers a near-frictionless platform that is used to perform relative motion actuation with electrostatics in a terrestrial atmospheric environment. Potentials up to 30 kV are used to actuate a cart over a translational range of motion of 40 cm. A challenge to both theoretical and hardware implemented electrostatic actuation developments is correctly modeling the forces between finite charged bodies, outside a vacuum. To remedy this, studies of Earth orbit plasmas and Coulomb force theory is used to derive and propose a model of the Coulomb force between finite spheres in close proximity, in a plasma. This plasma force model is then used as a basis for a candidate terrestrial force model. The plasma-like parameters of this terrestrial model are estimated using charged motion data from fixed-potential, single-direction experiments on the testbed. The testbed is advanced to the level of autonomous feedback position control using solely Coulomb force actuation. This allows relative motion repositioning on a flat and level track as well as an inclined track that mimics the dynamics of two charged spacecraft that are aligned with the principal orbit axis. This controlled motion is accurately predicted with simulations using the terrestrial force model. This demonstrates similarities between the partial charge shielding of space-based plasmas to the electrostatic screening in the laboratory atmosphere.

Expermental Investigation of Supercavitating Motion of Bodies

DTIC Science & Technology

2001-02-01

information is ensured by studying of the model motion kinematics and photo- cinematography of its flow pictures. 4-9 Synchronization of work of the...on the depth 0.5 m along the flume axis. Photo- cinematography of the flow pictures was realized through the glass windows in walls of the flume and

Performance Evaluation of the Honeywell GG1308 Miniature Ring Laser Gyroscope

DTIC Science & Technology

1993-01-01

information. The final display line provides the current DSB configuration status. An external strobe was established between the Contraves motion...components and systems. The core of the facility is a Contraves -Goerz Model 57CD 2-axis motion simulator capable of highly precise position, rate and

Friction Effects on Inertia Compensators used for Heliostat Base Motion Isolation.

DTIC Science & Technology

The base motion isolation of an optical beam deflector with a two-axis gimbal support ( heliostat ) is discussed. The use of an auxiliary inertia...coupled between the elevation gimbal and the heliostat mirror to produce a compensating torque referred to as a gear compensator and a belt compensator

System and method for injecting fuel

DOEpatents

Uhm, Jong Ho; Johnson, Thomas Edward

2012-12-04

According to various embodiments, a system includes a staggered multi-nozzle assembly. The staggered multi-nozzle assembly includes a first fuel nozzle having a first axis and a first flow path extending to a first downstream end portion, wherein the first fuel nozzle has a first non-circular perimeter at the first downstream end portion. The staggered multi-nozzle assembly also includes a second fuel nozzle having a second axis and a second flow path extending to a second downstream end portion, wherein the first and second downstream end portions are axially offset from one another relative to the first and second axes. The staggered multi-nozzle assembly further includes a cap member disposed circumferentially about at least the first and second fuel nozzles to assemble the staggered multi-nozzle assembly.

Five-Axis Ultrasonic Additive Manufacturing for Nuclear Component Manufacture

NASA Astrophysics Data System (ADS)

Hehr, Adam; Wenning, Justin; Terrani, Kurt; Babu, Sudarsanam Suresh; Norfolk, Mark

2017-03-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact with the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. It is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.

Five-axis ultrasonic additive manufacturing for nuclear component manufacture

DOE PAGES

Hehr, Adam; Wenning, Justin; Terrani, Kurt A.; ...

2016-01-01

Ultrasonic additive manufacturing (UAM) is a three-dimensional metal printing technology which uses high-frequency vibrations to scrub and weld together both similar and dissimilar metal foils. There is no melting in the process and no special atmosphere requirements are needed. Consequently, dissimilar metals can be joined with little to no intermetallic compound formation, and large components can be manufactured. These attributes have the potential to transform manufacturing of nuclear reactor core components such as control elements for the High Flux Isotope Reactor at Oak Ridge National Laboratory. These components are hybrid structures consisting of an outer cladding layer in contact withmore » the coolant with neutron-absorbing materials inside, such as neutron poisons for reactor control purposes. UAM systems are built into a computer numerical control (CNC) framework to utilize intermittent subtractive processes. These subtractive processes are used to introduce internal features as the component is being built and for net shaping. The CNC framework is also used for controlling the motion of the welding operation. Lastly, it is demonstrated here that curved components with embedded features can be produced using a five-axis code for the welder for the first time.« less

Foot Placement Modification for a Biped Humanoid Robot with Narrow Feet

PubMed Central

Hattori, Kentaro; Otani, Takuya; Lim, Hun-Ok; Takanishi, Atsuo

2014-01-01

This paper describes a walking stabilization control for a biped humanoid robot with narrow feet. Most humanoid robots have larger feet than human beings to maintain their stability during walking. If robot's feet are as narrow as humans, it is difficult to realize a stable walk by using conventional stabilization controls. The proposed control modifies a foot placement according to the robot's attitude angle. If a robot tends to fall down, a foot angle is modified about the roll axis so that a swing foot contacts the ground horizontally. And a foot-landing point is also changed laterally to inhibit the robot from falling to the outside. To reduce a foot-landing impact, a virtual compliance control is applied to the vertical axis and the roll and pitch axes of the foot. Verification of the proposed method is conducted through experiments with a biped humanoid robot WABIAN-2R. WABIAN-2R realized a knee-bended walking with 30 mm breadth feet. Moreover, WABIAN-2R mounted on a human-like foot mechanism mimicking a human's foot arch structure realized a stable walking with the knee-stretched, heel-contact, and toe-off motion. PMID:24592154

Foot placement modification for a biped humanoid robot with narrow feet.

PubMed

Hashimoto, Kenji; Hattori, Kentaro; Otani, Takuya; Lim, Hun-Ok; Takanishi, Atsuo

2014-01-01

This paper describes a walking stabilization control for a biped humanoid robot with narrow feet. Most humanoid robots have larger feet than human beings to maintain their stability during walking. If robot's feet are as narrow as humans, it is difficult to realize a stable walk by using conventional stabilization controls. The proposed control modifies a foot placement according to the robot's attitude angle. If a robot tends to fall down, a foot angle is modified about the roll axis so that a swing foot contacts the ground horizontally. And a foot-landing point is also changed laterally to inhibit the robot from falling to the outside. To reduce a foot-landing impact, a virtual compliance control is applied to the vertical axis and the roll and pitch axes of the foot. Verification of the proposed method is conducted through experiments with a biped humanoid robot WABIAN-2R. WABIAN-2R realized a knee-bended walking with 30 mm breadth feet. Moreover, WABIAN-2R mounted on a human-like foot mechanism mimicking a human's foot arch structure realized a stable walking with the knee-stretched, heel-contact, and toe-off motion.

Molecular motions of [Beta]-carotene and a carotenoporphyrin dyad in solution. A carbon-13 NMR spin-lattice relaxation time study

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

Li, S.; Swindle, S.L.; Smith, S.K.

1995-03-09

Analysis of [sup 13]C NMR spin-lattice relaxation times (T[sub 1]) yields information concerning both overall tumbling of molecules in solution and internal rotations about single bonds. Relaxation time and nuclear Overhauser effect data have been obtained for [Beta]-carotene and two related molecules, squalane and squalene, for zinc meso-tetraphenylporphyrin, and for a dyad consisting of a porphyrin covalently linked to a carotenoid polyene through a trimethylene bridge. Squalane and squalene, which lack conjugated double bonds, behave essentially as limp string, with internal rotations at least as rapid as overall isotropic tumbling motions. In contrast, [Beta]-carotene reorients as a rigid rod, withmore » internal motions which are too slow to affect relaxation times. Modeling it as an anisotropic rotor yields a rotational diffusion coefficient for motion about the major axis which is 14 times larger than that for rotation about axes perpendicular to that axis. The porphyrin reorients more nearly isotropically and features internal librational motions about the single bonds to the phenyl groups. The relaxation time data for the carotenoporphyrin are consistent with internal motions similar to those of a medieval military flail. 31 refs., 3 figs., 5 tabs.« less

Particle motion is broadly represented in the vestibular medulla of the bullfrog across larval development.

PubMed

Simmons, Andrea Megela; Flores, Victoria

2012-04-01

In their shallow-water habitats, bullfrog (Rana catesbeiana) tadpoles are exposed to both underwater and airborne sources of acoustic stimulation. We probed the representation of underwater particle motion throughout the tadpole's dorsal medulla to determine its spatial extent over larval life. Using neurobiotin-filled micropipettes, we recorded neural activity to z-axis particle motion (frequencies of 40-200 Hz) in the medial vestibular nucleus, lateral vestibular nucleus, dorsal medullary nucleus (DMN), and along the dorsal arcuate pathway. Sensitivity was comparable in the medial and lateral vestibular nuclei, with estimated thresholds between 0.016 and 12.5 μm displacement. Neither best responding frequency nor estimated threshold varied significantly over larval stage. Transport of neurobiotin from active recording sites was also stable over development. The DMN responded poorly to z-axis particle motion, but did respond to low-frequency pressure stimulation. These data suggest that particle motion is represented widely and stably in the tadpole's vestibular medulla. This is in marked contrast to the representation of pressure stimulation in the auditory midbrain, where a transient "deaf period" of non-responsiveness and decreased connectivity occurs immediately prior to metamorphic climax. We suggest that, in bullfrogs, sensitivity to particle motion and to pressure follows different developmental trajectories.

Particle motion is broadly represented in the vestibular medulla of the bullfrog across larval development

PubMed Central

Flores, Victoria

2012-01-01

In their shallow-water habitats, bullfrog (Rana catesbeiana) tadpoles are exposed to both underwater and airborne sources of acoustic stimulation. We probed the representation of underwater particle motion throughout the tadpole’s dorsal medulla to determine its spatial extent over larval life. Using neurobiotin-filled micropipettes, we recorded neural activity to z-axis particle motion (frequencies of 40–200 Hz) in the medial vestibular nucleus, lateral vestibular nucleus, dorsal medullary nucleus (DMN), and along the dorsal arcuate pathway. Sensitivity was comparable in the medial and lateral vestibular nuclei, with estimated thresholds between 0.016 and 12.5 μm displacement. Neither best responding frequency nor estimated threshold varied significantly over larval stage. Transport of neurobiotin from active recording sites was also stable over development. The DMN responded poorly to z-axis particle motion, but did respond to low-frequency pressure stimulation. These data suggest that particle motion is represented widely and stably in the tadpole’s vestibular medulla. This is in marked contrast to the representation of pressure stimulation in the auditory midbrain, where a transient “deaf period” of non-responsiveness and decreased connectivity occurs immediately prior to metamorphic climax. We suggest that, in bullfrogs, sensitivity to particle motion and to pressure follows different developmental trajectories. PMID:22198742

Stability of large horizontal-axis axisymmetric wind turbines. Ph.D. Thesis - Delaware Univ.

NASA Technical Reports Server (NTRS)

Hirschbein, M. S.; Young, M. I.

1980-01-01

The stability of large horizontal axis, axi-symmetric, power producing wind turbines was examined. The analytical model used included the dynamic coupling of the rotor, tower and power generating system. The aerodynamic loading was derived from blade element theory. Each rotor blade was permitted tow principal elastic bending degrees of freedom, one degree of freedom in torsion and controlled pitch as a rigid body. The rotor hub was mounted in a rigid nacelle which may yaw freely or in a controlled manner. The tower can bend in two principal directions and may twist. Also, the rotor speed can vary and may induce perturbation reactions within the power generating equipment. Stability was determined by the eigenvalues of a set of linearized constant coefficient differential equations. All results presented are based on a 3 bladed, 300 ft. diameter, 2.5 megawatt wind turbine. Some of the parameters varied were; wind speed, rotor speed structural stiffness and damping, the effective stiffness and damping of the power generating system and the principal bending directions of the rotor blades. Unstable or weakly stable behavior can be caused by aerodynamic forces due to motion of the rotor blades and tower in the plane of rotation or by mechanical coupling between the rotor system and the tower.

Formations Near the Libration Points: Design Strategies Using Natural and Non-Natural Arcs

NASA Technical Reports Server (NTRS)

Howell, K. C.; Marchand, B. G.

2004-01-01

Space based observatory and interferometry missions, such as Terrestrial Planet Finder (TPF), Stellar Imager, and MAXIM, have sparked great interest in multi-spacecraft formation flight in the vicinity of the Sun-Earth/Moon (SEM) libration points. The initial phase of this research considered the formation keeping problem from the perspective of continuous control as applied to non-natural formations. In the present study, closer inspection of the flow, corresponding to the stable and center manifolds near the reference orbit, reveals some interesting natural relative motions as well as some discrete control strategies for deployment. A hybrid control strategy is also employed that combines both the natural formation dynamics with non-natural motions via input feedback linearization techniques.

The effect of a multi-axis suspension on whole body vibration exposures and physical stress in the neck and low back in agricultural tractor applications.

PubMed

Kim, Jeong Ho; Dennerlein, Jack T; Johnson, Peter W

2018-04-01

Whole body vibration (WBV) exposures are often predominant in the fore-aft (x) or lateral (y) axis among off-road agricultural vehicles. However, as the current industry standard seats are designed to reduce mainly vertical (z) axis WBV exposures, they may be less effective in reducing drivers' exposure to multi-axial WBV. Therefore, this laboratory-based study aimed to determine the differences between a single-axial (vertical) and multi-axial (vertical + lateral) suspension seat in reducing WBV exposures, head acceleration, self-reported discomfort, and muscle activity (electromyography) of the major muscle of the low back, neck and shoulders. The results showed that the multi-axial suspension seat had significantly lower WBV exposures compared to the single-axial suspension seats (p' < 0.04). Similarly, the multi-axial suspension seat had lower head acceleration and muscle activity of the neck, shoulder, and low back compared to the single-axial suspension seat; some but not all of the differences were statistically significant. These results indicate that the multi-axial suspension seat may reduce the lateral WBV exposures and associated muscular loading in the neck and low back in agricultural vehicle operators. Copyright © 2017 Elsevier Ltd. All rights reserved.

Research on Measurement Accuracy of Laser Tracking System Based on Spherical Mirror with Rotation Errors of Gimbal Mount Axes

NASA Astrophysics Data System (ADS)

Shi, Zhaoyao; Song, Huixu; Chen, Hongfang; Sun, Yanqiang

2018-02-01

This paper presents a novel experimental approach for confirming that spherical mirror of a laser tracking system can reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy. By simplifying the optical system model of laser tracking system based on spherical mirror, we can easily extract the laser ranging measurement error caused by rotation errors of gimbal mount axes with the positions of spherical mirror, biconvex lens, cat's eye reflector, and measuring beam. The motions of polarization beam splitter and biconvex lens along the optical axis and vertical direction of optical axis are driven by error motions of gimbal mount axes. In order to simplify the experimental process, the motion of biconvex lens is substituted by the motion of spherical mirror according to the principle of relative motion. The laser ranging measurement error caused by the rotation errors of gimbal mount axes could be recorded in the readings of laser interferometer. The experimental results showed that the laser ranging measurement error caused by rotation errors was less than 0.1 μm if radial error motion and axial error motion were within ±10 μm. The experimental method simplified the experimental procedure and the spherical mirror could reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy of the laser tracking system.

Adaptive tracking control of leader-following linear multi-agent systems with external disturbances

NASA Astrophysics Data System (ADS)

Lin, Hanquan; Wei, Qinglai; Liu, Derong; Ma, Hongwen

2016-10-01

In this paper, the consensus problem for leader-following linear multi-agent systems with external disturbances is investigated. Brownian motions are used to describe exogenous disturbances. A distributed tracking controller based on Riccati inequalities with an adaptive law for adjusting coupling weights between neighbouring agents is designed for leader-following multi-agent systems under fixed and switching topologies. In traditional distributed static controllers, the coupling weights depend on the communication graph. However, coupling weights associated with the feedback gain matrix in our method are updated by state errors between neighbouring agents. We further present the stability analysis of leader-following multi-agent systems with stochastic disturbances under switching topology. Most traditional literature requires the graph to be connected all the time, while the communication graph is only assumed to be jointly connected in this paper. The design technique is based on Riccati inequalities and algebraic graph theory. Finally, simulations are given to show the validity of our method.

Self-rotations in simulated microgravity: performance effects of strategy training.

PubMed

Stirling, Leia; Newman, Dava; Willcox, Karen

2009-01-01

This research studies reorientation methodologies in a simulated microgravity environment using an experimental framework to reduce astronaut adaptation time and provide for a safety countermeasure during extravehicular activity. There were 20 subjects (10 men, 10 women, mean age of 23.6 +/- 3.5) who were divided into 2 groups, fully trained and minimally trained, which determined the amount of motion strategy training received. Subjects performed a total of 48 rotations about their pitch, roll, and yaw axes in a suspension system that simulated microgravity. In each trial subjects either rotated 90 degrees in pitch, 90 degrees in roll, or 180 degrees in yaw. Experimental measures include subject coordination, performance time, cognitive workload assessments, and qualitative motion control strategies. Subjects in the fully trained group had better initial performance with respect to performance time and workload scores for the pitch and yaw rotations. Further, trained subjects reached a steady-state performance time in fewer trials than those with minimal training. The subjects with minimal training tended to use motions that were common in an Earth environment since no technique was provided. For roll rotations they developed motions that would have led to significant off-axis (pitch and yaw) rotations in a true microgravity environment. We have shown that certain body axes are easier to rotate about than others and that fully trained subjects had an easier time performing the body rotations than the minimally trained subjects. This study has provided the groundwork for the development of an astronaut motion-control training program.

Comparison of three control methods for an autonomous vehicle

NASA Astrophysics Data System (ADS)

Deshpande, Anup; Mathur, Kovid; Hall, Ernest

2010-01-01

The desirability and challenge of developing a completely autonomous vehicle and the rising need for more efficient use of energy by automobiles motivate this research- a study for an optimum solution to computer control of energy efficient vehicles. The purpose of this paper is to compare three control methods - mechanical, hydraulic and electric that have been used to convert an experimental all terrain vehicle to drive by wire which would eventually act as a test bed for conducting research on various technologies for autonomous operation. Computer control of basic operations in a vehicle namely steering, braking and speed control have been implemented and will be described in this paper. The output from a 3 axis motion controller is used for this purpose. The motion controller is interfaced with a software program using WSDK (Windows Servo Design Kit) as an intermediate tuning layer for tuning and parameter settings in autonomous operation. The software program is developed in C++. The voltage signal sent to the motion controller can be varied through the control program for desired results in controlling the steering motor, activating the hydraulic brakes and varying the vehicle's speed. The vehicle has been tested for its basic functionality which includes testing of street legal operations and also a 1000 mile test while running in a hybrid mode. The vehicle has also been tested for control when it is interfaced with devices such as a keyboard, joystick and sensors under full autonomous operation. The vehicle is currently being tested in various safety studies and is being used as a test bed for experiments in control courses and research studies. The significance of this research is in providing a greater understanding of conventional driving controls and the possibility of improving automobile safety by removing human error in control of a motor vehicle.

Underwater (UW) Unexploded Ordnance (UXO) Multi-Sensor Data Base (MSDB) Collection

DTIC Science & Technology

2009-07-01

11 FIGURE 6 RTG SENSOR. FOUR SENSOR TRIADS ARE SHOWN, EACH WITH A 3-AXIS FLUXGATE MAGNETOMETER ...used by RTG to measure the gradients. Each triad includes a 3-axis fluxgate magnetometer and a set of feedback coils. The outputs of three triad...each with a 3-axis fluxgate magnetometer (internal, not clearly visible) and a set of 3 feedback coils. The upper triad 3-axis magnetometer

A compensation method of lever arm effect for tri-axis hybrid inertial navigation system based on fiber optic gyro

NASA Astrophysics Data System (ADS)

Liu, Zengjun; Wang, Lei; Li, Kui; Gao, Jiaxin

2017-05-01

Hybrid inertial navigation system (HINS) is a new kind of inertial navigation system (INS), which combines advantages of platform INS, strap-down INS and rotational INS. HINS has a physical platform to isolate the angular motion as platform INS does, HINS also uses strap-down attitude algorithms and applies rotation modulation technique. Tri-axis HINS has three gimbals to isolate the angular motion in the dynamic base, in which way the system can reduce the effects of angular motion and improve the positioning precision. However, the angular motion will affect the compensation of some error parameters, especially for the lever arm effect. The lever arm effect caused by position errors between the accelerometers and rotation center cannot be ignored due to the rapid rotation of inertial measurement unit (IMU) and it will cause fluctuation and stage in velocity in HINS. The influences of angular motion on the lever arm effect compensation are analyzed firstly in this paper, and then the compensation method of lever arm effect based on the photoelectric encoders in dynamic base is proposed. Results of experiments on turntable show that after compensation, the fluctuations and stages in velocity curve disappear.

Quaternion-Based Unscented Kalman Filter for Accurate Indoor Heading Estimation Using Wearable Multi-Sensor System

PubMed Central

Yuan, Xuebing; Yu, Shuai; Zhang, Shengzhi; Wang, Guoping; Liu, Sheng

2015-01-01

Inertial navigation based on micro-electromechanical system (MEMS) inertial measurement units (IMUs) has attracted numerous researchers due to its high reliability and independence. The heading estimation, as one of the most important parts of inertial navigation, has been a research focus in this field. Heading estimation using magnetometers is perturbed by magnetic disturbances, such as indoor concrete structures and electronic equipment. The MEMS gyroscope is also used for heading estimation. However, the accuracy of gyroscope is unreliable with time. In this paper, a wearable multi-sensor system has been designed to obtain the high-accuracy indoor heading estimation, according to a quaternion-based unscented Kalman filter (UKF) algorithm. The proposed multi-sensor system including one three-axis accelerometer, three single-axis gyroscopes, one three-axis magnetometer and one microprocessor minimizes the size and cost. The wearable multi-sensor system was fixed on waist of pedestrian and the quadrotor unmanned aerial vehicle (UAV) for heading estimation experiments in our college building. The results show that the mean heading estimation errors are less 10° and 5° to multi-sensor system fixed on waist of pedestrian and the quadrotor UAV, respectively, compared to the reference path. PMID:25961384

Gravitomagnetic Acceleration of Black Hole Accretion Disk Matter to Polar Jets

NASA Astrophysics Data System (ADS)

Poirier, John; Mathews, Grant

2015-04-01

It is shown that the motion of the neutral masses in an accretion disk orbiting a black hole creates a magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near the accretion disk away from the disk and then inward toward the axis of the accretion disk. Moreover, as the accelerated material nears the axis, a frame-dragging effect twists the trajectories around the axis thus contributing to the formation of a narrow polar jet emanating from the poles.

Two-axis angular effector

DOEpatents

Vaughn, Mark R.; Robinett, III, Rush D.; Phelan, John R.; Van Zuiden, Don M.

1997-01-21

A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.

High brightness MEMS mirror based head-up display (HUD) modules with wireless data streaming capability

NASA Astrophysics Data System (ADS)

Milanovic, Veljko; Kasturi, Abhishek; Hachtel, Volker

2015-02-01

A high brightness Head-Up Display (HUD) module was demonstrated with a fast, dual-axis MEMS mirror that displays vector images and text, utilizing its ~8kHz bandwidth on both axes. Two methodologies were evaluated: in one, the mirror steers a laser at wide angles of <48° on transparent multi-color fluorescent emissive film and displays content directly on the windshield, and in the other the mirror displays content on reflective multi-color emissive phosphor plates reflected off the windshield to create a virtual image for the driver. The display module is compact, consisting of a single laser diode, off-the-shelf lenses and a MEMS mirror in combination with a MEMS controller to enable precise movement of the mirror's X- and Y-axis. The MEMS controller offers both USB and wireless streaming capability and we utilize a library of functions on a host computer for creating content and controlling the mirror. Integration with smart phone applications is demonstrated, utilizing the mobile device both for content generation based on various messages or data, and for content streaming to the MEMS controller via Bluetooth interface. The display unit is highly resistant to vibrations and shock, and requires only ~1.5W to operate, even with content readable in sunlit outdoor conditions. The low power requirement is in part due to a vector graphics approach, allowing the efficient use of laser power, and also due to the use of a single, relatively high efficiency laser and simple optics.

Analytic theory of orbit contraction

NASA Technical Reports Server (NTRS)

Vinh, N. X.; Longuski, J. M.; Busemann, A.; Culp, R. D.

1977-01-01

The motion of a satellite in orbit, subject to atmospheric force and the motion of a reentry vehicle are governed by gravitational and aerodynamic forces. This suggests the derivation of a uniform set of equations applicable to both cases. For the case of satellite motion, by a proper transformation and by the method of averaging, a technique appropriate for long duration flight, the classical nonlinear differential equation describing the contraction of the major axis is derived. A rigorous analytic solution is used to integrate this equation with a high degree of accuracy, using Poincare's method of small parameters and Lagrange's expansion to explicitly express the major axis as a function of the eccentricity. The solution is uniformly valid for moderate and small eccentricities. For highly eccentric orbits, the asymptotic equation is derived directly from the general equation. Numerical solutions were generated to display the accuracy of the analytic theory.

Wind energy system time-domain (WEST) analyzers

NASA Technical Reports Server (NTRS)

Dreier, M. E.; Hoffman, J. A.

1981-01-01

A portable analyzer which simulates in real time the complex nonlinear dynamics of horizontal axis wind energy systems was constructed. Math models for an aeroelastic rotor featuring nonlinear aerodynamic and inertial terms were implemented with high speed digital controllers and analog calculation. This model was combined with other math models of elastic supports, control systems, a power train and gimballed rotor kinematics. A stroboscopic display system graphically depicting distributed blade loads, motion, and other aerodynamic functions on a cathode ray tube is included. Limited correlation efforts showed good comparison between the results of this analyzer and other sophisticated digital simulations. The digital simulation results were successfully correlated with test data.

Maskless deposition technique for the physical vapor deposition of thin film and multilayer coatings with subnanometer precision and accuracy

DOEpatents

Vernon, Stephen P.; Ceglio, Natale M.

2000-01-01

The invention is a method for the production of axially symmetric, graded and ungraded thickness thin film and multilayer coatings that avoids the use of apertures or masks to tailor the deposition profile. A motional averaging scheme permits the deposition of uniform thickness coatings independent of the substrate radius. Coating uniformity results from an exact cancellation of substrate radius dependent terms, which occurs when the substrate moves at constant velocity. If the substrate is allowed to accelerate over the source, arbitrary coating profiles can be generated through appropriate selection and control of the substrate center of mass equation of motion. The radial symmetry of the coating profile is an artifact produced by orbiting the substrate about its center of mass; other distributions are obtained by selecting another rotation axis. Consequently there is a direct mapping between the coating thickness and substrate equation of motion which can be used to tailor the coating profile without the use of masks and apertures.

Means and method of balancing multi-cylinder reciprocating machines

DOEpatents

Corey, John A.; Walsh, Michael M.

1985-01-01

A virtual balancing axis arrangement is described for multi-cylinder reciprocating piston machines for effectively balancing out imbalanced forces and minimizing residual imbalance moments acting on the crankshaft of such machines without requiring the use of additional parallel-arrayed balancing shafts or complex and expensive gear arrangements. The novel virtual balancing axis arrangement is capable of being designed into multi-cylinder reciprocating piston and crankshaft machines for substantially reducing vibrations induced during operation of such machines with only minimal number of additional component parts. Some of the required component parts may be available from parts already required for operation of auxiliary equipment, such as oil and water pumps used in certain types of reciprocating piston and crankshaft machine so that by appropriate location and dimensioning in accordance with the teachings of the invention, the virtual balancing axis arrangement can be built into the machine at little or no additional cost.