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Sample records for active vibration damper

  1. Active Vibration Dampers For Rotating Machinery

    NASA Technical Reports Server (NTRS)

    Kascack, Albert F.; Ropchock, John J.; Lakatos, Tomas F.; Montague, Gerald T.; Palazzolo, Alan; Lin, Reng Rong

    1994-01-01

    Active dampers developed to suppress vibrations in rotating machinery. Essentially feedback control systems and reciprocating piezoelectric actuators. Similar active damper containing different actuators described in LEW-14488. Concept also applicable to suppression of vibrations in stationary structures subject to winds and earthquakes. Active damper offers adjustable suppression of vibrations. Small and lightweight and responds faster to transients.

  2. Hybrid dampers for active vibration control

    SciTech Connect

    Gordaninejad, F.; Ray, A.

    1994-12-31

    In the present investigation feasibility of using hybrid electrorheological (ER) fluid dampers for active vibration control is examined. Small-scale, three-electrode hybrid dampers were designed and built such that they have two separate compartments to contain a viscous oil and an ER fluid. The results were compared to those obtained using a three-electrode ER fluid damper. It was shown that the use of hybrid ER fluid damper can enhance the damping. It was also found that the bang-bang and linear proportional control algorithms have similar effects on the amplitude-time response obtained from hybrid and ER fluid dampers.

  3. Active Inertial Vibration Isolators And Dampers

    NASA Technical Reports Server (NTRS)

    Laughlin, Darren; Blackburn, John; Smith, Dennis

    1994-01-01

    Report describes development of active inertial vibration isolators and dampers in which actuators electromagnet coils moving linearly within permanent magnetic fields in housings, somewhat as though massive, low-frequency voice coils in loudspeakers. Discusses principle of operation, electrical and mechanical considerations in design of actuators, characteristics of accelerometers, and frequency responses of control systems. Describes design and performance of one- and three-degree-of-freedom vibration-suppressing system based on concept.

  4. Compact Vibration Damper

    NASA Technical Reports Server (NTRS)

    Ivanco, Thomas G. (Inventor)

    2014-01-01

    A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

  5. Reduction of Floor Shock Vibration by Active Momentum Exchange Impact Damper

    NASA Astrophysics Data System (ADS)

    Son, Lovely; Yamada, Keisuke; Hara, Susumu; Utsuno, Hideo; Matsuhisa, Hiroshi

    This paper proposes an active control type of momentum exchange impact damper (AMEID) and its application to reducing shock vibration of the floor. The floor is modeled as a one-degree-of-freedom system. The active component of AMEID is realized by using a linear motor. The controller design of AMEID is based on the LQR optimal control theory. The simulation results show that the performance of AMEID is not affected by the mass ratio. In addition, the performance of AMEID is compared with the conventional passive momentum exchange impact damper (PMEID), the active mass damper (AMD) and the conventional active control method in reducing the floor shock vibration. It is shown that the shock reduction performance obtained by AMEID is larger than that obtained by PMEID. The power consumption and the stroke of the actuator for AMEID are lower than those of AMD. Furthermore, the transmitted force obtained by AMEID is smaller than that of the conventional active control.

  6. Maximizing semi-active vibration isolation utilizing a magnetorheological damper with an inner bypass configuration

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Wereley, Norman M.; Hu, Wei

    2015-05-01

    A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between which the key structure, i.e., the inner bypass, is formed and MR fluids are energized, is designed to provide large dynamic range (i.e., ratio of field-on damping force to field-off damping force) and damping force range. The damping force performance of the MR damper is modeled using phenomenological model and verified by the experimental tests. In order to assess its feasibility and capability in vibration control systems, the mathematical model of a SDOF semi-active vibration control system based on the MR damper and skyhook control strategy is established. Using an MTS 244 hydraulic vibration exciter system and a dSPACE DS1103 real-time simulation system, experimental study for the SDOF semi-active vibration control system is also conducted. Simulation results are compared to experimental measurements.

  7. Maximizing semi-active vibration isolation utilizing a magnetorheological damper with an inner bypass configuration

    SciTech Connect

    Bai, Xian-Xu; Wereley, Norman M.; Hu, Wei

    2015-05-07

    A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between which the key structure, i.e., the inner bypass, is formed and MR fluids are energized, is designed to provide large dynamic range (i.e., ratio of field-on damping force to field-off damping force) and damping force range. The damping force performance of the MR damper is modeled using phenomenological model and verified by the experimental tests. In order to assess its feasibility and capability in vibration control systems, the mathematical model of a SDOF semi-active vibration control system based on the MR damper and skyhook control strategy is established. Using an MTS 244 hydraulic vibration exciter system and a dSPACE DS1103 real-time simulation system, experimental study for the SDOF semi-active vibration control system is also conducted. Simulation results are compared to experimental measurements.

  8. Airfoil Vibration Dampers program

    NASA Technical Reports Server (NTRS)

    Cook, Robert M.

    1991-01-01

    The Airfoil Vibration Damper program has consisted of an analysis phase and a testing phase. During the analysis phase, a state-of-the-art computer code was developed, which can be used to guide designers in the placement and sizing of friction dampers. The use of this computer code was demonstrated by performing representative analyses on turbine blades from the High Pressure Oxidizer Turbopump (HPOTP) and High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). The testing phase of the program consisted of performing friction damping tests on two different cantilever beams. Data from these tests provided an empirical check on the accuracy of the computer code developed in the analysis phase. Results of the analysis and testing showed that the computer code can accurately predict the performance of friction dampers. In addition, a valuable set of friction damping data was generated, which can be used to aid in the design of friction dampers, as well as provide benchmark test cases for future code developers.

  9. The Influence of Semi-active Dampers on the Vibration Behaviour of Passenger Cars

    NASA Astrophysics Data System (ADS)

    Schneider, Sebastian; Brechter, Daniel; Janßen, Andreas; Mauch, Heiko

    The number of mechatronic components in modern car suspensions is increasing continuously to solve conflicts concerning design goals. Thus, changes in the vibration behaviour of the vehicle are caused. It needs to be ascertained whether this influence has to be taken into account when determining the fatigue life of a car and its components. Therefore, changes of the loads are studied in measurements and multi-body simulations of a passenger car with semi-active dampers. The evaluation of the forces at the wheel centre and at the shock absorber tower shows that different settings of semi-active dampers have an influence on fatigue life of the chassis and the car body. It is concluded that these effects need to be taken into account when determining fatigue life. Furthermore, multi-body simulations have been successfully applied to study the influence of semi-active dampers on the loads.

  10. Active vibration control of periodic disturbances using a DEAP damper

    NASA Astrophysics Data System (ADS)

    Sarban, Rahimullah; Jones, Richard W.; Mace, Brian; Rustighi, Emiliano

    2010-04-01

    A potential problem that could possibly restrict the application of dielectric electro-active polymer (DEAP) actuators for active vibration damping is highlighted in this contribution. If a periodic electric field is applied to a DEAP actuator to counteract a periodic vibratory disturbance, a very common vibration attenuation problem, then the mechanical output will be the square of the periodic input. This will result in an actuator output with several harmonics. Therefore from a vibration damping perspective not only does the first harmonic of the periodic disturbance need to be considered but also additional harmonics, introduced by the actuator itself. Feedforward active damping of periodic vibratory disturbances using a tubular DEAP actuator is addressed in this contribution. Initially the addition of a d.c. bias offset to the periodic voltage signal applied to the actuator is investigated to try and reduce the effect of the higher harmonics. The use of a linearizing gain schedule is then also examined. Using a comparatively large d.c. bias voltage offset has a linearizing affect on the voltage-strain characteristics of the tubular actuator thereby reducing the influence of the higher harmonics on the resulting vibration damping characteristics. The disadvantage of this approach is that the operating range, in terms of the actuator stroke that can be achieved, is decreased. The use of a linearizing gain schedule also reduces the influence of the higher harmonics but provides less of a constraint on the operating range of the actuator.

  11. Semi-active vibration absorber based on real-time controlled MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.

    2014-06-01

    A semi-active vibration absorber with real-time controlled magnetorheological damper (MR-SVA) for the mitigation of harmonic structural vibrations is presented. The MR damper force targets to realize the frequency and damping adaptations to the actual structural frequency according to the principle of the undamped vibration absorber. The relative motion constraint of the MR-SVA is taken into account by an adaptive nonlinear control of the internal damping of the MR-SVA. The MR-SVA is numerically and experimentally validated for harmonic excitation of the primary structure when the natural frequency of the passive mass spring system of the MR-SVA is correctly tuned to the targeted structural resonance frequency and when de-tuning is present. The results demonstrate that the MR-SVA outperforms the passive TMD at structural resonance frequency by at least 12.4% and up to 60.0%.

  12. High-Temperature Vibration Damper

    NASA Technical Reports Server (NTRS)

    Clarke, Alan; Litwin, Joel; Krauss, Harold

    1987-01-01

    Device for damping vibrations functions at temperatures up to 400 degrees F. Dampens vibrational torque loads as high as 1,000 lb-in. but compact enough to be part of helicopter rotor hub. Rotary damper absorbs energy from vibrating rod, dissipating it in turbulent motion of viscous hydraulic fluid forced by moving vanes through small orifices.

  13. Active mass damper system employing time delay control algorithm for vibration mitigation of building structure

    NASA Astrophysics Data System (ADS)

    Jang, Dong-Doo; Park, Jeongsu; Jung, Hyung-Jo

    2013-04-01

    The feasibility of an active mass damper (AMD) system employing the time delay control (TDC) algorithm, which is one of the robust and adaptive control algorithms, for effectively suppressing the wind-induced vibration of a building structure is investigated. The TDC algorithm has several attractive features such as the simplicity and the excellent robustness to unknown system dynamics and disturbance. Based on the characteristics of the algorithm, it has the potential to be an effective control system for mitigating excessive vibration of civil engineering structures such as buildings, bridges and towers. However, it has not been used for structural response reduction yet. In order to verify the effectiveness of the proposed active control method combining an AMD system with the TDC algorithm, a series of labscale tests are carried out.

  14. Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control

    NASA Astrophysics Data System (ADS)

    Ullah Khan, Irfan; Wagg, David; Sims, Neil D.

    2016-08-01

    This paper presents a new hybrid active and semi-active control method for vibration suppression in flexible structures. The method uses a combination of a semi-active device and an active control actuator situated elsewhere in the structure to suppress vibrations. The key novelty is to use the hybrid controller to enable the magneto-rheological damper to achieve a performance as close to a fully active device as possible. This is achieved by ensuring that the active actuator can assist the magneto-rheological damper in the regions where energy is required. In addition, the hybrid active and semi-active controller is designed to minimize the switching of the semi-active controller. The control framework used is the immersion and invariance control technique in combination with sliding mode control. A two degree-of-freedom system with lightly damped resonances is used as an example system. Both numerical and experimental results are generated for this system, and then compared as part of a validation study. The experimental system uses hardware-in-the-loop to simulate the effect of both the degrees-of-freedom. The results show that the concept is viable both numerically and experimentally, and improved vibration suppression results can be obtained for the magneto-rheological damper that approach the performance of an active device.

  15. Cable connected active tuned mass dampers for control of in-plane vibrations of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Fitzgerald, B.; Basu, B.

    2014-11-01

    In-plane vibrations of wind turbine blades are of concern in modern multi-megawatt wind turbines. Today's turbines with capacities of up to 7.5 MW have very large, flexible blades. As blades have grown longer the increasing flexibility has led to vibration problems. Vibration of blades can reduce the power produced by the turbine and decrease the fatigue life of the turbine. In this paper a new active control strategy is designed and implemented to control the in-plane vibration of large wind turbine blades which in general is not aerodynamically damped. A cable connected active tuned mass damper (CCATMD) system is proposed for the mitigation of in-plane blade vibration. An Euler-Lagrangian wind turbine model based on energy formulation has been developed for this purpose which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations and also the interaction between the blades and the tower including the CCATMDs. The CCATMDs are located inside the blades and are controlled by an LQR controller. The turbine is subject to turbulent aerodynamic loading simulated using a modification to the classic Blade Element Momentum (BEM) theory with turbulence generated from rotationally sampled spectra. The turbine is also subject to gravity loading. The effect of centrifugal stiffening of the rotating blades has also been considered. Results show that the use of the proposed new active control scheme significantly reduces the in-plane vibration of large, flexible wind turbine blades.

  16. The effect of time delay on control stability of an electromagnetic active tuned mass damper for vibration control

    NASA Astrophysics Data System (ADS)

    Hassan, A.; Torres-Perez, A.; Kaczmarczyk, S.; Picton, P.

    2016-05-01

    The aim of this paper is to investigate the effect of time delays on the stability of a zero-placement position and velocity feedback law for a vibratory system comprising harmonic excitation equipped with an electromagnetic active tuned mass damper (ATMD). The purpose of the active control is broadening the vibration attenuation envelope of a primary mass to a higher frequency region identified as from 50±0.5Hz with a passive tuned mass damper (TMD) to a wider range of 50±5Hz with an ATMD. Stability conditions of the closed-loop system are determined by studying the position of the system closed-loop poles after the introduction of time delays for different excitation frequencies. A computer simulation of the model predicted that the proposed control system is subject to instability after a critical time delay margin dependent upon the frequency of excitation and the finding were experimentally validated. Three solutions are derived and experimentally tested for minimising the effect of time delays on the stability of the control system. The first solution is associated with the introduction of more damping in the absorber system. The second incorporates using a time-delayed ATMD by tuning its original natural resonant frequency to beyond the nominal operational frequency range of the composite system. The third involves an online gain tuning of filter coefficients in a dual arrangement of low-pass and high-pass filters to eliminate the effect time delays by manipulating the signal phase shifts.

  17. Vibration and shock isolation performance of a pressure-limited hydraulic damper

    NASA Astrophysics Data System (ADS)

    Su, Hong; Rakheja, S.; Sankar, T. S.

    1989-01-01

    A pressure-limited hydraulic damper is proposed to achieve variable damping within a vibration isolation system. The variation in damping parameters is achieved passively by limiting the pressure differential across the damper piston, using pressure relief valves. The pressure-limited hydraulic damper is modeled as a non-linear dynamical system incorporating control valve dynamics. The significance of the pressure differential across the damper piston is discussed in view of vibration isolation, and a methodology for estimation of a suitable value of the limiting pressure is proposed. The vibration and shock isolation characteristics of the passive pressure-limited damper are investigated through computer simulation. The vibration and shock isolation performance of the proposed damper is compared to those of passive and semi-active "on-off" vibration isolators. A comparison of the simulation results reveals that the vibration and shock isolation performance of the pressure-limited damper is superior to that of a conventional passive damper, and is comparable to that of a semi-active "on-off" damper. The proposed pressure-limited damper can be realised passively and does not require the sophisticated control devices and feedback instrumentation essential for a semi-active "on-off" vibration isolation system.

  18. Viscous-pendulum damper suppresses structural vibrations

    NASA Technical Reports Server (NTRS)

    Reed, W. H., III

    1964-01-01

    The viscous pendulum damper consists of a cylinder containing round trays on which round lead slugs rest. When assembled, the container is filled with a viscous liquid and attached, with axis vertical, to the structure. The device permits varying the damping of structural vibrations.

  19. Viscoelastic Vibration Dampers for Turbomachine Blades

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan

    2003-01-01

    Simple viscoelastic dampers have been invented for use on the root attachments of turbomachine blades. These dampers suppress bending- and torsion-mode blade vibrations, which are excited by unsteady aerodynamic forces during operation. In suppressing vibrations, these dampers reduce fatigue (thereby prolonging blade lifetimes) while reducing noise. These dampers can be installed in new turbomachines or in previously constructed turbomachines, without need for structural modifications. Moreover, because these dampers are not exposed to flows, they do not affect the aerodynamic performances of turbomachines. Figure 1 depicts a basic turbomachine rotor, which includes multiple blades affixed to a hub by means of dovetail root attachments. Prior to mounting of the blades, thin layers of a viscoelastic material are applied to selected areas of the blade roots. Once the blades have been installed in the hub and the rotor is set into rotation, centrifugal force compresses these layers between the mating load-bearing surfaces of the hub and the blade root. The layers of viscoelastic material provide load paths through which the vibration energy of the blade can be dissipated. The viscoelasticity of the material converts mechanical vibration energy into shear strain energy and then from shear strain energy to heat. Of the viscoelastic materials that have been considered thus far for this application, the one of choice is a commercial polyurethane that is available in tape form, coated on one side with an adhesive that facilitates bonding to blade roots. The thickness of the tape can be chosen to suit the specific application. The typical thickness of 0.012 in. (.0.3 mm) is small enough that the tape can fit in the clearance between the mating blade-root and hub surfaces in a typical turbomachine. In an experiment, a blade was mounted in a test fixture designed to simulate the blade-end conditions that prevail in a turbocompressor. Vibrations were excited in the blade by

  20. Effect of the active damper coil system on the lateral displacement of the magnetically levitated bogie

    SciTech Connect

    Ohashi, S.; Ohsaki, H.; Masada, E.

    1999-09-01

    Numerical simulation of the superconducting magnetically levitated bogie (JR Maglev) has been studied. The active damper coil system is introduced. In this levitation system, the interaction between levitation and guidance is strong. This active damper coil system is designed for reducing the vertical vibration of the bogie. Using the numerical simulation, its effect on the lateral displacement of the bogie is assessed. The active damper coil system for the vertical vibration is shown to works as a passive damper for the lateral vibration.

  1. A Study on Design and Analysis of Hybrid Vibration Damper with Energy Harvesting and Optimal Damping Effect

    NASA Astrophysics Data System (ADS)

    Hanumantha Rao, T. V.; Srinivasa Rao, M. S. S.; Apparao, B. V.; Satyanarayana, K.

    2014-04-01

    The basic purpose of a damper is to reduce the vibration and to have a better ride comfort, road handling and safety to the rider. Recent developments show that an active vibration damper can effectively work much better than a passive damper. The effectiveness and reliability can be further enhanced by using hybrid dampers, which is a combination of active and passive dampers. But the need to have energy optimization in any field need not be stressed. Consequently, novel suspension concepts are required, not only to improve the vehicle's dynamic performance, but also to see that the energy generated during vibration can be harvested by utilizing regeneration functions. Hence if a hybrid damper with energy harvesting capability be designed, it would serve both purposes. In the hybrid damper a combination of hydraulic damper to act as a passive damper and an electromagnetic (EM) damper to act as an active damper is considered. The hydraulic system has more reliability and is time tested and the EM system acts as a dynamic vibration system as well as energy harvester. In this study a hybrid EM damper is modeled, analyzed and validity is shown for frequency response functions and energy balance for its active use. It is also shown how the effectiveness of the suspension system can be enhanced by using a hybrid damper.

  2. Study on optimal impact damper using collision of vibrators

    NASA Astrophysics Data System (ADS)

    Iwata, Yoshio; Komatsuzaki, Toshihiko; Kitayama, Satoshi; Takasaki, Tatsuya

    2016-01-01

    In this paper, we propose an impact damper which consists of multiple vibrators installed on a main structure and dissipates the vibrational energy by collisions between the vibrators. Transient vibration of the main system subject to an impact rapidly converges to zero by the impact damper. DE (Differential Evolution) method which is one of the optimization methods is employed to determine mass and spring constant of the every vibrators to maximize damping effect. We discuss the effect of a coefficient of restitution of vibrators, a ratio of total mass of the vibrators to the main structure mass and the number of the vibrators on the damping performance. The damping effect of the impact damper with three vibrators is demonstrated experimentally.

  3. Application of impact dampers in vibration control of flexible structures

    NASA Technical Reports Server (NTRS)

    Akl, Fred A.; Butt, Aamir S.

    1995-01-01

    Impact dampers belong to the category of passive vibration devices used to attenuate the vibration of discrete and continuous systems. An impact damper generally consists of a mass which is allowed to travel freely between two defined stops. Under the right conditions, the vibration of the structure to which the impact damper is attached will cause the mass of the impact damper to strike the structure. Previous analytical and experimental research work on the effect of impact dampers in attenuating the vibration of discrete and continuous systems have demonstrated their effectiveness. It has been shown in this study that impact dampers can increase the intrinsic damping of a lightly-damped flexible structure. The test structure consists of a slender flexible beam supported by a pin-type support at one end and supported by a linear helical flexible spring at another location. Sinusoidal excitation spanning the first three natural frequencies was applied in the horizontal plane. The orientation of the excitation and the test structure in the horizontal plane minimizes the effect of gravity on the behavior of the test structure. The excitation was applied using a linear sine sweep technique. The span of the test structure, the mass of the impact damper, the distance of travel, and the location of the impact damper along the span of the test structure were varied. The damping ratio are estimated for sixty test configurations. The results show that the impact damper significantly increases the damping ratio of the test structure. Statistical analysis of the results using the method of multiple linear regression indicates that a reasonable fit has been accomplished. It is concluded that additional experimental analysis of flexible structures in microgravity environment is needed in order to achieve a better understanding of the behavior of impact damper under conditions of microgravity. Numerical solution of the behavior of flexible structures equipped with impact

  4. Optimal damper location in the vibration control of large space structures

    NASA Technical Reports Server (NTRS)

    Wang, B. P.; Pilkey, W. D.

    1981-01-01

    The problem of finding the optimal location of active dampers for the vibration control of space structures is investigated. The optimal location is where maximum damping can be introduced to a particular vibration mode. To this end, classical root locus techniques are used to study the effect on eigenvalues of placing a damper on an undamped structure. An efficient formulation is derived which avoids the solution of the damped eigenvalue problem. Based on the observation of the results for a free-free beam model, a Minimum Constrained Frequency Criterion (MCFC) for locating the optimal damper location is proposed.

  5. Design and vibration control of military vehicle suspension system using magnetorheological damper and disc spring

    NASA Astrophysics Data System (ADS)

    Ha, Sung Hoon; Seong, Min-Sang; Choi, Seung-Bok

    2013-06-01

    This paper proposes a new type of magnetorheological (MR) fluid based suspension system and applies it to military vehicles for vibration control. The suspension system consists of a gas spring, a MR damper and a safety passive damper (disc spring). Firstly, a dynamic model of the MR damper is derived by considering the pressure drop due to the viscosity and the yield stress of the MR fluid. A dynamic model of the disc spring is then established for its evaluation as a safety damper with respect to load and pressure. Secondly, a full military vehicle is adopted for the integration of the MR suspension system. A skyhook controller associated with a semi-active actuating condition is then designed to reduce the imposed vibration. In order to demonstrate the effectiveness of the proposed MR suspension system, a computer simulation is undertaken showing the vibration control performance of such properties as vertical displacement and pitch angle, evaluated for a bumpy road profile.

  6. Experimental study of a self-powered and sensing MR-damper-based vibration control system

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan

    2011-10-01

    The paper deals with a semi-active vibration control system based on a magnetorheological (MR) damper. The study outlines the model and the structure of the system, and describes its experimental investigation. The conceptual design of this system involves harvesting energy from structural vibrations using an energy extractor based on an electromagnetic transduction mechanism (Faraday's law). The system consists of an electromagnetic induction device (EMI) prototype and an MR damper of RD-1005 series manufactured by Lord Corporation. The energy extracted is applied to control the damping characteristics of the MR damper. The model of the system was used to prove that the proposed vibration control system is feasible. The system was realized in the semi-active control strategy with energy recovery and examined through experiments in the cases where the control coil of the MR damper was voltage-supplied directly from the EMI or voltage-supplied via the rectifier, or supplied with a current control system with two feedback loops. The external loop used the sky-hook algorithm whilst the internal loop used the algorithm switching the photorelay, at the output from the rectifier. Experimental results of the proposed vibration control system were compared with those obtained for the passive system (MR damper is off-state) and for the system with an external power source (conventional system) when the control coil of the MR damper was supplied by a DC power supply and analogue voltage amplifier or a DC power supply and a photorelay. It was demonstrated that the system is able to power-supply the MR damper and can adjust itself to structural vibrations. It was also found that, since the signal of induced voltage from the EMI agrees well with that of the relative velocity signal across the damper, the device can act as a 'velocity-sign' sensor.

  7. Vibration control of a structure using Magneto-Rheological grease damper

    NASA Astrophysics Data System (ADS)

    Sugiyama, Shinya; Sakurai, Tomoki; Morishita, Shin

    2013-09-01

    This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval due to the density difference between the particles and their career fluid. To overcome this defect, we have developed a new type of controllable working fluid using grease as the career of magnetic particles. Network of thickener in grease is expected to hold the magnetic particles and prevent them from settled down. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder of damper. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper worked effectively as a semi-active damper.

  8. Quasi-active suspension design using magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Potter, Jack N.; Neild, Simon A.; Wagg, David J.

    2011-05-01

    Quasi-active damping is a method of coupled mechanical and control system design using multiple semi-active dampers. By designing the systems such that the desired control force may always be achieved using a combination of the dampers, quasi-active damping seeks to approach levels of vibration isolation achievable through active damping, whilst retaining the desirable attributes of semi-active systems. In this article a design is proposed for a quasi-active, base-isolating suspension system. Control laws are firstly defined in a generalised form, where semi-active dampers are considered as idealised variable viscous dampers. This system is used to demonstrate in detail the principles of quasi-active damping, in particular the necessary interaction between mechanical and control systems. It is shown how such a system can produce a tunable, quasi-active region in the frequency response of very low displacement transmissibility. Quasi-active control laws are then proposed which are specific for use with magnetorheological dampers. These are validated in simulation using a realistic model of the damper dynamics, again producing a quasi-active region in the frequency response. Finally, the robustness of the magnetorheological, quasi-active suspension system is demonstrated.

  9. Vibration power generator for a linear MR damper

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan

    2010-10-01

    The paper describes the structure and the results of numerical calculations and experimental tests of a newly developed vibration power generator for a linear magnetorheological (MR) damper. The generator consists of permanent magnets and coil with foil winding. The device produces electrical energy according to Faraday's law of electromagnetic induction. This energy is applied to vary the damping characteristics of the MR damper attached to the generator by the input current produced by the device. The objective of the numerical calculations was to determine the magnetic field distribution in the generator as well as the electric potential and current density in the generator's coil during the idle run and under the load applied to the MR damper control coil. The results of the calculations were used during the design and manufacturing stages of the device. The objective of the experimental tests carried out on a dynamic testing machine was to evaluate the generator's efficiency and to compare the experimental and predicted data. The experimental results demonstrate that the engineered device enables a change in the kinetic energy of the reciprocal motion of the MR damper which leads to variations in the damping characteristics. That is why the generator may be used to build up MR damper based vibration control systems which require no external power.

  10. Structural vibration control by tuned mass damper using central pattern generator

    NASA Astrophysics Data System (ADS)

    Iba, Daisuke; Hongu, Junichi

    2011-04-01

    This paper proposes a new control method for active mass dampers using a Central Pattern Generator in vibration mitigation. The active mass dampers (or active dynamic absorbers) have been applied to structural vibration control of high-rise buildings, bridges and so on. In this case, the mass of the active mass damper must oscillate in an appropriate phase in relation to the control object, and generally, the damper has been designed by linear control theory as pole placement method, optimal control method or H infinity control method, and all the rest. On the other hand, on walking of animate beings like mammals or insects, both side feet have appropriate phase relations; moreover, it is possible to keep moving on irregular ground. That is, algorithms for the walking would be embedded into the animate beings to control the complicated and redundant bodies with ease and robustness. In biological study, the Central Pattern Generators in bodies playing a significant role in the walking have been learned over the last few decades, and some studies said that some animate beings are able to control their feet by using the generators without their brains in the walking. Moreover, mathematical models of the pattern generators have been proposed, and some researchers have been studying to realize walking of biped-robots using the pattern generators embedded in a computer. In this study, the algorithm is installed into a controller for the active mass damper; furthermore, validation of the controller is performed by numerical simulation.

  11. On a Self-Tuning Impact Vibration Damper for Rotating Turbomachinery

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Bagley, Ronald L.; Mehmed, Oral; Choi, Ben (Technical Monitor)

    2000-01-01

    A self-tuning impact damper is investigated analytically and experimentally as a device to inhibit vibration and increase the fatigue life of rotating components in turbomachinery. High centrifugal loads in rotors can inactivate traditional impact dampers because of friction or misalignment of the damper in the g-field. Giving an impact damper characteristics of an acceleration tuned-mass damper enables the resulting device to maintain damper mass motion and effectiveness during high-g loading. Experimental results presented here verify that this self-tuning impact damper can be designed to follow an engine order line. damping rotor component resonance crossings.

  12. Shock and vibration control systems using a self-sensing magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Wang, Dai-Hua

    2014-04-01

    The theoretical analysis and the prototype testing of the integrated relative displacement self-sensing magnetorheological damper (IRDSMRD) indicate that the controllable damping force performance and the relative displacement sensing performance influence each other for varying applied currents. Aiming at verifying the feasibility and capability of the IRDSMRD to constitute semi-active shock and vibration control systems, this study presents a single-degree-of-freedom (SDOF) shock and vibration control system based on the IRDSMRD. The mathematical model of the IRDSMRD, including the control damping force and the linearity of the integrated relative displacement sensor (IRDS), is established, and the governing equation for the SDOF system based on the IRDSMRD is derived. A skyhook control algorithm is utilized to improve the shock and vibration control performance of the SDOF semi-active control systems. The simulated control performances of the SDOF systems individually using the IRDSMRD without any extra-set dynamic sensor, the conventional MR damper with a linear variable differential transformer (LVDT), and the passive damper, under shock loads due to vertical pulses (the maximum initial velocity is as high as 10 m/s), and sinusoidal vibrations with a frequency range of 0-25 Hz, are evaluated, compared, and analyzed.

  13. A magnetic damper for first mode vibration reduction in multimass flexible rotors

    NASA Technical Reports Server (NTRS)

    Kasarda, M. E. F.; Allaire, P. E.; Humphris, R. R.; Barrett, L. E.

    1989-01-01

    Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems, and would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. An experimental test rig is described which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.

  14. Viscous dampers cut vibration in heater drain line

    SciTech Connect

    Mays, B.; Rencher, D. ); Keowen, R.S.; Hueffmann, G.K.

    1993-06-01

    This article discusses the control of unacceptable vibration levels that persisted for about two years in a 400 F heater drain piping system at Comanche Peak's 1100-MW Unit 1. The system in this PWR nuclear power plant is made up of approximately 300 ft of 8-in., Schedule 40 piping that runs from the steam generator heater to two 10-ft-diameter horizontal drain tanks. During start-up and shut-down operations, flashing of the 400 F water to steam occurs at the intakes of the tanks. This flashing caused severe vibration in the 8-in. piping from the tanks to about 80 ft upstream. Peak displacements of approximately three inches were measured. Viscous dampers were installed to solve the problem.

  15. Effectiveness of a disk-type magnetorheologic fluid damper for rotor system vibration control

    NASA Astrophysics Data System (ADS)

    Zhu, Changsheng; Robb, David A.; Ewins, David J.

    2001-07-01

    A disk-type MR fluid damper based on shear operation mode is presented in this paper. The magnetic field of the disk-type MR fluid damper is analysed by the finite element method. The effect of excitation current in the coil on the magnetic flux density in the axial gaps filled with MR fluid is studied both theoretically and experimentally. Finally, the effectiveness of the disk-type MR fluid damper for attenuating vibration of rotor systems and of a simple open-loop on-off control based on the feedback of rotational speed on controlling vibration of rotor systems are experimentally studied. It is shown that the dynamic characteristics of the disk-type MR fluid damper can be controlled by a simple magnetic coil with a low voltage, and the disk-type MR fluid damper is very effective to attenuate vibration of rotor systems.

  16. 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.

  17. Cable vibration control with both lateral and rotational dampers attached at an intermediate location

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Sun, Limin; Nagarajaiah, Satish

    2016-09-01

    Lateral dampers have been extensively studied and implemented for supplementing modal damping in cable vibration mitigation. When considering the cable flexural stiffness that is actually present, albeit small, there is another degree of freedom of the cable at the lateral damper, namely the rotation, that can be constrained by a rotational damper to achieve larger additional damping. This is of particular significance for long cables where the near-anchorage lateral damper alone is usually insufficient. The problem of a cable with bending stiffness, attached with both lateral and rotational dampers at an intermediate point, is therefore considered in this study. The characteristic equation of the resulting system is formulated by assembling the dynamic stiffness from the two segments divided by the damper, which is subsequently solved using argument principle method. Dynamics of the controlled system is thus discussed in general through parametric analysis. For the case where the damper location is close to the anchorage, asymptotic solutions for complex frequency and damping ratio are provided; explicit formulas for determining the optimal damper coefficients are also derived. It is found that when the lateral and rotational damper coefficients are properly balanced, the proposed strategy can achieve up to 30 percent damping enhancement compared to the case with only the lateral damper, in practical cable bending stiffness range.

  18. Vibration suppression of printed circuit boards using an external particle damper

    NASA Astrophysics Data System (ADS)

    Veeramuthuvel, P.; Sairajan, K. K.; Shankar, K.

    2016-03-01

    Particle damping is an effective method of passive vibration control, of recent research interest. The novel use of particle damper capsule on a Printed Circuit Board (PCB) and the development of Radial Basis Function neural network to accurately predict the acceleration response is presented here. The prediction of particle damping using this neural network is studied in comparison with the Back Propagation Neural network. Extensive experiments are carried out on a PCB for different combinations of particle damper parameters such as particle size, particle density, packing ratio, and the input force during the primary modes of vibration and the obtained results are used for training and testing of neural networks. Based on the prediction from the better trained network, useful design guidelines for the particle damper suitable for PCB are arrived at. The effectiveness of particle dampers for vibration suppression of PCB under random vibration environment is demonstrated based on these design guidelines.

  19. Semi-active control of seat suspension with MR damper

    NASA Astrophysics Data System (ADS)

    Yao, H. J.; Fu, J.; Yu, M.; Peng, Y. X.

    2013-02-01

    The vibration control of a seat suspension system with magnetorheological (MR) damper is investigated in this study. Firstly, a dynamical model of the seat suspension system with parameter uncertainties (such as mass, stiffness, damping) and actuator saturation is established. Secondly, based on Lyapunov functional theory and considering constraint conditions for damping force, the semi-active controller is designed, and the controller parameters are derived in terms of linear matrix inequalities (LMIs), which guarantees performance index. Finally, compared control strategy and the passive, skyhook control strategy, the simulation results in time and frequency domains demonstrate the proposed approach can achieve better vertical acceleration attenuation for the seat suspension system and improve ride comfort.

  20. Potential of viscous dampers for vibration mitigation of transmission overhead lines

    NASA Astrophysics Data System (ADS)

    Bassam, A.; Soltani, Amir

    2015-04-01

    One of the important parameters in the design of transmission lines is the evaluation of the susceptibility of these cables to vibrations and if necessary, providing proper means to mitigate these vibrations. Transmission lines are especially susceptible to vibrations as a result of their light weight. Viscous dampers are one of the tools that can be applied to mitigate cable vibrations. However, the damping ratio obtained by these dampers is very limited. The present study provides a finite element formulation for an isoparametric cable element. A comparison is made between the results of presented approach with finite series method to validate the model. Additionally, a comparison is made between linear and non-linear behavior of a cable under sweep sinusoidal excitations with different amplitudes. Finally, a case study is conducted to investigate the potential of additional damping provided by a third viscous damper for the case in which two rubber bushings are already attached to the cable near the anchorages. Based on this case study, the dependency between the third damper location and optimum viscosity for maximum vibration mitigation that can be given to a cable with rubber bushings is investigated. The results of the present study show that although rubber bushings may help mitigating vibrations, they reduce the effect of additional damping devices. Additionally, for non-sagged cables, the nonlinearity is negligible in moderate vibrations. Lastly, if the third damper viscosity is selected properly, it can be very effective in further mitigating the vibrations amplitudes.

  1. Semi-active tuned mass dampers with phase control

    NASA Astrophysics Data System (ADS)

    Chung, Lap-Loi; Lai, Yong-An; Walter Yang, Chuang-Sheng; Lien, Kuan-Hua; Wu, Lai-Yun

    2013-07-01

    The present study aims at proposing an innovative phase control methodology for semi-active tuned mass dampers (SA-TMDs) that intend to minimize the off-tuned problems associated with passive tuned mass dampers (P-TMDs). The phase control algorithm is first developed, the essential of which is to apply the variable friction force to slow down the mass block at specific moments when the phase lag of the SA-TMD with respect to the structure is different from 90°, resulting in the SA-TMD back to the desired phase lag, i.e., -90° phase deviation, so that the SA-TMD has the maximum power flow to reduce the structural vibration. The feasibility of the application of the phase control in SA-TMDs is verified by performing numerical analyses of a simplified Taipei 101 structure model with a SA-TMD subjected to sinusoidal loads and design level wind loads. The numerical simulation results show that the SA-TMD implemented with phase control can enable the mass block to vibrate in a manner with a phase lag close to the -90° when the structure model is under sinusoidal excitations with frequencies different from the structural fundamental mode. The SA-TMD with phase control not only exhibits better performance than the optimal P-TMD in terms of suppressing the structural vibration, but also enhances its robustness, particularly when the SA-TMD is off-tuned to the structure.

  2. Mitigation of edgewise vibrations in wind turbine blades by means of roller dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Zili; Li, Jie; Nielsen, Søren R. K.; Basu, Biswajit

    2014-10-01

    Edgewise vibrations in wind turbine blades are lightly damped, and large amplitude vibrations induced by the turbulence may significantly shorten the fatigue life of the blade. This paper investigates the performance of roller dampers for mitigation of edgewise vibrations in rotating wind turbine blades. Normally, the centrifugal acceleration of the rotating blade can reach to a magnitude of 7-8g, which makes it possible to use this kind of damper with a relatively small mass ratio for suppressing edgewise vibrations effectively. The parameters of the damper to be optimized are the mass ratio, the frequency ratio, the coefficient of rolling friction and the position of the damper in the blade. The optimization of these parameters has been carried out on a reduced 2-DOF nonlinear model of the rotating wind turbine blade equipped with a roller damper in terms of a ball or a cylinder, ignoring the coupling with other degrees of freedom of the wind turbine. The edgewise modal loading on the blade has been calculated from a more sophisticated 13-DOF aeroelastic wind turbine model with due consideration to the indicated couplings, the turbulence and the aerodynamic damping. Various turbulence intensities and mean wind speeds have been considered to evaluate the effectiveness of the roller damper in reducing edgewise vibrations when the working conditions of the wind turbine are changed. Further, the optimized roller damper is incorporated into the 13-DOF wind turbine model to verify the application of the decoupled optimization. The results indicate that the proposed damper can effectively improve the structural response of wind turbine blades.

  3. Semi-active friction damper for buildings subject to seismic excitation

    NASA Astrophysics Data System (ADS)

    Mantilla, Juan S.; Solarte, Alexander; Gomez, Daniel; Marulanda, Johannio; Thomson, Peter

    2016-04-01

    Structural control systems are considered an effective alternative for reducing vibrations in civil structures and are classified according to their energy supply requirement: passive, semi-active, active and hybrid. Commonly used structural control systems in buildings are passive friction dampers, which add energy dissipation through damping mechanisms induced by sliding friction between their surfaces. Semi-Active Variable Friction Dampers (SAVFD) allow the optimum efficiency range of friction dampers to be enhanced by controlling the clamping force in real time. This paper describes the development and performance evaluation of a low-cost SAVFD for the reduction of vibrations of structures subject to earthquakes. The SAVFD and a benchmark structural control test structure were experimentally characterized and analytical models were developed and updated based on the dynamic characterization. Decentralized control algorithms were implemented and tested on a shaking table. Relative displacements and accelerations of the structure controlled with the SAVFD were 80% less than those of the uncontrolled structure

  4. The Effects of Manufacturing Tolerances on the Vibration of Aero-engine Rotor-damper Assemblies

    NASA Technical Reports Server (NTRS)

    Sykes, J. E. H.; Holmes, R.

    1991-01-01

    A range of rotor assemblies incorporating one and two squeeze film dampers with various static misalignments is investigated. Waterfall diagrams are constructed which demonstrate the effects of such misalignment and damper support flexibility on the nature and severity of subsynchronous resonance and jump phenomena. Vibration signatures of similar rotor-bearing assemblies are shown to contrast strongly due to different accumulations of tolerances during manufacture, fitting, and operation.

  5. Tuned rolling-ball dampers for vibration control in wind turbines

    NASA Astrophysics Data System (ADS)

    Chen, Junling; Georgakis, Christos T.

    2013-10-01

    With wind turbines growing in size and cost, it is necessary to reduce their dynamic responses and improve their fatigue lifetime. A passive tuned-mass damper (TMD) is a very efficient solution for vibration control in structures subjected to wind excitations. In this study, a tuned rolling-ball damper characterized by single or multiple steel balls rolling in a spherical container is proposed to be mounted on the top of wind turbines to reduce the wind-induced vibration. A 1/20 scale shaking table model was developed to evaluate the control effectiveness of the damper. The wind-induced dynamic responses of the test model with and without TMD were obtained from the shaking table tests. The test results indicated that the rolling-ball dampers could effectively suppress the wind-induced vibration of wind turbines. The damper with three balls in one container had better control effectiveness than that with only one ball because of the impact effect and the rolling friction. The control effectiveness of the damper cannot be improved further when the number of balls is increased beyond a certain point.

  6. A new vibration isolation bed stage with magnetorheological dampers for ambulance vehicles

    NASA Astrophysics Data System (ADS)

    Chae, Hee Dong; Choi, Seung-Bok

    2015-01-01

    The vibration experienced in an ambulance can lead to secondary injury to a patient and discourage a paramedic from providing emergency care. In this study, with the goal of resolving this problem, a new vibration isolation bed stage associated with magnetorheological (MR) dampers is proposed to ensure ride quality as well as better care for the patient while he/she is being transported. The bed stage proposed in this work can isolate vibrations in the vertical, rolling and pitching directions to reflect the reality that occurs in the ambulance. Firstly, an appropriate-sized MR damper is designed based on the field-dependent rheological properties of MR fluid, and the damping force characteristics of a MR damper are evaluated as a function of the current. A mechanical model of the proposed vibration isolation bed stage is then established to derive the governing equations of motion. Subsequently, a sliding mode controller is formulated to control the vibrations caused from the imposed excitation signals; those signals are directly measured using a real ambulance subjected to bump-and-curve road conditions. Using the controller based on the dynamic motion of the bed stage, the vibration control performance is evaluated in both the vertical and pitch directions. It is demonstrated that the magnitude of the vibration in the patient compartment of the ambulance can be significantly reduced by applying an input current to the MR dampers installed for the new bed stage.

  7. A disk-type magneto-rheological fluid damper for rotor system vibration control

    NASA Astrophysics Data System (ADS)

    Zhu, Changsheng

    2005-05-01

    Based on the particular characteristic of a magneto-rheological (MR) fluid, i.e., a rapid, reversible and dramatic change in its rheological properties produced by the application of an external magnetic field, a simple disk-type MR fluid damper operating in shear flow mode is presented in this paper. The magnetic field of the disk-type MR fluid damper is analyzed by the finite element method in order to show if the design is reasonable. The effect of excitation current in the coil on the magnetic flux density in the axial gaps filled with the MR fluid is studied both theoretically and experimentally. Finally, the effectiveness of the disk-type MR fluid damper for attenuating the vibration of rotor systems and of a simple open-loop on-off control based on the feedback of rotational speed for controlling vibration of rotor systems are experimentally studied in a flexible rotor system. It is shown that the dynamic characteristics of the disk-type MR fluid damper can be easily controlled by a steady magnetic field produced by a simple electrical magnetic coil with a low DC current (less than 1 A) and that the disk-type MR fluid damper is very effective for attenuating and controlling the vibration of the rotor systems. It is possible to supply the optimum supporting damping for every vibration mode in the rotor system by using the disk-type MR damper, if the location of the disk-type MR fluid damper in the rotor is properly chosen.

  8. Magnetorheological composites as semi-active elements of dampers

    NASA Astrophysics Data System (ADS)

    Kaleta, Jerzy; Lewandowski, Daniel; Zając, Piotr; Kustroń, Pawel

    2009-02-01

    An original magnetorheological composite (MRC) with porous elastomeric matrix and filled with magnetorheological fluid was created at the work. It was used later on to build a damper working in the shearing mode without friction against external surfaces of the so-called skid. This prototype construction was used for damping free vibrations in the beam. An analysis of the effectiveness in the magnetic field function steering the damper was performed. As a result an important relationship between the change of damping in the material under the influence of the magnetic field and the length of time needed for damping the vibrations in the beam was demonstrated.

  9. Experimental evaluation of a tuned electromagnetic damper for vibration control of cryogenic turbopump rotors

    NASA Technical Reports Server (NTRS)

    Dirusso, Eliseo; Brown, Gerald V.

    1990-01-01

    Experiments were performed on a passive tuned electromagnetic damper that could be used for damping rotor vibrations in cryogenic turbopumps for rocket engines. The tests were performed in a rig that used liquid nitrogen to produce cryogenic turbopump temperatures. This damper is most effective at cryogenic temperatures and is not a viable damper at room temperature. The unbalanced amplitude response of the rotor shaft was measured for undamped (baseline) and damped conditions at the critical speeds of the rotor (approx. 5900 to 6400 rpm) and the data were compared. The tests were performed for a speed range between 900 and 10 000 rpm. The tests revealed that the damper is very effective for damping single-mode narrow bandwidth amplitude response but is less effective in damping broadband response or multimode amplitude response.

  10. Optimal design of a shear magnetorheological damper for turning vibration suppression

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Zhang, Y. L.

    2013-09-01

    The intelligent material, so-called magnetorheological (MR) fluid, is utilized to control turning vibration. According to the structure of a common lathe CA6140, a shear MR damper is conceived by designing its structure and magnetic circuit. The vibration suppression effect of the damper is proved with dynamic analysis and simulation. Further, the magnetic circuit of the damper is optimized with the ANSYS parametric design language (APDL). In the optimization course, the area of the magnetic circuit and the damping force are considered. After optimization, the damper’s structure and its efficiency of electrical energy consumption are improved. Additionally, a comparative study on damping forces acquired from the initial and optimal design is conducted. A prototype of the developed MR damper is fabricated and magnetic tests are performed to measure the magnetic flux intensities and the residual magnetism in four damping gaps. Then, the testing results are compared with the simulated results. Finally, the suppressing vibration experimental system is set up and cylindrical turning experiments are performed to investigate the working performance of the MR damper.

  11. Vibration Reduction of Helicopter Blade Using Variable Dampers: A Feasibility Study

    NASA Technical Reports Server (NTRS)

    Lee, George C.; Liang, Zach; Gan, Quan; Niu, Tiecheng

    2002-01-01

    In the report, the investigation of controlling helicopter-blade lead-lag vibration is described. Current practice of adding passive damping may be improved to handle large dynamic range of the blade with several peaks of vibration resonance. To minimize extra-large damping forces that may damage the control system of blade, passive dampers should have relatively small damping coefficients, which in turn limit the effectiveness. By providing variable damping, a much larger damping coefficient to suppress the vibration can be realized. If the damping force reaches the maximum allowed threshold, the damper will be automatically switched into the mode with smaller damping coefficient to maintain near-constant damping force. Furthermore, the proposed control system will also have a fail-safe feature to guarantee the basic performation of a typical passive damper. The proposed control strategy to avoid resonant regions in the frequency domain is to generate variable damping force in combination with the supporting stiffness to manipulate the restoring force and conservative energy of the controlled blade system. Two control algorithms are developed and verified by a prototype variable damper, a digital controller and corresponding algorithms. Primary experiments show good potentials for the proposed variable damper: about 66% and 82% reductions in displacement at 1/3 length and the root of the blade respectively.

  12. A nonlinear auxetic structural vibration damper with metal rubber particles

    NASA Astrophysics Data System (ADS)

    Ma, Yanhong; Scarpa, Fabrizio; Zhang, Dayi; Zhu, Bin; Chen, Lulu; Hong, Jie

    2013-08-01

    The work describes the mechanical performance of a metal rubber particles (MRP) damper design based on an auxetic (negative Poisson’s ratio) cellular configuration. The auxetic damper configuration is constituted by an anti-tetrachiral honeycomb, where the cylinders are filled with the MRP material. The MRP samples have been subjected to quasi-static loading to measure the stiffness and loss factor from the static hysteresis curve. A parametric experimental analysis has been carried out to investigate the effect of relative density and filling percentage on the static performance of the MRP, and to identify design guidelines for best use of MRP devices. An experimental assessment of the integrated auxetic-MRP damper concept has been provided through static and dynamic force response techniques.

  13. Analysis of semi-active vehicle suspension system using airspring and MR damper

    NASA Astrophysics Data System (ADS)

    Tesfay, A. H.; Goel, V. K.

    2015-12-01

    With the new advancements in vibration control strategies and controllable actuator manufacturing, semi-active actuators and dampers are finding their way as an essential part of vibration isolators, particularly in vehicle suspension systems. This is attributed to the fact that in a semi-active system, the damping coefficients can be adjusted to improve ride comfort and road handling performances. The currently available semi-active damper technology uses MR fluid to control the damping characteristics of the suspension system. In addition to MR dampers, combining air springs in a semi-active suspension system leads to better handling and ride performance in vehicles. Furthermore, the use of air spring in semi-active suspension system helps to ease design of variable spring stiffness. This easy design opportunity leads to independent control of stiffness and ride height of the vehicle. This paper deals with the design and modelling of variable stiffness air spring for semi-active suspension system, modelling of semi-active suspension systems with variable stiffness and MR damper, and study their

  14. A calculation method for torsional vibration of a crankshafting system with a conventional rubber damper by considering rubber form

    SciTech Connect

    Kodama, Tomoaki; Honda, Yasuhiro; Wakabayashi, Katsuhiko; Iwamoto, Shoichi

    1996-09-01

    The cheap and compact rubber dampers of shear-type have been widely employed as the torsional vibration control of the crankshaft system of high-speed, automobile diesel engines. The conventional rubber dampers have various rubber forms owing to the thorough investigation of optimum dampers in the design stage. Their rubber forms can be generally grouped into three classes such as the disk type, the bush type and the composite type. The disk type and the bush type rubber dampers are called the basic-pattern rubber dampers hereafter. The composite type rubber part is supposed to consist of the disk type and the bush type parts, regarded respectively as the basic patterns of the rubber part, at large. The dynamic characteristics of the vibration isolator rubber depend generally on temperature, frequency, strain amplitude, shape and size effect,s so it is difficult to estimate accurately their characteristics. With the present technical level, it is also difficult to determine the suitable rubber geometry which optimizes the vibration control effect. The study refers to the calculation method of the torsional vibration of a crankshaft system with a shear-type rubber damper having various rubber forms in order to offer the useful method for optimum design. In this method, the rheological formula of the three-element Maxwell model, from which the torsional stiffness and the damping coefficient of the damper rubber part in the equivalent vibration system are obtained, are adopted in order to decide the dynamic characteristics of the damper rubber part.

  15. Semi-active H∞ control of high-speed railway vehicle suspension with magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Zong, Lu-Hang; Gong, Xing-Long; Xuan, Shou-Hu; Guo, Chao-Yang

    2013-05-01

    In this paper, semi-active H∞ control with magnetorheological (MR) dampers for railway vehicle suspension systems to improve the lateral ride quality is investigated. The proposed semi-active controller is composed of a H∞ controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse MR damper model as the damper controller. First, a 17-degree-of-freedom model for a full-scale railway vehicle is developed and the random track irregularities are modelled. Then a modified Bouc-Wen model is built to characterise the forward dynamic characteristics of the MR damper and an inverse MR damper model is built with the ANFIS technique. Furthermore, a H∞ controller composed of a yaw motion controller and a rolling pendulum motion (lateral motion+roll motion) controller is established. By integrating the H∞ controller with the ANFIS inverse model, a semi-active H∞ controller for the railway vehicle is finally proposed. Simulation results indicate that the proposed semi-active suspension system possesses better attenuation ability for the vibrations of the car body than the passive suspension system.

  16. Analytical and experimental investigation on a multiple-mass-element pendulum impact damper for vibration mitigation

    NASA Astrophysics Data System (ADS)

    Egger, Philipp; Caracoglia, Luca

    2015-09-01

    Impact dampers are often used in the field of civil, mechanical and aerospace engineering for reducing structural vibrations. The behavior of this type of passive control device has been investigated for several decades. In this research a distributed-mass impact damper, similar to the "chain damper" used in wind engineering, has been examined and applied to the vibration reduction on a slender line-like structural element (stay-cable). This study is motivated by a practical problem and describes the derivation of a reduced-order model for explaining the behavior, observed during a field experiment on a prototype system. In its simplest form, the dynamics of the apparatus is modeled as a "resilient damper", composed of mass-spring-dashpot secondary elements, attached to the primary structure. Various sources of excitation are analyzed: free vibration, external harmonic force and random excitation. The proposed model is general and potentially applicable to the analysis of several structural systems. The study also shows that the model can adequately describe and explain the experimentally observed behavior.

  17. Study of liquid viscosity dampers in octo-strut platform for whole-spacecraft vibration isolation

    NASA Astrophysics Data System (ADS)

    Likun, Liu; Gangtie, Zheng; Wenhu, Huang

    2006-05-01

    Whole-spacecraft vibration isolation is a direct and effective technique toward improving the dynamic environment that a spacecraft experiences during its journey to the orbit. Liquid viscosity dampers are the major component of an octo-strut vibration isolation platform for isolating the vibration of the whole spacecraft. To study the model and influence factors of the damper on the performance of the platform, a three-parameter dynamic model of the single strut is built, in which the effective elasticity of the liquid volume as a part of the strut is represented by a spring in series with the damper. By modeling the vibration isolation platform with Newton-Euler method, the design parameters of a single strut are defined by achieving optimal isolation performance along the longitudinal direction. From numerical analysis results with a rigid spacecraft and a flexible spacecraft on the top of the platform, it is found that the elasticity of the liquid volume is a key factor in defining the transmissibility. With a proper choice of the effective elasticity of the liquid volume, a better isolation performance than the commonly used two-parameter strut can be obtained.

  18. Design, testing, and model validation of an MR squeeze-flow vibration damper

    NASA Astrophysics Data System (ADS)

    Sims, Neil D.; Stanway, Roger; Johnson, Andrew R.; Mellor, Phillip

    2001-07-01

    Ongoing research at the University of Sheffield is currently concerned with the design and construction of magneto- rheological (MR) squeeze-flow vibration damper. Previous work has demonstrated the feasibility of employing such a device as the key component in a controllable vibration isolator. The work also demonstrated the inadequacies of existing mathematical models which do not account for the observed behavior of MR fluids in squeeze flow. In parallel with investigations into the behavior of MR dampers, a collaborative programme between the Universities of Liverpool and Sheffield is also in progress. Here attention is focussed on ER fluids in squeeze-flow and a new test facility has been constructed for use in the development and validation of mathematical models. It is anticipated that this collaborative programme will assist in the development of both ER and MR squeeze-flow models. In this paper, the authors present a summary of progress to date.

  19. Bifurcations and chaos of a vibration isolation system with magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Zhang, Hailong; Zhang, Ning; Min, Fuhong; Yan, Wei; Wang, Enrong

    2016-03-01

    Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.

  20. Robustness study of the pounding tuned mass damper for vibration control of subsea jumpers

    NASA Astrophysics Data System (ADS)

    Li, Hongnan; Zhang, Peng; Song, Gangbing; Patil, Devendra; Mo, Yilung

    2015-09-01

    A previous study by the authors proposed a new type of damper, the pounding tuned mass damper (PTMD), which uses the impact of a tuned mass with viscoelastic materials to effectively dissipate vibration energy, for structural vibration control. However, the control performance is unknown if the PTMD is not tuned to the targeted frequency of the primary structure. This paper aims to study the robustness of the PTMD against the detuning effect both numerically and experimentally. The control object was chosen as a subsea jumper, which is a flexible M-shaped pipeline structure commonly used in offshore oil and gas production. In this paper, a 15.2 m (50 feet) long jumper incorporated with a PTMD was set up. To enable the numerical study, the equation of motion of the jumper along with the PTMD was derived. Three testing cases were numerically studied: free vibration, forced vibration and forced vibration with varied frequencies. In all cases, the PTMD can effectively suppress the structural vibration when the natural frequency was off-tuned. Furthermore, experimental studies were conducted. The experimental results also implied the robustness of the proposed PTMD.

  1. Robust semi-active control for uncertain structures and smart dampers

    NASA Astrophysics Data System (ADS)

    Yeganeh Fallah, Arash; Taghikhany, Touraj

    2014-09-01

    Recent developments in semi-active control technology have led to its application in civil infrastructures as an efficient strategy to protect susceptible structures against seismic and wind induced vibration. The reliable and robust performance of semi-active systems depends on the level of uncertainties in the structural parameters as well as on the sensors’ measurement and on smart mechanical dampers. A common source of uncertainties in semi-active control devices is related to the inherent nonlinear nature of these devices, thermal variation, or their malfunctioning. This study deals with the robust H∞ control problem and aims to model different sources of uncertainty. The uncertainty of the structural model and damper force are assumed to be norm bounded random variables. By using linear fractional transformation (LFT), the uncertain part of the system is decoupled from the nominal parameters of the system. The robust H∞ controller is designed to achieve consistent performance in structures including nominal and perturbed dynamics. Additionally, to reduce the uncertainty of the damper force, an inverse model of the magnetorheological (MR) damper is developed based on an adaptive neuro-fuzzy inference system (ANFIS). The robustness of the proposed algorithm is validated by numerical simulations.

  2. Experimental study on semi-active control of frame-shear wall eccentric structure using MR dampers

    NASA Astrophysics Data System (ADS)

    Li, Xiu Ling, Sr.; Li, Hong Nan, Sr.

    2006-03-01

    Magnetorheological (MR) damper is a kind of intelligent actuator, which shows immense potential in the field of structural vibration control. The construction and mechanical behavior of MR damper are introduced firstly, and then a new mechanical model--double sigmoid model is proposed based on the experimental study of MR damper. The simulation system of the 3-floor frame-shear wall eccentric structure with MR dampers was built according to the coupled translation and torsion response control using MR damper, based on Matlab/Simulink software environment and hardware/software resources of dSPACE. The shaking table experiment of the structural model was implemented by using rapid control prototyping (RCP) technology. The validity of two passive control strategies and one semi-active control strategy is verified under three input earthquake excitation with different peak value. The experimental results show that the coupled translation and torsion response is significantly mitigated, and the semi-active control strategies can achieve higher performance levels as compared to those of the two passive control cases. Moreover, the location of the MR damper has an important effect on the control results.

  3. Effect of magneto rheological damper on tool vibration during hard turning

    NASA Astrophysics Data System (ADS)

    Paul, P. Sam; Varadarajan, A. S.

    2012-12-01

    Recently, the concept of hard turning has gained considerable attention in metal cutting as it can apparently replace the traditional process cycle of turning, heat treating, and finish grinding for assembly of hard wear resistant steel parts. The present investigation aims at developing a magneto rheological (MR) fluid damper for suppressing tool vibration and promoting better cutting performance during hard turning. The magneto rheological Fluid acts as a viscoelastic spring with non-linear vibration characteristics that are controlled by the composition of the magneto rheological fluid, the shape of the plunger and the electric parameters of the magnetizing field. Cutting experiments were conducted to arrive at a set of electrical, compositional and shape parameters that can suppress tool vibration and promote better cutting performance during turning of AISI 4340 steel of 46 HRC with minimal fluid application using hard metal insert with sculptured rake face. It was observed that the use of MR fluid damper reduces tool vibration and improves the cutting performance effectively. Also commercialization of this idea holds promise to the metal cutting industry.

  4. Preparation research on novel dampers used in large optical telescope's noise and vibrations attenuating system

    NASA Astrophysics Data System (ADS)

    Dong, Xiu-ping; Yang, Jian-chun; Zhang, Li

    2010-10-01

    General rubber damping materials used in noise and vibrations attenuating system can not adapt large optical telescope's working temperatures and environments. While Metal Rubber material which has loose, reticulate structures can endure high or low temperatures, rigorous space environments, erosions, aging, volatilization and radiations due to its metallic properties because it is made of stainless steel wires of φ 0.1~0.3 mm. When the MR damping component is uploaded with vibrating force, the displacement will cause intense frictions between wires' surfaces which will dissipate abundant energy and thus it can serve as dampers like natural rubbers. Since Metal Rubber components are prepared by compression moulding, various complex shapes of dampers can be produced conveniently to fulfill large optical telescope's noise and vibrations attenuating tasks. Based on the Metal Rubber component's four preparation approaches, helix-making, planar roughcast-weaving, planar roughcast-rolling and 3D roughcast punching, a ring-shaped 3D parametrical numerical model is founded by CAD technology. Definitely, this modeling research work may support the optimization of the current trial and try preparation of MR component and it will provide necessary foundations for its further application in noise and vibrations attenuating system in large optical telescopes.

  5. Active control of train bogies with MR dampers

    NASA Astrophysics Data System (ADS)

    Fotoohi, Abbas; Yousefi-Koma, Aghil; Yasrebi, Naser

    2006-03-01

    This research is conducted to demonstrate the advantages of skyhook semi-active dampers in railway vehicle suspension systems. This semi- active suspension system consists of four actuators on each bogie that locate in the secondary suspension position instead of passive dampers. Employing equations of skyhook control scheme, the semi- active damping force (actuator force) is determined by absolute velocity of car body instead of relative velocity. An integration of a control design tool, i.e. MATLAB, together with a tool for railway vehicle simulation, i.e. ADAMS/Rail is utilized for modeling and control analysis simultaneously. Analysis has been performed on a traditional bogie model with passive secondary suspension and on a new bogie model with semi-active suspension. The effects of suspension system on displacement and acceleration in passenger seats have been investigated in various points of car body. Results show that the semi-active suspension improves the ride comfort by reducing accelerations, in comparison with passive model. Finally, according to the damper force obtained from Sky-hook controller, a Magnetorheological (MR) damper has been designed for the semi-active suspension system.

  6. Magnetostrictive vibration damper and energy harvester for rotating machinery

    NASA Astrophysics Data System (ADS)

    Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.

    2015-04-01

    Vibrations generated by machine driveline components can cause excessive noise and structural dam- age. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron- dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum av- erage electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.

  7. Magnetostrictive Vibration Damper and Energy Harvester for Rotating Machinery

    NASA Technical Reports Server (NTRS)

    Deng, Zhangxian; Asnani, Vivake M.; Dapino, Marcelo J.

    2015-01-01

    Vibrations generated by machine driveline components can cause excessive noise and structural damage. Magnetostrictive materials, including Galfenol (iron-gallium alloys) and Terfenol-D (terbium-iron-dysprosium alloys), are able to convert mechanical energy to magnetic energy. A magnetostrictive vibration ring is proposed, which generates electrical energy and dampens vibration, when installed in a machine driveline. A 2D axisymmetric finite element (FE) model incorporating magnetic, mechanical, and electrical dynamics is constructed in COMSOL Multiphysics. Based on the model, a parametric study considering magnetostrictive material geometry, pickup coil size, bias magnet strength, flux path design, and electrical load is conducted to maximize loss factor and average electrical output power. By connecting various resistive loads to the pickup coil, the maximum loss factors for Galfenol and Terfenol-D due to electrical energy loss are identified as 0.14 and 0.34, respectively. The maximum average electrical output power for Galfenol and Terfenol-D is 0.21 W and 0.58 W, respectively. The loss factors for Galfenol and Terfenol-D are increased to 0.59 and 1.83, respectively, by using an L-C resonant circuit.

  8. Combined passive magnetic bearing element and vibration damper

    DOEpatents

    Post, Richard F.

    2001-01-01

    A magnetic bearing system contains magnetic subsystems which act together to support a rotating element in a state of dynamic equilibrium and dampen transversely directed vibrations. Mechanical stabilizers are provided to hold the suspended system in equilibrium until its speed has exceeded a low critical speed where dynamic effects take over, permitting the achievement of a stable equilibrium for the rotating object. A state of stable equilibrium is achieved above a critical speed by use of a collection of passive elements using permanent magnets to provide their magnetomotive excitation. In a improvement over U.S. Pat. No. 5,495,221, a magnetic bearing element is combined with a vibration damping element to provide a single upper stationary dual-function element. The magnetic forces exerted by such an element, enhances levitation of the rotating object in equilibrium against external forces, such as the force of gravity or forces arising from accelerations, and suppresses the effects of unbalance or inhibits the onset of whirl-type rotor-dynamic instabilities. Concurrently, this equilibrium is made stable against displacement-dependent drag forces of the rotating object from its equilibrium position.

  9. Efficiency improvement in a vibration power generator for a linear MR damper: numerical study

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan; Krupa, Stanisław

    2013-04-01

    This paper summarizes a numerical analysis of the electromagnetic field, voltage and circuit properties and the cogging force in a vibration power generator comprising permanent magnets and a coil with a foil winding. The device converts the energy harvested from vibrations into electrical energy which is next used to vary the damping characteristics of a linear MR damper attached to the generator. The objective of the study is to propose a sufficiently efficient generator whose finally developed (target) version could be integrated with a small-scale MR damper to build a single device. Two design options for the device are numerically studied, the previously engineered generator 1 and the newly devised generator 2. Generator 1 incorporates two magnet systems having four magnets each and a single-section coil, while generator 2 comprises three magnet systems with four magnets each and a two-section coil. Calculations were performed to determine the electromagnetic field, voltage and current properties and the cogging force in the generators. The electromagnetic field parameters include the distribution of the magnetic field, the electrical potential field and the current density in the open turn and closed turn of the generators’ coils. The voltage and current properties include electromotive force (emf) in the generators and the voltage, current, instantaneous power and energy of the magnetic field in the MR damper control coil which is represented by resistance parameter R and inductance parameter L. The cogging force expresses the magnetic interactions between the permanent magnet systems and ferromagnetic structural components of the generators. The occurrence of this force is very unfavourable and attempts should be made to reduce it through control of the parameters of the magnetic circuit components. On one hand, comparison of the numerical results for the electromagnetic field parameters and voltage and current properties revealed that for the

  10. Suppression of maglev vehicle-girder self-excited vibration using a virtual tuned mass damper

    NASA Astrophysics Data System (ADS)

    Zhou, D. F.; Hansen, C. H.; Li, J.

    2011-02-01

    The self-excited vibration that occurs between a stationary Electromagnetic Suspension (EMS) maglev vehicle and a girder is a practical problem that greatly degrades the performance of a maglev system. As of today, this problem has not been fully solved. In this article, the principle underlying the self-excited vibration problem is explored, and it is found that the fundamental resonance frequency of the maglev girder plays a vital role in the initiation of the self-excited vibration. To suppress the self-excited vibration, a scheme applying a tuned mass damper (TMD) to the maglev girder is proposed, and the stability of the combined system is analyzed. Furthermore, a novel concept of a virtual TMD is introduced, which uses an electromagnetic force to emulate the force of a real TMD acting on the girder. However, in the presence of the time delay caused by the inductance of the electromagnets, the stability analysis of the levitation system combined with the virtual TMD becomes complex. Analysis of the stability shows that there exist some repeated time delay zones within which the overall system is stable. Based on this rule, time delay control is introduced to stabilize the system with a virtual TMD, and a procedure to determine the optimal time delay and gain is proposed. Numerical simulation indicates that the proposed virtual TMD scheme can significantly suppress the self-excited vibration caused by one unstable vibration mode, and is suitable for application to EMS maglev systems.

  11. Shaking table experimentation on adjacent structures controlled by passive and semi-active MR dampers

    NASA Astrophysics Data System (ADS)

    Basili, M.; De Angelis, M.; Fraraccio, G.

    2013-06-01

    This paper presents the results of shaking table tests on adjacent structures controlled by passive and semi-active MR dampers. The aim was to demonstrate experimentally the effectiveness of passive and semi-active strategies in reducing structural vibrations due to seismic excitation. The physical model at issue was represented by two adjacent steel structures, respectively of 4 and 2 levels, connected at the second level by a MR damper. When the device operated in semi-active mode, an ON-OFF control algorithm, derived by the Lyapunov stability theory, was implemented and experimentally validated. Since the experimentation concerned adjacent structures, two control objectives have been reached: global and selective protection. In case of global protection, the attention was focused on protecting both structures, whereas, in case of selective protection, the attention was focused on protecting only one structure. For each objective the effectiveness of passive control has been compared with the situation of no control and then the effectiveness of semi-active control has been compared with the passive one. The quantities directly compared have been: measured displacements, accelerations and force-displacement of the MR damper, moreover some global response quantities have been estimated from experimental measures, which are the base share force and the base bending moment, the input energy and the energy dissipated by the device. In order to evaluate the effectiveness of the control action in both passive and semi-active case, an energy index EDI, previously defined and already often applied numerically, has been utilized. The aspects investigated in the experimentation have been: the implementation and validation of the control algorithm for selective and global protection, the MR damper input voltage influence, the kind of seismic input and its intensity.

  12. Analysis of the Vibration Damping of Bonded Beams with a Single-Lap-Joint and Partial Dampers

    NASA Astrophysics Data System (ADS)

    Choi, Nak-Sam; Park, Jeong-Il

    A theoretical analysis model for the lateral vibration of beams with a bonded single-lap-joint and partial layered dampers has been proposed in this paper. Both shear and normal forces acting along the interface between the elastic and viscoelastic layers were considered in the vibration analysis. The analytical results were comparable to those obtained by the modal strain energy method and the harmonic response analysis, which were based on a finite element model. The effects of the location and thickness of the partial dampers on the system loss factor ηs were studied. The characteristic variations of ηs, with changes of the modulus and loss factor of the viscoelastic layer in the lap joint part and partial dampers were also studied. Consequently, the geometrical and material conditions at maximizing ηs were suggested.

  13. Active damping of spacecraft structural appendage vibrations

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V. (Inventor)

    1990-01-01

    An active vibration damper system, for bending in two orthogonal directions and torsion, in each of three mutually perpendicular axes is located at the extremities of the flexible appendages of a space platform. The system components for each axis includes: an accelerometer, filtering and signal processing apparatus, and a DC motor-inertia wheel torquer. The motor torquer, when driven by a voltage proportional to the relative vibration tip velocity, produces a reaction torque for opposing and therefore damping a specific modal velocity of vibration. The relative tip velocity is obtained by integrating the difference between the signal output from the accelerometer located at the end of the appendage with the output of a usually carried accelerometer located on a relatively rigid body portion of the space platform. A selector switch, with sequential stepping logic or highest modal vibration energy logic, steps to another modal tip velocity channel and receives a signal voltage to damp another vibration mode. In this manner, several vibration modes can be damped with a single sensor/actuator pair. When a three axis damper is located on each of the major appendages of the platform, then all of the system vibration modes can be effectively damped.

  14. Semi-active sliding mode control of vehicle suspension with magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Zhang, Hailong; Wang, Enrong; Zhang, Ning; Min, Fuhong; Subash, Rakheja; Su, Chunyi

    2015-01-01

    The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity ( F- v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.

  15. Dual clearance squeeze film damper

    NASA Technical Reports Server (NTRS)

    Fleming, D. P. (Inventor)

    1985-01-01

    A dual clearance hydrodynamic liquid squeeze film damper for a gas turbine engine is described. Under normal operating conditions, the device functions as a conventional squeeze film damper, using only one of its oil films. When an unbalance reaches abusive levels, as may occur with a blade loss or foreign object damage, a second, larger clearance film becomes active, controlling vibration amplitudes in a near optimum manner until the engine can be safely shut down and repaired.

  16. Active vibration control of lightweight floor systems

    NASA Astrophysics Data System (ADS)

    Baader, J.; Fontana, M.

    2016-04-01

    Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices. The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain. A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

  17. Analysis and testing of an inner bypass magnetorheological damper for shock and vibration mitigation

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Hu, Wei; Wereley, Norman M.

    2013-04-01

    Aiming at fundamentally improving the performance of MR dampers, including maximizing dynamic range (i.e., ratio of field-on to field-off damping force) while simultaneously minimizing field-off damping force, this study presents the principle of an inner bypass magnetorheological damper (IBMRD). The IBMRD is composed of a pair of twin tubes, i.e., the inner tube and outer concentric tube, a movable piston-shaft arrangement, and an annular MR fluid flow gap sandwiched between the concentric tubes. In the IBMRD, the inner tube serves simultaneously as the guide for the movable piston and the bobbin for the electromagnetic coil windings, and five active rings on the inner tube, annular MR fluid flow gap, and outer tube forms five closed magnetic circuits. The annular fluid flow gap is an inner bypass annular valve where the rheology of the MR fluids, and hence the damping force of the MR damper, is controlled. Based on the structural principle of the IBMRD, the IBMRD is configured and its finite element analysis (FEA) is implemented. After theoretically constructing the hydro-mechanical model for the IBMRD, its mathematical model is established using a Bingham-plastic nonlinear fluid model. The characteristics of the IBMRD are theoretically evaluated and compared to those of a conventional piston-bobbin MR damper with an identical active length and cylinder diameter. In order to validate the theoretical results predicted by the mathematical model, the prototype IBMRD is designed, fabricated, and tested. The servo-hydraulic testing machine (type: MTS 810) and rail-guided drop tower are used to provide sinusoidal displacement excitation and shock excitation to the IBMRD, respectively.

  18. Frequency domain control based on quantitative feedback theory for vibration suppression in structures equipped with magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Zapateiro, Mauricio; Karimi, Hamid Reza; Luo, Ningsu; Spencer, Billie F., Jr.

    2009-09-01

    This paper addresses the problem of designing quantitative feedback theory (QFT) based controllers for the vibration reduction in a structure equipped with an MR damper. In this way, the controller is designed in the frequency domain and the natural frequencies of the structure can be directly accounted for in the process. Though the QFT methodology was originally conceived of for linear time invariant systems, it can be extended to nonlinear systems. A new methodology is proposed for characterizing the nonlinear hysteretic behavior of the MR damper through the uncertainty template in the Nichols chart. The resulting controller performance is evaluated in a real-time hybrid testing experiment.

  19. Experimental and analytical investigation of hybrid squeeze film dampers

    SciTech Connect

    El Shafei, A. )

    1993-04-01

    A new concept for actively controlling high-speed rotating machinery is investigated both analytically and experimentally. The controlling mechanism consists of a hybrid squeeze film damper (patent pending) that can be adaptively controlled to change its characteristics according to the instructions of a controller. In an extreme case the hybrid damper can act as a long damper, which is shown to be effective in reducing the amplitude of vibration of rotating machinery. In the other extreme the hybrid damper acts as a short damper, which is shown to be effective in reducing the force transmitted to the support. In the long damper configuration the oil flow is circumferential, while in the short damper configuration the oil flow is predominantly axial. The hybrid damper is designed to operate in either the short or the long damper configuration by controlling the positions of two movable sealing rings. The hybrid damper was tested on a Bently Nevada Rotor Kit and it is shown experimentally that the long damper configuration is extremely efficient at controlling the amplitude of vibration and the short damper configuration reduces the force transmitted to the support.

  20. Design and parametric study on energy harvesting from bridge vibration using tuned dual-mass damper systems

    NASA Astrophysics Data System (ADS)

    Takeya, Kouichi; Sasaki, Eiichi; Kobayashi, Yusuke

    2016-01-01

    A bridge vibration energy harvester has been proposed in this paper using a tuned dual-mass damper system, named hereafter Tuned Mass Generator (TMG). A linear electromagnetic transducer has been applied to harvest and make use of the unused reserve of energy the aforementioned damper system absorbs. The benefits of using dual-mass systems over single-mass systems for power generation have been clarified according to the theory of vibrations. TMG parameters have been determined considering multi-domain parameters, and TMG has been tuned using a newly proposed parameter design method. Theoretical analysis results have shown that for effective energy harvesting, it is essential that TMG has robustness against uncertainties in bridge vibrations and tuning errors, and the proposed parameter design method for TMG has demonstrated this feature.

  1. Dual-Functional Energy-Harvesting and Vibration Control: Electromagnetic Resonant Shunt Series Tuned Mass Dampers.

    PubMed

    Zuo, Lei; Cui, Wen

    2013-10-01

    This paper proposes a novel retrofittable approach for dual-functional energy-harvesting and robust vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based numeric method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is found that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant-shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performances optimized for vibration suppression are close to those optimized for energy harvesting, and the performance is not sensitive to the resistance of the charging circuit or electrical load. PMID:23918165

  2. Performance analysis of a semi-active railway vehicle suspension featuring MR dampers

    NASA Astrophysics Data System (ADS)

    Kim, Hwan-Choong; Choi, Seung-Bok; Lee, Gyu-Seop; An, Chae-Hun; You, Won-Hee

    2014-03-01

    This paper presents performance analysis of semi-active railway vehicle suspension system using MR damper. In order to achieve this goal, a mathematical dynamic model of railway vehicle is derived by integrating car body, bogie frame and wheel-set which can be able to represent lateral, yaw and roll motion. Based on this model, the dynamic range of MR damper at the railway secondary suspension system and design parameters of MR damper are calculated. Subsequently, control performances of railway vehicle including car body lateral motion and acceleration of MR damper are evaluated through computer simulations. Then, the MR damper is manufactured to be retrofitted with the real railway vehicle and its characteristics are experimentally measured. Experimental performance of MR damper is assessed using test rig which is composed of a car body and two bogies.

  3. Vibration control of bridge subjected to multi-axle vehicle using multiple tuned mass friction dampers

    NASA Astrophysics Data System (ADS)

    Pisal, Alka Y.; Jangid, R. S.

    2016-06-01

    The effectiveness of tuned mass friction damper (TMFD) in reducing undesirable resonant response of the bridge subjected to multi-axle vehicular load is investigated. A Taiwan high-speed railway (THSR) bridge subjected to Japanese SKS (Salkesa) train load is considered. The bridge is idealized as a simply supported Euler-Bernoulli beam with uniform properties throughout the length of the bridge, and the train's vehicular load is modeled as a series of moving forces. Simplified model of vehicle, bridge and TMFD system has been considered to derive coupled differential equations of motion which is solved numerically using the Newmark's linear acceleration method. The critical train velocities at which the bridge undergoes resonant vibration are investigated. Response of the bridge is studied for three different arrangements of TMFD systems, namely, TMFD attached at mid-span of the bridge, multiple tuned mass friction dampers (MTMFD) system concentrated at mid-span of the bridge and MTMFD system with distributed TMFD units along the length of the bridge. The optimum parameters of each TMFD system are found out. It has been demonstrated that an optimized MTMFD system concentrated at mid-span of the bridge is more effective than an optimized TMFD at the same place with the same total mass and an optimized MTMFD system having TMFD units distributed along the length of the bridge. However, the distributed MTMFD system is more effective than an optimized TMFD system, provided that TMFD units of MTMFD system are distributed within certain limiting interval and the frequency of TMFD units is appropriately distributed.

  4. Compliant liquid column damper modified by shape memory alloy device for seismic vibration control

    NASA Astrophysics Data System (ADS)

    Gur, Sourav; Mishra, Sudib Kumar; Bhowmick, Sutanu; Chakraborty, Subrata

    2014-10-01

    Liquid column dampers (LCDs) have long been used for the seismic vibration control of flexible structures. In contrast, tuning LCDs to short-period structures poses difficulty. Various modifications have been proposed on the original LCD configuration for improving its performance in relatively stiff structures. One such system, referred to as a compliant-LCD has been proposed recently by connecting the LCD to the structure with a spring. In this study, an improvement is attempted in compliant LCDs by replacing the linear spring with a spring made of shape memory alloy (SMA). Considering the dissipative, super-elastic, force-deformation hysteresis of SMA triggered by stress-induced micro-structural phase transition, the performance is expected to improve further. The optimum parameters for the SMA-compliant LCD are obtained through design optimization, which is based on a nonlinear random vibration response analysis via stochastic linearization of the force-deformation hysteresis of SMA and dissipation by liquid motion through an orifice. Substantially enhanced performance of the SMA-LCD over a conventional compliant LCD is demonstrated, the consistency of which is further verified under recorded ground motions. The robustness of the improved performance is also validated by parametric study concerning the anticipated variations in system parameters as well as variability in seismic loading.

  5. Dual-Actuator Active Vibration-Control System

    NASA Technical Reports Server (NTRS)

    Kascak, Albert F.; Kiraly, Louis J.; Montague, Gerald T.; Palazzolo, Alan B.; Manchala, Daniel

    1994-01-01

    Dual-actuator active vibration-control (DAAVC) system is developmental system of type described in "Active Vibration Dampers for Rotating Machinery" (LEW-15427). System features sensors and actuators positioned and oriented at bearings to measure and counteract vibrations of shaft along either of two axes perpendicular to axis of rotation. Effective in damping vibrations of helicopter-engine test stand, making it safer to operate engine at speeds near and above first resonance of engine/test-stand system. Opens new opportunities for engine designers to draw more power from engine, and concept applicable to other rotating machines.

  6. An investigation on a semi-active magnetorheological tuned liquid column damper (MR-TLCD)

    NASA Astrophysics Data System (ADS)

    Sun, H. X.; Wang, X. Y.

    2016-04-01

    this paper, a novel semi-active magnetorheological tuned liquid column damper (MR-TLCD) device combining tuned liquid column damper (TLCD) and magnetorheological damper (MRD) is devised for wind or earthquake vibration control of civil structures. In this device, a traditional moving head loss in the TLCD is replaced with a controlled MRD in the bottom or one side of the vertical column, which can easily and rapidly adjust the damping of the device. A semi-active experimental prototype MR-TLCD consisting of a shear rotary MRD and a TLCD is built. Based on the four basic presumptions, a dynamic model of the devised MR-TLCD is established using the Lagrange equation. In this equation, the formula of MRD employs the Bingham Boltzmann model. The natural frequency of the MR-TLCD is determined by the total central length and spring stiffness. It is worth noting that the natural frequency differs with the simple TLCD, because the device adds a joint spring. An equivalent linear damping expression is developed under harmonic excitation, and its mechanical model is developed using the equivalent period displacement and the coulomb friction force of MRD. At the same time, the equivalent damping can be adjusted by the real-time applied current, which can achieve the semi-active control performance. To validate the proposed frequency and damping model, Experimental test is conducted on a section area 150mm × 150mm and a total length 2.24m of the MR-TLCD dimensions. Comparisons are made between predicted and measured TLCD liquid surface displacement motion. The result shows the error of its nature frequency is only 2.29%.

  7. Experimental investigation of active machine tool vibration control

    NASA Astrophysics Data System (ADS)

    Rojas, J.; Liang, Chen; Geng, Zheng J.

    1996-05-01

    The successful vibration reduction of machine tools during machining process can improve productivity, increase quality, and reduce tool wear. This paper will present our initial investigation in the application of smart material technologies in machine tool vibration control using magnetostrictive actuators and electrorheological elastomer dampers on an industrial Sheldon horizontal lathe. The dynamics of the machining process are first studied, which reveals the complexity in the machine tool vibration response and the challenge to the active control techniques. The active control experiment shows encouraging results. The use of electrorheological elastomer damping device for active/passive vibration control provides significant vibration reduction in the high frequency range and great improvement in the workpiece surface finishing. The research presented in this paper demonstrates that the combination of active and active/passive vibration control techniques is very promising for successful machine tool vibration control.

  8. Health monitoring of fluid dampers for vibration control of structures: experimental investigation

    NASA Astrophysics Data System (ADS)

    Konstantinidis, Dimitrios; Makris, Nicos; Kelly, James M.

    2014-03-01

    This paper presents results from a comprehensive experimental program on medium-size and large-size fluid dampers in an effort to extract their force output during cyclic loading by simply measuring the strain on the damper housing and the end-spacer. The paper first discusses the stress path within the damper and subsequently via the use of linear elasticity shows that the experimental data obtained with commercially available strain gauges yield a force output of the damper that is in good agreement with the readings from the load cell. The paper then examines the performance of a portable data acquisition system that can be used to collect and transmit data from a damper installed on a bridge to a nearby location. The data show that the proposed arrangement is promising for monitoring in-situ the force output of fluid dampers and detecting possible loss of their energy dissipation capability.

  9. An enhanced nonlinear damping approach accounting for system constraints in active mass dampers

    NASA Astrophysics Data System (ADS)

    Venanzi, Ilaria; Ierimonti, Laura; Ubertini, Filippo

    2015-11-01

    Active mass dampers are a viable solution for mitigating wind-induced vibrations in high-rise buildings and improve occupants' comfort. Such devices suffer particularly when they reach force saturation of the actuators and maximum extension of their stroke, which may occur in case of severe loading conditions (e.g. wind gust and earthquake). Exceeding actuators' physical limits can impair the control performance of the system or even lead to devices damage, with consequent need for repair or substitution of part of the control system. Controllers for active mass dampers should account for their technological limits. Prior work of the authors was devoted to stroke issues and led to the definition of a nonlinear damping approach, very easy to implement in practice. It consisted of a modified skyhook algorithm complemented with a nonlinear braking force to reverse the direction of the mass before reaching the stroke limit. This paper presents an enhanced version of this approach, also accounting for force saturation of the actuator and keeping the simplicity of implementation. This is achieved by modulating the control force by a nonlinear smooth function depending on the ratio between actuator's force and saturation limit. Results of a numerical investigation show that the proposed approach provides similar results to the method of the State Dependent Riccati Equation, a well-established technique for designing optimal controllers for constrained systems, yet very difficult to apply in practice.

  10. Semi-active control of torsional vibrations using an MR fluid brake

    NASA Astrophysics Data System (ADS)

    Williams, Keith A.; Ye, Shaochun

    2004-07-01

    Control of torsional vibrations in an automotive crankshaft is a classical vibration control problem. The most common solution is to mount a crankshaft damper at one end of the crankshaft. Typical crankshaft dampers are composed of parallel stiffness and damping elements connecting a rotational inertia to the crankshaft. Appropriate design of the damper elements may result in substantial crankshaft vibration. Conventional couplings include elastomeric spring-damper elements and purely viscous fluid couplings. While those approaches result in satisfactory reduction of crankshaft vibration, it may be that a semi-active approach can achieve improved performance. To that end, an investigation of a semi-active crankshaft damper using magneto-rheological (MR) fluid has been initiated. A torsional MR fluid brake was obtained and applied to a scale model of a crankshaft for a common eight-cylinder engine. Experiments were performed with the MR brake as a fixed-friction device. In addition, a simple stick-slip control algorithm was developed such that the MR brake became an on-line variable friction device. While a good deal of work remains to be performed in future efforts, the preliminary experimental results have demonstrated that a torsional damper composed of an MR fluid brake has potential application in the field of torsional vibration control.

  11. Robust hybrid mass damper

    NASA Astrophysics Data System (ADS)

    Collette, C.; Chesné, S.

    2016-08-01

    In this paper, the design of a hybrid mass damper (HMD) is proposed for the reduction of the resonant vibration amplitude of a multiple degree-of-freedom structure. HMD includes both passive and active elements. Combining these elements the system is fail-safe and its performances are comparable to usual purely active systems. The control law is a revisited direct velocity feedback. Two zeros are added to the controller to interact with the poles of the plant. The developed control law presents the particularity to be simple and hyperstable. The proposed HMD is compared to other classical control approaches for similar purpose in term of vibration attenuation, power consumption and stroke.

  12. Aeromechanical stability augmentation using semi-active friction-based lead-lag damper

    NASA Astrophysics Data System (ADS)

    Agarwal, Sandeep

    2005-11-01

    Lead-lag dampers are present in most rotors to provide the required level of damping in all flight conditions. These dampers are a critical component of the rotor system, but they also represent a major source of maintenance cost. In present rotor systems, both hydraulic and elastomeric lead-lag dampers have been used. Hydraulic dampers are complex mechanical components that require hydraulic fluids and have high associated maintenance costs. Elastomeric dampers are conceptually simpler and provide a "dry" rotor, but are rather costly. Furthermore, their damping characteristics can degrade with time without showing external signs of failure. Hence, the dampers must be replaced on a regular basis. A semi-active friction based lead-lag damper is proposed as a replacement for hydraulic and elastomeric dampers. Damping is provided by optimized energy dissipation due to frictional forces in semi-active joints. An actuator in the joint modulates the normal force that controls energy dissipation at the frictional interfaces, resulting in large hysteretic loops. Various selective damping strategies are developed and tested for a simple system containing two different frequency modes in its response, one of which needs to be damped out. The system reflects the situation encountered in rotor response where 1P excitation is present along with the potentially unstable regressive lag motion. Simulation of the system response is obtained to compare their effectiveness. Next, a control law governing the actuation in the lag damper is designed to generate the desired level of damping for performing adaptive selective damping of individual blade lag motion. Further, conceptual design of a piezoelectric friction based lag damper for a full-scale rotor is presented and various factors affecting size, design and maintenance cost, damping capacity, and power requirements of the damper are discussed. The selective semi-active damping strategy is then studied in the context of classical

  13. Active vibration control of civil structures

    SciTech Connect

    Farrar, C.; Baker, W.; Fales, J.; Shevitz, D.

    1996-11-01

    This is a final report of a one year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Active vibration control (AVC) of structural and mechanical systems is one of the rapidly advancing areas of engineering research. The multifaceted nature of AVC covers many disciplines, such as sensors and instrumentation, numerical modeling, experimental mechanics, and advanced power systems. This work encompassed a review of the literature on active control of structures focusing both on active control hardware and on control algorithms, a design of an isolation systems using magneto-rheological fluid-filled (MRF) dampers and numerical simulations to study the enhanced vibration mitigation effects of this technology.

  14. A chambered porous damper for rotor vibration control: Part 1. Concept development

    SciTech Connect

    Tecza, J.; Walton, J. )

    1993-04-01

    In this paper a novel, high-load chambered porous damper design, supporting analysis, and experimental results are presented. It was demonstrated that significant damping can be generated from the viscous discharge losses of capillary tubes arranged in chambered segments with large radial clearances and that the resulting damping is predictable and fairly constant with speed and eccentricity operation of conventional squeeze film dampers. Controlled orbit tests with a porous chambered configuration were completed and favorably compared with theoretical predictions. The ability to accommodate high steady-state and transient imbalance conditions makes this damper well suited to a wide range of rotating machinery, including aircraft gas turbine engines.

  15. Modeling of Semi-Active Vehicle Suspension with Magnetorhological Damper

    NASA Astrophysics Data System (ADS)

    Hasa, Richard; Danko, Ján; Milesich, Tomáš; Magdolen, Ľuboš

    2014-12-01

    Modeling of suspension is a current topic. Vehicle users require both greater driving comfort and safety. There is a space to invent new technologies like magnetorheological dampers and their control systems to increase these conflicting requirements. Magnetorheological dampers are reliably mathematically described by parametric and nonparametric models. Therefore they are able to reliably simulate the driving mode of the vehicle. These simulations are important for automotive engineers to increase vehicle safety and passenger comfort.

  16. A chambered porous damper for rotor vibration control: Part 2. Imbalance response and blade loss simulation

    SciTech Connect

    Walton, J.; Martin, M. )

    1993-04-01

    In this paper, results of experimental rotordynamic evaluations of a novel, high load chambered porous damper design are presented. The chambered porous damper concept was evaluated for gas turbine engine application since this concept avoids the nonlinearities associated with high-eccentricity operation of conventional squeeze film dampers. The rotordynamic testing was conducted under large steady-state imbalance and simulated transient blade-loss conditions for up to 0.254 mm (0.01 in.) mass c.g offset or 180 g-cm (2.5 oz-in.) imbalance. The chambered porous damper demonstrated that the steady-state imbalance and simulated blade-loss transient response of a flexible rotor operating above its first bending critical speed could be readily controlled. Rotor system imbalance sensitivity and logarithmic decrement are presented showing the characteristics of the system with the damper installed. The ability to accommodate high steady-state and transient imbalance conditions makes this damper well suited to a wide range of rotating machinery, including aircraft gas turbine engines.

  17. The experimental identification of magnetorheological dampers and evaluation of their controllers

    NASA Astrophysics Data System (ADS)

    Metered, H.; Bonello, P.; Oyadiji, S. O.

    2010-05-01

    Magnetorheological (MR) fluid dampers are semi-active control devices that have been applied over a wide range of practical vibration control applications. This paper concerns the experimental identification of the dynamic behaviour of an MR damper and the use of the identified parameters in the control of such a damper. Feed-forward and recurrent neural networks are used to model both the direct and inverse dynamics of the damper. Training and validation of the proposed neural networks are achieved by using the data generated through dynamic tests with the damper mounted on a tensile testing machine. The validation test results clearly show that the proposed neural networks can reliably represent both the direct and inverse dynamic behaviours of an MR damper. The effect of the cylinder's surface temperature on both the direct and inverse dynamics of the damper is studied, and the neural network model is shown to be reasonably robust against significant temperature variation. The inverse recurrent neural network model is introduced as a damper controller and experimentally evaluated against alternative controllers proposed in the literature. The results reveal that the neural-based damper controller offers superior damper control. This observation and the added advantages of low-power requirement, extended service life of the damper and the minimal use of sensors, indicate that a neural-based damper controller potentially offers the most cost-effective vibration control solution among the controllers investigated.

  18. SSME blade damper technology

    NASA Technical Reports Server (NTRS)

    Kielb, Robert E.; Griffin, Jerry H.

    1987-01-01

    Before 1975 turbine blade damper designs were based on experience and very simple mathematical models. Failure of the dampers to perform as expected showed the need to gain a better understanding of the physical mechanism of friction dampers. Over the last 10 years research on friction dampers for aeronautical propulsion systems has resulted in methods to optimize damper designs. The first-stage turbine blades on the Space Shuttle Main Engine (SSME) high-pressure oxygen pump have experienced cracking problems due to excessive vibration. A solution is to incorporate a well-designed friction dampers to attenuate blade vibration. The subject study, a cooperative effort between NASA Lewis and Carnegie-Mellon University, represents an application of recently developed friction damper technology to the SSME high-pressure oxygen turbopump. The major emphasis was the contractor's design known as the two-piece damper. Damping occurs at the frictional interface between the top half of the damper and the underside of the platforms of the adjacent blades. The lower half of the damper is an air seal to retard airflow in the volume between blade necks.

  19. Semi-active seismic response control of base-isolated building with MR damper

    NASA Astrophysics Data System (ADS)

    Soda, Satsuya; Kusumoto, Haruhide; Chatani, Ryosuke; Iwata, Norio; Fujitani, Hideo; Shiozaki, Yoichi; Hiwatashi, Takeshi

    2003-07-01

    This study deals with a shake table test on a three-story base-isolated steel frame. The frame rests on four roller bearings for isolation and is equipped with four laminated rubbers as shear spring. An MR damper is used in the test to perform semi-active seismic response control. The basic control algorithm applied in the study is to simulate the load-deflection of an origin-restoring friction damper (ORFD) which is a sort of friction damper that looses its resistance when it moves toward the origin, making sure for the base-isolated system to minimize residual displacement even after an extremely strong ground motion. Also attempted is a hybrid type control that superposes viscous damping on the ORFD when the damper moves from the peak displacement toward the origin.

  20. Damping force control of frictionless MR damper associated with hysteresis modeling

    NASA Astrophysics Data System (ADS)

    Seong, M. S.; Choi, S. B.; Kim, C. H.

    2013-02-01

    This study presents hysteresis modelling and damping force control of the frictionless magnetorheological (MR) damper for semiconductor manufacturing stage. The vibration sources of the semiconductor stage can be classified as two. The one is environmental vibration from the floor, and the other is transient vibration occurred from the stage moving. The transient vibration has serious adverse effect to the process because the vibration scale is quite larger than other vibrations. Therefore, in this research, the semi-active MR damper which can control the transient vibration is devised. In addition, the stage needs to be isolated from tiny vibration to achieve high grade vibration level. At the high frequency range, MR damper acts like a rigid body if the dry friction exists. So the tiny vibration is transferred to the stage directly. Therefore, a dry friction of the MR damper must be removed. In order to achieve this goal, a frictionless MR damper is originally designed. After then, a designed MR damper is manufactured and it's damping force characteristics and hysteresis behaviors are evaluated by experiment. The biviscous hysteresis model of MR damper is formulated and its accuracies are evaluated. Finally, damping force control performances using the hysteresis model is experimentally evaluated.

  1. Self-Tuning Impact Dampers Designed for Turbomachinery Blade Vibration Suppression

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Mehmed, Oral

    2002-01-01

    Turbomachinery blades are subject to aerodynamic forces that can lead to high-cycle-fatigue (HCF) failures. These failures will only increase as engineers begin to design blades without shrouds or as integrally bladed disks (blisks). These new designs will decrease blade damping significantly because the mechanical damping from shroud and blade joints will be eliminated. Also, it is difficult to design dampers for the engine environment with its extremely high centrifugal loads and high temperatures. The self-tuning impact damper has been designed to provide the additional damping required to avoid HCF while withstanding the harsh engine environment. In addition, the damper is placed within the engine blade itself rather than external to it.

  2. A semi-active control suspension system for railway vehicles with magnetorheological fluid dampers

    NASA Astrophysics Data System (ADS)

    Wei, Xiukun; Zhu, Ming; Jia, Limin

    2016-07-01

    The high-speed train has achieved great progress in the last decades. It is one of the most important modes of transportation between cities. With the rapid development of the high-speed train, its safety issue is paid much more attention than ever before. To improve the stability of the vehicle with high speed, extra dampers (i.e. anti-hunting damper) are used in the traditional bogies with passive suspension system. However, the curving performance of the vehicle is undermined due to the extra lateral force generated by the dampers. The active suspension systems proposed in the last decades attempt to solve the vehicle steering issue. However, the active suspension systems need extra actuators driven by electrical power or hydraulic power. There are some implementation and even safety issues which are not easy to be overcome. In this paper, an innovative semi-active controlled lateral suspension system for railway vehicles is proposed. Four magnetorheological fluid dampers are fixed to the primary suspension system of each bogie. They are controlled by online controllers for enhancing the running stability on the straight track line on the one hand and further improving the curving performance by controlling the damper force on the other hand. Two control strategies are proposed in the light of the pure rolling concept. The effectiveness of the proposed strategies is demonstrated by SIMPACK and Matlab co-simulation for a full railway vehicle with two conventional bogies.

  3. Investigation on dynamic coupling between stay cable and magneto-rheological fluid (MR) damper

    NASA Astrophysics Data System (ADS)

    Liu, Min; Li, H.; Guan, X. Ch..; Li, J. H.; Ou, J. P.

    2009-03-01

    In this paper, experimental investigation on vibration control is carried out on a stay cable model incorporated with one small size magnetorheological fluid (MR) damper. The control efficiency of the MR dampers to reduce the cable vibration under sinusoidal excitation using passive control strategy is firstly tested. The dynamic coupling between the cable and MR damper with the passive control strategy is obviously observed. Dynamic coupling models between stay cable and MR damper with constant and fluctuating current input are proposed respectively. The proposed dynamic coupling model corresponding to the MR damper with constant current input is validated by the numerical simulations of the measured experimental data. Furthermore, using the proposed dynamic coupling corresponding to the MR damper with fluctuating current input, experimental investigation on the cable vibration control subjected to sinusoidal excitation using semi-active control strategy is then conducted. Experimental results demonstrate that the semi-active MR damper can achieve much better mitigation efficacy than the passive MR dampers with different constant current inputs due to negative stiffness provided by the semi-active MR damper.

  4. Evaluation method for a controller of active mass damper using central pattern generator

    NASA Astrophysics Data System (ADS)

    Hongu, Junichi; Iba, Daisuke; Nakamura, Morimasa; Moriwaki, Ichiro

    2013-04-01

    This paper proposes an evaluation method for a CPG controller designed for active mass dampers. Neural oscillators composing the CPG have nonlinear and entrainment properties. Therefore, the proposed controller has possibility to have flexibility, when the structural parameters, i.e. stiffness or damping, are changed by the effect of earthquakes and the like. However, there has been no study to evaluate the controller's above-mentioned properties. For tuning into practical application, the reliability and flexibility along with the controller's performance must be analyzed. In our previous study, the phase reduction theory was tried to appraise the synchronization between a structure and a single neural oscillator and the synchronization region of the neural oscillator was obtained as basic research. However, the information from the synchronization region was insufficient to evaluate the system, because the neural oscillator has a phase difference called a phase locking point between the structure and the neural oscillator during the synchronization. Then, in this paper, the phase locking point within the synchronization region between a structure and a single neural oscillator is focused on, and the phase locking point and the vibration mitigation effect are considered with the simple object model.

  5. Design and testing of a magnetorheological damper to control both vibration and shock loads for a vehicle crew seat

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew; Hu, Wei; Hiemenz, Gregory J.; Wereley, Norman M.

    2010-04-01

    A magnetorheological shock absorber (MRSA) prototype is designed, fabricated and tested to integrate semiactive shock and vibration mitigation technology into the existing Expeditionary Fighting Vehicle (EFV) forward seating positions. Utilizing Bingham-Plastic (BP) constitutive fluid relationships and a steady state fluid flow model, the MR valve parameters are determined using magnetic circuit analysis, and subsequently validated via electromagnetic finite element analysis (FEA). Low speed (up to 0.9 m/s) simulations of normal vibration mode operation are conducted on the MRSA prototype using single frequency sinusoidal displacements by a servohydraulic testing machine. The high speed (up to 2.2 m/s) design procedure is verified by using a rail-guided drop test stand to impact a known payload mass onto the damper shaft. A refined hydromechanical model of the MRSA under both cyclic and impact loadings is developed and validated using the measured test data. This ratedependent, mechanisms-based model predicts the time response of the MRSA under both loading conditions. The hydromechanical analysis marks a significant improvement over previous linear models. Key design considerations for the MRSA to accommodate both vibration and shock spectra using a single MR device are presented.

  6. Dual clearance squeeze film damper for high load conditions

    NASA Technical Reports Server (NTRS)

    Fleming, D. P.

    1984-01-01

    Squeeze film dampers are widely used to control vibrations in aircraft turbine engines and other rotating machinery. However, if shaft unbalance rises appreciably above the design value (e.g., due to a turbine blade loss), a conventional squeeze film becomes overloaded, and is no longer effective in controlling vibration amplitudes and bearing forces. A damper concept characterized by two oil films is described. Under normal conditions, only one low-clearance film is active, allowing precise location of the shaft centerline. Under high unbalance conditions, both films are active, controlling shaft vibration in a near-optimum manner, and allowing continued operation until a safe shutdown can be made.

  7. Enhanced damping for bridge cables using a self-sensing MR damper

    NASA Astrophysics Data System (ADS)

    Chen, Z. H.; Lam, K. H.; Ni, Y. Q.

    2016-08-01

    This paper investigates enhanced damping for protecting bridge stay cables from excessive vibration using a newly developed self-sensing magnetorheological (MR) damper. The semi-active control strategy for effectively operating the self-sensing MR damper is formulated based on the linear-quadratic-Gaussian (LQG) control by further considering a collocated control configuration, limited measurements and nonlinear damper dynamics. Due to its attractive feature of sensing-while-damping, the self-sensing MR damper facilitates the collocated control. On the other hand, only the sensor measurements from the self-sensing device are employed in the feedback control. The nonlinear dynamics of the self-sensing MR damper, represented by a validated Bayesian NARX network technique, are further accommodated in the control formulation to compensate for its nonlinearities. Numerical and experimental investigations are conducted on stay cables equipped with the self-sensing MR damper operated in passive and semi-active control modes. The results verify that the collocated self-sensing MR damper facilitates smart damping for inclined cables employing energy-dissipative LQG control with only force and displacement measurements at the damper. It is also demonstrated that the synthesis of nonlinear damper dynamics in the LQG control enhances damping force tracking efficiently, explores the features of the self-sensing MR damper, and achieves better control performance over the passive MR damping control and the Heaviside step function-based LQG control that ignores the damper dynamics.

  8. A regenerative damper with MR fluids working between gear transmissions

    NASA Astrophysics Data System (ADS)

    Chan, Yan; Chen, Chao; Liao, Wei-Hsin

    2013-04-01

    Magnetorheological (MR) dampers are used for semi-active vibration control of various dynamic systems. Existing MR dampers are usually cylinder-piston based design, which may limit the shapes and have constraints to the design of MR devices. In this paper, we propose a new MR-fluid working operation, in which MR fluids work between gear transmissions. This operation could provide more design flexibility. A prototype of the regenerative damper with MR fluids working between gear transmissions was designed, fabricated, and tested. This MR damper has the capability of power generation and velocity sensing. The feasibilities of the controllable MR damping force, power generation and velocity sensing are experimentally verified. The results of this research would be beneficial to advance the design and multiple functions of MR dampers while not limited to traditional piston-type design.

  9. The two-mass flywheel - a torsional vibration damper for the power train of passenger cars - state-of-the-art and further technical development

    SciTech Connect

    Sebulke, A.

    1987-01-01

    The rotational irregularities of an engine, which are primarily caused by the forces generated by the combustion gases during the periodic combustion process, are transmitted to the driveline and there lead to vibration and noise. Since 1985, BMW has been using its two-mass flywheel on certain gasoline and diesel engines. This is a mechanical low-pass filter, which largely isolates rotational irregularities and vibration from the complete driveline and therefore reduces the noise level inside the vehicle. Running speeds significantly exceeding 5000 rpm however cause a severe increase in wear on the internal components of the torsional vibration damper, as a consequence of the higher centrifugal forces.

  10. Semi-active control of floor isolation system using MR-damper

    NASA Astrophysics Data System (ADS)

    Lin, Pei-Yang; Loh, Chin-Hsiung

    2008-03-01

    This paper presents the performance evaluation of a semi-active controlled floor isolation system for earthquake reduction. The floor isolation system consists of a rolling pendulum system and a semi-active controlled MR damper. The modified Bouc-Wen model is used to represent the behavior of the MR damper. A serious of performance test of the MR damper is made and been used for system identification. Two contrasting control methods including LQR with continuous-optimal control and Fuzzy Logic control are experimentally investigated as potential algorithms and comparisons are made from the results. Unlike the clipped-optimal control, LQR with continuous-optimal control can output the continuous command voltage to control the MR damper, and get smoother control effect. A three-story steel structure with the floor isolation system on the 2nd floor is tested on the shake table. Scaled historical near- and far-field seismic records are employed to examine controller performance with respect to frequency content and PGA level. Experimental results show that both control algorithms can suppress the acceleration of the isolated floor during small and large PGA levels, and alleviate both displacement and acceleration simultaneously in larger, near-field events. Both control algorithms are adaptive and robust to various intensity of excitation. This investigation demonstrates the feasibility and capabilities of a smart semi-active controlled floor-isolation system.

  11. An electroviscous damper

    NASA Technical Reports Server (NTRS)

    Nikolajsen, Jorgen L.; Hoque, M. S.

    1989-01-01

    A new type of vibration damper for rotor systems was developed and tested. The damper contains electroviscous fluid which solidifies and provides Coulomb damping when an electric voltage is imposed across the fluid. The damping capacity is controlled by the voltage. The damper was incorporated in a flexible rotor system and found to be able to damp out high levels of unbalanced excitation. Other proven advantages include controllability, simplicity, and no requirement for oil supply. Still unconfirmed are the capabilities to eliminate critical speeds and to suppress rotor instabilities.

  12. Active sensor/actuator assemblies for vibration damping, compensation, measurement, and testing

    NASA Astrophysics Data System (ADS)

    Ryaboy, Vyacheslav M.; Kasturi, Prakash S.

    2010-04-01

    The vibration control module known as IQ damper had been developed as part of active vibration damping system for optical tables and other precision vibration isolated platforms. The present work describes steps to expand the application of these units to other tasks, namely, (1) dynamic testing of structures and (2) compensation of forced vibration in local areas. The sensor-actuator assembly, including signal conditioning circuits, is designed as a compact dynamically symmetric module with mechanical interface to an optical table. The test data show that the vibration control modules can be used to measure dynamic compliance characteristics of optical tables with precision comparable to that of dedicated vibration measurement systems. Stable concerted work of active vibration control modules compensating forced harmonic vibration is demonstrated experimentally.

  13. Thermally conductive metal wool-silicone rubber material can be used as shock and vibration damper

    NASA Technical Reports Server (NTRS)

    Hough, W. W.

    1964-01-01

    Bronze wool pads, impregnated with silicon rubber, meet the requirement for a thermally conductive, shock and vibration absorbing material. They serve as spacers in equipment mounting and are resistant to high temperatures.

  14. Stochastic optimal semi-active control of hysteretic systems by using a magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Cheng, H.; Zhu, W. Q.; Ying, Z. G.

    2006-06-01

    A stochastic optimal semi-active control strategy for stochastically excited hysteretic systems by using a magneto-rheological (MR) damper is proposed. The dynamics of both the hysteretic system and the MR damper is characterized by using the Bouc-Wen hysteretic model. The control force produced by the damper is split into a passive part and a semi-active part. The passive part is combined with the uncontrolled system to form a passively controlled system. Then the system is converted into an equivalent nonlinear non-hysteretic stochastic system, from which a partially averaged Itô stochastic differential equation is derived by using the stochastic averaging method of the energy envelope. For the ergodic control problem, a dynamical programming equation is established based on the stochastic dynamical programming principle and solved to yield the optimal semi-active control law. The fully averaged Itô equation is obtained by substituting the optimal semi-active control force into the partially averaged Itô equation and completing the averaging. Finally, the response of the semi-actively controlled system is obtained from solving the Fokker-Planck-Kolmogorov equation associated with the fully averaged Itô equation. The efficacy of the proposed control strategy is illustrated by the numerical results and comparison with clipped LQG control for an example.

  15. Novel design of a self powered and self sensing magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Meftahul Ferdaus, Mohammad; Rashid, M. M.; Bhuiyan, M. M. I.; Muthalif, Asan Gani Bin Abdul; Hasan, M. R.

    2013-12-01

    Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.

  16. Experimental and numerical investigations on the performance of particle dampers attached to a primary structure undergoing free vibration in the horizontal and vertical directions

    NASA Astrophysics Data System (ADS)

    Wang, Yanrong; Liu, Bin; Tian, Aimei; Tang, Wei

    2016-06-01

    Particle damping (PD) has been well known for its simplicity and high efficiency in attenuating structure vibration. Recent studies on PD have focused mainly on new types of dampers and applications. Meanwhile, excitation applied to the primary structure is still limited to either horizontal or vertical direction, perpendicular or parallel to gravity. In this study, the characteristics of PD under horizontal-vertical excitations (HVE) are investigated numerically and experimentally. The particle damper, which is attached to the top free end of an L-shaped cantilever beam, is simultaneously excited in the horizontal and vertical directions in the context of free decay. An equivalent model capable of motion in both the horizontal and vertical directions is generated. Given an initial displacement disturbance, this model starts vibrating freely in the vertical plane. A code based on the 3D discrete element method is programmed, and the high coincidence between the numerical and experimental results shows that this equivalent model is capable of high-fidelity simulation for PD under HVE. Parametric studies have been implemented to characterize the basic nonlinear damping capacity of particle dampers under this new operating condition. The effects of seven dimensionless independent parameters on the specific damping capacity (SDC) are investigated, including dimensionless acceleration amplitude, particle mass ratio, dimensionless horizontal and vertical impact clearances, coefficients of friction and restitution, and amplitude ratio of the horizontal excitation to the vertical excitation. The results show that the basic damping properties of PD under HVE are similar to those of PD under only vertical excitation. However, PD under HVE signifies its own characteristics because of the existence of horizontal excitation: (1) The impact clearances in both the horizontal and vertical directions have significant effects on the SDC because of the significant increase in oblique

  17. Simulation and experimental tests on active mass damper control system based on Model Reference Adaptive Control algorithm

    NASA Astrophysics Data System (ADS)

    Tu, Jianwei; Lin, Xiaofeng; Tu, Bo; Xu, Jiayun; Tan, Dongmei

    2014-09-01

    In the process of sudden natural disasters (such as earthquake or typhoon), the active mass damper (AMD) system can reduce the structural vibration response optimally, which serves as a frequently applied but less mature vibration-reducing technology in wind and earthquake resistance of high-rise buildings. As the core of this technology, the selection of control algorithm is extremely challenging due to the uncertainty of structural parameters and the randomness of external loads. It is not necessary for the Model Reference Adaptive Control (MRAC) based on the Minimal Controller Synthesis (MCS) algorithm to know in advance the structural parameters, which produces special advantages in conditions of real-time change of system parameters, uncertain external disturbance, and the nonlinear dynamic system. This paper studies the application of the MRAC into the AMD active control system. The principle of MRAC algorithm is recommended and the dynamic model and the motion differential equation of AMD system based on MRAC is established under seismic excitation. The simulation analysis for linear and nonlinear structures when the structural stiffness is degenerated is performed under AMD system controlled by MRAC algorithm. To verify the validity of the MRAC over the AMD system, experimental tests are carried out on a linear structure and a structure with variable stiffness with the AMD system under seismic excitation on the shake table, and the experimental results are compared with those of the traditional pole assignment control algorithm.

  18. Nutation damper

    NASA Technical Reports Server (NTRS)

    Evans, J. (Inventor)

    1973-01-01

    A nutation damper for use on a spinning body is disclosed. The damper is positioned parallel to the spin axis of the body and radially displaced therefrom. The damper is partially filled with a fluid and contains a porous media to impede the flow of the fluid induced by nutation.

  19. A self-sensing magnetorheological damper with power generation

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Liao, Wei-Hsin

    2012-02-01

    Magnetorheological (MR) dampers are promising for semi-active vibration control of various dynamic systems. In the current MR damper systems, a separate power supply and dynamic sensor are required. To enable the MR damper to be self-powered and self-sensing in the future, in this paper we propose and investigate a self-sensing MR damper with power generation, which integrates energy harvesting, dynamic sensing and MR damping technologies into one device. This MR damper has self-contained power generation and velocity sensing capabilities, and is applicable to various dynamic systems. It combines the advantages of energy harvesting—reusing wasted energy, MR damping—controllable damping force, and sensing—providing dynamic information for controlling system dynamics. This multifunctional integration would bring great benefits such as energy saving, size and weight reduction, lower cost, high reliability, and less maintenance for the MR damper systems. In this paper, a prototype of the self-sensing MR damper with power generation was designed, fabricated, and tested. Theoretical analyses and experimental studies on power generation were performed. A velocity-sensing method was proposed and experimentally validated. The magnetic-field interference among three functions was prevented by a combined magnetic-field isolation method. Modeling, analysis, and experimental results on damping forces are also presented.

  20. System and method for damping vibration in a drill string using a magnetorheological damper

    DOEpatents

    Wassell, Mark Ellsworth; Burgess, Daniel E.; Barbely, Jason R.

    2012-01-03

    A system for damping vibration in a drill string can include a magnetorheological fluid valve assembly having a supply of a magnetorheological fluid, a first member, and a second member capable of moving in relation to first member in response to vibration of the drill bit. The first and second members define a first and a second chamber for holding the fluid. Fluid can flow between the first and second chambers in response to the movement of the second member in relation to the first member. The valve assembly can also include a coil for inducing a magnetic field that alters the resistance of the magnetorheological fluid to flow between the first and second chambers, thereby increasing the damping provided by the valve. A remnant magnetic field is induced in one or more components of the magnetorheological fluid valve during operation that can be used to provide the magnetic field for operating the valve so as to eliminate the need to energize the coils during operation except temporarily when changing the amount of damping required, thereby eliminating the need for a turbine alternator power the magnetorheological fluid valve. A demagnetization cycle can be used to reduce the remnant magnetic field when necessary.

  1. Nano-micro composite magnetic fluids: Magnetic and magnetorheological evaluation for rotating seal and vibration damper applications

    NASA Astrophysics Data System (ADS)

    Marinică, Oana; Susan-Resiga, Daniela; Bălănean, Florica; Vizman, Daniel; Socoliuc, Vlad; Vékás, Ladislau

    2016-05-01

    In this paper, static magnetic properties and magnetorheological behavior of a set of 12 nano-micro composite magnetic fluids (CMFs) were studied. The samples with a ferromagnetic particle volume fraction ranging in a large interval φFe = (1 ÷ 44) % were prepared by adding carbonyl iron powder in a highly concentrated transformer oil-based ferrofluid (FF). The ferrofluid has the magnetite volume fraction of φFe3O4 = 22.90 % and saturation magnetization of Ms = 74 kA / m (930 Gs). No further additives were used in order to prevent sedimentation. It was noticed an increase of the static yield stress, of about 3 orders of magnitude, with the increase of the total solid volume fraction of samples and with the increase of the magnetic field, which varied between 0 kA/m and 950 kA/m. The dynamic yield stress (Herschel-Bulkley model) τHB of the samples strongly increases with the magnetic field and shows a slight tendency of saturation for higher intensities of the magnetic field. There is a less pronounced increase of τHB, about an order of magnitude with the increasing volume fraction of the iron particles. The relative viscosity increase induced by the magnetic field reaches a maximum for both considered shear rates: γ ṡ = 7.85s-1 and γ ṡ = 88.41s-1 and it was revealed an optimal volume fraction of Fe particles, φFe = 20 % , corresponding to a total volume fraction of φtot ≈ 38 % , at which the magnetoviscous effect has its maximum value. The magnetic properties and also the magnetorheological and the magnetoviscous behavior of highly concentrated ferrofluid-based CMFs can be controlled by the addition of iron microparticles in order to attain the optimal concentration for the envisaged engineering applications, rotating seals and magnetorheological vibration dampers.

  2. Demonstrating the Effect of Particle Impact Dampers on the Random Vibration Response and Fatigue Life of Printed Wiring Assemblies

    NASA Technical Reports Server (NTRS)

    Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert

    2013-01-01

    In a recent experimental study, small Particle Impact Dampers (PID) were bonded directly to the surface of printed circuit board (PCB) or printed wiring assemblies (PWA), reducing the random vibration response and increasing the fatigue life. This study provides data verifying practicality of this approach. The measured peak strain and acceleration response of the fundamental out of plane bending mode was significantly attenuated by adding a PID device. Attenuation of this mode is most relevant to the fatigue life of a PWA because the local relative displacements between the board and the supported components, which ultimately cause fatigue failures of the electrical leads of the board-mounted components are dominated by this mode. Applying PID damping at the board-level of assembly provides mitigation with a very small mass impact, especially as compared to isolation at an avionics box or shelf level of assembly. When compared with other mitigation techniques at the PWA level (board thickness, stiffeners, constrained layer damping), a compact PID device has the additional advantage of not needing to be an integral part of the design. A PID can simply be bonded to heritage or commercial off the shelf (COTS) hardware to facilitate its use in environments beyond which it was originally qualified. Finite element analysis and test results show that the beneficial effect is not localized and that the attenuation is not due to the simple addition of mass. No significant, detrimental reduction in frequency was observed. Side-by-side life testing of damped and un-damped boards at two different thicknesses (0.070" and 0.090") has shown that the addition of a PID was much more significant to the fatigue life than increasing the thickness. High speed video, accelerometer, and strain measurements have been collected to correlate with analytical results.

  3. Design of a new adaptive fuzzy controller and its application to vibration control of a vehicle seat installed with an MR damper

    NASA Astrophysics Data System (ADS)

    Phu, Do Xuan; Shin, Do Kyun; Choi, Seung-Bok

    2015-08-01

    This paper presents a new adaptive fuzzy controller featuring a combination of two different control methodologies: H infinity control technique and sliding mode control. It is known that both controllers are powerful in terms of high performance and robust stability. However, both control methods require an accurate dynamic model to design a state variable based controller in order to maintain their advantages. Thus, in this work a fuzzy control method which does not require an accurate dynamic model is adopted and two control methodologies are integrated to maintain the advantages even in an uncertain environment of the dynamic system. After a brief explanation of the interval type 2 fuzzy logic, a new adaptive fuzzy controller associated with the H infinity control and sliding mode control is formulated on the basis of Lyapunov stability theory. Subsequently, the formulated controller is applied to vibration control of a vehicle seat equipped with magnetorheological fluid damper (MR damper in short). An experimental setup for realization of the proposed controller is established and vibration control performances such as acceleration at the driver’s seat are evaluated. In addition, in order to demonstrate the effectiveness of the proposed controller, a comparative work with two existing controllers is undertaken. It is shown through simulation and experiment that the proposed controller can provide much better vibration control performance than the two existing controllers.

  4. Semi-active damping with negative stiffness for multi-mode cable vibration mitigation: approximate collocated control solution

    NASA Astrophysics Data System (ADS)

    Weber, F.; Distl, H.

    2015-11-01

    This paper derives an approximate collocated control solution for the mitigation of multi-mode cable vibration by semi-active damping with negative stiffness based on the control force characteristics of clipped linear quadratic regulator (LQR). The control parameters are derived from optimal modal viscous damping and corrected in order to guarantee that both the equivalent viscous damping coefficient and the equivalent stiffness coefficient of the semi-active cable damper force are equal to their desired counterparts. The collocated control solution with corrected control parameters is numerically validated by free decay tests of the first four cable modes and combinations of these modes. The results of the single-harmonic tests demonstrate that the novel approach yields 1.86 times more cable damping than optimal modal viscous damping and 1.87 to 2.33 times more damping compared to a passive oil damper whose viscous damper coefficient is optimally tuned to the targeted mode range of the first four modes. The improvement in case of the multi-harmonic vibration tests, i.e. when modes 1 and 3 and modes 2 and 4 are vibrating at the same time, is between 1.55 and 3.81. The results also show that these improvements are obtained almost independent of the cable anti-node amplitude. Thus, the proposed approximate real-time applicable collocated semi-active control solution which can be realized by magnetorheological dampers represents a promising tool for the efficient mitigation of stay cable vibrations.

  5. Semi-active control of helicopter vibration using controllable stiffness and damping devices

    NASA Astrophysics Data System (ADS)

    Anusonti-Inthra, Phuriwat

    Semi-active concepts for helicopter vibration reduction are developed and evaluated in this dissertation. Semi-active devices, controllable stiffness devices or controllable orifice dampers, are introduced; (i) in the blade root region (rotor-based concept) and (ii) between the rotor and the fuselage as semi-active isolators (in the non-rotating frame). Corresponding semi-active controllers for helicopter vibration reduction are also developed. The effectiveness of the rotor-based semi-active vibration reduction concept (using stiffness and damping variation) is demonstrated for a 4-bladed hingeless rotor helicopter in moderate- to high-speed forward flight. A sensitivity study shows that the stiffness variation of root element can reduce hub vibrations when proper amplitude and phase are used. Furthermore, the optimal semi-active control scheme can determine the combination of stiffness variations that produce significant vibration reduction in all components of vibratory hub loads simultaneously. It is demonstrated that desired cyclic variations in properties of the blade root region can be practically achieved using discrete controllable stiffness devices and controllable dampers, especially in the flap and lag directions. These discrete controllable devices can produce 35--50% reduction in a composite vibration index representing all components of vibratory hub loads. No detrimental increases are observed in the lower harmonics of blade loads and blade response (which contribute to the dynamic stresses) and controllable device internal loads, when the optimal stiffness and damping variations are introduced. The effectiveness of optimal stiffness and damping variations in reducing hub vibration is retained over a range of cruise speeds and for variations in fundamental rotor properties. The effectiveness of the semi-active isolator is demonstrated for a simplified single degree of freedom system representing the semi-active isolation system. The rotor

  6. a Stochastic Optimal Semi-Active Control Strategy for Er/mr Dampers

    NASA Astrophysics Data System (ADS)

    Ying, Z. G.; Zhu, W. Q.; Soong, T. T.

    2003-01-01

    A stochastic optimal semi-active control strategy for randomly excited systems using electrorheological/magnetorheological (ER/MR) dampers is proposed. A system excited by random loading and controlled by using ER/MR dampers is modelled as a controlled, stochastically excited and dissipated Hamiltonian system with n degrees of freedom. The control forces produced by ER/MR dampers are split into a passive part and an active part. The passive control force is further split into a conservative part and a dissipative part, which are combined with the conservative force and dissipative force of the uncontrolled system, respectively, to form a new Hamiltonian and an overall passive dissipative force. The stochastic averaging method for quasi-Hamiltonian systems is applied to the modified system to obtain partially completed averaged Itô stochastic differential equations. Then, the stochastic dynamical programming principle is applied to the partially averaged Itô equations to establish a dynamical programming equation. The optimal control law is obtained from minimizing the dynamical programming equation subject to the constraints of ER/MR damping forces, and the fully completed averaged Itô equations are obtained from the partially completed averaged Itô equations by replacing the control forces with the optimal control forces and by averaging the terms involving the control forces. Finally, the response of semi-actively controlled system is obtained from solving the final dynamical programming equation and the Fokker-Planck-Kolmogorov equation associated with the fully completed averaged Itô equations of the system. Two examples are given to illustrate the application and effectiveness of the proposed stochastic optimal semi-active control strategy.

  7. Synthesis of a system with active vibration isolation, considering the vibroacoustical characteristics of the source and of the isolated object

    NASA Technical Reports Server (NTRS)

    Genkin, M. D.; Yelezov, V. G.; Yablonskiy, V. V.

    1973-01-01

    The efficiency and resistance of an active vibration isolation system (AVI) are analyzed for the case of unidirectional vibrations of a mass on a spring, with a damper, resting on a rigid base. The effect of certain vibroacoustical characteristics of real objects on AVI resistance and synthesis of AVI, which are effective over a wide frequency band are considered. A numerical analysis of the response of a mechanical system with AVI features is presented.

  8. Passive vibration control in a building-like structure using a tuned-mass-damper and an autoparametric cantilever beam absorber

    NASA Astrophysics Data System (ADS)

    Enriquez-Zarate, J.; Abundis-Fong, H. F.; Silva-Navarro, G.

    2015-04-01

    This article considers a theoretical and experimental comparative analysis in the responses of a three-story building-like structure using two different schemes of passive vibration control. These control schemes are designed to reduce the effects of resonant vibrations generated by an electromechanical shaker located in the base of the building-like structure. The first control scheme consists on the design of a Tuned-Mass-Damper located over the third floor of the structure, and the second control scheme considers the implementation of an autoparametric cantilever beam absorber. The mathematical model of the overall system is obtained using Euler-Lagrange method. In order to validate the frequency response of the main system a finite element model is completed. Some numerical and experimental results are included to show the dynamic behavior and stability performance of the overall mechanical system.

  9. Fuzzy logic control of the building structure with CLEMR dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang-Cheng; Xu, Zhao-Dong; Huang, Xing-Huai; Zhu, Jun-Tao

    2013-04-01

    The semi-active control technology has been paid more attention in the field of structural vibration control due to its high controllability, excellent control effect and low power requirement. When semi-active control device are used for vibration control, some challenges must be taken into account, such as the reliability and the control strategy of the device. This study presents a new large tonnage compound lead extrusion magnetorheological (CLEMR) damper, whose mathematical model is introduced to describe the variation of damping force with current and velocity. Then a current controller based on the fuzzy logic control strategy is designed to determine control currents of the CLEMR dampers rapidly. A ten-floor frame structure with CLEMR dampers using the fuzzy logic control strategy is built and calculated by using MATLAB. Calculation results show that CLEMR dampers can reduce the seismic responses of structures effectively. Calculation results of the fuzzy logic control strategy are compared with those of the semi-active limit Hrovat control structure, the passive-off control structure, and the uncontrolled structure. Comparison results show that the fuzzy logic control strategy can determine control currents of CLEMR dampers quickly and can reduce seismic responses of the structures more effectively than the passive-off control strategy and the uncontrolled structure.

  10. Overview of coupled bunch active damper systems at FNAL

    SciTech Connect

    Steimel, J.; Crisp, J.; Ma, Hengjie; Marriner, J.; McGinnis, D.

    1996-05-01

    Beam intensities in all of the accelerators at Fermilab will increase significantly when the Main Injector becomes operational and will cause unstable oscillations in transverse position and energy. Places where the coupled bunch oscillations could dilute emittances include the Booster, Main Injector, and Tevatron. This paper provides an overview of the active feedback system upgrades which will be used to counteract the problem. It will explain the similarities between all the systems and will also explain design differences between longitudinal and transverse systems, fast sweeping systems, and systems for partially filled machines. Results from operational systems will also be shown. 7 refs., 4 figs., 1 tab.

  11. Overview of coupled-bunch active damper systems at FNAL

    SciTech Connect

    Steimel, J.; Crisp, J.; Ma, H.; Marriner, J.; McGinnis, D.

    1997-01-01

    Beam intensities in all of the accelerators at Fermilab will increase significantly when the Main Injector becomes operational and will cause unstable oscillations in transverse position and energy. Places where the coupled bunch oscillations could dilute emittances include the Booster, Main Injector, and Tevatron. This paper provides an overview of the active feedback system upgrades which will be used to counteract the problem. It will explain the similarities between all the systems and will also explain design differences between longitudinal and transverse systems, fast sweeping systems, and systems for partially filled machines. Results from operational systems will also be shown. {copyright} {ital 1997 American Institute of Physics.}

  12. Modular Wideband Active Vibration Absorber

    NASA Technical Reports Server (NTRS)

    Smith, David R.; Zewari, Wahid; Lee, Kenneth Y.

    1999-01-01

    A comparison of space experiments with previous missions shows a common theme. Some of the recent experiments are based on the scientific fundamentals of instruments of prior years. However, the main distinguishing characteristic is the embodiment of advances in engineering and manufacturing in order to extract clearer and sharper images and extend the limits of measurement. One area of importance to future missions is providing vibration free observation platforms at acceptable costs. It has been shown by researchers that vibration problems cannot be eliminated by passive isolation techniques alone. Therefore, various organizations have conducted research in the area of combining active and passive vibration control techniques. The essence of this paper is to present progress in what is believed to be a new concept in this arena. It is based on the notion that if one active element in a vibration transmission path can provide a reasonable vibration attenuation, two active elements in series may provide more control options and better results. The paper presents the functions of a modular split shaft linear actuator developed by NASA's Goddard Space Flight Center and University of Massachusetts Lowell. It discusses some of the control possibilities facilitated by the device. Some preliminary findings and problems are also discussed.

  13. Active vibration control of structures undergoing bending vibrations

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor)

    1995-01-01

    An active vibration control subassembly for a structure (such as a jet engine duct or a washing machine panel) undergoing bending vibrations caused by a source (such as the clothes agitator of the washing machine) independent of the subassembly. A piezoceramic actuator plate is vibratable by an applied electric AC signal. The plate is connected to the structure such that vibrations in the plate induced by the AC signal cause canceling bending vibrations in the structure and such that the plate is compressively pre-stressed along the structure when the structure is free of any bending vibrations. The compressive prestressing increases the amplitude of the canceling bending vibrations before the critical tensile stress level of the plate is reached. Preferably, a positive electric DC bias is also applied to the plate in its poling direction.

  14. Comparisons of the dynamic characteristics of magnetorheological and hydraulic dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Oyadiji, S. O.

    2015-04-01

    A magnetorheological (MR) damper can adapt its dynamic performance to the vibration environment by controlling the current applied. Compared to other types of dampers, the MR damper has a wider range of dynamic characteristics. Two different dampers: hydraulic, and MR dampers were tested under forced sinusoidal excitations of low to high frequencies. Also, different currents were applied on the MR damper to investigate its performance under varying electromagnetic fields. The results reveal that the two dampers have nonlinear dynamic characteristics and that characteristics of the hydraulic damper are different from those of the MR damper. The hydraulic damper provides slight nonlinear damping force whereas the MR damper shows a strong nonlinear property. In addition, the hydraulic damper is designed to provide an asymmetric damping force of rebound and compression whereas the MR damper provides a symmetric damping force. In the experiments conducted, the excitation frequency was varied from 3 Hz to 11 Hz and the amplitude from 2.5 mm to 12 mm. For the hydraulic damper, the lowest compression damping force only increases by about 0.54 kN while the rebound force increases by about 1.9 kN. In contrast, the variations of compression and rebound forces of the MR damper are 1.9 and 2.0 kN, respectively. Furthermore, the damping force of the MR damper increases as the current increases from 0 to 0.75 A.

  15. Active vibration attenuating seat suspension for an armored helicopter crew seat

    NASA Astrophysics Data System (ADS)

    Sztein, Pablo Javier

    An Active Vibration Attenuating Seat Suspension (AVASS) for an MH-60S helicopter crew seat is designed to protect the occupants from harmful whole-body vibration (WBV). Magnetorheological (MR) suspension units are designed, fabricated and installed in a helicopter crew seat. These MR isolators are built to work in series with existing Variable Load Energy Absorbers (VLEAs), have minimal increase in weight, and maintain crashworthiness for the seat system. Refinements are discussed, based on testing, to minimize friction observed in the system. These refinements include the addition of roller bearings to replace friction bearings in the existing seat. Additionally, semi-active control of the MR dampers is achieved using special purpose built custom electronics integrated into the seat system. Experimental testing shows that an MH-60S retrofitted with AVASS provides up to 70.65% more vibration attenuation than the existing seat configuration as well as up to 81.1% reduction in vibration from the floor.

  16. Energy-Recycling Semi-Active Vibration Suppression Experiment of a Truss with Piezoelectric Transducer

    NASA Astrophysics Data System (ADS)

    Makihara, K.

    2002-01-01

    inherent performance in damping is enhanced. Several semi-active vibration suppression approaches have been proposed based on variable-stiffness members, variable-friction devices, or variable-viscosity dampers, and the performance of each of these systems has been studied. The semi-active approach exploits passive energy-dissipation mechanisms, and supplies the system with no additional energy. Semi-active vibration suppression thus ensures that the system is always stable. This is its advantage. However, its performance in vibration suppression is usually inferior to active vibration suppression. have proposed collection of the energy taken from a vibrating system in suppressing its vibration. Using the collected energy to more quickly suppress the vibration is an attractive possibility. Additional energy is still not supplied to the system, and the vibration energy is finally dissipated. Therefore, this is a kind of semi-active approach, and retains the quality of that the system with it is always stable. method of energy-recycling semi-active vibration suppression is described and its performance is demonstrated by an experiment. A five bay truss beam with a piezoelectric transducer was used, and a simple electric circuit with switches was connected to the transducers. Then the switches were controlled by a processor so that the vibration was quickly suppressed by exploiting the collected electric energy. The results of the experiment demonstrated that the performance in vibration suppression of energy-recycling semi-active vibration suppression with actual hardware is much better than that of a traditional semi-active control. The effects of some non-ideal characteristics of real hardware on the performance in vibration suppression are also investigated.

  17. Semi-active magnetorheological seat suspensions for enhanced crashworthiness and vibration isolation of rotorcraft seats

    NASA Astrophysics Data System (ADS)

    Hiemenz, Gregory J.

    current state-of-the-art rotorcraft seat suspensions which can provide no better than 20% risk of occupant injury. Finally, an MR-based seat suspension designed solely for the purposes of vibration isolation was designed, analyzed, and experimentally demonstrated. MR dampers were integrated into the current crashworthy SH-60 crew seat with minimal weight impact such that the original crashworthy capabilities were maintained. Then, utilizing semi-active control, experimental vibration testing demonstrated that the system reduced vertical cockpit vibrations transmitted to the occupant by 76%. This is a significant advance over current state-of-the-art rotorcraft seats which provide no attenuation of cockpit vibrations.

  18. Feasibility study of self-powered magnetorheological damper systems

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Liao, Wei-Hsin

    2012-04-01

    This paper is aimed to provide a feasibility study of self-powered magnetorheological (MR) damper systems, which could convert vibration and shock energy into electrical energy to power itself under control. The self-powered feature could bring merits such as higher reliability, energy saving, and less maintenance for the MR damper systems. A self-powered MR damper system is proposed and modeled. The criterion whether the MR damper system is self-powered or not is proposed. A prototype of MR damper with power generation is designed, fabricated, and tested. The modeling of this damper is experimentally validated. Then the damper is applied to a 2 DOF suspension system under on-off skyhook controller, to obtain the self-powered working range and vibration control performance. Effects of key factors on the self-powered MR damper systems are studied. Design considerations are given in order to increase the self-powered working range.

  19. The damper placement problem for large flexible space structures

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.

    1992-01-01

    The damper placement problem for large flexible space truss structures is formulated as a combinatorial optimization problem. The objective is to determine the p truss members of the structure to replace with active (or passive) dampers so that the modal damping ratio is as large as possible for all significant modes of vibration. Equivalently, given a strain energy matrix with rows indexed on the modes and the columns indexed on the truss members, we seek to find the set of p columns such that the smallest row sum, over the p columns, is maximized. We develop a tabu search heuristic for the damper placement problems on the Controls Structures Interaction (CSI) Phase 1 Evolutionary Model (10 modes and 1507 truss members). The resulting solutions are shown to be of high quality.

  20. A design procedure for active control of beam vibrations

    NASA Technical Reports Server (NTRS)

    Dickerson, S. L.; Jarocki, G.

    1983-01-01

    The transverse vibrations of beams is discussed and a methodology for the design of an active damping device is given. The Bernoulli-Euler equation is used to derive a transcendental transfer function, which relates a torque applied at one end of the beam to the rotational position and velocity at that point. The active damping device consists of a wire, a linear actuator and a short torque arm attached to one end of the beam. The action of the actuator varies a tension in the wire and creates a torque which opposes the rotation of the beam and thus damps vibration. A design procedure for such an active damper is given. This procedure shows the relationships and trade-offs between the actuator stroke, power required, stress levels in the wire and beam and the geometry of the beam and wire. It is shown that by consideration of the frequency response at the beam natural frequencies, the aforementioned relationships can be greatly simplified. Similarly, a simple way of estimating the effective damping ratios and eigenvalue locations of actively controlled beams is presented.

  1. NASDA's activities on vibration isolation technology

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The National Space Development Agency's (NASDA) activities in providing various vibration isolation technologies for the Space Station Mission are covered in viewgraph form. Technologies covered include an active vibration isolation system for extra sensitive missions in the low frequency range, a passive damping system consisting of a damping rack for the reduction of resonance amplification, and an isolator for vibration isolation from low frequencies. Information is given in viewgraph form on the active vibration isolation concept, voice coil type electromagnetic suspension, a profile of an active vibration isolation system, a three degree of freedom ground experiment, and acceleration feedback.

  2. Dampers for Stationary Labyrinth Seals

    NASA Technical Reports Server (NTRS)

    El-Aini, Yehia; Mitchell, William; Roberts, Lawrence; Montgomery, Stuart; Davis, Gary

    2011-01-01

    Vibration dampers have been invented that are incorporated as components within the stationary labyrinth seal assembly. These dampers are intended to supplement other vibration-suppressing features of labyrinth seals in order to reduce the incidence of high-cycle-fatigue failures, which have been known to occur in the severe vibratory environments of jet engines and turbopumps in which labyrinth seals are typically used. A vibration damper of this type includes several leaf springs and/or a number of metallic particles (shot) all held in an annular seal cavity by a retaining ring. The leaf springs are made of a spring steel alloy chosen, in conjunction with design parameters, to maintain sufficient preload to ensure effectiveness of damping at desired operating temperatures. The cavity is vented via a small radial gap between the retaining ring and seal housing. The damping mechanism is complex. In the case of leaf springs, the mechanism is mainly friction in the slippage between the seal housing and individual dampers. In the case of a damper that contains shot, the damping mechanism includes contributions from friction between individual particles, friction between particles and cavity walls, and dissipation of kinetic energy of impact. The basic concept of particle/shot vibration dampers has been published previously; what is new here is the use of such dampers to suppress traveling-wave vibrations in labyrinth seals. Damping effectiveness depends on many parameters, including, but not limited to, coefficient of friction, mode shape, and frequency and amplitude of vibrational modes. In tests, preloads of the order of 6 to 15 lb (2.72 to 6.8 kilograms) per spring damper were demonstrated to provide adequate damping levels. Effectiveness of shot damping of vibrations having amplitudes from 20 to 200 times normal terrestrial gravitational acceleration (196 to 1,960 meters per square second) and frequencies up to 12 kHz was demonstrated for shot sizes from 0.032 to

  3. Novel active vibration absorber with magnetorheological fluid

    NASA Astrophysics Data System (ADS)

    Gerlach, T.; Ehrlich, J.; Böse, H.

    2009-02-01

    Disturbing vibrations diminish the performance of technical high precision devices significantly. In search of a suitable solution for reducing these vibrations, a novel concept of active vibration reduction was developed which exploits the special properties of magnetorheological fluids. In order to evaluate the concept of such an active vibration absorber (AVA) a demonstrator was designed and manufactured. This demonstrator generates a force which counteracts the motion of the vibrating body. Since the counterforce is generated by a centrifugal exciter, the AVA provides the capability to compensate vibrations even in two dimensions. To control the strength of the force transmitted to the vibrating body, the exciter is based on a tunable MR coupling. The AVA was integrated in an appropriate testing device to investigate its performance. The recorded results show a significant reduction of the vibration amplitudes by an order of magnitude.

  4. Model Of Bearing With Hydrostatic Damper

    NASA Technical Reports Server (NTRS)

    Goggin, David G.

    1991-01-01

    Improved mathematical model of rotational and vibrational dynamics of bearing package in turbopump incorporates effects of hydrostatic damper. Part of larger finite-element model representing rotational and vibrational dynamics of rotor and housing of pump. Includes representations of deadband and nonlinear stiffness and damping of ball bearings, nonlinear stiffness and damping of hydrostatic film, and stiffness of bearing support. Enables incorporation of effects of hydrostatic damper into overall rotor-dynamic mathematical model without addition of mathematical submodel of major substructure.

  5. Application of particle damper on electronic packages for spacecraft

    NASA Astrophysics Data System (ADS)

    Veeramuthuvel, P.; Shankar, K.; Sairajan, K. K.

    2016-10-01

    Particle damping is an effective method of passive vibration control, which is of recent research interest. This paper presents a novel application of particle damper on an electronic package of a spacecraft, tested at ISRO Satellite Centre. The effectiveness of particle damper on the random vibration response of electronic package for spacecraft application exposed to random vibration environments experienced during the launch is studied. The use of particle damper under shock environments are also demonstrated. Optimal particle damper parameters were used based on the design guidelines derived from previous publications of the authors. The comparison of particle damper effectiveness under random vibration loads with respect to the shape of the particle damper capsule and packing ratio are also examined.

  6. Semi-active tuned liquid column damper implementation with real-time hybrid simulations

    NASA Astrophysics Data System (ADS)

    Riascos, Carlos; Marulanda Casas, Johannio; Thomson, Peter

    2016-04-01

    Real-time hybrid simulation (RTHS) is a modern cyber-physical technique used for the experimental evaluation of complex systems, that treats the system components with predictable behavior as a numerical substructure and the components that are difficult to model as an experimental substructure. Therefore it is an attractive method for evaluation of the response of civil structures under earthquake, wind and anthropic loads. In this paper, the response of three-story shear frame controlled by a tuned liquid column damper (TLCD) and subject to base excitation is considered. Both passive and semi-active control strategies were implemented and are compared. While the passive TLCD achieved a reduction of 50% in the acceleration response of the main structure in comparison with the structure without control, the semi-active TLCD achieved a reduction of 70%, and was robust to variations in the dynamic properties of the main structure. In addition, a RTHS was implemented with the main structure modeled as a linear, time-invariant (LTI) system through a state space representation and the TLCD, with both control strategies, was evaluated on a shake table that reproduced the displacement of the virtual structure. Current assessment measures for RTHS were used to quantify the performance with parameters such as generalized amplitude, equivalent time delay between the target and measured displacement of the shake table, and energy error using the measured force, and prove that the RTHS described in this paper is an accurate method for the experimental evaluation of structural control systems.

  7. Simulation of adaptive semi-active magnetorheological seat damper for vehicle occupant blast protection

    NASA Astrophysics Data System (ADS)

    Yoo, Jin-Hyeong; Murugan, Muthuvel; Wereley, Norman M.

    2013-04-01

    This study investigates a lumped-parameter human body model which includes lower leg in seated posture within a quarter-car model for blast injury assessment simulation. To simulate the shock acceleration of the vehicle, mine blast analysis was conducted on a generic land vehicle crew compartment (sand box) structure. For the purpose of simulating human body dynamics with non-linear parameters, a physical model of a lumped-parameter human body within a quarter car model was implemented using multi-body dynamic simulation software. For implementing the control scheme, a skyhook algorithm was made to work with the multi-body dynamic model by running a co-simulation with the control scheme software plug-in. The injury criteria and tolerance levels for the biomechanical effects are discussed for each of the identified vulnerable body regions, such as the relative head displacement and the neck bending moment. The desired objective of this analytical model development is to study the performance of adaptive semi-active magnetorheological damper that can be used for vehicle-occupant protection technology enhancements to the seat design in a mine-resistant military vehicle.

  8. Active Suppression Of Vibrations On Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio

    1995-01-01

    Method of active suppression of nonlinear and nonstationary vibrations developed to reduce sonic fatigue and interior noise in high-speed aircraft. Structure of aircraft exhibits periodic, chaotic, and random vibrations when forced by high-intensity sound from jet engines, shock waves, turbulence, and separated flows. Method of suppressing vibrations involves feedback control: Strain gauges or other sensors mounted in paths of propagation of vibrations on structure sense vibrations; outputs of sensors processed into control signal applied to actuator mounted on structure, inducing compensatory forces.

  9. Regenerative magnetorheological dampers for vehicle suspensions

    NASA Astrophysics Data System (ADS)

    Chen, Chao; Zou, Li; Liao, Wei-Hsin

    2015-04-01

    Magnetorheological (MR) dampers are promising for vehicle suspensions, by virtue of their adaptive properties. During the everyday use of vehicles, a lot of energy is wasted due to the energy dissipation by dampers under the road irregularities. On the other hand, extra batteries are required for the current MR damper systems. To reduce the energy waste and get rid of the dependence on extra batteries, in this paper, regenerative MR dampers are proposed for vehicle suspensions, which integrate energy harvesting and controllable damping functions. The wasted vibration energy can be converted into electrical energy and power the MR damper coil. A regenerative MR damper for vehicle suspensions is developed. Damping force and power generation characteristics of the regenerative MR damper were modeled and analyzed. Then the damper is applied to a 2 DOF suspension system for system simulation under various road conditions. Simulation results show that riding comfort can be significantly improved, while harvesting energy for other use in addition to supply power for the controlled MR damper.

  10. DOWNHOLE VIBRATION MONITORING AND CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2003-02-01

    The purpose of this program is to develop the Drilling Vibration Monitoring & Control System (DVMCS) to both record and reduce drilling vibrations in a ''smart'' drill string. It is composed of two main elements. The first is a multi-axis active vibration damper to minimize harmful axial, lateral and torsional vibrations, and thereby increase both rate of penetration (ROP) and bit life, as well that the life of other drillstring components. The hydraulic impedance (hardness) of this damper will be continuously adjusted using unique technology that is robust, fast-acting and reliable. The second component is a real-time system to monitor 3-axis drillstring vibration, and related parameters including weight- and torque-on-bit (TOB) and temperature. This monitor will determine the current vibration environment and adjust the damper accordingly. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. Phase I of this program addresses an evaluation of the environment in which the DVMCS will operate; modeling of a drillstring response including the active damper; a top-level design of the mechanical and electronic systems; analyzing the anticipated performance of the damper by modeling and laboratory testing of small prototypes; and doing preliminary economic, market, environmental and financing analyses. This phase is scheduled to last fourteen months, until November 30, 2003. During this first quarter, significant progress was achieved on the first two objectives, and work was begun on several others. Initial designs of the DVMCS are underway.

  11. Passive and Variable Active Switching Control by Mechanical Energy with Dual Structural Mass Damper

    NASA Astrophysics Data System (ADS)

    Abe, Naoto; Nishioka, Nobuhiro

    Switching vibration control between dynamic absorber and active control has been proposed for the dual structural vibration device on the basis of the kinetic energy as the threshold. For the active control with a fixed feedback gain, the threshold of switching should be set conservative and the effect of the active control was not enough. Therefore, a variable feedback gain control is introduced, which is assumed the mechanical energy as an indicator. It is expected that the actuator moves in a stroke range as possible and the performance will be better than the conventional switching control. In this paper, the effective variable feedback and switching control on the basis of mechanical energy as the two threshold are considered by experimental results.

  12. Super harmonic nonlinear lateral vibrations of a segmented driveline incorporating a tuned damper excited by non-constant velocity joints

    NASA Astrophysics Data System (ADS)

    Browne, Michael; Palazzolo, Alan

    2009-06-01

    Typical industrial vibration problem solving includes utilization of linear vibration measurement and analysis techniques. These techniques have appeared to be sufficient with most vibration problem solving requirements. This is partially due to the lack of proper identification of the nonlinear dynamic response in measured data of actual engineering systems. Therefore, as an example, a vehicle driveshaft exhibits a nonlinear super harmonic jump due to universal joint excitations. This phenomenon is partially responsible for objectionable audible noise in the vehicle. Previously documented measurements or analytical predictions of vehicle driveshaft systems do not indicate nonlinear jump as a typical vibration mode. Physical measurements of the phenomena will be provided with subsequent analysis. Second, the secondary moment exciting the driveshaft system is derived with subsequent analysis showing the harmonic and super harmonic excitations. Third, a derivation of a model incorporating the linear and nonlinear modeling of a large degree of freedom system is introduced. Finally, simulations with the derived model with the universal joint excitations will be presented showing the correlation to physical test results. Therefore, a typical automotive driveshaft system is capable of producing nonlinear response, and thus the assumption of linearity is not sufficient for design validation or problem resolution in this case.

  13. Electromagnetic dampers for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Dirusso, Eliseo

    1988-01-01

    Cryogenic turbomachinery of the type used to pump high-pressure liquid hydrogen at -423 F and liquid oxygen at -297 F to the main engines of the Space Shuttle are subjected to lateral rotor vibrations from unbalance forces and transient loads. Conventional dampers which utilize viscous fluids such as lubricating oil cannot be used in turbopumps because the bearing components are filled with either liquid hydrogen or liquid oxygen, which have viscosity comparable to air and, therefore, are not effective in viscous dampers. Electromagentic dampers are currently being explored as a means of providing damping in cryogenic turbopumps because their damping effectiveness increases as temperature decreases and because they are compatible with the liquid hydrogen or liquid oxygen in the turbopumps.

  14. Actively controlled vibration welding system and method

    SciTech Connect

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  15. Earthquake response reduction of mid-story isolated system due to semi-active control using magnetorheological rotary inertia mass damper

    NASA Astrophysics Data System (ADS)

    Ito, Mai; Yoshida, Shohei; Fujitani, Hideo; Sato, Yusuke

    2015-04-01

    The dynamic characteristics of mid-story isolated buildings and seismic response reduction due to a semi-active control system were investigated using a three-lumped-mass model that simplified the sixteen story building with an isolation layer in the sixth story. A semi-active control method using a rotary inertia mass damper filled with magnetorheological fluid (MR fluid) was proposed. The damper shows both mass amplification effect due to rotational inertia and variable damping effect due to the MR fluid. The damping force is controlled by the strength of the magnetic field that is applied to the MR fluid. It is determined by using the electric current, which is calculated by the proposed semi-active control method based on the velocity of the isolation layer relative to the layer just underneath it. Real-time hybrid tests using an actual damper and simulations using a building model were conducted to check the damper model; the test results were in good agreement with the simulation results. The simulation results suggest that the response displacement of the structure above the isolation layer is significantly reduced, without increasing the response acceleration of the entire structure against near-fault pulse and long-period ground motions. The proposed semi-active control using an MR rotary inertia mass damper was confirmed to be effective for mid-story isolated buildings.

  16. A comparison of vibration damping methods for ground based telescopes

    NASA Astrophysics Data System (ADS)

    Anderson, Eric H.; Glaese, Roger M.; Neill, Douglas

    2008-07-01

    Vibration is becoming a more important element in design of telescope structures as these structures become larger and more compliant and include higher bandwidth actuation systems. This paper describes vibration damping methods available for current and future implementation and compares their effectiveness for a model of the Large Synoptic Survey Telescope (LSST), a structure that is actually stiffer than most large telescopes. Although facility and mount design, structural stiffening and occasionally vibration isolation have been adequate in telescopes built to date, vibration damping offers a mass-efficient means of reducing vibration response, whether the vibration results from external wind disturbances, telescope slewing, or other internal disturbances from translating or rotating components. The paper presents several damping techniques including constrained layer viscoelastics, viscous and magnetorheological (MR) fluid devices, passive and active piezoelectric dampers, tuned mass dampers (vibration absorbers) and active resonant dampers. Basic architectures and practical implementation considerations are discussed and expected performance is assessed using a finite element model of the LSST. With a goal of reducing settling time during the telescope's surveys, and considering practicalities of integration with the telescope structure, two damping methods were identified as most appropriate: passive tuned mass dampers and active electromagnetic resonant dampers.

  17. Effects of the lower extremities muscle activation during muscular strength training on an unstable platform with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Piao, YongJun; Choi, YounJung; Kim, JungJa; Kwan, TaeKyu; Kim, Nam-Gyun

    2009-03-01

    Adequate postural balance depends on the spatial and temporal integration of vestibular, visual, and somatosensory information. Especially, the musculoskeletal function (range of joint, flexibility of spine, muscular strength) is essential in maintaining the postural balance. Muscular strength training methods include the use of commercialized devices and repeatable resistance training tools (rubber band, ball, etc). These training systems cost high price and can't control of intensity. Thus we suggest a new training system which can adjust training intensity and indicate the center of pressure of a subject while the training was passively controlled by applying controlled electric current to the Magneto- Rheological damper. And we performed experimental studies on the muscular activities in the lower extremities during maintaining, moving and pushing exercises on an unstable platform with Magneto rheological dampers. A subject executed the maintaining, moving and pushing exercises which were displayed in a monitor. The electromyographic signals of the eight muscles in lower extremities were recorded and analyzed in the time and frequency domain: the muscles of interest were rectus femoris, biceps femoris, tensor fasciae latae, vastus lateralis, vastus medialis, gastrocnemius, tibialis anterior, and soleus. The experimental results showed the difference of muscular activities at the four moving exercises and the nine maintaining exercises. The rate of the increase in the muscular activities was affected by the condition of the unstable platform with MR dampers for the maintaining and moving exercises. The experimental results suggested the choice of different maintaining and moving exercises could selectively train different muscles with varying intensity. Furthermore, the findings also suggested the training using this system can improve the ability of postural balance.

  18. Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper

    NASA Astrophysics Data System (ADS)

    Lin, Wei; Li, Zhongxian; Ding, Yang

    2008-12-01

    In the field of civil engineering, magneto rheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a trust-region method based instantaneous optimal semi-active control algorithm (TIOC) is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semiactive control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc-Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.

  19. [Raman active vibrations of aluminosilicates].

    PubMed

    Pan, Feng; Yu, Xue-hui; Mo, Xuan-xue; You, Jing-lin; Wang, Chen; Chen, Hui; Jiang, Guo-chang

    2006-10-01

    Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations. PMID:17205741

  20. Analysis and testing of an integrated semi-active seat suspension for both longitudinal and vertical vibration control

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Jiang, Peng; Pan, Hui; Qian, Li-Jun

    2016-04-01

    An integrated semi-active seat suspension for both longitudinal and vertical vibration control is analyzed and tested in this paper. The seat suspension consists of a switching mechanism transforming both longitudinal and vertical motions into a rotary motion and a real-time damping-controllable system-a rotary magnetorheological (MR) damper working in pure shear mode and its corresponding control system. The switching mechanism employs the parallelogram frames as a motion guide which keeps the seat moving longitudinally and vertically. At the same time, both longitudinal and vertical motions are transformed into a reciprocating rotary motion that is transmitted to the rotary MR damper after an amplification by a gear mechanism. Both the longitudinal and vertical vibrations can be attenuated in real time through controlling the damping force (or torque) of the rotary MR damper. The mathematical model of the seat suspension system is established, simulated, and analyzed. The experimental test based on the test rig in Hefei University of Technology is implemented, and the results of simulation and experimental test are compared and analyzed.

  1. Active Vibration Damping of Solar Arrays

    NASA Astrophysics Data System (ADS)

    Reinicke, Gunar; Baier, Horst; Grillebeck, Anton; Scharfeld, Frank; Hunger, Joseph; Abou-El-Ela, A.; Lohberg, Andreas

    2012-07-01

    Current generations of large solar array panels are lightweight and flexible constructions to reduce net masses. They undergo strong vibrations during launch. The active vibration damping is one convenient option to reduce vibration responses and limit stresses in facesheets. In this study, two actuator concepts are used for vibration damping. A stack interface actuator replaces a panel hold down and is decoupled from bending moments and shear forces. Piezoelectric patch actuators are used as an alternative, where the number, position and size of actuators are mainly driven by controllability analyses. Linear Quadratic Gaussian control is used to attenuate vibrations of selected mode shapes with both actuators. Simulations as well as modal and acoustic tests show the feasibility of selected actuator concepts.

  2. Numerical modeling of pendulum dampers in torsional systems

    SciTech Connect

    Johnston, P.R.; Shusto, L.M.

    1986-01-01

    Centrifugal pendulum-design dampers are utilized in torsional systems to reduce the vibration amplitude at certain objectionable torsional speeds. The damper is tuned by proper design of its mass, dimensions, and position on a carrier disk, which is rigidly attached to the torsional system. The effects of the pendulum damper on the response of the torsional system may be included by modifying the structural model to include a separate damper element representing each order of the pendulum damper. The stiffness and mass matrices for a damper element are dependent upon the order of vibration being dampened, the mass, and the geometry of the damper. A general form of the mass and stiffness equations for a simple centrifugal pendulum damper are derived from first principles using Lagrange's equations of motion. The analysis of torsional systems with pendulum dampers utilizing the mass and stiffness properties developed is included in the program SHAMS. SHAMS calculates the steady-state response of a system of springs and masses to harmonic loads using modal superposition. The response of a crankshaft system with and without the pendulum dampers are included as a case study.

  3. A study on semi-active Tuned Liquid Column Dampers (sTLCDs) for structural response reduction under random excitations

    NASA Astrophysics Data System (ADS)

    Sonmez, E.; Nagarajaiah, S.; Sun, C.; Basu, B.

    2016-02-01

    This paper proposes a new model for semi-active Tuned Liquid Column Damper (sTLCD) where the sTLCD is connected to the primary structure using an adaptive spring. Short time Fourier transformation (STFT) based control algorithms (feedforward and feedback) are developed to control the stiffness of the spring such that the sTLCD is tuned in real-time when the dominant excitation frequency varies or damage occurs to the primary structure. The effectiveness of the proposed sTLCD and the associated control algorithms is examined numerically under random excitations including stationary and non-stationary excitations. Root Mean Square (RMS) response is computed in three cases: with no TLCD, with a passive Tuned Liquid Column Damper (pTLCD) and with the sTLCD. Results indicate that the developed control algorithms are effective in tuning the frequency of the sTLCD in real-time. As a result, the sTLCD provides more robust reduction than the pTLCD because the pTLCD becomes off-tuned and loses its effectiveness when the properties of the excitations or the primary structure vary.

  4. Evaluation of shear mounted elastomeric damper

    NASA Technical Reports Server (NTRS)

    Zorzi, E.; Walton, J.

    1982-01-01

    Viton-70 elastomeric shear mounted damper was built and tested on a T-55 power turbine spool in the rotor's high speed balancing rig. This application of a shear mounted elastomeric damper demonstrated for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear damper design was selected because it was compatible with actual gas turbine engine radial space constraints, could accommodate both the radial and axial thrust loads present in gas turbine engines, and was capable of controlled axial preload. The shear damper was interchangeable with the production T-55 power turbine roller bearing support so that a direct comparison between the shear damper and the production support structure could be made. Test results show that the Viton-70 elastomer damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing up to the maximum rotor speed of 16,000 rpm. Excellent correlation between the predicted and experienced critical speeds, mode shapes and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

  5. Semi-active friction tendons for vibration control of space structures

    NASA Astrophysics Data System (ADS)

    Garrido, Hernán; Curadelli, Oscar; Ambrosini, Daniel

    2014-10-01

    Semi-active vibration control systems are becoming popular because they offer both the reliability of passive systems and the versatility of active control without high power demands. In this work, a new semi-active control system is proposed and studied numerically. The system consists of variable-friction dampers linked to the structure through cables. Auxiliary soft springs in parallel with these friction dampers allow them to return to their initial pre-tensioned state. Using cables makes the system suitable for deployable, flexible and lightweight structures, such as space structures (spacecraft). A control system with three control laws applied to a single-degree-of-freedom structure is studied. Two of these laws are derived by using Lyapunov theory, whereas the third one is developed heuristically. In order to assess the performance of the control system, a parametric study is carried out through numerical simulations. An application of the proposed method to multi-degree-of-freedom structures is also presented and demonstrated through a numerical example. The system in semi-active mode is more effective than in passive mode and its effectiveness is less sensitive to loss of pre-tension.

  6. Active structures to reduce torsional vibrations

    NASA Astrophysics Data System (ADS)

    Matthias, M.; Schlote, D.; Atzrodt, H.

    2013-03-01

    This paper describes the development of different active measures to reduce torsional vibrations in power trains. The measures are based on concepts developed for active mounts to reduce the transmission of structure-borne sound. To show the potential of these active measures and investigate their mode of operation to influence torsional vibrations, numerical simulations of powertrains with different active measures were done. First experimental results from tests on an experimental (reduced size) power train were used to align the numerical models. The work was done within the project 'LOEWE-Zentrum AdRIA: Adaptronik - Research, Innovation, Application' funded by the German federal state of Hessen, and the Project AKTos: 'Active control of torsional vibrations by coupling elements' placed in the research Framework program 'Navigation and Maritime Technology for the 21st Century' funded by the German Federal Ministry of Economics and Technology.

  7. A Dynamic Absorber With Active Vibration Control

    NASA Astrophysics Data System (ADS)

    Huang, S.-J.; Lian, R.-J.

    1994-12-01

    The design and construction of a dynamic absorber incorporating active vibration control is described. The absorber is a two-degrees-of-freedom spring — lumped mass system sliding on a guide pillar, with two internal vibration disturbance sources. Both the main mass and the secondary absorber mass are acted on by DC servo motors, respectively, to suppress the vibration amplitude. The state variable technique is used to model this dynamic system and a decoupling PID control method is used. First, the discrete time state space model is identified by using the commercial software MATLAB. Then the decoupling controller of this multi-input/multi-output system is derived from the identified model. Finally the results of some experiments are presented. The experimental results show that the system is effective in suppressing vibration. Also, the performance of this control strategy for position tracking control is evaluated based on experimental data.

  8. Dielectric elastomers for active vibration control applications

    NASA Astrophysics Data System (ADS)

    Herold, S.; Kaal, W.; Melz, T.

    2011-04-01

    Dielectric elastomers (DE) have proved to have high potential for smart actuator applications in many laboratory setups and also in first commercially available components. Because of their large deformation capability and the inherent fast response to external stimulation they proffer themselves to applications in the field of active vibration control, especially for lightweight structures. These structures typically tend to vibrate with large amplitudes even at low excitation forces. Here, DE actuators seem to be ideal components for setting up control loops to suppress unwanted vibrations. Due to the underlying physical effect DE actuators are generally non-linear elements with an approximately quadratic relationship between in- and output. Consequently, they automatically produce higher-order frequencies. This can cause harmful effects for vibration control on structures with high modal density. Therefore, a linearization technique is required to minimize parasitic effects. This paper shows and quantifies the nonlinearity of a commercial DE actuator and demonstrates the negative effects it can have in technical applications. For this purpose, two linearization methods are developed. Subsequently, the actuator is used to implement active vibration control for two different mechanical systems. In the first case a concentrated mass is driven with the controlled actuator resulting in a tunable oscillator. In the second case a more complex mechanical structure with multiple resonances is used. Different control approaches are applied likewise and their impact on the whole system is demonstrated. Thus, the potential of DE actuators for vibration control applications is highlighted.

  9. Principle and validation of modified hysteretic models for magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Xu; Chen, Peng; Qian, Li-Jun

    2015-08-01

    Magnetorheological (MR) dampers, semi-active actuators for vibration and shock control systems, have attracted increasing attention during the past two decades. However, it is difficult to establish a precise mathematical model for the MR dampers and their control systems due to their intrinsic strong nonlinear hysteretic behavior. A phenomenological model based on the Bouc-Wen model can be used to effectively describe the nonlinear hysteretic behavior of the MR dampers, but the structure of the phenomenological model is complex and the Bouc-Wen model is functionally redundant. In this paper, based on the phenomenological model, (1) a normalized phenomenological model is derived through incorporating a ‘normalization’ concept, and (2) a restructured model, also incorporating the ‘normalization’ concept, is proposed and realized. In order to demonstrate this, a multi-islands genetic algorithm (GA) is employed to identify the parameters of the restructured model, the normalized phenomenological model, and the phenomenological model. The performance of the three models for describing and predicting the damping force characteristics of the MR dampers are compared and analyzed using the identified parameters. The research results indicate that, as compared with the phenomenological model and the normalized phenomenological model, (1) the restructured model can not only effectively decrease the number of the model parameters and reduce the complexity of the model, but can also describe the nonlinear hysteretic behavior of MR dampers more accurately, and (2) the meanings of several model parameters of the restructured model are clearer and the initial ranges of the model parameters are more explicit, which is of significance for parameter identification.

  10. Semi-active vibration control in cable-stayed bridges under the condition of random wind load

    NASA Astrophysics Data System (ADS)

    Heo, G.; Joonryong, Jeon

    2014-07-01

    This paper aims at an experimental study on the real-time vibration control of bridge structures using a semi-active vibration control method that has been in the spotlight recently. As structures are becoming larger and larger, structural harmful vibration caused by unspecified external forces such as earthquakes, gusts of wind, and collisions has been brought to attention as an important issue. These harmful vibrations can cause not only user anxiety but also severe structural damage or even complete failure of structures. Therefore, in view of structural safety and economical long-term maintenance, real-time control technology of the harmful structural vibration is urgently required. In this paper, a laboratory-scale model of a cable-stayed bridge was built, and a shear-type MR damper and a semi-active vibration control algorithm (Lyapunov and clipped optimal) were applied for the control of harmful vibration of the model bridge, in real time. On the basis of the test results, each semi-active control algorithm was verified quantitatively.

  11. Non-linear identification of a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Stanway, Roger; Mottershead, John; Firoozian, Riaz

    1987-01-01

    Described is an experimental study to identify the damping laws associated with a squeeze-film vibration damper. This is achieved by using a non-linear filtering algorithm to process displacement responses of the damper ring to synchronous excitation and thus to estimate the parameters in an nth-power velocity model. The experimental facility is described in detail and a representative selection of results is included. The identified models are validated through the prediction of damper-ring orbits and comparison with observed responses.

  12. Booster's coupled bunch damper upgrade

    SciTech Connect

    William A. Pellico and D. W. Wildman

    2003-08-14

    A new narrowband active damping system for longitudinal coupled bunch (CB) modes in the Fermilab Booster has recently been installed and tested. In the past, the Booster active damper system consisted of four independent front-ends. The summed output was distributed to the 18, h=84 RF accelerating cavities via the RF fan-out system. There were several problems using the normal fan-out system to deliver the longitudinal feedback RF. The high power RF amplifiers normally operate from 37 MHz to 53 MHz whereas the dampers operate around 83MHz. Daily variations in the tuning of the RF stations created tuning problems for the longitudinal damper system. The solution was to build a dedicated narrowband, Q {approx} 10, 83MHz cavity powered with a new 3.5kW solid-state amplifier. The cavity was installed in June 2002 and testing of the amplifier and damper front-end began in August 2002. A significant improvement has been made in both operational stability and high intensity beam damping. At present there are five CB modes being damped and a sixth mode module is being built. The new damper hardware is described and data showing the suppression of the coupled-bunch motion at high intensity is presented.

  13. DGA-based approach for optimal design of active mass damper for nonlinear structures considering ground motion effect

    NASA Astrophysics Data System (ADS)

    Mohebbi, Mohtasham; Rasouli Dabbagh, Hamed; Moradpour, Solmaz; Shakeri, Kazem; Tarbali, Karim

    2015-04-01

    This paper presents an effective method to design active mass dampers (AMDs) for mitigating the seismic response of nonlinear frames. The method is based on using the Newmark-based instantaneous optimal control algorithm for designing AMD, as well as using distributed genetic algorithm (DGA) for optimization of the active control system. To this end, an optimization problem has been defined which considers the parameters of the active control system as design variables and minimization of the maximum required control force of AMD as the objective function with some constraints defined on the maximum stroke length of AMD. Also, the effect of design excitation on performance of AMD under testing earthquakes has been studied. To assess the capabilities of the proposed method, a numerical example has been worked out where an AMD has been designed to control the response of an eight-story nonlinear shear building frame with hysteretic bilinear elasto-plastic behavior under white noise and real earthquake excitations. The designed control systems have been tested under a number of scaled and real earthquakes including both near and far-field earthquakes. Controller’s robustness against variations of structural parameters has also been assessed. The results of numerical simulations show the effectiveness, simplicity and capability of the proposed method in designing AMDs for nonlinear frames. Also comparing the performance of AMD system with that of passive tuned mass damper and active tendon control shows that the AMD has been more effective in reducing the seismic response of nonlinear frames under design and different testing earthquakes.

  14. Stochastic seismic response of building with super-elastic damper

    NASA Astrophysics Data System (ADS)

    Gur, Sourav; Mishra, Sudib Kumar; Roy, Koushik

    2016-05-01

    Hysteretic yield dampers are widely employed for seismic vibration control of buildings. An improved version of such damper has been proposed recently by exploiting the superelastic force-deformation characteristics of the Shape-Memory-Alloy (SMA). Although a number of studies have illustrated the performance of such damper, precise estimate of the optimal parameters and performances, along with the comparison with the conventional yield damper is lacking. Presently, the optimal parameters for the superelastic damper are proposed by conducting systematic design optimization, in which, the stochastic response serves as the objective function, evaluated through nonlinear random vibration analysis. These optimal parameters can be employed to establish an initial design for the SMA-damper. Further, a comparison among the optimal responses is also presented in order to assess the improvement that can be achieved by the superelastic damper over the yield damper. The consistency of the improvements is also checked by considering the anticipated variation in the system parameters as well as seismic loading condition. In spite of the improved performance of super-elastic damper, the available variant of SMA(s) is quite expensive to limit their applicability. However, recently developed ferrous SMA are expected to offer even superior performance along with improved cost effectiveness, that can be studied through a life cycle cost analysis in future work.

  15. Clutch damper

    SciTech Connect

    Umeyama, M.; Wakahara, K.; Kobayashi, N.; Ohtani, H.; Kametaka, K.; Kinoshita, M.

    1987-09-15

    A clutch damper is described comprising a hub having an approximately cylindrical shape with an outwardly spread first plate provided at one axial end. The hub is slipped over a shaft. A first buffer member is formed into an annular body of a rubber-like resilient material and fitted and secured in the outer periphery of the hub. There is also a boss having an approximately cylindrical shape and fitted and secured in the outer periphery of the first buffer member, a second buffer member formed into an annular body of a rubber-like resilient material and secured in the outer periphery of the boss, a cylindrical body and a second plate provided with a double-ring like plate spread outwardly from the cylindrical body and secured in the outer periphery of the second buffer member. A stopper mechanism for stopping relative rotation within a predetermined angle is disposed between the hub and the boss and between the first plate of the hub and the double-ring like plate of the second plate, and spacer means for restraining play in both axial and diametrical directions is interposed between the hub and the boss. The spacer means consists of a center plate, a plate spring, a bearing plate and a fluorine-resin plate.

  16. Bilinear Robust Control for Vertical Vibration in Railway Vehicle with Semi-Active Suspensions

    NASA Astrophysics Data System (ADS)

    Umehara, Ryuichi; Otsuki, Masatsugu; Yoshida, Kazuo

    It is well known that the vibration control problem for automobiles and railway vehicles with semi-active suspensions is classified as a control problem in a bilinear system. Bullet trains and railway vehicles have lighter body in order to improve acceleration; these vibrations in the body are easily induced by various disturbances due to rigid and elastic dynamics. Currently, passive dampers such as air suspensions and axle springs are installed on railway vehicle trucks as countermeasures for such vibrations. This study presents an effective controller, based on the H∞ theory, for vibration suppression in railway vehicles and describes a method of synthesizing this robust controller by considering unstructured and structured uncertainties that are applicable to a bilinear system. The performance of the proposed controller and its robustness toward uncertainties are examined by numerical calculations that simulate a railway vehicle subjected to disturbances due to vertical uneven railway tracks, the variations in its mass due to boarding passengers, and the modeling errors caused by non-controlled modes. This enables a comparison of the proposed control method with the conventional one in terms of the robustness toward parameter variation. Thus, this result shows the high robustness and usefulness of the proposed controller.

  17. Applications of tuned mass dampers to improve performance of large space mirrors

    NASA Astrophysics Data System (ADS)

    Yingling, Adam J.; Agrawal, Brij N.

    2014-01-01

    In order for future imaging spacecraft to meet higher resolution imaging capability, it will be necessary to build large space telescopes with primary mirror diameters that range from 10 m to 20 m and do so with nanometer surface accuracy. Due to launch vehicle mass and volume constraints, these mirrors have to be deployable and lightweight, such as segmented mirrors using active optics to correct mirror surfaces with closed loop control. As a part of this work, system identification tests revealed that dynamic disturbances inherent in a laboratory environment are significant enough to degrade the optical performance of the telescope. Research was performed at the Naval Postgraduate School to identify the vibration modes most affecting the optical performance and evaluate different techniques to increase damping of those modes. Based on this work, tuned mass dampers (TMDs) were selected because of their simplicity in implementation and effectiveness in targeting specific modes. The selected damping mechanism was an eddy current damper where the damping and frequency of the damper could be easily changed. System identification of segments was performed to derive TMD specifications. Several configurations of the damper were evaluated, including the number and placement of TMDs, damping constant, and targeted structural modes. The final configuration consisted of two dampers located at the edge of each segment and resulted in 80% reduction in vibrations. The WFE for the system without dampers was 1.5 waves, with one TMD the WFE was 0.9 waves, and with two TMDs the WFE was 0.25 waves. This paper provides details of some of the work done in this area and includes theoretical predictions for optimum damping which were experimentally verified on a large aperture segmented system.

  18. Quantifying Ant Activity Using Vibration Measurements

    PubMed Central

    Oberst, Sebastian; Baro, Enrique Nava; Lai, Joseph C. S.; Evans, Theodore A.

    2014-01-01

    Ant behaviour is of great interest due to their sociality. Ant behaviour is typically observed visually, however there are many circumstances where visual observation is not possible. It may be possible to assess ant behaviour using vibration signals produced by their physical movement. We demonstrate through a series of bioassays with different stimuli that the level of activity of meat ants (Iridomyrmex purpureus) can be quantified using vibrations, corresponding to observations with video. We found that ants exposed to physical shaking produced the highest average vibration amplitudes followed by ants with stones to drag, then ants with neighbours, illuminated ants and ants in darkness. In addition, we devised a novel method based on wavelet decomposition to separate the vibration signal owing to the initial ant behaviour from the substrate response, which will allow signals recorded from different substrates to be compared directly. Our results indicate the potential to use vibration signals to classify some ant behaviours in situations where visual observation could be difficult. PMID:24658467

  19. Optimal active vibration absorber - Design and experimental results

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.

    1993-01-01

    An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

  20. Optimal active vibration absorber: Design and experimental results

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina; Juang, Jer-Nan; Sulla, Jeffrey L.

    1992-01-01

    An optimal active vibration absorber can provide guaranteed closed-loop stability and control for large flexible space structures with collocated sensors/actuators. The active vibration absorber is a second-order dynamic system which is designed to suppress any unwanted structural vibration. This can be designed with minimum knowledge of the controlled system. Two methods for optimizing the active vibration absorber parameters are illustrated: minimum resonant amplitude and frequency matched active controllers. The Controls-Structures Interaction Phase-1 Evolutionary Model at NASA LaRC is used to demonstrate the effectiveness of the active vibration absorber for vibration suppression. Performance is compared numerically and experimentally using acceleration feedback.

  1. Experimental validation and testing of components for active damping control for micromachined mechanical vibration isolation filters using electrostatic actuation

    NASA Astrophysics Data System (ADS)

    Dean, Robert; Flowers, George; Sanders, Nicole; Horvath, Roland; Johnson, Wayne; Kranz, Michael; Whitley, Michael

    2006-03-01

    Missiles, rockets and certain types of industrial machinery are exposed extreme vibration environments, with high frequency/amplitude mechanical vibrations which may be detrimental to components that are sensitive to these high frequency mechanical vibrations, such as MEMS gyroscopes and resonators, oscillators and some micro optics. Exposure to high frequency mechanical vibrations can lead to a variety of problems, from reduced sensitivity and an increased noise floor to the outright mechanical failure of the device. One approach to mitigate such effects is to package the sensitive device on a micromachined vibration isolator tuned to the frequency range of concern. In this regard, passive micromachined silicon lowpass filter structures (spring-mass-damper) have been developed and demonstrated. However, low damping (especially if operated in near-vacuum environments) and a lack of tunability after fabrication has limited the effectiveness and general applicability of such systems. Through the integration of a electrostatic actuator, a relative velocity sensor and the passive filter structure, an active micromachined mechanical lowpass vibration isolation filter can be realized where the damping and resonant frequency can be tuned. This paper presents the development and validation of a key component of the micromachined active filter, a sensor for measuring the relative velocity between micromachined structures.

  2. Vibration damping with active carbon fiber structures

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Kunze, Holger; Riedel, Mathias; Roscher, Hans-Jürgen

    2007-04-01

    This paper presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was done with a finite element model (ANSYS). This paper describes how state space models are generated out of a structure based on the finite element model and how controller codes are integrated into finite element models for transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.

  3. Study of the response time of MR dampers

    NASA Astrophysics Data System (ADS)

    Guan, Xinchun; Guo, Pengfei; Ou, Jinping

    2009-07-01

    Response time is an important parameter which determines the applied fields and practical vibration reduction effects of magnetorheological (MR) dampers. However, up to now, only a few papers discuss the test and analysis of response times. In this paper, the response time of a large-scale MR damper at different velocities and currents was firstly tested. Then, the transient magnetic field excited by the time-variant excitation current was simulated by finite element method (FEM). Based on the variation of the shear yield stress of magnetorheological fluids in the gap between the cylinder and the piston, the response time of the MR damper was investigated. Influences of eddy current and excitation current response time on the damper's response were also explored. Results show that by utilizing finite elements method, the calculated average effective shear yield strength can be used to predict the response time of a MR damper. Electromagnetic response is the predominant factor influencing the response time of a MR damper, and reducing eddy currents is the key to accelerate the response of a MR damper. Moreover, influence of eddy currents is much larger under stepping down excitation currents than stepping up currents, and with a same magnitude of step, no matter when the current increases or decreases, the smaller the initial current, the greater the eddy current affects a damper's response and the longer the response time of damping force is. A fast response excitation current may induce large eddy currents which reduce the response of the damper instead.

  4. Skyhook-based semi-active control of full-vehicle suspension with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Hailong; Wang, Enrong; Min, Fuhong; Subash, Rakheja; Su, Chunyi

    2013-05-01

    The control study of vehicle semi-active suspension with magneto-rheological (MR) dampers has been attracted much attention internationally. However, a simple, real time and easy implementing semi-active controller has not been proposed for the MR full-vehicle suspension system, and a systematic analysis method has not been established for evaluating the multi-objective suspension performances of MR full-vehicle vertical, pitch and roll motions. For this purpose, according to the 7-degree of freedom (DOF) full-vehicle dynamic system, a generalized 7-DOF MR and passive full-vehicle dynamic model is set up by employing the modified Bouc-wen hysteretic force-velocity ( F-v) model of the MR damper. A semi-active controller is synthesized to realize independent control of the four MR quarter-vehicle sub-suspension systems in the full-vehicle, which is on the basis of the proposed modified skyhook damping scheme of MR quarter-vehicle sub-suspension system. The proposed controller can greatly simplify the controller design complexity of MR full-vehicle suspension and has merits of easy implementation in real application, wherein only absolute velocities of sprung and unsprung masses with reference to the road surface are required to measure in real time when the vehicle is moving. Furthermore, a systematic analysis method is established for evaluating the vertical, pitch and roll motion properties of both MR and passive full-vehicle suspensions in a more realistic road excitation manner, in which the harmonic, rounded pulse and real road measured random signals with delay time are employed as different road excitations inserted on the front and rear two wheels, by considering the distance between front and rear wheels in full-vehicle. The above excitations with different amplitudes are further employed as the road excitations inserted on left and right two wheels for evaluating the roll motion property. The multi-objective suspension performances of ride comfort and

  5. Design and analysis of a sensorless magnetic damper

    SciTech Connect

    Chen, H.M.

    1997-01-01

    An industrial vertical rotor supported by rolling element bearings was originally designed to operate below its first critical speed. Since the rotor accumulated unbalance during operation, which was a potential problem, it was proposed that a soft magnetic bearing replace the lower rolling element bearing. The magnetic bearing (hereafter referred to as a damper) tends to make the rotor spin at its mass center and reduces the unbalance force to ground by an order of magnitude. The damper is an actively controlled electromagnetic device, and its desires stiffness and damping properties can be readily achieved by using a conventional PID controller with displacement sensors. However, because these sensors are expensive and unreliable in the hot, hostile environment around the rotor, there is a high incentive to design a sensorless controller. An analytical method for designing magnetic bearing controllers with no displacement sensors has been developed and laboratory tested. The method was applied to the design of a sensorless magnetic damper for replacing a rolling element bearing of a vertical rotor with a large unbalance. The synchronous vibration force transmitted to ground was predicted to be reduced by a factor of ten.

  6. Active control of vibration transmission through struts

    NASA Astrophysics Data System (ADS)

    Pelinescu, Ion; Balachandran, Balakumar

    1998-07-01

    In this work, analytical investigations into active control of longitudinal and flexural vibrations transmitted through a cylindrical strut are conducted. A mechanics based model for a strut fitted with a piezoelectric actuator is developed. For harmonic disturbances, a linear dynamic formulation describing the motion of the actuator is integrated with the formulation describing wave transmission through the strut, and the resulting system is studied in the frequency domain. Open-loop studies are conducted with the aid of numerical simulations, and the potential of active control schemes to attenuate the transmitted vibrations over the frequency range of 10 Hz to 6000 Hz is examined. The relevance of the current work to control of helicopter cabin interior noise is also discussed.

  7. Experimental study of uncentralized squeeze film dampers

    NASA Technical Reports Server (NTRS)

    Quinn, R. D.

    1983-01-01

    The vibration response of a rotor system supported by a squeeze film damper (SFD) was experimentally investigated in order to provide experimental data in support of the Rotor/Stator Interactive Finite Element theoretical development. Part of the investigation required the designing and building of a rotor/SFD system that could operate with or without end seals in order to accommodate different SFD lengths. SFD variables investigated included clearance, eccentricity mass, fluid pressure, and viscosity and temperature. The results show inlet pressure, viscosity and clearance have significant influence on the damper performance and accompanying rotor response.

  8. Active mass damper system for high-rise buildings using neural oscillator and position controller considering stroke limitation of the auxiliary mass

    NASA Astrophysics Data System (ADS)

    Hongu, J.; Iba, D.; Nakamura, M.; Moriwaki, I.

    2016-04-01

    This paper proposes a problem-solving method for the stroke limitation problem, which is related to auxiliary masses of active mass damper systems for high-rise buildings. The proposed method is used in a new simple control system for the active mass dampers mimicking the motion of bipedal mammals, which has a neural oscillator synchronizing with the acceleration response of structures and a position controller. In the system, the travel distance and direction of the auxiliary mass of the active mass damper is determined by reference to the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using a PID controller. The one of the purpose of the previouslyproposed system is stroke restriction problem avoidance of the auxiliary mass during large earthquakes by the determination of the desired value within the stroke limitation of the auxiliary mass. However, only applying the limited desired value could not rigorously restrict the auxiliary mass within the limitation, because the excessive inertia force except for the control force produced by the position controller affected on the motion of the auxiliary mass. In order to eliminate the effect on the auxiliary mass by the structural absolute acceleration, a cancellation method is introduced by adding a term to the control force of the position controller. We first develop the previously-proposed system for the active mass damper and the additional term for cancellation, and verity through numerical experiments that the new system is able to operate the auxiliary mass within the restriction during large earthquakes. Based on the comparison of the proposed system with the LQ system, a conclusion was drawn regarding which the proposed neuronal system with the additional term appears to be able to limit the stroke of the auxiliary mass of the AMD.

  9. Sliding mode fault detection and fault-tolerant control of smart dampers in semi-active control of building structures

    NASA Astrophysics Data System (ADS)

    Yeganeh Fallah, Arash; Taghikhany, Touraj

    2015-12-01

    Recent decades have witnessed much interest in the application of active and semi-active control strategies for seismic protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its fault detection observer and fault-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ faults which are used for calculating a fault distribution matrix. Then the fault-tolerant sliding mode controller reconfigures itself by the fault distribution matrix and accommodates the fault effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed fault-tolerant control system. It was shown that the fault-tolerant control system maintains the performance of the structure at an acceptable level in the post-fault case.

  10. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2004-10-13

    The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed. The month of June, 2004 was primarily occupied with the writing of the Phase I Final Report, the sole deliverable of Phase I, which will be submitted in the next quarter. Redesign of the laboratory prototype and design of the downhole (Phase II) prototype was begun.

  11. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2004-08-31

    The deep hard rock drilling environment induces severe vibrations into the drillstring, which can cause reduced rates of penetration (ROP) and premature failure of the equipment. The only current means of controlling vibration under varying conditions is to change either the rotary speed or the weight-on-bit (WOB). These changes often reduce drilling efficiency. Conventional shock subs are useful in some situations, but often exacerbate the problems. The objective of this project is development of a unique system to monitor and control drilling vibrations in a ''smart'' drilling system. This system has two primary elements: (1) The first is an active vibration damper (AVD) to minimize harmful axial, lateral and torsional vibrations. The hardness of this damper will be continuously adjusted using a robust, fast-acting and reliable unique technology. (2) The second is a real-time system to monitor drillstring vibration, and related parameters. This monitor adjusts the damper according to local conditions. In some configurations, it may also send diagnostic information to the surface via real-time telemetry. The AVD is implemented in a configuration using magnetorheological (MR) fluid. By applying a current to the magnetic coils in the damper, the viscosity of the fluid can be changed rapidly, thereby altering the damping coefficient in response to the measured motion of the tool. Phase I of this program entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype. Phase I of the project was completed by the revised end date of May 31, 2004. The objectives of this phase were met, and all prerequisites for Phase II have been completed.

  12. Active isolation of vibrations with adaptive structures

    NASA Technical Reports Server (NTRS)

    Guigou, C.; Fuller, C. R.; Wagstaff, P. R.

    1991-01-01

    Vibration transmission in structures is controlled by means of a technique which employs distributed arrays of piezoelectric transducers bonded to the supporting structure. Distributed PVDF piezoelectric strips are employed as error sensors, and a two-channel feedforward adaptive LMS algorithm is used for minimizing error signals and thereby controlling the structure. A harmonic force input excites a thick plate, and a receiving plate is configured with three pairs of piezoelectric actuators. Modal analyses are performed to determine the resonant frequencies of the system, and a scanning laser vibrometer is used to study the shape of the response of the receiving plate during excitation with and without the control algorithm. Efficient active isolation of the vibrations is achieved with modal suppression, and good control is noted in the on-resonance cases in which increased numbers of PVDF sensors and piezoelectric actuators are employed.

  13. Electrorheological fluid damper for seismic protection of structures

    NASA Astrophysics Data System (ADS)

    Makris, Nicos; Hill, Davide; Burton, Scott; Jordan, Mabel

    1995-05-01

    An electrorheological (ER) fluid damper suitable for vibration and seismic protection of civil structures has been designed, constructed and is under testing. The damper consist of an outer cylinder and a piston rod that pushes the ER-fluid through a stationary annular duct. The design of the damper was based on approximate calculations based on the Hagen-Poiseille flow theory. It is found that the Hagen-Poiseille theory predicts satisfactorily the damper response at moderate values of the flow rate. Experimental results on the damper response with and without the presence of electric field are presented. The average fluid velocity in the ER-duct has to be kept relatively small so that viscous stresses do not dominate over `yield' stresses.

  14. Using magnetorheological fluids in an innovative hybrid bicycle damper

    NASA Astrophysics Data System (ADS)

    Shiao, Y. J.; Nguyen, T. S.

    2015-12-01

    Magnetorheological fluids are capable of changing their viscosity quickly. This can provide good controllability and fast dynamic response. A conventional passive suspension system with air spring or hydraulic damper has simple design and financial benefit for bicycles, but its operation is uncontrollable and non-adaptive. This paper presented a semi-active hybrid bicycle suspension system which combines conventional air spring and a new magnetorheological damping brake together to reduce vibration of a bicycle. A multi-layer magnetorheological brake and linkage mechanism are connected to bike fork to form the adaptive damping part of the innovative hybrid suspension system. The simulation results proved that the semi-active suspension system can reduce bike vibration effectively.

  15. Camshaft damper

    SciTech Connect

    Ferguson, R.J.

    1989-07-18

    This patent describes a drive sprocket for an internal combustion engine camshaft. It comprises, in combination, a circular body having a hub region, an outer periphery and an axis of rotation, means defined in the hub region for attaching the body to the end of the camshaft in torsion-transmitting relationship, radial extending drive surfaces defined on the body periphery for meshing with a flexible tension-transmitting member, a cylindrical surface homogeneously defined on the body concentric to the axis, an annular ring of synthetic elastomeric material mounted upon the cylindrical surface, and an annular inertia ring mounted upon the elastomeric material. The inertial ring including an inner cylindrical surface, the elastomeric material being bonded to the compressed between the cylindrical surfaces of the sprocket body and the inertia ring, the sprocket body cylindrical surface, elastomeric material and the inertia ring comprising torsional damping means direction mounted upon the body and integral with the body for damping torsional vibrations about the body axis. The sprocket including a web radially extending between the hub region and the outer periphery. The inertia ring, body cylindrical surface and elastomeric material being located adjacent to and in axial alignment with the web, and an oil passage defined in the sprocket hub region extending from the hub region to adjacent the body outer periphery along the web for lubricating the tension transmitting member.

  16. Investigation on modeling and controability of a magnetorheological gun recoil damper

    NASA Astrophysics Data System (ADS)

    Hu, Hongsheng; Wang, Juan; Wang, Jiong; Qian, Suxiang; Li, Yancheng

    2009-07-01

    Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.

  17. Tuning the vibration of a rotor with shape memory alloy metal rubber supports

    NASA Astrophysics Data System (ADS)

    Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Scarpa, Fabrizio; Liu, Baolong; Hong, Jie

    2015-09-01

    The paper describes a novel smart rotor support damper with variable stiffness made with a new multifunctional material - the shape memory alloy metal rubber (SMA-MR). SMA-MR gives high load bearing capability (yield limit up to 100 MPa and stiffness exceeding 1e8 N/m), high damping (loss factor between 0.15 and 0.3) and variable stiffness (variation of 2.6 times between martensite and austenite phases). The SMA-MR has been used to replace a squeeze film damper and combined with an elastic support. The mechanical performance of the smart support damper has been investigated at room and high temperatures on a rotor test rig. The vibration tuning capabilities of the SMA-MR damper have been evaluated through FEM simulations and experimental tests. The study shows the feasibility of using the SMA-MR material for potential applications of active vibration control at different temperatures in rotordynamics systems.

  18. Dynamic behavior of stay cables with passive negative stiffness dampers

    NASA Astrophysics Data System (ADS)

    Shi, Xiang; Zhu, Songye; Li, Jin-Yang; Spencer, Billie F., Jr.

    2016-07-01

    This paper systematically investigates the dynamic behavior of stay cables with passive negative stiffness dampers (NSD) installed close to the cable end. A passive NSD is modeled as a combination of a negative stiffness spring and a viscous damper. Through both analytical and numerical approaches, parametric analysis of negative stiffness and viscous damping are conducted to systematically evaluate the vibration control performance of passive NSD on stay cables. Since negative stiffness is an unstable element, the boundary of passive negative stiffness for stay cables to maintain stability is also derived. Results reveal that the asymptotic approach is only applicable to passive dampers with positive or moderate negative stiffness, and loses its accuracy when a passive NSD possesses significant negative stiffness. It has been found that the performance of passive NSD can be much better than those of conventional viscous dampers. The superior control performance of passive NSD in cable vibration mitigation is validated through numerical simulations of a full-scale stay cable.

  19. Electrorheological damper with annular ducts for seismic protection applications

    NASA Astrophysics Data System (ADS)

    Makris, Nicos; Burton, Scott A.; Taylor, Douglas P.

    1996-10-01

    This paper presents the design, analysis, testing and modeling of an electrorheological (ER) fluid damper developed for vibration and seismic protection of civil structures. The damper consists of a main cylinder and a piston rod that pushes an ER fluid through a stationary annular duct. The behavior of the damper can be approximated with Hagen - Poiseuille flow theory. The basic equations that describe the fluid flow across an annular duct are derived. Experimental results on the damper response with and without the presence of electric field are presented. As the rate of deformation increases, viscous stresses prevail over field-induced yield stresses and a smaller fraction of the total damper force can be controlled. Simple physically motivated phenomenological models are considered to approximate the damper response with and without the presence of electric field. Subsequently, the performance of a multilayer neural network constructed and trained by an efficient algorithm known as the Dependence Identification Algorithm is examined to predict the response of the electrorheological damper. A combination of a simple phenomenological model and a neural network is then proposed as a practical tool to approximate the nonlinear and velocity-dependent damper response.

  20. Energy-harvesting linear MR damper: prototyping and testing

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan

    2014-03-01

    The present study is concerned with an energy-harvesting linear MR (EH-LMR) damper which is able to recover energy from external excitations using an electromagnetic energy extractor, and to adjust itself to excitations by varying the damping characteristics. The device has three main components: an MR part having a damper piston assembly movable in relation to the damper cylinder under an external excitation, a power generator to produce electrical power according to the relative movement between the damper piston and the cylinder assembly, and a conditioning electronics unit to interface directly with the generator and the MR damper. The EH-LMR damper integrates energy harvesting, dynamic sensor and MR damping technologies in a single device. The objective of the study is to get a better insight into the structure of EH-LMR damper components, to investigate the performance of each component and a device as a whole, and to compare results of experimental study against numerical data obtained in simulations conducted at the design stage. The research work demonstrates that the proposed EH-LMR damper provides a smart and compact solution with the potential of application to vibration isolation. The advantage of the device is its adaptability to external excitations and the fact that it does not need any extra power supply unit or sensor on account of its self-powered and self-sensing capabilities.

  1. Active Vibration Control For Lasers And Spacecraft

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome

    1983-12-01

    The Active Control of Space Structures (ACOSS) program of the Defense Advanced Research Projects Agency has identified problems in active vibration control of structural modes in extremely flexible space structures and in precisely pointed optics. The Air Force Wright Aeronautical Laboratories programs are an outgrowth of the ACOSS program. They are aimed at the problems of sensors, actuators, and their dynamic interactions with the structure to be controlled, and at the problem of system identification by one-g laboratory experiments. The VCOSS-1 and VCOSS-2 programs (Vibration Control of Space Structures) address the dynamic interactions of the sensor-actuator-structure; the Benchless Laser program and the Airborne Laser Mirror-Control program address the active control of HEL mirrors; the Experimental Modal Analysis and Component Synthesis and the Large Space Structure Dynamics programs address the problems of system identification and testing. Closer coordination with NASA and DARPA is being sought in support of on-orbit dynamic testing using the Space Shuttle and in the development of a national facility for one-g dynamics testing of large space structures.

  2. Magnetic bearings for vibration control

    NASA Technical Reports Server (NTRS)

    Schweitzer, G.

    1985-01-01

    A survey is presented on the research of the Institute of Mechanics of the ETH in the field of vibration control with magnetic bearings. It shows a method for modelling an elastic rotor so that it can be represented by a low order model amenable to control techniques. It deals with the control law and spill-over effects, and it also discusses experimental results for an active resonance damper.

  3. Viscous damper

    NASA Technical Reports Server (NTRS)

    Dean, W. C.

    1968-01-01

    Damping device exhibiting no hysteresis effect and capable of preload is used in place of a preload spring in an aneroid bellows to provide viscous damping. It operates about the action of a pressure sensing outer bellows attached to an active header above and a static header below.

  4. Prediction of ER long-stroke damper response: model updating methods

    NASA Astrophysics Data System (ADS)

    Sims, Neil D.; Stanway, Roger; Wong, C. X.

    2002-06-01

    Smart fluid devices are now seen as an attractive solution to vibration damping problems. They offer superior performance compared to passive devices, without involving the cost, weight and complexity of fully active damping strategies. However, the inherent non-linearity of smart fluid dampers makes it difficult to fully exploit their capabilities, due the problems in applying an effective control strategy. In the past much of the research focused on complex controllers involving techniques such as neural networks and fuzzy logic. In recent years, however, an alternative approach has been adopted, whereby classical control techniques are used to linearise the damper's response. As a result some applications for smart fluid damping now use combinations of proportional, integral, or derivative control methods. However, it appears that these controllers can become unstable in much the same way as for a truly linear system. In order to investigate this instability it is suggested that a sufficiently accurate model of the damper's response is required, so that the onset of instability can be reproduced numerically. In this contribution, a model updating technique is described whereby an existing ER damper model is updated in line with experimental data. The paper begins with an overview of the experimental test facility and the modeling approach. The updating algorithm is then described, and it is shown how the updated model improves significantly on the accuracy of the model predictions.

  5. Active vibration control using mechanical and electrical analogies

    NASA Astrophysics Data System (ADS)

    Torres-Perez, A.; Hassan, A.; Kaczmarczyk, S.; Picton, P.

    2016-05-01

    Mechanical-electrical analogous circuit models are widely used in electromechanical system design as they represent the function of a coupled electrical and mechanical system using an equivalent electrical system. This research uses electrical circuits to establish a discussion of simple active vibration control principles using two scenarios: an active vibration isolation system and an active dynamic vibration absorber (DVA) using a voice coil motor (VCM) actuator. Active control laws such as gain scheduling are intuitively explained using circuit analysis techniques. Active vibration control approaches are typically constraint by electrical power requirements. The electrical analogous is a fast approach for specifying power requirements on the experimental test platform which is based on a vibration shaker that provides the based excitation required for the single Degree- of-Freedom (1DoF) vibration model under study.

  6. Optimum Dynamic Characteristics of Stockbridge Dampers for Dead-End Spans

    NASA Astrophysics Data System (ADS)

    Markiewicz, M.

    1995-11-01

    Stockbridge dampers are commonly used to protect conductors of overhead transmission lines from aeolian vibrations. Standard Stockbridge dampers are designed so that their mechanical impedance matches as closely as possible the optimum damper impedance determined for the cable to be protected. Since the optimum impedance is evaluated assuming that the cable is clamped at its extremity, the optimally tuned standard dampers will work efficiently only when they are mounted near suspension clamps. In some spans, however, conductors are connected to the tower by means of special tension equipment which may influence the efficiency of the mounted standard damper. The present analysis shows that the optimum damper impedance required for such spans (called dead-end spans) differs significantly from the optimum impedance of the standard damper. The reason for this is the dynamic interaction between the tension insulator assembly and the damper itself. This interaction cannot be neglected for vibration frequencies which are close to the resonance frequencies of the tension insulator assembly. This paper presents a method and computational model for the evaluation of the optimum dynamic characteristics of Stockbridge dampers to be mounted near tension insulator assemblies. It also shows how the efficiency of a standard damper used in such spans may be improved by its proper location on a cable.

  7. Piezoelectric Power Requirements for Active Vibration Control

    NASA Technical Reports Server (NTRS)

    Brennan, Matthew C.; McGowan, Anna-Maria Rivas

    1997-01-01

    This paper presents a method for predicting the power consumption of piezoelectric actuators utilized for active vibration control. Analytical developments and experimental tests show that the maximum power required to control a structure using surface-bonded piezoelectric actuators is independent of the dynamics between the piezoelectric actuator and the host structure. The results demonstrate that for a perfectly-controlled system, the power consumption is a function of the quantity and type of piezoelectric actuators and the voltage and frequency of the control law output signal. Furthermore, as control effectiveness decreases, the power consumption of the piezoelectric actuators decreases. In addition, experimental results revealed a non-linear behavior in the material properties of piezoelectric actuators. The material non- linearity displayed a significant increase in capacitance with an increase in excitation voltage. Tests show that if the non-linearity of the capacitance was accounted for, a conservative estimate of the power can easily be determined.

  8. Active balance system and vibration balanced machine

    NASA Technical Reports Server (NTRS)

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2005-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.

  9. Skylab viscous damper study

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The proposed magnetically anchored viscous fluid damper can maintain the Skylab in a gravity-gradient stabilized mode at the anticipated reboost altitudes. The parameters influencing damper performance (and thereby affecting the degree of risk) are: (1) amount of skylab pitch bias in the orbit plane which will result from aerodynamic trim conditions of the post-reboost configuration Skylab; (2) the lowest altitude to which the post-reboost Skylab will be allowed to decay prior to the next rendezvous; (3) maximum allowable weight and size of the proposed damper in order to match shuttle/TRS mission constraints; (4) the amount of magnetic materials expected to be in the vicinity of the damper.

  10. Viscous shear dampers

    SciTech Connect

    Zilahi-Szabo, I.

    1980-10-07

    In a viscous shear damper, the seismic mass is chamfered at all its corners. Thus, the clearances between the seismic mass and its casing are gaps with oppositely widening out sections separated by middle sections of smallest widths.

  11. Nonlinear longitudinal oscillations of fuel in rockets feed lines with gas-liquid damper

    NASA Astrophysics Data System (ADS)

    Avramov, K. V.; Filipkovsky, S.; Tonkonogenko, A. M.; Klimenko, D. V.

    2016-03-01

    The mathematical model of the fuel oscillations in the rockets feed lines with gas-liquid dampers is derived. The nonlinear model of the gas-liquid damper is suggested. The vibrations of fuel in the feed lines with the gas-liquid dampers are considered nonlinear. The weighted residual method is applied to obtain the finite degrees of freedom nonlinear model of the fuel oscillations. Shaw-Pierre nonlinear normal modes are applied to analyze free vibrations. The forced oscillations of the fuel at the principle resonances are analyzed. The stability of the forced oscillations is investigated. The results of the forced vibrations analysis are shown on the frequency responses.

  12. Significant Attenuation of Lightly Damped Resonances Using Particle Dampers

    NASA Technical Reports Server (NTRS)

    Smith, Andrew; LaVerde, Bruce; Hunt, Ron; Knight, Joseph Brent

    2015-01-01

    When equipment designs must perform in a broad band vibration environment it can be difficult to avoid resonances that affect life and performance. This is especially true when an organization seeks to employ an asset from a heritage design in a new, more demanding vibration environment. Particle dampers may be used to provide significant attenuation of lightly damped resonances to assist with such a deployment of assets by including only a very minor set of modifications. This solution may be easier to implement than more traditional attenuation schemes. Furthermore, the cost in additional weight to the equipment can be very small. Complexity may also be kept to a minimum, because the particle dampers do not require tuning. Attenuating the vibratory response with particle dampers may therefore be simpler (in a set it and forget it kind of way) than tuned mass dampers. The paper will illustrate the use of an "equivalent resonance test jig" that can assist designers in verifying the potential resonance attenuation that may be available to them during the early trade stages of the design. An approach is suggested for transforming observed attenuation in the jig to estimated performance in the actual service design. KEY WORDS: Particle Damper, Performance in Vibration Environment, Damping, Resonance, Attenuation, Mitigation of Vibration Response, Response Estimate, Response Verification.

  13. Frequency analysis of a semi-active suspension with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Andronic, Florin; Mihai, Ioan; Suciu, Cornel; Beniuga, Marius

    2015-02-01

    Suspension systems for motor vehicles are constantly evolving in order to ensure vehicle stability and traffic safety under all driving conditions. The present work aims to highlight the influence factors in the case of a quarter car model for semi-active suspensions. The functions that must be met by such suspension systems are first presented. Mathematical models for passive systems are first illustrated and then customized for the semi-active case. A simulation diagram was conceived for Matlab Simulink. The obtained simulation results allow conducting a frequency analysis of the passive and semi-active cases of the quarter car model. Various charts for Passive Suspension Transmissibility and for the Effect of Damping on Vertical Acceleration Response were obtained for both passive and semi-active situations. Analysis of obtained results allowed evaluating of the suspension systems behavior and their frequency dependence. Significant differences were found between the behaviors of passive and semi-active suspensions. It was found that semi-active suspensions ensure damping in accordance to the chosen control method, and are much more efficient than passive ones.

  14. Vibrating surface actuators for active flow control

    NASA Astrophysics Data System (ADS)

    Calkins, Frederick T.; Clingman, Dan J.

    2002-07-01

    Current research has shown that aircraft can gain significant aerodynamic performance benefits from active flow control (AFC). AFC seeks to control large scale flows by exploiting natural response triggered by small energy inputs. The principal target application is download alleviation of the V-22 Osprey under the DARPA sponsored Boeing Active Flow Control System program. One method of injecting energy into the flow over the V22 wings is to use an active vibrating surface on the passive seal between the wing and flapperon. The active surface is an oscillating cantilevered beam which injects fluid into the flow, similar to a synthetic jet, and interacts with the flow field. Two types of actuators, or flipperons, are explored. The first is a multilayer piezoelectric polyvinylidene fluoride cantilevered bender. The second is a single crystal piezoelectric (SCP)d31 poled wafer mounted on a cantilevered spring steel substrate. This paper details the development effort including fabrication, mechanical and electrical testing, and modeling for both types of actuators. Both flipperons were mounted on the passive seal between a 1/10th scale V22 wing and flapperon and the aerodynamic performance evaluated in low speed wind tunnel. The SCP flipperon demonstrated significant cruise benefits, with increase of 10 percent lift and 20 percent angle of attack capability. The PVDF flipperon provided a 16 percent drag reduction in the hover mode.

  15. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2005-04-27

    The objective of this program is to develop a system to both monitor the vibration of a bottomhole assembly, and to adjust the properties of an active damper in response to these measured vibrations. Phase I of this program, which entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype, was completed on May 31, 2004. The principal objectives of Phase II are: more extensive laboratory testing, including the evaluation of different feedback algorithms for control of the damper; design and manufacture of a field prototype system; and, testing of the field prototype in drilling laboratories and test wells. As a result of the lower than expected performance of the MR damper noted last quarter, several additional tests were conducted. These dealt with possible causes of the lack of dynamic range observed in the testing: additional damping from the oil in the Belleville springs; changes in properties of the MR fluid; and, residual magnetization of the valve components. Of these, only the last was found to be significant. By using a laboratory demagnetization apparatus between runs, a dynamic range of 10:1 was achieved for the damper, more than adequate to produce the needed improvements in drilling. Additional modeling was also performed to identify a method of increasing the magnetic field in the damper. As a result of the above, several changes were made in the design. Additional circuitry was added to demagnetize the valve as the field is lowered. The valve was located to above the Belleville springs to reduce the load placed upon it and offer a greater range of materials for its construction. In addition, to further increase the field strength, the coils were relocated from the mandrel to the outer housing. At the end of the quarter, the redesign was complete and new parts were on order. The project is approximately three months behind schedule at this time.

  16. Advanced magnetorheological damper with a spiral channel bypass valve

    NASA Astrophysics Data System (ADS)

    McLaughlin, G.; Hu, W.; Wereley, N. M.

    2014-05-01

    Magnetorheological (MR) fluid has a yield stress that is readily controllable using an applied magnetic field. MR dampers adjust this yield stress in a magnetic valve to accommodate a wide range of shock or vibration loads. In this study, the performance of an MR damper with a spiral channel bypass valve is examined. Three bypass damper configurations, i.e., a spiral channel, a spiral channel with beads, and a straight channel with beads, are subject to sinusoidal forcing at constant amplitude, while varying frequency, and applied field (current). These configurations are characterized using tortuosity and porosity parameters. The spiral channel without beads had the largest porosity and smallest tortuosity, which produced the smallest damper force, but the widest controllable damping range. The spiral channel with beads had the smallest porosity, and a comparable tortuosity, which produced the largest damping force, but similar controllable damping range to the straight channel with beads.

  17. Self-Tuning Impact Damper for Rotating Blades

    NASA Technical Reports Server (NTRS)

    Pufy, Kirsten P. (Inventor); Brown, Gerald V. (Inventor); Bagley, Ronald L. (Inventor)

    2004-01-01

    A self-tuning impact damper is disclosed that absorbs and dissipates vibration energy in the blades of rotors in compressors and/or turbines thereby dramatically extending their service life and operational readiness. The self-tuning impact damper uses the rotor speed to tune the resonant frequency of a rattling mass to an engine order excitation frequency. The rating mass dissipates energy through collisions between the rattling mass and the walls of a cavity of the self-tuning impact damper, as well as though friction between the rattling mass and the base of the cavity. In one embodiment, the self-tuning impact damper has a ball-in-trough configuration with tire ball serving as the rattling mass.

  18. Experimental evaluation of a neural-oscillator-driven active mass damper system

    NASA Astrophysics Data System (ADS)

    Iba, Daisuke; Hongu, Junichi

    2014-03-01

    This paper proposes a new active dynamic absorber control system for high-rise buildings using a neural oscillator and a map, which estimates the amplitude level of the oscillator, and shows some experimental results by using an apparatus, which realizes the proposed control algorithm. The proposed system decides the travel distance and direction of the auxiliary mass of the dynamic absorber using the output of oscillator, which is the filtering result of structure acceleration responses by the property of the oscillator, and Amplitude-Phase map (AP-map) for estimation of the structural response in specific frequency between synchronization region, and then, transfer the auxiliary mass to the predetermined location by using a position controller. In addition, the developed active dynamic absorber system is mounted on the top of the experimental single degree of freedom structure, which represents high-rise buildings, and consists of the auxiliary mass, a DC motor, a ball screw, a microcomputer, a laser displacement sensor, and an acceleration sensor. The proposed AP-map and the algorithm to determine the travel direction of the mass using the oscillator output are embedded in the microcomputer. This paper starts by illuminating the relation among subsystems of the proposed system with reference to a block diagram, and then, shows experimental responses of the whole system excited by earthquakes to confirm the validity of the proposed system.

  19. Driving an Active Vibration Balancer to Minimize Vibrations at the Fundamental and Harmonic Frequencies

    NASA Technical Reports Server (NTRS)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations of a principal machine are reduced at the fundamental and harmonic frequencies by driving the drive motor of an active balancer with balancing signals at the fundamental and selected harmonics. Vibrations are sensed to provide a signal representing the mechanical vibrations. A balancing signal generator for the fundamental and for each selected harmonic processes the sensed vibration signal with adaptive filter algorithms of adaptive filters for each frequency to generate a balancing signal for each frequency. Reference inputs for each frequency are applied to the adaptive filter algorithms of each balancing signal generator at the frequency assigned to the generator. The harmonic balancing signals for all of the frequencies are summed and applied to drive the drive motor. The harmonic balancing signals drive the drive motor with a drive voltage component in opposition to the vibration at each frequency.

  20. Influence of MR damper modeling on vehicle dynamics

    NASA Astrophysics Data System (ADS)

    de-J Lozoya-Santos, Jorge; Morales-Menendez, Ruben; Ramirez-Mendoza, Ricardo A.; Vivas-Lopez, Carlos A.

    2013-12-01

    The influence of magneto-rheological damper modeling in vehicle dynamics analysis is studied. Several tests using CarSim™ compare a four-corner controlled semi-active suspension for two different magneto-rheological damper models. The magneto-rheological damper characteristics were identified from experimental data. A model-free controller discards the influence of control and emphasizes the compliance of the magneto-rheological damper model; the characteristics of the vehicle index performance considered were comfort, road holding, handling, roll and suspension deflection. The comparison for magneto-rheological damper dynamics and semi-active suspension covers the automotive bandwidth. The results show that high precision of a magneto-rheological damper model as an isolated feature is not enough. The magneto-rheological damper model, as a component of a vehicle suspension, needs to simulate with passive precision and variable damping forces. The findings exhibit the requisite of accurate models for evaluation of semi-active control systems in classic tests. The lack of the friction component in a magneto-rheological damper model leads to an overestimation in handling and stability.

  1. Specification of Flow Conditions in the Mathematical Model of Hydraulic Damper

    NASA Astrophysics Data System (ADS)

    Svoboda, Rudolf; Škliba, Jan; Matějec, Radek

    Hydraulic dampers represent one of the basic instruments for absorption of vibration in dynamic systems. The damper is substituted either by its hydraulic velocity characteristic, or directly by a mathematical model as a dynamic subsystem. The standard damper model does not provide satisfactory results especially those concerning the strokes of all four damper valves. To improve these results it is necessary to simulate the flows through valves more precisely and, last but not least, to set adequately correct values to all essential parameters of both mechanical and hydraulic parts of the damper. In the paper is presented a new, corrected formula for discharge flow coefficients based on the measurements of flow characteristics of throttle elements of the damper with constant as well as variable slot width. The experimental equipment used for identification process is described as well.

  2. Transitions to chaos in squeeze-film dampers

    NASA Astrophysics Data System (ADS)

    Inayat-Hussain, Jawaid I.; Mureithi, Njuki W.

    2006-09-01

    This work reports on a numerical study undertaken to investigate the imbalance response of a rigid rotor supported by squeeze-film dampers. Two types of damper configurations were considered, namely, dampers without centering springs, and eccentrically operated dampers with centering springs. For a rotor fitted with squeeze-film dampers without centering springs, the study revealed the existence of three regimes of chaotic motion. The route to chaos in the first regime was attributed to a sequence of period-doubling bifurcations of the period-1 (synchronous) rotor response. A period-3 (one-third subharmonic) rotor whirl orbit, which was born from a saddle-node bifurcation, was found to co-exist with the chaotic attractor. The period-3 orbit was also observed to undergo a sequence of period-doubling bifurcations resulting in chaotic vibrations of the rotor. The route to chaos in the third regime of chaotic rotor response, which occurred immediately after the disappearance of the period-3 orbit due to a saddle-node bifurcation, was attributed to a possible boundary crisis. The transitions to chaotic vibrations in the rotor supported by eccentric squeeze-film dampers with centering springs were via the period-doubling cascade and type 3 intermittency routes. The type 3 intermittency transition to chaos was due to an inverse period-doubling bifurcation of the period-2 (one-half subharmonic) rotor response. The unbalance response of the squeeze-film-damper supported rotor presented in this work leads to unique non-synchronous and chaotic vibration signatures. The latter provide some useful insights into the design and development of fault diagnostic tools for rotating machinery that operate in highly nonlinear regimes.

  3. Active noise and vibration control for vehicular applications

    SciTech Connect

    Lewis, P.S.; Ellis, S.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project investigated semi-active suspension systems based on real time nonlinear control of magneto-rheological (MR) shock absorbers. This effort was motivated by Laboratory interactions with the automobile industry and with the Defense Department. Background research and a literature search on semi-active suspensions was carried out. Numerical simulations of alternative nonlinear control algorithms were developed and adapted for use with an MR shock absorber. A benchtop demonstration system was designed, including control electronics and a mechanical demonstration fixture to hold the damper/spring assembly. A custom-made MR shock was specified and procured. Measurements were carried out at Los Alamos to characterize the performance of the device.

  4. Vibration attenuation of aircraft structures utilizing active materials

    NASA Astrophysics Data System (ADS)

    Agnes, Gregory S.; Whitehouse, Stephen R.; Mackaman, John R.

    1993-09-01

    The need for active vibration control for airborne laser systems was demonstrated during the late 1970s by the Airborne Laser Laboratory. Other possible applications include sonic fatigue alleviation, reduction of buffet induced fatigue, vibration control for embedded antennae, and active aeroelastic control. The purpose of this paper is to present an overview of active vibration control technology and its application to aircraft. Classification of classic aircraft vibration problems and currently available solutions are used to provide a framework for the study. Current solutions are classified as being either passive or active and by the methodology (modal modification or addition) used to reduce vibration. Possible applications for this technology in aircraft vibration control are presented within this framework to demonstrate the increased versatility active materials technologies provide the designer. An in- depth study of an active pylon to reduce wing/store vibration is presented as an example. Finally, perceived gaps in the existing technology base are identified and both on-going and future research plans in these areas are discussed.

  5. A Study of a Human Arm-Type Damper with Two Links and Three Joints

    NASA Astrophysics Data System (ADS)

    Ohmata, Kenichiro; Matsuoka, Taichi; Kohno, Shinya

    In this paper, a new type of arm-type damper consisting of two links and three joints (human type joints with friction) has been developed. The damper is able to suppress six modes of vibration of a machine, three in translational modes and three in rotational modes. The trial damper was made and its resisting force characteristics in three translational and three rotational directions were discussed theoretically and experimentally. The seismic responses of a three-degree-offreedom translational system and a two-degree-of-freedom translational-rotational system and the frequency responses of a single-degree-of-freedom translational system, which consist of a mass and four coil springs and supported by the damper, were measured using a three-dimensional permanent magnet type shaking table. The experimental results were compared with the calculated ones, and the effects of vibration suppression of the damper in three translational and rotational directions and the propriety of the calculations were confirmed.

  6. Eddy current damper

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  7. Nutation Damper System

    NASA Technical Reports Server (NTRS)

    Sevilla, D. R.

    1983-01-01

    The Nutation Damper System is a three function mechanism designed for the Galileo Spacecraft, a spin stabilized deep-space probe to Jupiter. By damping the movement of a large deployable science boom acting as an outboard pendulum, the nutation damper rapidly stabilizes the spacecraft from dynamic irregularities. The system includes the boom deployment device and the ultra-low friction boom hinge. This paper describes the mechanism, the degree to which friction, stiction and lost motion have been eliminated, and the unique test methods that allow its performance to be measured.

  8. Evaluating the Vibration Isolation of Soft Seat Cushions Using AN Active Anthropodynamic Dummy

    NASA Astrophysics Data System (ADS)

    LEWIS, C. H.; GRIFFIN, M. J.

    2002-05-01

    Seat test standards require human subjects to be used for measuring the vibration isolation of vehicle seats. Anthropodynamic dummies, based on passive mass-spring- damper systems, have been developed for testing seats but their performance has been limited at low excitation magnitudes by non-linear phenomena, such as friction in the mechanical components that provide damping. The use of an electrodynamic actuator to generate damping forces, controlled by feedback from acceleration and force transducers, may help to overcome these limitations and provide additional benefits. The transmissibilities of five foam cushions have been measured using an actively controlled anthropodynamic dummy, in which damping and spring forces were supplied by an electrodynamic actuator. The dummy could be set up to approximate alternative single-degree-of-freedom and two-degree-of-freedom apparent mass models of the seated human body by varying motion feedback parameters. Cushion transmissibilities were also measured with nine human subjects, having an average seated weight similar to the dummy. At frequencies greater than 4 Hz, mean cushion transmissibilities measured with subjects were in closer agreement with the transmissibilities obtained with a two degree-of-freedom dummy than with a single degree-of-freedom dummy. However, at frequencies between 2 and 4 Hz, cushion transmissibilities obtained with the two-degree-of-freedom dummy showed consistently larger differences from mean transmissibilities with subjects than single-degree-of-freedom dummies, indicating a need for further development of human apparent mass models to account for the effects of magnitude and spectral content of the input motion. Vertical vibration isolation efficiencies (SEAT values) of the five foams were measured with four input motions, including three motions measured in a car. The SEAT values obtained using the active dummy were highly correlated with the median SEAT values obtained with the nine human

  9. Development of active vibration isolation system for precision machines

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Lin, W. J.; Yang, G. L.

    2009-12-01

    It is a common understanding by manufacturers of precision machines that vibrations are a potentially disastrous threat to precision and throughput. To satisfy the quest for more stable processes and tighter critical dimension control in the microelectronics manufacturing industry, active vibration control becomes increasingly important for high-precision equipment developers. This paper introduced the development of an active vibration isolation system for precision machines. Innovative mechatronic approaches are investigated that can effectively suppress both environmental and payload-generated vibration. In this system, accelerometers are used as the feedback sensor, voice coil motors are used to generate the counter force, and a TI DSP controller is used to couple sensor measurements to actuator forces via specially designed control algorithms in real-time to counteract the vibration disturbances. Experimental results by using the developed AVI prototype showed promising performance on vibration attenuation. It demonstrated a reduction of the settling time from 2s to 0.1s under impulsive disturbances; and a vibration attenuation level of more than 20dB for harmonic disturbances. The technology can be used to suppress vibration for a wide range of precision machines to achieve fast settling time and higher accuracy.

  10. Development of active vibration isolation system for precision machines

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Lin, W. J.; Yang, G. L.

    2010-03-01

    It is a common understanding by manufacturers of precision machines that vibrations are a potentially disastrous threat to precision and throughput. To satisfy the quest for more stable processes and tighter critical dimension control in the microelectronics manufacturing industry, active vibration control becomes increasingly important for high-precision equipment developers. This paper introduced the development of an active vibration isolation system for precision machines. Innovative mechatronic approaches are investigated that can effectively suppress both environmental and payload-generated vibration. In this system, accelerometers are used as the feedback sensor, voice coil motors are used to generate the counter force, and a TI DSP controller is used to couple sensor measurements to actuator forces via specially designed control algorithms in real-time to counteract the vibration disturbances. Experimental results by using the developed AVI prototype showed promising performance on vibration attenuation. It demonstrated a reduction of the settling time from 2s to 0.1s under impulsive disturbances; and a vibration attenuation level of more than 20dB for harmonic disturbances. The technology can be used to suppress vibration for a wide range of precision machines to achieve fast settling time and higher accuracy.

  11. Forced response of a cantilever beam with a dry friction damper attached. I - Theory. II - Experiment

    NASA Technical Reports Server (NTRS)

    Dowell, E. H.; Schwartz, H. B.

    1983-01-01

    A theoretical and experimental study of the forced vibration response of a cantilevered beam with Coulomb damping nonlinearity is described. Viscous damping in the beam is neglected. Beam and dry friction damper configurations of interest for applications to turbine blade vibrations are considered. It is shown that the basic phenomena found by Dowell (1983) for a simply supported beam with an attached dry friction damper of specific geometry also apply to a cantilevered beam and a more general representation of the dry friction damper and its associated mass and stiffness.

  12. Calculation of multi-layer plate damper under one-axial load

    NASA Astrophysics Data System (ADS)

    Hui, Yan; Lu, Zhang; Hong-Yuan, Jiang; Alexander, M. Ulanov

    2016-02-01

    A multi-layer damper with waved plates under one-axial load is considered. A method of theoretical calculation of its energy dissipation coefficient is proposed. An experimental research of own frequencies and vibration transfer ratios for different parameters of damper structure, harmonic vibration load and random load is performed. Results of this research are approximated by functions; it is possible to use these functions for the calculation of the damper too. Project supported by the Programme of Introducing Talents of Discipline to Universities (Grant No. B07018).

  13. Active Vibration Control for Suspension by Considering Its Stroke Limitation

    NASA Astrophysics Data System (ADS)

    Nishimura, Hidekazu; Takahashi, Nobuo

    When large external forces come from the road, a suspension stroke reaches its limitation and riding comfort may decrease. To overcome this problem, we propose a new control method for an active suspension that can avoid reaching the stroke limitation. A sliding mode controller is designed by considering the rigidity variation of a spring. Also, in order to estimate the internal state of the suspension, a variable structural system (VSS) observer is designed without the information of nonlinear force occurring in the rigidity variation when the suspension reaches the stroke limitation. By carrying out simulation and experiment of a quarter-car model, it is verified that the performance of the controller is superior to that of the method, which switches to a passive damper near the stroke limitation from a linear quadratic regulator (LQR) in a small stroke range.

  14. Passive and Active Vibration Control With Piezoelectric Fiber Composites

    SciTech Connect

    Vigier, Yves; Agbossou, Amen; Richard, Claude

    2002-07-01

    The possibility of dissipating mechanical energy with piezoelectric fiber composites (PFC) is investigated. The techniques for manufacturing an active beam with integrated (PFC) are presented and applied to a cantilevered beam experiment. We evaluated experimentally the performances of the active beam in passive energy dissipation. Three vibration cases were analysed: electrodes of the PFCs are (i) in open circuit, (ii) short circuit and (iii) shunted with electrical impedance designed to dissipate the electrical energy, which has been converted from the beam mechanical energy by the PFCs. Then we presented numerical models to analyze the vibration of active beams connect to electrical impedance. The proposed models point out with an accurate order of magnitude the change in vibration amplitude of the analysed beam. Hence we validate experimentally and numerically the concept of vibration control with PFCs and point out some new contributions of PFCs in active or passive damping. (authors)

  15. A Survey of Active Vibration Isolation Systems for Microgravity Applications

    NASA Technical Reports Server (NTRS)

    Grodsinsky, Carlos M.; Whorton, Mark S.

    2000-01-01

    In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration sensitive experiments has gained increasing visibility. To date, three active microgravity vibration isolation systems have successfully been demonstrated in flight. This paper provides a tutorial discussion of the microgravity vibration isolation problem including a description of the acceleration environment of the International Space Station and attenuation requirements as well as a comparison of the dynamics of passive isolation, active rack-level isolation, and active payload-level isolation. This paper also surveys the flight test results of the three demonstrated systems: Suppression of Transient Accelerations By Levitation (STABLE); the Microgravity Vibration Isolation Mount (MIM); and the Active Rack Isolation System (ARIS).

  16. Survey of Active Vibration Isolation Systems for Microgravity Applications

    NASA Technical Reports Server (NTRS)

    Grodsinsky, Carlos M.; Whorton, Mark S.

    2000-01-01

    In view of the utility of space vehicles as orbiting science laboratories, the need for vibration isolation systems for acceleration-sensitive experiments has gained increasing visibility. To date, three active microgravity vibration isolation systems have successfully been demonstrated in flight. A tutorial discussion of the microgravity vibration isolation problem, including a description of the acceleration environment of the International Space Station and attenuation requirements, as well as a comparison or the dynamics of passive isolation, active rack-level isolation, and active payload-level isolation is provided. The flight test results of the three demonstrated systems: suppression of transient accelerations by levitation, the microgravity vibration isolation mount, and the active rack isolation system are surveyed.

  17. Piezoelectric pushers for active vibration control of rotating machinery

    NASA Technical Reports Server (NTRS)

    Palazzolo, Alan B.; Kascak, Albert F.

    1988-01-01

    The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers have been discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Tests are currently being conducted with piezoelectric pusher-based active vibration control. Results from tests performed on NASA test rigs as preliminary verification of the related theory are presented.

  18. An inverse model for magnetorheological dampers based on a restructured phenomenological model

    NASA Astrophysics Data System (ADS)

    Qian, Li-Jun; Liu, Bo; Chen, Peng; Bai, Xian-Xu

    2016-04-01

    Magnetorheological dampers (MRDs), a semi-active actuator based on MR effect, have great potential in vibration/shock control systems. However, it is difficult to establish its inverse model due to its intrinsic strong nonlinear hysteresis behaviors, and sequentially the precise, fast and effective control could not be realized effectively. This paper presents an inverse model for MRDs based on a restructured phenomenological model with incorporation of the "normalization" concept. The proposed inverse model of MRDs is validated by the simulation of the force tracking. The research results indicate that the inverse model could be applied for the damping force control with consideration of the strong nonlinear hysteresis behaviors of the MRDs.

  19. Smart hybrid rotary damper

    NASA Astrophysics Data System (ADS)

    Yang, C. S. Walter; DesRoches, Reginald

    2014-03-01

    This paper develops a smart hybrid rotary damper using a re-centering smart shape memory alloy (SMA) material as well as conventional energy-dissipating metallic plates that are easy to be replaced. The ends of the SMA and steel plates are inserted in the hinge. When the damper rotates, all the plates bend, providing energy dissipating and recentering characteristics. Such smart hybrid rotary dampers can be installed in structures to mitigate structural responses and to re-center automatically. The damaged energy-dissipating plates can be easily replaced promptly after an external excitation, reducing repair time and costs. An OpenSEES model of a smart hybrid rotary was established and calibrated to reproduce the realistic behavior measured from a full-scale experimental test. Furthermore, the seismic performance of a 3-story moment resisting model building with smart hybrid rotary dampers designed for downtown Los Angeles was also evaluated in the OpenSEES structural analysis software. Such a smart moment resisting frame exhibits perfect residual roof displacement, 0.006", extremely smaller than 18.04" for the conventional moment resisting frame subjected to a 2500 year return period ground motion for the downtown LA area (an amplified factor of 1.15 on Kobe earthquake). The smart hybrid rotary dampers are also applied into an eccentric braced steel frame, which combines a moment frame system and a bracing system. The results illustrate that adding smart hybrid rotaries in this braced system not only completely restores the building after an external excitation, but also significantly reduces peak interstory drifts.

  20. Dynamic analogy between an electromagnetic shunt damper and a tuned mass damper

    NASA Astrophysics Data System (ADS)

    Zhu, Songye; Shen, Wenai; Qian, Xin

    2013-11-01

    An electromagnetic shunt damper (EMSD) is composed of an electromagnetic damper connected to one or more RLC shunt circuits. Through a theoretical comparison, this paper reveals the similarity and difference between an EMSD and a tuned mass damper (TMD), both of which are resonant-type vibration absorbers. The equivalent mass, stiffness and damping coefficient of the EMSD are derived based on the transfer functions of structures with a TMD or an EMSD, and the functions of circuit capacitance and inductance are discussed accordingly. The optimal parameters of the RLC circuit in the EMSD are obtained through H∞ optimization. Despite their different optimal parameters, the EMSD and TMD exhibit comparable control performance with the same equivalent mass ratio. The dynamic analogy between these two types of dampers offers a new perspective for understanding novel EMSDs, given that TMDs have previously been extensively studied. The potentials and constraints of the EMSD are further discussed through numerical case studies in which EMSD control performance is examined in different situations.

  1. Mechanisms of the Space Active Vibration Isolation (SAVI)

    NASA Technical Reports Server (NTRS)

    Schmitt, Frank

    1992-01-01

    The Space Active Vibration Isolation (SAVI) is a concept for vibration isolation of one body from another with simultaneous precise control in 6 Degrees Of Freedom (DOF). SAVI achieves this using a combination of electromechanical linear actuators and magnetic actuators. Other mechanisms of interest include a structure for simulating the body being pointed, an apparatus to simulate the body that is the vibration source, and mechanisms to off-load the weight of each of these two bodies from the experiment to approximate a zero-g condition. A SAVI was built and tested to demonstrate these capabilities.

  2. Nonlinear modeling of a rotational MR damper via an enhanced Bouc-Wen model

    NASA Astrophysics Data System (ADS)

    Miah, Mohammad S.; Chatzi, Eleni N.; Dertimanis, Vasilis K.; Weber, Felix

    2015-10-01

    The coupling of magnetorheological (MR) dampers with semi-active control schemes has proven to be an effective and failsafe approach for vibration mitigation of low-damped structures. However, due to the nonlinearities inherently relating to such damping devices, the characterization of the associated nonlinear phenomena is still a challenging task. Herein, an enhanced phenomenological modeling approach is proposed for the description of a rotational-type MR damper, which comprises a modified Bouc-Wen model coupled with an appropriately selected sigmoid function. In a first step, parameter optimization is performed on the basis of individual models in an effort to approximate the experimentally observed response for varying current levels and actuator force characteristics. In a second step, based on the previously identified parameters, a generalized best-fit model is proposed by performing a regression analysis. Finally, model validation is carried out via implementation on different sets of experimental data. The proposed model indeed renders an improved representation of the actually observed nonlinear behavior of the tested rotational MR damper.

  3. The cancellation of repetitive noise and vibration by active nethods

    NASA Astrophysics Data System (ADS)

    Eghtesadi, Kh.; Chaplin, G. B. B.

    The active attenuation of diesel engine noise is discussed as well as the active control of vibration. The system used is found to work best with repetitive sources of noise. Applications of active noise attentuation include noise inside helicopters and propellor aircraft, auxilliary generators and large compressors, and noise on emergency vehicles such as fire engines and snow cats.

  4. Elements of active vibration control for rotating machinery

    NASA Technical Reports Server (NTRS)

    Ulbrich, Heinz

    1990-01-01

    The success or failure of active vibration control is determined by the availability of suitable actuators, modeling of the entire system including all active elements, positioning of the actuators and sensors, and implementation of problem-adapted control concepts. All of these topics are outlined and their special problems are discussed in detail. Special attention is given to efficient modeling of systems, especially for considering the active elements. Finally, design methods for and the application of active vibration control on rotating machinery are demonstrated by several real applications.

  5. Space Shuttle Damper System for Ground Wind Load Tests

    NASA Technical Reports Server (NTRS)

    Robinson, G. D.; Holt, J. R.; Chang, C. S.

    1973-01-01

    An active damper system which was originally developed for a 5.5% Saturn IB/Skylab Ground Winds Model was modified and used for similar purposes in a Space Shuttle model. A second damper system which was originally used in a 3% Saturn V/Dry Workshop model was also modified and made compatible with the Space Shuttle model to serve as a back-up system. Included in this final report are descriptions of the modified damper systems and the associated control and instrumentation.

  6. Low nutation-rate dampers

    NASA Technical Reports Server (NTRS)

    Tossman, B. E.

    1971-01-01

    Mission requirements plus spacecraft weight and power constraints often reduce the excitation frequency of a nutation damper below 1 cpm. Since attitude stability is determined by damper performance, maximum effectiveness at low rates is demanded. Presented are design considerations that low-frequency dampers require, along with descriptions of two low-frequency systems: the Direct Measurement Explorer 1 and the Small Astronomy Satellite A (SAS-A).

  7. A new type of damper with friction-variable characteristics

    NASA Astrophysics Data System (ADS)

    Zhou, Xiyuan; Peng, Lingyun

    2009-12-01

    Professor T. T. Soong is one of the early pioneers in field of earthquake response control of structures. A new type of smart damper, which is based on an Energy Dissipating Restraint (EDR), is presented in this paper. The EDR by Nims and Kelly, which has a triangle hysteretic loop, behaves like an active variable stiffness system (AVS) and possesses the basic characteristics of a linear viscous damper but has difficulty in capturing the output and large stroke simultaneously needed for practical applicataions in engineering structures. In order to overcome this limitation, the friction surface in the original Sumitomo EDR is divided into two parts with low and high friction coefficients in this paper. The results of finite element analysis studies show that the new type of smart friction damper enables large friction force in proportion to relative displacement between two ends of the damper and has a large allowable displacement to fit the demands of engineering applications. However, unlike the EDR by Nims and Kelly, this type of friction variable damper cannot self re-center. However, the lateral stiffness can be used to restore the structure. The nonlinear time history analysis of earthquake response for a structure equipped with the proposed friction variable dampers was carried out using the IDARC computer program. The results indicate that the proposed damper can successfully reduce the earthquake response of a structure.

  8. Active vibration control of basic structures using macro fiber composites

    NASA Astrophysics Data System (ADS)

    Yi, Guo; Wang, Jinming; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2011-03-01

    In the modern naval battle, as the anti-detection technique developing fleetly, enhancing submarine's hidden ability is becoming more and more important. However, in view of the worse control effect at low-frequency and weak adjustability to external influence, conventional passive vibration control can't satisfy the modern naval rigorous demands. Fortunately, active vibration control technology not only monitors the structure's real-time vibration, but also has more remarkable control effects and superior suitability. At the present time, it has a primary application in the vibration damping of ship engineering. In addition, due to functional materials rapidly developing, with the coming of piezoelectric composite materials, the advanced active control techniques have more applicability, lager damp amplitude and wider applied field, which basing on the piezoelectric-effect and inverse- piezoelectric-effect of piezoelectric materials. Especially, in the end of nineties, NASA had successfully manufactured the excellent macro fiber composite (MFC), which assembles actuating and sensing abilities. Comparing with the conventional piezoelectric ceramic materials, it provides the required durability, excellent flexibility, higher electromechanical coupling factors and stronger longitudinal actuating force by using interdigital electrodes. On the basis of the application of cantilever beam' active vibration control by using MFC actuators, this paper started with the mechanical characteristics of its actuating and sensing equations, and then investigated its piezoelectric feedback scale factor when equipped on the honeycomb aluminous panel. Finally, in order to validate the theoretical analysis method, the vibration control experiment of cantilever beam and honeycomb aluminous panel are built and tested with different activating force. The experimental results verify that MFC used in submarine structures' active vibration control are feasible and effective.

  9. Active Blade Vibration Control Being Developed and Tested

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter

    2003-01-01

    Gas turbine engines are currently being designed to have increased performance, lower weight and manufacturing costs, and higher reliability. Consequently, turbomachinery components, such as turbine and compressor blades, have designs that are susceptible to new vibration problems and eventual in-service failure due to high-cycle fatigue. To address this problem, researchers at the NASA Glenn Research Center are developing and testing innovative active blade vibration control concepts. Preliminary results of using an active blade vibration control system, involving a rotor supported by an active magnetic bearing in Glenn's Dynamic Spin Rig, indicate promising results (see the photograph). Active blade vibration control was achieved using feedback of blade strain gauge signals within the magnetic bearing control loop. The vibration amplitude was reduced substantially (see the graphs). Also, vibration amplitude amplification was demonstrated; this could be used to enhance structural mode identification, if desired. These results were for a nonrotating two-bladed disk. Tests for rotating blades are planned. Current and future active blade vibration control research is planned to use a fully magnetically suspended rotor and smart materials. For the fully magnetically suspended rotor work, three magnetic bearings (two radial and one axial) will be used as actuators instead of one magnetic bearing. This will allow additional degrees of freedom to be used for control. For the smart materials work, control effectors located on and off the blade will be considered. Piezoelectric materials will be considered for on-the-blade actuation, and actuator placement on a stator vane, or other nearby structure, will be investigated for off-the-blade actuation. Initial work will focus on determining the feasibility of these methods by performing basic analysis and simple experiments involving feedback control.

  10. Active vibration control based on piezoelectric smart composite

    NASA Astrophysics Data System (ADS)

    Gao, Le; Lu, Qingqing; Fei, Fan; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2013-12-01

    An aircraft’s vertical fin may experience dramatic buffet loads in high angle of attack flight conditions, and these buffet loads would cause huge vibration and dynamic stress on the vertical fin structure. To reduce the dynamic vibration of the vertical fin structure, macro fiber composite (MFC) actuators were used in this paper. The drive moment equations and sensing voltage equations of the MFC actuators were developed. Finite element analysis models based on three kinds of models of simplified vertical fin structures with surface-bonded MFC actuators were established in ABAQUS. The equivalent damping ratio of the structure was employed in finite element analysis, in order to measure the effectiveness of vibration control. Further, an open-loop test for the active vibration control system of the vertical fin with MFC actuators was designed and developed. The experimental results validated the effectiveness of the MFC actuators as well as the developed methodology.

  11. Active and passive vibration suppression for space structures

    NASA Technical Reports Server (NTRS)

    Hyland, David C.

    1991-01-01

    The relative benefits of passive and active vibration suppression for large space structures (LSS) are discussed. The intent is to sketch the true ranges of applicability of these approaches using previously published technical results. It was found that the distinction between active and passive vibration suppression approaches is not as sharp as might be thought at first. The relative simplicity, reliability, and cost effectiveness touted for passive measures are vitiated by 'hidden costs' bound up with detailed engineering implementation issues and inherent performance limitations. At the same time, reliability and robustness issues are often cited against active control. It is argued that a continuum of vibration suppression measures offering mutually supporting capabilities is needed. The challenge is to properly orchestrate a spectrum of methods to reap the synergistic benefits of combined advanced materials, passive damping, and active control.

  12. Active control of cantilever-beam vibration

    NASA Astrophysics Data System (ADS)

    Serbyn, M. Roman

    2002-11-01

    A bang-bang control system previously developed for the stabilization of a rigid platform [ISA Trans. 21, 55-59 (1982)] has been adapted to the problem of reducing flexural vibrations of a beam. The electromechanical system develops an appropriate control signal for the actuator from samples of the disturbance by analog and digital signal processing using integrated circuits. The effectiveness of this approach is predicated upon the sampling rate being much higher than the maximum vibration frequency to be silenced. It is also robust with respect to the waveform of the disturbance. Noise reductions of 10-20 dB have been achieved, depending on the bandwidth of the noise. The cantilever, chosen because of its mechanical and theoretical simplicity, provides a good foundation for the study of more complex structures, like airfoils and nonrigid platforms. In both experimental and analytical investigations the emphasis has been on the optimization of control parameters, particularly with regard to the application of the cancellation signal. Reduction in size and cost of the control unit is possible by incorporating the latest technological advances in electronic and electromechanical devices, such as FPGA boards and MEMS components.

  13. Active damping of modal vibrations by force apportioning

    NASA Technical Reports Server (NTRS)

    Hallauer, W. L., Jr.

    1980-01-01

    Force apportioning, a method of active structural damping based on that used in modal vibration testing of isolating modes by multiple shaker excitation, was analyzed and numerically simulated. A distribution of as few forces as possible on the structure is chosen so as to maximally affect selected vibration modes while minimally exciting all other modes. The accuracy of numerical simulations of active damping, active damping of higher-frequency modes, and studies of imperfection sensitivity are discussed. The computer programs developed are described and possible refinements of the research are examined.

  14. Adaptive control of an active seat for occupant vibration reduction

    NASA Astrophysics Data System (ADS)

    Gan, Zengkang; Hillis, Andrew J.; Darling, Jocelyn

    2015-08-01

    The harmful effects on human performance and health caused by unwanted vibration from vehicle seats are of increasing concern. This paper presents an active seat system to reduce the vibration level transmitted to the seat pan and the occupants' body under low frequency periodic excitation. Firstly, the detail of the mechanical structure is given and the active seat dynamics without external load are characterized by vibration transmissibility and frequency responses under different excitation forces. Owing the nonlinear and time-varying behaviour of the proposed system, a Filtered-x least-mean-square (FXLMS) adaptive control algorithm with on-line Fast-block LMS (FBLMS) identification process is employed to manage the system operation for high vibration cancellation performance. The effectiveness of the active seat system is assessed through real-time experimental tests using different excitation profiles. The system identification results show that an accurate estimation of the secondary path is achieved by using the FBLMS on-line technique. Substantial reduction is found for cancelling periodic vibration containing single and multiple frequencies. Additionally, the robustness and stability of the control system are validated through transient switching frequency tests.

  15. Integrated active sensor system for real time vibration monitoring

    NASA Astrophysics Data System (ADS)

    Liang, Qijie; Yan, Xiaoqin; Liao, Xinqin; Cao, Shiyao; Lu, Shengnan; Zheng, Xin; Zhang, Yue

    2015-11-01

    We report a self-powered, lightweight and cost-effective active sensor system for vibration monitoring with multiplexed operation based on contact electrification between sensor and detected objects. The as-fabricated sensor matrix is capable of monitoring and mapping the vibration state of large amounts of units. The monitoring contents include: on-off state, vibration frequency and vibration amplitude of each unit. The active sensor system delivers a detection range of 0-60 Hz, high accuracy (relative error below 0.42%), long-term stability (10000 cycles). On the time dimension, the sensor can provide the vibration process memory by recording the outputs of the sensor system in an extend period of time. Besides, the developed sensor system can realize detection under contact mode and non-contact mode. Its high performance is not sensitive to the shape or the conductivity of the detected object. With these features, the active sensor system has great potential in automatic control, remote operation, surveillance and security systems.

  16. Integrated active sensor system for real time vibration monitoring

    PubMed Central

    Liang, Qijie; Yan, Xiaoqin; Liao, Xinqin; Cao, Shiyao; Lu, Shengnan; Zheng, Xin; Zhang, Yue

    2015-01-01

    We report a self-powered, lightweight and cost-effective active sensor system for vibration monitoring with multiplexed operation based on contact electrification between sensor and detected objects. The as-fabricated sensor matrix is capable of monitoring and mapping the vibration state of large amounts of units. The monitoring contents include: on-off state, vibration frequency and vibration amplitude of each unit. The active sensor system delivers a detection range of 0–60 Hz, high accuracy (relative error below 0.42%), long-term stability (10000 cycles). On the time dimension, the sensor can provide the vibration process memory by recording the outputs of the sensor system in an extend period of time. Besides, the developed sensor system can realize detection under contact mode and non-contact mode. Its high performance is not sensitive to the shape or the conductivity of the detected object. With these features, the active sensor system has great potential in automatic control, remote operation, surveillance and security systems. PMID:26538293

  17. Integrated active sensor system for real time vibration monitoring.

    PubMed

    Liang, Qijie; Yan, Xiaoqin; Liao, Xinqin; Cao, Shiyao; Lu, Shengnan; Zheng, Xin; Zhang, Yue

    2015-01-01

    We report a self-powered, lightweight and cost-effective active sensor system for vibration monitoring with multiplexed operation based on contact electrification between sensor and detected objects. The as-fabricated sensor matrix is capable of monitoring and mapping the vibration state of large amounts of units. The monitoring contents include: on-off state, vibration frequency and vibration amplitude of each unit. The active sensor system delivers a detection range of 0-60 Hz, high accuracy (relative error below 0.42%), long-term stability (10000 cycles). On the time dimension, the sensor can provide the vibration process memory by recording the outputs of the sensor system in an extend period of time. Besides, the developed sensor system can realize detection under contact mode and non-contact mode. Its high performance is not sensitive to the shape or the conductivity of the detected object. With these features, the active sensor system has great potential in automatic control, remote operation, surveillance and security systems. PMID:26538293

  18. Heat transfer from fail-safe magnetorheological fluid dampers

    NASA Astrophysics Data System (ADS)

    Dogruoz, M. Baris; Gordaninejad, Faramarz; Wang, Eric L.; Stipanovich, Arthur J.

    2001-07-01

    This study focuses on an experimental study of heat transfer from magneto-rheological fluid (MRF) dampers. Two semi- active automotive size MRF dampers, one with fins and the other without fins, were constructed and tested. The experimental results were compared with those of a previously developed theoretical model. It is demonstrate that especially at high peak velocities, the temperature rise is significant and heat transfer from these devices can be enhanced considerably by utilizing fins.

  19. Active control of flexural vibrations in beams

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.

    1987-01-01

    The feasibility of using piezoelectric actuators to control the flexural oscillations of large structures in space is investigated. Flexural oscillations are excited by impulsive loads. The vibratory response can degrade the pointing accuracy of cameras and antennae, and can cause high stresses at structural node points. Piezoelectric actuators have the advantage of exerting localized bending moments. In this way, vibration is controlled without exciting rigid body modes. The actuators are used in collocated sensor/driver pairs to form a feedback control system. The sensor produces a voltage that is proportional to the dynamic stress at the sensor location, and the driver produces a force that is proportional to the voltage applied to it. The analog control system amplifies and phase shifts the sensor signal to produce the voltage signal that is applied to the driver. The feedback control is demonstrated to increase the first mode damping in a cantilever beam by up to 100 percent, depending on the amplifier gain. The damping efficiency of the control system when the piezoelectrics are not optimally positioned at points of high stress in the beam is evaluated.

  20. Introduction to passive nutation dampers

    NASA Technical Reports Server (NTRS)

    Herzl, G. C.

    1971-01-01

    Coning motion can prevent photographic and TV cameras and other oriented spacecraft experiments from maintaining a steady scan, and it can introduce a ripple in the high-gain communication system. Nutation dampers are used to remove this type of spacecraft instability. The first nutation damper flown in a missile for the stabilization of the gyroscope consisted of a hollow ring that was partially filled with mercury, and the sloshing of the mercury dissipated the nutational energy. A similar mercury-ring damper was used in the Pioneer 1 lunar probe in 1958 and became the first nutation damper to be used in space. Since then many types of nutation dampers have been designed for spin-stabilized spacecraft ranging in size from small scientific satellites to large space stations.

  1. Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Holmes, R.; Dede, M.

    1987-01-01

    This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made.

  2. Elastomer damper performance - A comparison with a squeeze film for a supercritical power transmission shaft

    NASA Technical Reports Server (NTRS)

    Zorzi, E. S.; Burgess, G.; Cunningham, R.

    1980-01-01

    This paper describes the design and testing of an elastomer damper on a super-critical power transmission shaft. The elastomers were designed to provide acceptable operation through the fourth bending mode and to control synchronous as well as nonsynchronous vibration throughout the operating range. The design of the elastomer was such that it could be incorporated into the system as a replacement for a squeeze-film damper without a reassembly, which could have altered the imbalance of the shaft. This provided a direct comparison of the elastomer and squeeze-film dampers without having to assess the effect of shaft imbalance changes.

  3. Active Piezoelectric Vibration Control of Subscale Composite Fan Blades

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Min, James B.; Kray, Nicholas

    2012-01-01

    As part of the Fundamental Aeronautics program, researchers at NASA Glenn Research Center (GRC) are investigating new technologies supporting the development of lighter, quieter, and more efficient fans for turbomachinery applications. High performance fan blades designed to achieve such goals will be subjected to higher levels of aerodynamic excitations which could lead to more serious and complex vibration problems. Piezoelectric materials have been proposed as a means of decreasing engine blade vibration either through a passive damping scheme, or as part of an active vibration control system. For polymer matrix fiber composite blades, the piezoelectric elements could be embedded within the blade material, protecting the brittle piezoceramic material from the airflow and from debris. To investigate this idea, spin testing was performed on two General Electric Aviation (GE) subscale composite fan blades in the NASA GRC Dynamic Spin Rig Facility. The first bending mode (1B) was targeted for vibration control. Because these subscale blades are very thin, the piezoelectric material was surface-mounted on the blades. Three thin piezoelectric patches were applied to each blade two actuator patches and one small sensor patch. These flexible macro-fiber-composite patches were placed in a location of high resonant strain for the 1B mode. The blades were tested up to 5000 rpm, with patches used as sensors, as excitation for the blade, and as part of open- and closed-loop vibration control. Results show that with a single actuator patch, active vibration control causes the damping ratio to increase from a baseline of 0.3% critical damping to about 1.0% damping at 0 RPM. As the rotor speed approaches 5000 RPM, the actively controlled blade damping ratio decreases to about 0.5% damping. This occurs primarily because of centrifugal blade stiffening, and can be observed by the decrease in the generalized electromechanical coupling with rotor speed.

  4. Activities report of the Institute of Sound and Vibration Research

    NASA Astrophysics Data System (ADS)

    Research in fluid dynamics and acoustics (noise and vibration control); audiology and human effects (audiotory communication and hearing conservation); structures and machinery (automotive design); and shock analysis is summarized. Underwater acoustics; active noise control; aircraft noise; wind turbine noise; laminar flow fans; helmet design; and the acoustics of flow ducts were studied.

  5. Six degree of freedom active vibration damping for space application

    NASA Technical Reports Server (NTRS)

    Haynes, Leonard S.

    1993-01-01

    Work performed during the period 1 Jan. - 31 Mar. 1993 on six degree of freedom active vibration damping for space application is presented. A performance and cost report is included. Topics covered include: actuator testing; mechanical amplifier design; and neural network control system development and experimental evaluation.

  6. Powerful Low-Frequency Vibrators for Active Seismology

    SciTech Connect

    Alekseev, A.S.; Chichinin, I.S.; Korneev, V.A.

    2003-12-01

    In the past two decades, active seismology studies in Russia have made use of powerful (40- and 100-ton) low-frequency vibrators. These sources create a force amplitude of up to 100 tons and function in the 1.5 3, 3 6, and 5 10 Hz frequency bands. The mobile versions of the vibrator have a force amplitude of 40 tons and a 6 12 Hz frequency band. Recording distances for the 100-ton vibrator are as large as 350 km, enabling the refracted waves to penetrate down to 50 km depths. Vibrator operation sessions are highly repeatable, having distinct summer or winter spectral patterns. A long profile of seismic records allows estimation of fault zone depths using changes in recorded spectra. Other applications include deep seismic profiling, seismic hazard mapping, structural testing, stress-induced anisotropy studies, seismic station calibration, and large-structure integrity testing. The theoretical description of the low-frequency vibrator is given in the appendices, which contain numerical examples.

  7. Theoretical and experimental study of vibration suppression for stayed cable

    NASA Astrophysics Data System (ADS)

    Huang, Shieh-Kung; Lin, Pei-Yang; Loh, Chin-Hsiung

    2011-04-01

    The objective of this study is to develop a numerical model of a stay cable interacted with deck, and to examine the vibration suppression technique of the stayed cable subject to external loading. First, a numerical model based on the finite difference method and the finite element method has been developed to simulate the effects of the bending stiffness and its sag-extensibility characteristics of the cable. Accurate vibration mode shapes and modal frequency of the interaction between stay cable and deck are examined. For the vibration control of cable, a MR-damper is used as control device. This damper can be achieved either through the passive control strategy or the semi-active control strategy employing decentralized sliding mode control (DSMC) and maximum energy dissipation (MED) on the staycable. To verify this study, a scaled-down cable structure is designed and constructed in NCREE, Taiwan. A small shaker is designed and mounted onto the cable to generate the sinusoid excitation with different amplitudes and frequencies. Dynamic characteristics of the cable-deck system are identified and the system model is developed for control purpose. The DSMC algorithm using MR damper was studied to reduce the cable vibration under different excitation frequencies.

  8. A semi-active H∞ control strategy with application to the vibration suppression of nonlinear high-rise building under earthquake excitations.

    PubMed

    Yan, Guiyun; Chen, Fuquan; Wu, Yingxiong

    2016-01-01

    Different from previous researches which mostly focused on linear response control of seismically excited high-rise buildings, this study aims to control nonlinear seismic response of high-rise buildings. To this end, a semi-active control strategy, in which H∞ control algorithm is used and magneto-rheological dampers are employed for an actuator, is presented to suppress the nonlinear vibration. In this strategy, a modified Kalman-Bucy observer which is suitable for the proposed semi-active strategy is developed to obtain the state vector from the measured semi-active control force and acceleration feedback, taking into account of the effects of nonlinearity, disturbance and uncertainty of controlled system parameters by the observed nonlinear accelerations. Then, the proposed semi-active H∞ control strategy is applied to the ASCE 20-story benchmark building when subjected to earthquake excitation and compared with the other control approaches by some control criteria. It is indicated that the proposed semi-active H∞ control strategy provides much better control performances by comparison with the semi-active MPC and Clipped-LQG control approaches, and can reduce nonlinear seismic response and minimize the damage in the buildings. Besides, it enhances the reliability of the control performance when compared with the active control strategy. Thus, the proposed semi-active H∞ control strategy is suitable for suppressing the nonlinear vibration of high-rise buildings. PMID:27462501

  9. Modeling and vibration control of an active membrane mirror

    NASA Astrophysics Data System (ADS)

    Ruggiero, Eric J.; Inman, Daniel J.

    2009-09-01

    The future of space satellite technology lies in ultra-large mirrors and radar apertures for significant improvements in imaging and communication bandwidths. The availability of optical-quality membranes drives a parallel effort for structural models that can capture the dominant dynamics of large, ultra-flexible satellite payloads. Unfortunately, the inherent flexibility of membrane mirrors wreaks havoc with the payload's on-orbit stability and maneuverability. One possible means of controlling these undesirable dynamics is by embedding active piezoelectric ceramics near the boundary of the membrane mirror. In doing so, active feedback control can be used to eliminate detrimental vibration, perform static shape control, and evaluate the health of the structure. The overall motivation of the present work is to design a control system using distributed bimorph actuators to eliminate any detrimental vibration of the membrane mirror. As a basis for this study, a piezoceramic wafer was attached in a bimorph configuration near the boundary of a tensioned rectangular membrane sample. A finite element model of the system was developed to capture the relevant system dynamics from 0 to 300 Hz. The finite element model was compared against experimental results, and fair agreement found. Using the validated finite element models, structural control using linear quadratic regulator control techniques was then used to numerically demonstrate effective vibration control. Typical results show that less than 12 V of actuation voltage is required to eliminate detrimental vibration of the membrane samples in less than 15 ms. The functional gains of the active system are also derived and presented. These spatially descriptive control terms dictate favorable regions within the membrane domain for placing sensors and can be used as a design guideline for structural control applications. The results of the present work demonstrate that thin plate theory is an appropriate modeling

  10. Downhole Vibration Monitoring and Control System

    SciTech Connect

    Martin E. Cobern

    2007-09-30

    The objective of this program is to develop a system to both monitor the vibration of a bottomhole assembly, and to adjust the properties of an active damper in response to these measured vibrations. The key feature of this system is its use of a magnetorheological fluid (MRF) to allow the damping coefficient to be changed extensively, rapidly and reversibly without the use of mechanical valves, but only by the application of a current. Phase I of this program, which entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype, was completed on May 31, 2004. Much of the effort was devoted to the design and testing of the MRF damper, itself. The principal objectives of Phase II were: more extensive laboratory testing, including the evaluation of different feedback algorithms for control of the damper; design and manufacture of a field prototype system; and, testing of the field prototype in a drilling laboratory. Phase II concluded on January 31, 2006, and a final report was issued. Work on Phase III of the project began during the first quarter, 2006, with the objectives of building precommercial prototypes, testing them in a drilling laboratory and the field; developing and implementing a commercialization plan. All of these have been accomplished. The Downhole Vibration Monitoring & Control System (DVMCS) prototypes have been successfully proven in testing at the TerraTek drilling facility and at the Rocky Mountain Oilfield Test Center (RMOTC.) Based on the results of these tests, we have signed a definitive development and distribution agreement with Smith, and commercial deployment is underway. This current version of the DVMCS monitors and controls axial vibrations. Due to time and budget constraints of this program, it was not possible to complete a system that would also deal with lateral and torsional (stick-slip) vibrations as originally planned; however, this effort is continuing without DOE

  11. Microgravity Active Vibration Isolation System on Parabolic Flights

    NASA Astrophysics Data System (ADS)

    Dong, Wenbo; Pletser, Vladimir; Yang, Yang

    2016-07-01

    The Microgravity Active Vibration Isolation System (MAIS) aims at reducing on-orbit vibrations, providing a better controlled lower gravity environment for microgravity physical science experiments. The MAIS will be launched on Tianzhou-1, the first cargo ship of the China Manned Space Program. The principle of the MAIS is to suspend with electro-magnetic actuators a scientific payload, isolating it from the vibrating stator. The MAIS's vibration isolation capability is frequency-dependent and a decrease of vibration of about 40dB can be attained. The MAIS can accommodate 20kg of scientific payload or sample unit, and provide 30W of power and 1Mbps of data transmission. The MAIS is developed to support microgravity scientific experiments on manned platforms in low earth orbit, in order to meet the scientific requirements for fluid physics, materials science, and fundamental physics investigations, which usually need a very quiet environment, increasing their chances of success and their scientific outcomes. The results of scientific experiments and technology tests obtained with the MAIS will be used to improve future space based research. As the suspension force acting on the payload is very small, the MAIS can only be operative and tested in a weightless environment. The 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, German Aerospace Centre) granted a flight opportunity to the MAIS experiment to be tested during its 27th parabolic flight campaign of September 2015 performed on the A310 ZERO-G aircraft managed by the French company Novespace, a subsidiary of the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency). The experiment results confirmed that the 6 degrees of freedom motion control technique was effective, and that the vibration isolation performance fulfilled perfectly the expectations based on theoretical analyses and simulations. This paper will present the design of the MAIS and the experiment results obtained during the

  12. Adaptive active control of periodic vibration using maglev actuators

    NASA Astrophysics Data System (ADS)

    An, Fengyan; Sun, Hongling; Li, Xiaodong

    2012-04-01

    In this paper, active control of periodic vibration is implemented using maglev actuators which exhibit inherent nonlinear behaviors. A multi-channel feedforward control algorithm is proposed to solve these nonlinear problems, in which maglev actuators are treated as single-input-single-output systems with unknown time-varying nonlinearities. A radial basis function network is used by the algorithm as its controller, whose parameters are adapted only with the model of the linear system in the secondary path. Compared with the strategies in the conventional magnetic-levitation system control as well as nonlinear active noise/vibration control, the proposed algorithm has the advantage that the nonlinear modeling procedure of maglev actuators and the usage of displacement sensors could be both avoided. Numerical simulations and real-time experiments are carried out based on a multiple-degree-of-freedom vibration isolation system. The results show that the proposed algorithm not only could efficiently compensate for the actuators' time-varying nonlinearities, but also has the ability to greatly attenuate the energy of periodic vibration.

  13. Neuroreceptor Activation by Vibration-Assisted Tunneling

    PubMed Central

    Hoehn, Ross D.; Nichols, David; Neven, Hartmut; Kais, Sabre

    2015-01-01

    G protein-coupled receptors (GPCRs) constitute a large family of receptor proteins that sense molecular signals on the exterior of a cell and activate signal transduction pathways within the cell. Modeling how an agonist activates such a receptor is fundamental for an understanding of a wide variety of physiological processes and it is of tremendous value for pharmacology and drug design. Inelastic electron tunneling spectroscopy (IETS) has been proposed as a model for the mechanism by which olfactory GPCRs are activated by a bound agonist. We apply this hyothesis to GPCRs within the mammalian nervous system using quantum chemical modeling. We found that non-endogenous agonists of the serotonin receptor share a particular IET spectral aspect both amongst each other and with the serotonin molecule: a peak whose intensity scales with the known agonist potencies. We propose an experiential validation of this model by utilizing lysergic acid dimethylamide (DAM-57), an ergot derivative, and its deuterated isotopologues; we also provide theoretical predictions for comparison to experiment. If validated our theory may provide new avenues for guided drug design and elevate methods of in silico potency/activity prediction. PMID:25909758

  14. Neuroreceptor activation by vibration-assisted tunneling.

    PubMed

    Hoehn, Ross D; Nichols, David; Neven, Hartmut; Kais, Sabre

    2015-01-01

    G protein-coupled receptors (GPCRs) constitute a large family of receptor proteins that sense molecular signals on the exterior of a cell and activate signal transduction pathways within the cell. Modeling how an agonist activates such a receptor is fundamental for an understanding of a wide variety of physiological processes and it is of tremendous value for pharmacology and drug design. Inelastic electron tunneling spectroscopy (IETS) has been proposed as a model for the mechanism by which olfactory GPCRs are activated by a bound agonist. We apply this hyothesis to GPCRs within the mammalian nervous system using quantum chemical modeling. We found that non-endogenous agonists of the serotonin receptor share a particular IET spectral aspect both amongst each other and with the serotonin molecule: a peak whose intensity scales with the known agonist potencies. We propose an experiential validation of this model by utilizing lysergic acid dimethylamide (DAM-57), an ergot derivative, and its deuterated isotopologues; we also provide theoretical predictions for comparison to experiment. If validated our theory may provide new avenues for guided drug design and elevate methods of in silico potency/activity prediction. PMID:25909758

  15. Analysis of high load dampers

    NASA Technical Reports Server (NTRS)

    Bhat, S. T.; Buono, D. F.; Hibner, D. H.

    1981-01-01

    High load damping requirements for modern jet engines are discussed. The design of damping systems which could satisfy these requirements is also discusseed. In order to evaluate high load damping requirements, engines in three major classes were studied; large transport engines, small general aviation engines, and military engines. Four damper concepts applicable to these engines were evaluated; multi-ring, cartridge, curved beam, and viscous/friction. The most promising damper concept was selected for each engine and performance was assessed relative to conventional dampers and in light of projected damping requirements for advanced jet engines.

  16. Experimental investigation of dynamic performance of a prototype hybrid tuned mass damper under human excitation

    NASA Astrophysics Data System (ADS)

    Noormohammadi, Nima; Reynolds, Paul

    2013-04-01

    Current sport stadia designs focus mainly on maximizing audience capacity and providing a clear view for all spectators. Hence, incorporation of one or more cantilevered tiers is typical in these designs. However, employing such cantilevered tiers, usually with relatively low damping and natural frequencies, can make grandstands more susceptible to excitation by human activities. This is caused by the coincidence between the activity frequencies (and their lowest three harmonics) and the structural natural frequencies hence raising the possibility of resonant vibration. This can be both a vibration serviceability and a safety issue. Past solutions to deal with observed or anticipated vibration serviceability problems have been mainly passive methods, such as tuned mass dampers (TMDs). These techniques have exhibited problems such as lack of performance and offtuning caused by human-structure interaction. To address this issue, research is currently underway to investigate the possible application of hybrid TMDs (HTMDs), which are a combination of active and passive control, to improve the vibration serviceability of such structures under human excitation. The work presented here shows a comparative experimental investigation of a passive TMD and a prototype HTMD applied on a slab strip structure. The most effective control algorithm to enhance the performance of the HTMD and also deal with the off-tuning problem is investigated. The laboratory structure used here is an in-situ cast simply-supported post-tensioned slab strip excited by forces from a range of human activities.

  17. Wireless sensor networks for active vibration control in automobile structures

    NASA Astrophysics Data System (ADS)

    Mieyeville, Fabien; Ichchou, Mohamed; Scorletti, Gérard; Navarro, David; Du, Wan

    2012-07-01

    Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control.

  18. Active vibration damping using smart material

    NASA Technical Reports Server (NTRS)

    Baras, John S.; Yan, Zhuang

    1994-01-01

    We consider the modeling and active damping of an elastic beam using distributed actuators and sensors. The piezoelectric ceramic material (PZT) is used to build the actuator. The sensor is made of the piezoelectric polymer polyvinylidene fluoride (PVDF). These materials are glued on both sides of the beam. For the simple clamped beam, the closed loop controller has been shown to be able to extract energy from the beam. The shape of the actuator and its influence on the closed loop system performance are discussed. It is shown that it is possible to suppress the selected mode by choosing the appropriate actuator layout. It is also shown that by properly installing the sensor and determining the sensor shape we can further extract and manipulate the sensor signal for our control need.

  19. Vibration control of cylindrical shells using active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  20. Fabrication and testing of an energy-harvesting hydraulic damper

    NASA Astrophysics Data System (ADS)

    Li, Chuan; Tse, Peter W.

    2013-06-01

    Hydraulic dampers are widely used to dissipate energy during vibration damping. In this paper, an energy-harvesting hydraulic damper is proposed for collecting energy while simultaneously damping vibration. Under vibratory excitation, the flow of hydraulic oil inside the cylinder of the damper is converted into amplified rotation via a hydraulic motor, whose output shaft is connected to an electromagnetic generator capable of harvesting a large amount of energy. In this way, the vibration is damped by both oil viscosity and the operation of an electrical mechanism. An electromechanical model is presented to illustrate both the electrical and mechanical responses of the system. A three-stage identification approach is introduced to facilitate the model parameter identification using cycle-loading experiments. A prototype device is developed and characterized in a test rig. The maximum power harvested during the experiments was 435.1 W (m s-1)-1, using a predefined harmonic excitation with an amplitude of 0.02 m, a frequency of 0.8 Hz, and an optimal resistance of 2 Ω. Comparison of the experimental and computational results confirmed the effectiveness of both the electromechanical model and the three-stage identification approach in realizing the proposed design.

  1. A phenomenological dynamic model of a magnetorheological damper using a neuro-fuzzy system

    NASA Astrophysics Data System (ADS)

    Zeinali, Mohammadjavad; Amri Mazlan, Saiful; Yasser Abd Fatah, Abdul; Zamzuri, Hairi

    2013-12-01

    A magnetorheological (MR) damper is a promising appliance for semi-active suspension systems, due to its capability of damping undesired movement using an adequate control strategy. This research has been carried out a phenomenological dynamic model of two MR dampers using an adaptive-network-based fuzzy inference system (ANFIS) approach. Two kinds of Lord Corporation MR damper (a long stroke damper and a short stroke damper) were used in experiments, and then modeled using the experimental results. In addition, an investigation of the influence of the membership function selection on predicting the behavior of the MR damper and obtaining a mathematical model was conducted to realize the relationship between input current, displacement, and velocity as the inputs and force as output. The results demonstrate that the proposed models for both short stroke and long stroke MR dampers have successfully predicted the behavior of the MR damper with adequate accuracy, and an equation is presented to precisely describe the behavior of each MR damper.

  2. Actively Controlled Landing Gear for Aircraft Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Daugherty, Robert H.; Martinson, Veloria J.

    1999-01-01

    Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.

  3. Piezoelectric pushers for active vibration control of rotating machinery

    NASA Technical Reports Server (NTRS)

    Palazzolo, A. B.; Kascak, A. F.; Lin, R. R.; Montague, J.; Alexander, R. M.

    1989-01-01

    The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers was discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Analyses are contained which extend quadratic regulator, pole placement and derivative feedback control methods to the prescribed displacement character of piezoelectric pushers. The structural stiffness of the pusher is also included in the theory. Tests are currently being conducted at NASA Lewis Research Center with piezoelectric pusher-based active vibration control. Results performed on the NASA test rig as preliminary verification of the related theory are presented.

  4. Multiple plate hydrostatic viscous damper

    SciTech Connect

    Ludwig, L.P.

    1981-02-01

    A device for damping radial motion of a rotating shaft is described. The damper comprises a series of spaced plates extending in a radial direction. A hydraulic piston is utilized to place a load in these plates. Each annular plate is provided with a suitable hydrostatic bearing geometry on at least one of its faces. This structure provides a high degree of dampening in a rotor case system of turbomachinery in general. The damper is particularly useful in gas turbine engines.

  5. Multiple plate hydrostatic viscous damper

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P. (Inventor)

    1981-01-01

    A device for damping radial motion of a rotating shaft is described. The damper comprises a series of spaced plates extending in a radial direction. A hydraulic piston is utilized to place a load in these plates. Each annular plate is provided with a suitable hydrostatic bearing geometry on at least one of its faces. This structure provides a high degree of dampening in a rotor case system of turbomachinery in general. The damper is particularly useful in gas turbine engines.

  6. ACTIVE VIBRATION SUPPRESSION R+D FOR THE NEXT LINEARCOLLIDER

    SciTech Connect

    Eriksson, Leif S.

    2002-08-20

    The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented.

  7. Active Vibration Suppression R and D for the NLC

    SciTech Connect

    Frisch, Josef C

    2001-12-17

    The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented.

  8. Active vibration control techniques for flexible space structures

    NASA Technical Reports Server (NTRS)

    Parlos, Alexander G.; Jayasuriya, Suhada

    1990-01-01

    Two proposed control system design techniques for active vibration control in flexible space structures are detailed. Control issues relevant only to flexible-body dynamics are addressed, whereas no attempt was made to integrate the flexible and rigid-body spacecraft dynamics. Both of the proposed approaches revealed encouraging results; however, further investigation of the interaction of the flexible and rigid-body dynamics is warranted.

  9. [Actuator placement for active sound and vibration control

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Two refereed journal publications and ten talks given at conferences, seminars, and colloquia resulted from research supported by NASA. They are itemized in this report. The two publications were entitled "Reactive Tabu and Search Sensor Selection in Active Structural Acoustic Control Problems" and "Quelling Cabin Noise in Turboprop Aircraft via Active Control." The conference presentations covered various aspects of actuator placement, including location problems, for active sound and vibration control of cylinders, of commuter jets, of propeller driven or turboprop aircraft, and for quelling aircraft cabin or interior noise.

  10. Medium to long term behavior of MR dampers for structural control

    NASA Astrophysics Data System (ADS)

    Caterino, N.; Azmoodeh, B. M.; Occhiuzzi, A.

    2014-10-01

    The medium to long term behavior of a prototype magnetorheological (MR) damper for structural control of earthquake induced vibrations is investigated herein. Unlike some applications for which MR devices experience frequent dynamic loads, seismic dampers might not be used for most of their life, staying dormant for a long period until an earthquake hits the hosting structure. This work aims to evaluate the effectiveness of a MR damper after years of inactivity. A MR device has been tested twice, first in 2008 and then in 2013, after five years of absolute inactivity. The comparison between the results of the two tests is made in terms of force-displacement loops. It is shown that, after a 5-year rest, only part of the first stroke of the damper is characterized by an unexpected response of the damper. After half a stroke, the damper quickly returned to behave like in 2008, even if a slight non-reversible decrease of the reacting force has been recorded. The latter is found to be more evident (5-7%) for larger currents, less visible in the case of zero magnetic field. From the point of view of civil engineering, this decay of performance is definitely acceptable, being largely bounded within the limits of the uncertainties typically involved and taken into account in the structural design. Finally, starting from a literature review, the paper discusses the possible causes of the observed changes in the mechanical response of the damper over time.

  11. Design and numerical evaluation of an innovative multi-directional shape memory alloy damper

    NASA Astrophysics Data System (ADS)

    Ren, Wenjie; Li, Hongnan; Song, Gangbing

    2007-04-01

    Superelastic shape memory alloy (SMA) is a potential candidate for use in structure damping devices due to its unique mechanical properties. In order to mitigate the vibration of a structure subjected to earthquake tremors from different directions, an innovative, multi-directional SMA-based damper is advanced. The damper, with two movable cylinders attached to four groups of SMA strands arranged in a radial symmetry, can not only function in a plane, but also can work vertically and rotationally. Based on experimentation, the Graesser model of superelastic SMA is determined. By analyzing the damper's mechanism working in different directions, the corresponding theoretical models are developed. Numerical simulations are conducted to attain the damper's hysteresis. Working in a plane, the damper, with a 3% initial strain, provides a rectangular hysteresis with the maximum amount of damping. A rectangular flag hysteresis can be supplied in the absence of a pre-stress in the wires, going through the origin with a moderate amount of energy dissipation and higher force capacity. Moreover, the damper has better working capacities (i.e. force, stroke and energy dissipation) if the deflection is parallel to the internal bisectors of the tension axes. Working vertically or rotationally, similar triangular flag hysteresis is generated with small energy dissipation and a self-centering capacity. For a given deflection, the initial strain (3%) increases the force of the damper, but decreases its stroke.

  12. Investigation on seismic resistance of high-rising buildings installed with viscoelastic-wall dampers

    NASA Astrophysics Data System (ADS)

    Liu, M.; Wang, Y.; Ren, J.

    2015-04-01

    Viscoelastic dampers are one of popular vibration mitigation devices applied to tall buildings to reduce seismic and wind-induced vibiration. In this paper,a new kind of viscoelastic-wall damper, which could be installed at the shearwall location of high-rising buildings, is proposed to enhance the energy disspation ability. The seismic resistance behaviors of one tall building installed with the viscoelastic-wall dampers are investigated by numerical analysis. The mechanical property testing of the viscoelastic-wall damper is carried to investigate its performance parameter under various exciting frequency and strain amplitude. According to the testing results, a mathematical model of viscoelastic - wall damper is modeled based on Kelvin model. On the basis of a 36-floor frame-shear wall structure and using the finite element software ABAQUS, two finite element models of the high-rising building with and without viscoelastic-wall dampers are set up. Elasto-plastic time-history analysis is used to compare the seismic performance of the two structures subjected to the frequently and rarely earthquakes. It is proved that the seismic response of the structure is mitigated effectively when it is equipped with viscoelastic-wall dampers.

  13. A mechanical energy harvested magnetorheological damper with linear-rotary motion converter

    NASA Astrophysics Data System (ADS)

    Chu, Ki Sum; Zou, Li; Liao, Wei-Hsin

    2016-04-01

    Magnetorheological (MR) dampers are promising to substitute traditional oil dampers because of adaptive properties of MR fluids. During vibration, significant energy is wasted due to the energy dissipation in the damper. Meanwhile, for conventional MR damping systems, extra power supply is needed. In this paper, a new energy harvester is designed in an MR damper that integrates controllable damping and energy harvesting functions into one device. The energy harvesting part of this MR damper has a unique mechanism converting linear motion to rotary motion that would be more stable and cost effective when compared to other mechanical transmissions. A Maxon motor is used as a power generator to convert the mechanical energy into electrical energy to supply power for the MR damping system. Compared to conventional approaches, there are several advantages in such an integrated device, including weight reduction, ease in installation with less maintenance. A mechanical energy harvested MR damper with linear-rotary motion converter and motion rectifier is designed, fabricated, and tested. Experimental studies on controllable damping force and harvested energy are performed with different transmissions. This energy harvesting MR damper would be suitable to vehicle suspensions, civil structures, and smart prostheses.

  14. Dynamic responses of two buildings connected by viscoelastic dampers under bidirectional earthquake excitations

    NASA Astrophysics Data System (ADS)

    Yang, Zhidong; Lam, Eddie S. S.

    2014-03-01

    In this study, dynamic responses of two buildings connected by viscoelastic dampers under bidirectional excitations are extensively investigated. The two buildings are a 10-story building and a 16-story building, with the shorter building on the left. Viscoelastic dampers are installed at all floors of the shorter building. Equations of motion are formulated using a fractional derivative model to represent the viscoelastic dampers. Three cases are considered with mass eccentricities at 0, 10% and -10% with respect to the dimensions of the buildings. The responses of the buildings are numerically predicted at different damper properties. The simulation results indicated that the maximum horizontal responses of the buildings without eccentricities are significantly mitigated. However, torsional effects are adversely increased. For asymmetric buildings, the effectiveness of the connecting dampers is affected by building eccentricities. As a result, mass eccentricities must be taken into account in damper selection. When compared with vibrations induced by unidirectional excitations, bidirectional excitations can increase the responses of coupled asymmetric buildings. In addition, installing dampers only at the top floor of the shorter building may cause a sudden change in lateral stiffness of the taller building. Consequently, the story shear envelopes of the taller building are changed.

  15. System and method of active vibration control for an electro-mechanically cooled device

    DOEpatents

    Lavietes, Anthony D.; Mauger, Joseph; Anderson, Eric H.

    2000-01-01

    A system and method of active vibration control of an electro-mechanically cooled device is disclosed. A cryogenic cooling system is located within an environment. The cooling system is characterized by a vibration transfer function, which requires vibration transfer function coefficients. A vibration controller generates the vibration transfer function coefficients in response to various triggering events. The environments may differ by mounting apparatus, by proximity to vibration generating devices, or by temperature. The triggering event may be powering on the cooling system, reaching an operating temperature, or a reset action. A counterbalance responds to a drive signal generated by the vibration controller, based on the vibration signal and the vibration transfer function, which adjusts vibrations. The method first places a cryogenic cooling system within a first environment and then generates a first set of vibration transfer function coefficients, for a vibration transfer function of the cooling system. Next, the cryogenic cooling system is placed within a second environment and a second set of vibration transfer function coefficients are generated. Then, a counterbalance is driven, based on the vibration transfer function, to reduce vibrations received by a vibration sensitive element.

  16. Spin Testing for Durability Began on a Self-Tuning Impact Damper for Turbomachinery Blades

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten; Mehmed, Oral

    2003-01-01

    NASA and Pratt & Whitney will collaborate under a Space Act Agreement to perform spin testing of the impact damper to verify damping effectiveness and durability. Pratt & Whitney will provide the turbine blade and damper hardware for the tests. NASA will provide the facility and perform the tests. Effectiveness and durability will be investigated during and after sustained sweeps of rotor speed through resonance. Tests of a platform wedge damper are also planned to compare its effectiveness with that of the impact damper. Results from baseline tests without dampers will be used to measure damping effectiveness. The self-tuning impact damper combines two damping methods-the tuned mass damper and the impact damper. It consists of a ball located within a cavity in the blade. This ball rolls back and forth on a spherical trough under centrifugal load (tuned mass damper) and can strike the walls of the cavity (impact damper). The ball s rolling natural frequency is proportional to the rotor speed and can be designed to follow an engine-order line (integer multiple of rotor speed). Aerodynamic forcing frequencies typically follow these engineorder lines, and a damper tuned to the engine order will most effectively reduce blade vibrations when the resonant frequency equals the engine-order forcing frequency. This damper has been tested in flat plates and turbine blades in the Dynamic Spin Facility. During testing, a pair of plates or blades rotates in vacuum. Excitation is provided by one of three methods--eddy-current engine-order excitation (ECE), electromechanical shakers, and magnetic bearing excitation. The eddy-current system consists of magnets located circumferentially around the rotor. As a blade passes a magnet, a force is imparted on the blade. The number of magnets used can be varied to change the desired engine order of the excitation. The magnets are remotely raised or lowered to change the magnitude of the force on the blades. The other two methods apply

  17. Temperature sensitive stability of feedback controllers for MR dampers

    NASA Astrophysics Data System (ADS)

    Batterbee, D. C.; Sims, N. D.

    2008-03-01

    Smart fluid dampers can undergo large temperature changes due to the heating associated with energy dissipation. Such heating will alter the fluid's properties and could degrade control system performance. For example, previous work by the authors has shown that the stability of an MR damper under feedback control is dependent on the fluid's compressibility and viscosity. In the present study, a temperature dependent model of a magnetorheological damper is developed from experimental data, and it is shown that the fluid's yield stress, viscosity and compressibility parameters vary significantly. An experimental and numerical control study is then performed to investigate the resulting effects of temperature on the stability of two feedback controllers - a PID controller, and a proportional controller. Experimental results indicate that both controllers can exhibit a reduction in stability with increasing temperature, particularly if the controller gains are not suitably chosen. The temperature dependent MR damper model predicts this behaviour well, and it is shown that the change in viscosity has the most significant effect on stability. Future work could focus on the resulting effect on a complete vibration system, devices with different modes of operation, and alternative controllers.

  18. Dynamics of the non-ideal autoparametric system with MR damper

    NASA Astrophysics Data System (ADS)

    Sado, Danuta

    2012-11-01

    The nonlinear response of a three degree of freedom autoparametric system with a double pendulum, including the magneto-rheological (MR) damper when the excitation comes from a DC motor which works with limited power supply, has been examined. The non-ideal source of power adds one degree of freedom which makes the system have four degrees of freedom. The influence of damping force in MR damper on the phenomenon of energy transfer has been studied. Near the internal and external resonance region, except periodic vibration also chaotic vibration has been observed.

  19. Coupled Torsional and Bending Vibrations of Actively Controlled Drillstrings

    NASA Astrophysics Data System (ADS)

    YIGIT, A. S.; CHRISTOFOROU, A. P.

    2000-06-01

    The dynamics of actively controlled drillstrings is studied. The equations of motion are derived using a lumped parameter model in which the coupling between torsional and bending vibrations is considered. The model also includes the dynamics of the rotary drive system which contains the rotary table, the gearbox and an armature controlled DC motor. The interactions between the drillstring and the borehole which are considered, include the impacts of collars with the borehole wall as well as bit rotation-dependent weight and torque on bit (WOB and TOB). Simulation results obtained by numerically solving the equations of motion are in close qualitative agreement with field and laboratory observations regarding stick-slip oscillations. A linear quadratic regulator (LQR) controller is designed based on a linearized model and is shown to be effective in eliminating this type of oscillations. It is also shown that for some operational parameters the control action may excite large bending vibrations due to coupling with the torsional motion.

  20. Modeling of Electromagnetic Damper for Automobile Suspension

    NASA Astrophysics Data System (ADS)

    Kawamoto, Yasuhiro; Suda, Yoshihiro; Inoue, Hirofumi; Kondo, Takuhiro

    In this paper, the modeling of the electromagnetic damper (EMD) for automobile suspension is presented and the validation of the model is demonstrated by comparing the numerical results with the experimental results obtained using shaker tests. EMD is used as an active suspension and controlled to have output force calculated from velocities of sprung and unsprung masses. The formulation of EMD system for active suspensions is first developed, and the validation of the EMD model is demonstrated by experiments of the EMD for automobile suspensions. The validity of the formulation of the EMD developed in this investigation is shown for the frequency responses as well as energy balance for its active use.

  1. Optimization of Magneto-Rheological Damper for Maximizing Magnetic Flux Density in the Fluid Flow Gap Through FEA and GA Approaches

    NASA Astrophysics Data System (ADS)

    Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil

    2016-06-01

    A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.

  2. Evaluation of Seismic Performance and Effectiveness of Multiple Slim-Type Damper System for Seismic Response Control of Building Structures

    PubMed Central

    Kim, David; Sung, Eun Hee; Park, Kwan-Soon; Park, Jaegyun

    2014-01-01

    This paper presents the evaluation of seismic performance and cost-effectiveness of a multiple slim-type damper system developed for the vibration control of earthquake excited buildings. The multiple slim-type damper (MSD) that consists of several small slim-type dampers and linkage units can control damping capacity easily by changing the number of small dampers. To evaluate the performance of the MSD, dynamic loading tests are performed with three slim-type dampers manufactured at a real scale. Numerical simulations are also carried out by nonlinear time history analysis with a ten-story earthquake excited building structure. The seismic performance and cost-effectiveness of the MSD system are investigated according to the various installation configurations of the MSD system. From the results of numerical simulation and cost-effectiveness evaluation, it is shown that combinations of the MSD systems can effectively improve the seismic performance of earthquake excited building structures. PMID:25301387

  3. Evaluation of seismic performance and effectiveness of multiple slim-type damper system for seismic response control of building structures.

    PubMed

    Kim, David; Sung, Eun Hee; Park, Kwan-Soon; Park, Jaegyun

    2014-01-01

    This paper presents the evaluation of seismic performance and cost-effectiveness of a multiple slim-type damper system developed for the vibration control of earthquake excited buildings. The multiple slim-type damper (MSD) that consists of several small slim-type dampers and linkage units can control damping capacity easily by changing the number of small dampers. To evaluate the performance of the MSD, dynamic loading tests are performed with three slim-type dampers manufactured at a real scale. Numerical simulations are also carried out by nonlinear time history analysis with a ten-story earthquake excited building structure. The seismic performance and cost-effectiveness of the MSD system are investigated according to the various installation configurations of the MSD system. From the results of numerical simulation and cost-effectiveness evaluation, it is shown that combinations of the MSD systems can effectively improve the seismic performance of earthquake excited building structures. PMID:25301387

  4. Active vibration and noise alleviation in rotorcraft using microflaps

    NASA Astrophysics Data System (ADS)

    Padthe, Ashwani Kumar

    This work presents a comprehensive analysis of active Gurney flaps, or microflaps, for on blade control of noise and vibration in rotorcraft. The initial portion of the work considered the two-dimensional unsteady aerodynamic characteristics of three different oscillating microflap configurations using a compressible computational fluid dynamics (CFD) flow solver. Among these the configuration most suitable for rotorcraft applications was chosen. An unsteady reduced order aerodynamic model (ROM) was developed for the microflap using the Rational Function Approximation approach and CFD based oscillatory aerodynamic load data. The resulting ROM is a state-space, time-domain model that accounts for unsteadiness, compressibility and time-varying freestream effects. The ROM was validated against direct CFD calculations for a wide range of flow conditions showing excellent agreement. Subsequently, the ROM was then incorporated into a comprehensive rotorcraft simulation code featuring a free-wake model, an acoustic prediction tool, and fully coupled flap-lag-torsional blade dynamics. The higher harmonic control (HHC) algorithm was used to simulate closed-loop active control with a 1.5% chord microflap on a hingeless rotor configuration resembling the MBB BO-105. Three span-wise configurations, single, dual, and a five-microflap configuration were considered. Results indicate that the microflap can achieve reductions ranging from 3-6 dB in the blade-vortex interaction (BVI) noise. Vibration reduction ranging from 70-90% was also demonstrated at both low-speed and high-speed flight conditions. It was also found that reduction in BVI noise results in an increase in vibrations and vice versa, a trend also noted in previous active control studies employing HHC and conventional partial span trailing-edge flaps. Next, simultaneous BVI noise and vibration reduction was studied. A reduction of 2-3 dB in the advancing and retreating side noise combined with a 55% reduction in the

  5. Stability of Intershaft Squeeze Film Dampers

    NASA Technical Reports Server (NTRS)

    El-Shafei, A.

    1991-01-01

    Intershaft squeeze film dampers were investigated for damping of dual rotor aircraft jet engines. It was thought that the intershaft damper would enhance the stability of the rotor-bearing system. Unfortunately, it was determined that the intershaft squeeze film damper was unstable above the engine's first critical speed. Here, a stability analysis of rotors incorporating intershaft squeeze film dampers is discussed. A rotor model consisting of two Jeffcott rotors with two intershaft squeeze film dampers was investigated. Examining the system characteristic equation for the conditions at which the roots indicate an ever-growing unstable motion results in the stability conditions. The cause of the instability is identified as the rotation of the oil in the damper clearance. Several proposed configurations of intershaft squeeze film dampers are discussed, and it is shown that the intershaft dampers are stable supercritically only with a configuration in which the oil film does not rotate.

  6. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2004-10-29

    The objective of this program is to develop a system to both monitor the vibration of a bottomhole assembly, and to adjust the properties of an active damper in response to these measured vibrations. Phase I of this program, which entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype, was completed on May 31, 2004. Phase II began on June 1, and the first month's effort were reported in the seventh quarterly report on the project.1 The principal objectives of Phase II are: more extensive laboratory testing, including the evaluation of different feedback algorithms for control of the damper; design and manufacture of a field prototype system; and, testing of the field prototype in drilling laboratories and test wells. The redesign and upgrade of the laboratory prototype was completed on schedule during this period, and assembly was complete at the end of this period. Testing will begin during the first week of October. This aspect of the project is thus approximately six weeks behind schedule. Design of the field prototype is progressing per schedule.

  7. DOWNHOLE VIBRATION MONITORING & CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2005-01-28

    The objective of this program is to develop a system to both monitor the vibration of a bottomhole assembly, and to adjust the properties of an active damper in response to these measured vibrations. Phase I of this program, which entailed modeling and design of the necessary subsystems and design, manufacture and test of a full laboratory prototype, was completed on May 31, 2004. The principal objectives of Phase II are: more extensive laboratory testing, including the evaluation of different feedback algorithms for control of the damper; design and manufacture of a field prototype system; and, testing of the field prototype in drilling laboratories and test wells. The redesign and upgrade of the laboratory prototype was completed on schedule and it was assembled during the last period. Testing was begin during the first week of October. Initial results indicated that the dynamic range of the damping was less than predicted and that the maximum damping was also less than required. A number of possible explanations for these results were posited, and test equipment was acquired to evaluate the various hypotheses. Testing was just underway at the end of this period.

  8. Rheological properties of bi-dispersed magnetorheological fluids based on plate-like iron particles with application to a small-sized damper

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Xuan Phu, Do; Choi, Seung-Bok

    2014-05-01

    In this study, the rheological properties and an application of bi-dispersed magnetorheological fluid (MRF) based on plate-like iron particles are experimentally investigated. A bi-dispersed MR Fluid is prepared using two different micron-scale sizes of plate-like iron particles. In the absence of a magnetic field, the properties of the fluid are isotropic. Upon the application of a magnetic field, the magnetized particles form a chain aligned in the direction of the field, which promotes the appearance of a yield stress. The reversible transition from solid to liquid is the basic requirement of MR applications. Due to the anisotropy in the shape and formation of a less compact structure in the iron plate-like particles, weak sedimentation and good redispersibility of the proposed MR fluid are created. The physical properties of the proposed MR fluids are evaluated and applied to the design of a small-sized controllable MR vibration damper, which can be used for vibration control of a washing machine. The MR damper is a semi-active device that dissipates energy during vibration motion to increase the stability of the application system. Three different weight fractions of the bi-dispersed MR fluids are prepared, and their rheological properties are presented and discussed. Based on their rheological properties, the figures of merit of the proposed MR fluids are derived. A comparison of these figures of merit gives the nominal behavior of the MR fluids, which are important in the design of the application device. A stability test is also performed to check the settling rate of MR fluids per day. The change in damping force due to the problem of particles settling in the MRF and the field-dependent damping force are measured with the MR damper operated just after filling the MRF and with the MR damper operated after waiting for 48 h after filling. With basic rheological properties and outstanding mechanical properties, it is clearly demonstrated that the proposed MR

  9. Prototype and test of a novel rotary magnetorheological damper based on helical flow

    NASA Astrophysics Data System (ADS)

    Yu, Jianqiang; Dong, Xiaomin; Wang, Wen

    2016-02-01

    To increase the output damping torque of a rotary magnetorheological (MR) damper with limited geometrical space, a novel rotary MR damper based on helical flow is proposed. A new working mode, helical flow mode, is discussed and applied to enlarge the flow path of MR fluids. The helical flow can improve the performance of the rotary damper by enlarging the length of the active region. Based on the idea, a rotary MR damper is designed. The rotary MR damper contains a spiral piston, dual-coil core, a rotating cylinder and a stator cylinder. Based on the Bingham model, the output damping torque of the damper is analytically derived. The finite element method (FEM) is applied to calculate the magnetic field of the active region. The multi-objective optimal design method is adopted to obtain the optimal geometric parameters. A prototype is fabricated based on the optimal results. To validate the proposed rotary MR damper, two types of experiments including the low rotation speed and the high rotation speed are investigated. The results show that the proposed rotary MR damper has high torque density and compact structure. The helical flow mode can increase the output damping torque with limited space.

  10. Use of piezoelectric dampers for improving the feel of golf clubs

    NASA Astrophysics Data System (ADS)

    Bianchini, Emanuele; Spangler, Ronald L., Jr.; Pandell, Tracy

    1999-06-01

    Several sports are based upon a tool (club, bat, stick) striking an object (ball, puck) across a field of play. Anytime two structures collide, vibration is created by the impact of the two. The impact of the objects excites the structural modes of the tool, creating a vibration that can be felt by the player, especially if the hit is not at a `sweet spot'. Vibration adversely affects both feel and performance. This paper explains how piezoelectric dampers were developed to reduce vibration and improve the feel of ball-impact sporting goods such as golf clubs. The paper describes how the dynamic characteristics of a golf club were calculated, at first in the free-free condition, and then during its operation conditions (the swing of the club, and the impact with the ball). The dynamic characteristics were used to develop a damper that addressed a specific, or multiple, modes of interest. The damper development and testing are detailed in this paper. Both objective laboratory tests and subjective player tests were performed to evaluate the effectiveness of the piezoelectric dampers. The results of the tests, along with published medical data on the sensitivity of the human body, were used to draw a correlation between human feel and vibration reduction.

  11. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  12. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  13. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  14. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  15. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  16. A nonlinear kinematic and dynamic modeling of Macpherson suspension systems with a magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Dutta, Saikat; Choi, Seung-Bok

    2016-03-01

    It is well known that Macpherson strut suspension systems are widely used in light and medium weight vehicles. The performance of these suspension systems can be enriched by incorporating magneto-rheological (MR) dampers and an appropriate dynamic model is required in order to find out the ride comfort and other performances properly in the sense of practical environment conditions. Therefore, in this work the kinematic and dynamic modeling of Macpherson strut suspension system with MR damper is presented and its responses are evaluated. The governing equations are formulated using the kinematic properties of the suspension system and adopting Lagrange’s equation. In the formulation of the model, both the rotation of the wheel assembly and the lateral stiffness of the tire are considered to represent the nonlinear characteristic of Macpherson type suspension system. The formulated mathematical model is then compared with equivalent conventional quarter car suspension model and the different dynamic responses such as the displacement of the sprung mass are compared to emphasize the effectiveness of the proposed model. Additionally, in this work the important kinematic properties of suspension system such as camber angle, king-pin angle and track width alteration, which cannot be obtained from conventional quarter car suspension model, are evaluated in time and frequency domains. Finally, vibration control responses of the proposed suspension system are presented in time and frequency domains which are achieved from the semi-active sky-hook controller.

  17. Experimental and theoretical investigation of passive damping concepts for member forced and free vibration

    NASA Technical Reports Server (NTRS)

    Razzaq, Zia; Mykins, David W.

    1987-01-01

    Potential passive damping concepts for use in space structures are identified. The effectiveness of copper brush, wool swab, and silly putty in chamber dampers is investigated through natural vibration tests on a tubular aluminum member. The member ends have zero translation and possess partial rotational restraints. The silly putty in chamber dampers provide the maximum passive damping efficiency. Forced vibration tests are then conducted with one, two, and three damper chambers containing silly putty. Owing to the limitation of the vibrator used, the performance of these dampers could not be evaluated experimentally until the forcing function was disengaged. Nevertheless, their performance is evaluated through a forced dynamic finite element analysis conducted as a part of this investigation. The theoretical results based on experimentally obtained damping ratios indicate that the passive dampers are considerably more effective under member natural vibration than during forced vibration. Also, the maximum damping under forced vibration occurs at or near resonance.

  18. Optimal Design of a Torsional Tuned Damper for Marine Diesel Engines Using Fluid-Structure Interaction Analysis

    NASA Astrophysics Data System (ADS)

    Kim, Young-Cheol; Lee, D. H.; Chung, T. Y.; Ham, D. Y.; Kim, Y. B.

    A torsional tuned damper is usually used in order to reduce the torsional vibration of the crank shaft system in marine diesel engines. The damper consists of leaf springs, fluid chambers, fluid channels, and intermediate masses. The leaf springs provide the stiffening force to the shaft system, and the fluid chambers and channels give the damping force. In this paper, FSI (fluid-structure interaction) analysis by using FEM is carried out for the calculation of the stiffness and damping coefficients of the designed damper. The numerical calculation result about the equivalent damping coefficients is compared to the value obtained from a simple damping simulation model.

  19. Digital control system for space structural dampers

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1984-01-01

    Digital control systems for space structural dampers, also referred to as inertia or proof-mass dampers are investigated. A damper concept is improved by adding a small taper to the proof-mass, and using a proximeter to determine position. Another damper using a three inch stroke rather than the standard one inch stroke is described. Provisions are made for a relative velocity feedback. In one approach, the digital controller is modified to accept the signal from a linear velocity transducer. In the other, the velocity feedback is included in the digital program. An overall system concept for the use of the dampers is presented.

  20. A new magnetorheological damper for seismic control

    NASA Astrophysics Data System (ADS)

    Ding, Yang; Zhang, Lu; Zhu, Hai-Tao; Li, Zhong-Xian

    2013-11-01

    This paper proposes a new MR damper with bidirectional adjusting damping forces to enhance the fail-safe property of the MR damper. The structure of the composite magnetic circuits is improved for the new damper. Four prototype dampers are fabricated and tested by magnetic field tests and dynamic tests. The magnetic field distribution in the damping path and the dynamic properties of the dampers with different input currents are obtained. The Gompertz model is proposed to portray the dynamic behavior of the prototype dampers. The study shows that, due to the improved structure of composite magnetic circuits, the prototype dampers can maintain a medium damping force with zero current input. This behavior may ensure a better fail-safe property and avoid settlement of MR fluid compared with conventional MR dampers. Furthermore, the minimum and maximum output powers of the proposed dampers can be obtained at the states of the negative peak and positive peak of currents inputs, respectively. In addition, the dynamic range of controllable force is wider than that of conventional MR dampers. The analysis further shows that the proposed Gompertz model can precisely portray the nonlinear hysteretic behavior of the proposed dampers without complicated function forms.

  1. Integrated passive/active vibration absorber for multi-story buildings

    NASA Technical Reports Server (NTRS)

    Lee-Glauser, Gina J.; Ahmadi, Goodarz; Horta, Lucas G.

    1995-01-01

    Passive isolator, active vibration absorber, and an integrated passive/active (hybrid) control are studied for their effectiveness in reducing structural vibration under seismic excitations. For the passive isolator, a laminated rubber bearing base isolator which has been studied and used extensively by researchers and seismic designers is considered. An active vibration absorber concept, which can provide guaranteed closed-loop stability with minimum knowledge of the controlled system, is used to reduce the passive isolator displacement and to suppress the top floor vibration. A three-story building model is used for the numerical simulation. The performance of an active vibration absorber and a hybrid vibration controller in reducing peak structural responses is compared with the passively isolated structural response and with absence of vibration control systems under the N00W component of El Centro 1940 and N90W component of the Mexico City earthquake excitation records. The results show that the integrated passive/active vibration control system is most effective in suppressing the peak structural acceleration for the El Centro 1940 earthquake when compared with the passive or active vibration absorber alone. The active vibration absorber, however, is the only system that suppresses the peak acceleration of the structure for the Mexico City 1985 earthquake.

  2. Design of the Active Elevon Rotor for Low Vibration

    NASA Technical Reports Server (NTRS)

    Fulton, Mark V.; Rutkowski, Michael (Technical Monitor)

    2000-01-01

    Helicopter fuselages vibrate more than desired, and traditional solutions have limited effectiveness and can impose an appreciable weight penalty. Alternative methods of combating high vibration, including Higher Harmonic Control (HHC) via harmonic swashplate motion and Individual Blade Control (IBC) via active pitch links, have been studied for several decades. HHC via an on-blade control surface was tested in 1977 on a full scale rotor using a secondary active swashplate and a mechanical control system. Recent smart material advances have prompted new research into the use of on-blade control concepts. Recent analytical studies have indicated that the use of on-blade control surfaces produces vibration reduction comparable to swashplate-based HHC but for less power. Furthermore, smart materials (such as piezoceramics) have been shown to provide sufficient control authority for preliminary rotor experiments. These experiments were initially performed at small scale for reduced tip speeds. More recent experiments have been conducted at or near full tip speeds, and a full-scale active rotor is under development by Boeing with Eurocopter et al. pursuing a similarly advanced full-scale implementation. The US Army Aeroflightdynamics Directorate has undertaken a new research program called the Active Elevon Rotor (AER) Focus Demo. This program includes the design, fabrication, and wind. tunnel testing of a four-bladed, 12.96 ft diameter rotor with one or two on-blade elevons per blade. The rotor, which will be Mach scaled, will use 2-5/rev elevon motion for closed-loop control and :will be tested in late 2001. The primary goal of the AER Focus Demo is the reduction of vibratory hub loads by 80% and the reduction of vibratory blade structural loads. A secondary goal is the reduction of rotor power. The third priority is the measurement and possible reduction of Blade Vortex Interaction (BVI) noise. The present study is focused on elevon effectiveness, that is, the elevon

  3. The design of an active-adaptive tuned vibration absorber based on magnetorheological elastomer and its vibration attenuation performance

    NASA Astrophysics Data System (ADS)

    Liao, G. J.; Gong, X. L.; Kang, C. J.; Xuan, S. H.

    2011-07-01

    This paper presents an active-adaptive tuned vibration absorber (AATVA) which is based on magnetorheological elastomer (MRE). A voice coil motor is attached to a conventional MRE adaptive tuned vibration absorber (ATVA) to improve its performance. In this study, two feedback types of the activation force were analyzed and the stability condition was obtained. In order to eliminate the time delay effect during the signal processing, a phase-lead compensator was incorporated. Based on the analysis, an MRE AATVA prototype was designed and its dynamic properties were experimentally investigated. The experimental results demonstrated that its resonant frequency could vary from 11 to 18 Hz and its damping ratio decreased to roughly 0.05 from 0.19 by adding the activation force. Besides, its vibration reduction abilities at the first two resonant frequencies of the experimental platform could reach 5.9 dB and 7.9 dB respectively.

  4. Vibrational spectra, structure and antioxidant activity of gossypol imine derivatives

    NASA Astrophysics Data System (ADS)

    Ilkevych, N. S.; Schroeder, G.; Rybachenko, V. I.; Chotiy, K. Y.; Makarova, R. A.

    2012-02-01

    The structures and tautomeric equilibria of natural polyphenol gossypol and four its imine derivatives were studied by FT-IR-, NMR-spectroscopy and quantum chemistry methods. It was shown that gossypol Schiff bases exist in solution as enamine-enamine tautomer and hydrazones as imine-imine tautomer. Infrared absorption spectra of studied compounds were simulated using the PM3 method. The fundamental vibrational frequencies were evaluated using various scale factors which yield a good agreement between observed and calculated frequencies. Free radical scavenging activity of gossypol and its imine derivatives was evaluated using DPPH method. Antioxidant activity of studied compounds was characterized. Gossypol hydrazones were shown to be more efficient, while Schiff base to be less efficient as antioxidants in comparison with gossypol itself.

  5. Actuator placement for active sound and vibration control of cylinders

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.

    1995-01-01

    Active structural acoustic control is a method in which the control inputs (used to reduce interior noise) are applied directly to a vibrating structural acoustic system. The control concept modeled in this work is the application of in-plane force inputs to piezoceramic patches bonded to the wall of a vibrating cylinder. The cylinder is excited by an exterior noise source -- an acoustic monopole -- located near the outside of the cylinder wall. The goal is to determine the force inputs and sites for the piezoelectric actuators so that (1) the interior noise is effectively damped; (2) the level of vibration of the cylinder shell is not increased; and (3) the power requirements needed to drive the actuators are not excessive. We studied external monopole excitations at two frequencies. A cylinder resonance of 100 Hz, where the interior acoustic field is driven in multiple, off-resonance cylinder cavity modes, and a cylinder resonance of 200 Hz are characterized by both near and off-resonance cylinder vibration modes which couple effectively with a single, dominant, low-order acoustic cavity mode at resonance. Previous work has focused almost exclusively on meeting objective (1) and solving a complex least-squares problem to arrive at an optimal force vector for a given set of actuator sites. In addition, it has been noted that when the cavity mode couples with cylinder vibration modes (our 200 Hz case) control spillover may occur in higher order cylinder shell vibrational modes. How to determine the best set of actuator sites to meet objectives (1)-(3) is the main contribution of our research effort. The selection of the best set of actuator sites from a set of potential sites is done via two metaheuristics -- simulated annealing and tabu search. Each of these metaheuristics partitions the set of potential actuator sites into two disjoint sets: those that are selected to control the noise (on) and those that are not (off). Next, each metaheuristic attempts to

  6. Active Flap Control of the SMART Rotor for Vibration Reduction

    NASA Technical Reports Server (NTRS)

    Hall, Steven R.; Anand, R. Vaidyanathan; Straub, Friedrich K.; Lau, Benton H.

    2009-01-01

    Active control methodologies were applied to a full-scale active flap rotor obtained during a joint Boeing/ DARPA/NASA/Army test in the Air Force National Full-Scale Aerodynamic Complex 40- by 80-foot anechoic wind tunnel. The active flap rotor is a full-scale MD 900 helicopter main rotor with each of its five blades modified to include an on-blade piezoelectric actuator-driven flap with a span of 18% of radius, 25% of chord, and located at 83% radius. Vibration control demonstrated the potential of active flaps for effective control of vibratory loads, especially normal force loads. Active control of normal force vibratory loads using active flaps and a continuous-time higher harmonic control algorithm was very effective, reducing harmonic (1-5P) normal force vibratory loads by 95% in both cruise and approach conditions. Control of vibratory roll and pitch moments was also demonstrated, although moment control was less effective than normal force control. Finally, active control was used to precisely control blade flap position for correlation with pretest predictions of rotor aeroacoustics. Flap displacements were commanded to follow specific harmonic profiles of 2 deg or more in amplitude, and the flap deflection errors obtained were less than 0.2 deg r.m.s.

  7. Improved Coulomb-Friction Damper

    NASA Technical Reports Server (NTRS)

    Campbell, G. E.

    1985-01-01

    Equal damping provided on forward and reverse strokes. Improved damper has springs and wedge rings symmetrically placed on both ends of piston wedge, so friction force same in both directions of travel. Unlike conventional automotive shock absorbers, they resemble on outside, both versions require no viscous liquid and operate over wide temperature range.

  8. The influence of vibration type, frequency, body position and additional load on the neuromuscular activity during whole body vibration.

    PubMed

    Ritzmann, Ramona; Gollhofer, Albert; Kramer, Andreas

    2013-01-01

    This study aimed to assess the influence of different whole body vibration (WBV) determinants on the electromyographic (EMG) activity during WBV in order to identify those training conditions that cause highest neuromuscular responses and therefore provide optimal training conditions. In a randomized cross-over study, the EMG activity of six leg muscles was analyzed in 18 subjects with respect to the following determinants: (1) vibration type (side-alternating vibration (SV) vs. synchronous vibration (SyV), (2) frequency (5-10-15-20-25-30 Hz), (3) knee flexion angle (10°-30°-60°), (4) stance condition (forefoot vs. normal stance) and (5) load variation (no extra load vs. additional load equal to one-third of the body weight). The results are: (1) neuromuscular activity during SV was enhanced compared to SyV (P < 0.05); (2) a progressive increase in frequency caused a progressive increase in EMG activity (P < 0.05); (3) the EMG activity was highest for the knee extensors when the knee joint was 60° flexed (P < 0.05); (4) for the plantar flexors in the forefoot stance condition (P < 0.05); and (5) additional load caused an increase in neuromuscular activation (P < 0.05). In conclusion, large variations of the EMG activation could be observed across conditions. However, with an appropriate adjustment of specific WBV determinants, high EMG activations and therefore high activation intensities could be achieved in the selected muscles. The combination of high vibration frequencies with additional load on an SV platform led to highest EMG activities. Regarding the body position, a knee flexion of 60° and forefoot stance appear to be beneficial for the knee extensors and the plantar flexors, respectively. PMID:22538279

  9. Study, Development, and Design of Replaceable Shear Yielding Steel Panel Damper

    SciTech Connect

    Murakami, Katsuhide; Keii, Michio

    2008-07-08

    For middle-high rise buildings, vibration controlled structures to reduce the damage of main frames are recently becoming general in Japan. A steel material damper is low price and excellent in the energy absorption efficiency at a large earthquake. Though the exchange of the dampers are necessary when an excessive accumulation of plasticity deformation occurs, a steel material damping system, which received an excessive accumulation of plasticity deformation after a large earthquake, can recover a seismic-proof performance and property value of the building after the replacement. In the paper, shear yielding steel panel dampers installed in the web of a beam connected with high tension bolt joint is introduced. This damper is made of low-yield point steel, and the advantages of this system are low cost, easy-production and easy-replacement. For this steel panel damper, the finite element method (FEM) analysis using the shell element model adjusted to 1/2 of 6.4 m beam span is executed to make the design most effective. Yielding property of the beam installing this damper, shape of the splice plate and the bolt orientation for the connecting are examined in this analysis. As a result, we found that the plastic strain extends uniformly to the entire damping panel when making the splice plate a trapezoidal shape. The basic performance confirmation examination was also done using the real scale examination model besides the FEM analysis, and the performance of the system was confirmed. In addition, design of a high rise building in which the steel shear-yielding panel dampers and oil dampers were adopted without disturbing an architectural plan is also introduced.

  10. Simulation and experimental research for piping damper with plunger-type accumulator

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Hui; Hu, Jun-Hua; Wang, Xiao-Bin; Niu, Zi-Hua

    2010-09-01

    It can be beneficial to reduce vibrations in shipboard piping, so the authors designed a new kind of piping damper with a plunger-type accumulator. Special requirements for the piping damper included low impact displacement, low speed, as well as an appropriate locking speed. Inside the damper, a plunger-type accumulator was installed and on the outside of the piston rod, a tube with exposed corrugations was added. Between the piston and the cylinder, a clearance seal was added. Using mathematical modeling, the effects of the dynamic performance of the damper’s impact displacement on vibrations were observed. Changes to the clearance between the piston and the cylinder, the stiffness of the spring in the accumulator, the throttle valve size, and locking speed resistance of the damper were respectively simulated and studied. Based on the results of the simulation, dampers with optimal parameters were developed and tested with different accumulator spring stiffnesses and different throttles. The simulation and experimental results showed that parameters such as seal clearance between piston and cylinder, accumulator spring stiffness and throttle parameters have significant effects on the damper’s impact displacement, low speed resistance and locking speed.

  11. Suppression of chaotic vibrations in a nonlinear half-car model

    NASA Astrophysics Data System (ADS)

    Tusset, Ángelo Marcelo; Piccirillo, Vinícius; Janzen, Frederic Conrad; Lenz, Wagner Barth; Balthazar, José Manoel; da Fonseca Brasil, Reyolando M. L. R.

    2014-12-01

    The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we using the 0-1 test for identify the chaotic motion. The principal objective of this study is to eliminate the chaotic behaviour of the chassis and reduce its vibration, and for this reason a control system for semi-active vehicle suspension with magnetorheological damper is proposed. The control mechanism is designed based on SDRE technique, where the control parameter is the voltage applied to the coil of the damper. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing therefore, passenger comfort.

  12. Suppression of chaotic vibrations in a nonlinear half-car model

    SciTech Connect

    Tusset, Ângelo Marcelo E-mail: piccirillo@utfpr.edu.br E-mail: wagner-barth@hotmail.com; Piccirillo, Vinícius E-mail: piccirillo@utfpr.edu.br E-mail: wagner-barth@hotmail.com; Janzen, Frederic Conrad E-mail: piccirillo@utfpr.edu.br E-mail: wagner-barth@hotmail.com; Lenz, Wagner Barth E-mail: piccirillo@utfpr.edu.br E-mail: wagner-barth@hotmail.com; Balthazar, José Manoel; Fonseca Brasil, Reyolando M. L. R. da

    2014-12-10

    The present work investigates the nonlinear response of a half-car model. The disturbances of the road are assumed to be sinusoidal. After constructing the bifurcation diagram, we using the 0-1 test for identify the chaotic motion. The principal objective of this study is to eliminate the chaotic behaviour of the chassis and reduce its vibration, and for this reason a control system for semi-active vehicle suspension with magnetorheological damper is proposed. The control mechanism is designed based on SDRE technique, where the control parameter is the voltage applied to the coil of the damper. Numerical results show that the proposed control method is effective in significantly reducing of the chassis vibration, increasing therefore, passenger comfort.

  13. Analysis and testing of electrorheological bypass dampers

    NASA Astrophysics Data System (ADS)

    Lindler, Jason E.; Wereley, Norman M.

    1998-06-01

    We experimentally validate nonlinear quasi-steady electrorheological (ER) and magnetorheological (MR) damper models, using an idealized Bingham plastic shear flow mechanism, for the flow mode of damper operation. An electrorheological valve or bypass damper was designed, and fabricated using predominantly commercial off-the-shelf hydraulic components. Both the hydraulic cylinder and the bypass duct have cylindrical geometry, and damping forces are developed in the annular bypass via Poiseuille (flow mode) flow. Damper models assume parallel plate geometry. Three nondimensional groups are used for damper analysis, namely, the Bingham number, Bi, the nondimensional plug thickness, (delta) , and the area coefficient defined as the ratio of the piston head area, A(rho ), to the cross-sectional area of the annular bypass, Ad. In the flow mode case, the damping coefficient, which is defined as the ratio of equivalent viscous damping of the Bingham plastic material, Ceq, to the Newtonian viscous damping, C, is a function of the nondimensional plug thickness only. The damper was tested using a mechanical damper dynamometer for sinusoidal stroke of 2 inches, over a range of frequencies below 0.63 Hz. The damping coefficient vs. nondimensional plug thickness diagram was experimentally validated using these data over a range of damper shaft velocities and applied electric field. Because the behaviors of ER and MR fluid are qualitatively similar, these ER damper modeling results may be extended to analysis of flow mode MR dampers.

  14. A wave-based design of semi-active piezoelectric composites for broadband vibration control

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Collet, M.; Ichchou, M.; Li, L.; Bareille, O.; Dimitrijevic, Z.

    2016-05-01

    This paper deals with the design of periodic piezoelectric structures for broadband vibration control. By shunting identical negative capacitances to the periodically distributed piezoelectric patches, a wide and continuous band gap is created so as to cover the frequency range of interest. This way the modal density of the structure is reduced and the modal shapes are localized at the boundaries. A large proportion of the energy can then be removed or dissipated by a small number of dampers or energy harvesters integrated within the negative capacitance circuits. A design process is proposed to achieve the wide band gap. The overall amount of piezoelectric materials is constrained in order to keep mass of structures low. The wave electromechanical coupling factor is proposed and used as a criterion. This allows to reach the largest width of the band gap by using a stable value of negative capacitance. The control of multiple high-order modes of a cantilever beam is considered as an example. The vibration reduction performance of the designed piezoelectric structures is presented and the influences of band gap resonance, resistor and the boundary condition are discussed. The proposed approach is fully based on wave characteristics and it does not rely on any modal information. It is therefore promising for applications at mid- and high frequencies where the access to the exact modal information is difficult.

  15. Active low-frequency vertical vibration isolation system for precision measurements

    NASA Astrophysics Data System (ADS)

    Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun

    2016-06-01

    Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.

  16. Voice Coil Actuator for Active Vibration Isolation in Microgravity

    NASA Astrophysics Data System (ADS)

    Brusa, E.; Carabelli, S.; Genta, G.; Maddaleno, F.; Silvagni, M.; Tonoli, A.

    2002-01-01

    Many microgravity experiments require very low levels of acceleration which cannot be achieved on the International Space Station due to the residual vibration. A vibration isolation system is then usually devised between the experiment and the space station to obtain the desired accelerations at the experiment level. The very low frequency threshold required by the isolation specifications makes passive solutions for the isolation difficult to implement. This is mainly due to the practical impossibility of achieving high values of compliance of the elastic suspension. Furthermore, the unavoidable connections of uncertain characteristics between the experiment and the space station makes the problem even more difficult to be addressed. Disturbance reduction can be performed by means of active vibration isolation, based on magnetic suspension technology acting both at rack and at scientific experiment levels. The stiffness and damping of the active suspension can be tuned by the control loop to minimise the acceleration of the payload. The mechatronic design of an active magnetic suspension for vibration isolation in microgravity has been performed by resorting to the so-called voice-coil configuration, after a preliminary trade-off analysis of the available magnetic actuators and materials. The optimisation of the actuator layout was developed with respect to the design airgap and force density (N/kg of actuator) and force resolution requirements, by demonstrating that the configuration based on Lorentz magnetic force is more suitable for the above application in terms of stability, bi- directionality of the actuation, cross coupling effects and linearity of the force. The aim of the design was the maximisation of the actuation force/mass ratio. The FEM analysis of the voice coil allowed to investigate the flux leakage and the cross coupling effects between the actuation forces along the three principal directions of the active device. A procedure for the numerical

  17. Tuning of active vibration controllers for ACTEX by genetic algorithm

    NASA Astrophysics Data System (ADS)

    Kwak, Moon K.; Denoyer, Keith K.

    1999-06-01

    This paper is concerned with the optimal tuning of digitally programmable analog controllers on the ACTEX-1 smart structures flight experiment. The programmable controllers for each channel include a third order Strain Rate Feedback (SRF) controller, a fifth order SRF controller, a second order Positive Position Feedback (PPF) controller, and a fourth order PPF controller. Optimal manual tuning of several control parameters can be a difficult task even though the closed-loop control characteristics of each controller are well known. Hence, the automatic tuning of individual control parameters using Genetic Algorithms is proposed in this paper. The optimal control parameters of each control law are obtained by imposing a constraint on the closed-loop frequency response functions using the ACTEX mathematical model. The tuned control parameters are then uploaded to the ACTEX electronic control electronics and experiments on the active vibration control are carried out in space. The experimental results on ACTEX will be presented.

  18. Active vibration and balance system for closed cycle thermodynamic machines

    NASA Technical Reports Server (NTRS)

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2004-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass. A method is also provided.

  19. Cryogenic Ion Vibrational Spectroscopy of - CH Activation Intermediates

    NASA Astrophysics Data System (ADS)

    Marsh, Brett; Garand, Etienne

    2013-06-01

    Despite the rather simple composition of alkanes the strength of their C-C and C-H bonds has made controlled, selective reaction of these compounds an unrealized goal of synthetic chemistry. The field was pioneered by Shilov and coworkers in 1969 when they observed the exchange of H and D in methane that was bubbled into an acidic solution of K_2PtCl_4. The Shilov reaction has since been extended to induce oxidation of methane selectively to methanol and has become the standard bearer of CH activation despite its limitations. The mechanism for the reaction, while inferred from kinetics studies, is still largely uncharacterized. Here, we present our work towards applying cryogenic ion vibrational spectroscopy (CIVS) to capture the intermediate species of this reaction with a focus on the σ-CH adduct formed between methane and Pt(II) complexes that is believed to be crucial to the selectivity and rate of this reaction.

  20. System design for active vibration control of aerospace structures

    NASA Astrophysics Data System (ADS)

    Shankar, V.; Nagaraja, B. V.; Balasubramaniam, R.; Shree S, Amrutha; Muthaiah, Skanda N.

    2003-10-01

    Instrumentation, electronics, digital signal processing and related software form the basic building blocks of a system for implementation of Active Vibration Control (AVC) for smart aerospace structures. This paper essentially deals with the design, development and implementation of a 4 channel analog input sub-system essentially consisting of charge amplifiers, filters, gain amplifiers & Analog to Digital Converters (ADC), the subsequent Digital Signal Processor (DSP) hardware for implementation of the controller and finally a 4 Channel analog output subsystem consisting of Digital to Analog Converters (DAC), reconstruction filters & high voltage amplifiers. This system essentially interfaces to a structure with piezo-ceramic sensors and actuators for implementation of real time AVC on a smart beam. The paper also highlights some of the new ideas that have been incorporated into the system design.

  1. Active control of sound fields in elastic cylinders by vibrational inputs

    NASA Technical Reports Server (NTRS)

    Jones, J. D.; Fuller, C. R.

    1987-01-01

    An experiment is performed to study the mechanisms of active control of sound fields in elastic cylinders via vibrational outputs. In the present method of control, a vibrational force input was used as the secondary control input to reduce the radiated acoustic field. For the frequencies considered, the active vibration technique provided good global reduction of interior sound even though only one actuator was used.

  2. Optimum connecting dampers to reduce the seismic responses of parallel structures

    NASA Astrophysics Data System (ADS)

    Zhu, H. P.; Ge, D. D.; Huang, X.

    2011-04-01

    Parameters of connecting dampers between two adjacent structures and twin-tower structure with large podium are optimized through theoretical analysis. The connecting visco-elastic damper (VED) is represented by the Kelvin model and the connecting viscous fluid damper (VFD) is represented by the Maxwell model. Two optimization criteria are selected to minimize the vibration energy of the primary structure and to minimize the vibration energy of both structures. Two representative numerical examples of adjacent structures and one three-dimensional finite element model of a twin-tower with podium structure are used to verify the correctness of the theoretical approach. On the one hand, by means of theoretical analysis, the first natural circular frequencies and total mass of the two structures can be taken as parameters in the general formula to get the optimal parameters of the coupling dampers. On the other hand, using the Kanai-Tajimi filtered white-noise ground motion model and several actual earthquake records, the appropriate parameters of two types of linking dampers are obtained through extensive parametric studies. By comparison, it can be found that the results of parametric studies are consistent with the results of theoretical studies for the two types of dampers under the two optimization criteria. The effectiveness of VED and VFD is investigated in terms of the seismic response reduction of the neighboring structures. The numerical results demonstrate that the seismic response and vibration energy of parallel structures are mitigated significantly. The performances of VED and VFD are comparable to one another. The explicit formula of VED and VFD can help engineers in application of coupled structure control strategies.

  3. Compact Active Vibration Control System for a Flexible Panel

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H. (Inventor); Cabell, Randolph H. (Inventor); Perey, Daniel F. (Inventor)

    2014-01-01

    A diamond-shaped actuator for a flexible panel has an inter-digitated electrode (IDE) and a piezoelectric wafer portion positioned therebetween. The IDE and/or the wafer portion are diamond-shaped. Point sensors are positioned with respect to the actuator and measure vibration. The actuator generates and transmits a cancelling force to the panel in response to an output signal from a controller, which is calculated using a signal describing the vibration. A method for controlling vibration in a flexible panel includes connecting a diamond-shaped actuator to the flexible panel, and then connecting a point sensor to each actuator. Vibration is measured via the point sensor. The controller calculates a proportional output voltage signal from the measured vibration, and transmits the output signal to the actuator to substantially cancel the vibration in proximity to each actuator.

  4. Temperature-dependent skyhook control of HMMWV suspension using a fail-safe magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Liu, Yanming; Gordaninejad, Faramarz; Evrensel, Cahit A.; Dogruer, Umit; Yeo, Moon-Su; Karakas, Enver S.; Fuchs, Alan

    2003-08-01

    In this paper, a theoretical study is presented to examine the behavior a fail-safe magneto-rheological fluid (MRF) damper based on a temperature compensated skyhook strategy for a quarter car model of a High Mobility Multi-purpose Wheeled Vehicle (HMMWV). A fail-safe MRF damper is a controllable semi-active device that in the event of power or control system failure behaves as a passive damper with certain viscous damping capacity. The damper's viscous force changes significantly with temperature. Vehicle suspension system is required to operate in a wide range of temperature. The temperature effects on the performance of MRF damper should be considered in the control system design. Displacement and acceleration response of the vehicle sprung mass for the quarter car model are discussed at the operating temperature range of a MRF damper. Simulation results under off-road excitation demonstrated that the compensated skyhook control system improves MRF damper performance in reducing the sprung mass displacement and acceleration compared to the uncompensated skyhook control system.

  5. Activities of the Institute of Sound and Vibration Research

    NASA Astrophysics Data System (ADS)

    Research in fluid dynamics, acoustics, automotive engineering, audiology, noise and vibration effects (on human beings), and structural response to noise and vibration was carried out. Aircraft noise, acoustics of flow duct systems and enclosures, acoustic modeling, sound propagation, and acoustic measurement techniques were studied. Auditory and vestibular functions and electrophysiology were investigated.

  6. Lateral dampers for thrust bearings

    NASA Technical Reports Server (NTRS)

    Hibner, D. H.; Szafir, D. R.

    1985-01-01

    The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

  7. Performance of active vibration control technology: the ACTEX flight experiments

    NASA Astrophysics Data System (ADS)

    Nye, T. W.; Manning, R. A.; Qassim, K.

    1999-12-01

    This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I (ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 °C to 129 °C. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed

  8. A new adaptive hybrid electromagnetic damper: modelling, optimization, and experiment

    NASA Astrophysics Data System (ADS)

    Asadi, Ehsan; Ribeiro, Roberto; Behrad Khamesee, Mir; Khajepour, Amir

    2015-07-01

    This paper presents the development of a new electromagnetic hybrid damper which provides regenerative adaptive damping force for various applications. Recently, the introduction of electromagnetic technologies to the damping systems has provided researchers with new opportunities for the realization of adaptive semi-active damping systems with the added benefit of energy recovery. In this research, a hybrid electromagnetic damper is proposed. The hybrid damper is configured to operate with viscous and electromagnetic subsystems. The viscous medium provides a bias and fail-safe damping force while the electromagnetic component adds adaptability and the capacity for regeneration to the hybrid design. The electromagnetic component is modeled and analyzed using analytical (lumped equivalent magnetic circuit) and electromagnetic finite element method (FEM) (COMSOL® software package) approaches. By implementing both modeling approaches, an optimization for the geometric aspects of the electromagnetic subsystem is obtained. Based on the proposed electromagnetic hybrid damping concept and the preliminary optimization solution, a prototype is designed and fabricated. A good agreement is observed between the experimental and FEM results for the magnetic field distribution and electromagnetic damping forces. These results validate the accuracy of the modeling approach and the preliminary optimization solution. An analytical model is also presented for viscous damping force, and is compared with experimental results The results show that the damper is able to produce damping coefficients of 1300 and 0-238 N s m-1 through the viscous and electromagnetic components, respectively.

  9. Vibrational spectra and antimicrobial activity of selected bivalent cation benzoates

    NASA Astrophysics Data System (ADS)

    Borawska, M. H.; Koczoń, P.; Piekut, J.; Świsłocka, R.; Lewandowski, W.

    2009-02-01

    Selected bands of FT-IR spectra of Mg(II), Ca(II), Cu(II) and Zn(II) benzoates of both solid state and water solution, were assigned to appropriate molecular vibrations. Next evaluation of electronic charge distribution in both carboxylic anion and aromatic ring of studied compounds was performed. Classical plate tests and turbidimetry measurements, monitoring growth of bacteria Escherichia coli, Bacillus subtilis and yeasts Pichia anomala and Saccharomyces cerevisiae during 24 h of incubation, in optimal growth conditions (control) and in medium with addition of studied benzoate (concentration of 0.01% expressed as the concentration of benzoic acid), proved antimicrobial activity of studied compounds against investigated micro-organisms. PLS (partially least square) and PCR (principal component regression) techniques were applied to build a model, correlating spectral data reflecting molecular structure of studied compounds, with degree of influence of those compounds on growth of studied micro-organisms. Statistically significant correlation within cross validation diagnostic of PLS-1 calibration was found, when log 1/T of selected spectral regions of water solution samples were used as input data. The correlation coefficients between predicted with PLS calibration based on created 1, 2 or 3 factor models, and actual values of antimicrobial activity were: 0.70; 0.76, 0.81 for P. anomala, B. subtilis, and E. coli, respectively. Log(PRESS) values of appropriate models were 2.10, 2,39 and 3.23 for P. anomala, B. subtilis, and E. coli, respectively.

  10. Damping performance of bean bag dampers in zero gravity environments

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Chen, Tianning; Wang, Xiaopeng

    2016-06-01

    Bean bag dampers (BBDs), developed from impact damping technology, have been widely applied in engineering field to attenuate the vibration of a structural system. The damping effect of a BBD on vibration control in ground gravity environments is good, but its performance in zero gravity environments is not clear, and there are few studies on it. Therefore, the damping effect of BBDs in zero gravity environments was investigated based on the discrete element method (DEM) in this paper. Firstly, a three-dimensional DEM model of a BBD was established, and the damping effects of the single degree of freedom (SDOF) systems with BBDs and non-obstructive particle dampers (NOPDs) in zero gravity environments were compared. Moreover, the influences of the diameter of the inner ball, the tightness of BBD, the vibration frequency of SDOF system and the gap between BBD and cavity on the vibration reduction effect of BBD in zero gravity environments were also studied, and the results were compared with the system with BBD in ground gravity environments. There are optimum ranges of the diameter of the inner ball, tightness and gap for BBD, and the effects of these parameters on the damping performances of BBD in gravity and zero gravity environments are similar in evolving trends, and the values are without big differences in the optimum ranges. Thereby the parameter selection in BBD design in zero gravity environments is similar to that in gravity environments. However, the diameter of BBD should be a slightly larger than the size of the cavity when the structures with BBD work in zero gravity environments. The BBD is supposed to be picked tightly when the vibration frequency is high, and the BBD has better to be picked more tightly in zero gravity environments. These results can be used as a guide in the design of BBDs in zero gravity environments.

  11. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    NASA Astrophysics Data System (ADS)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  12. Analysis of start-up transient for a powertrain system with a nonlinear clutch damper

    NASA Astrophysics Data System (ADS)

    Li, Laihang; Singh, Rajendra

    2015-10-01

    The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with a focus on the nonlinear characteristics of a multi-staged clutch damper. First, a four-degree-of-freedom torsional model with multiple discontinuous nonlinearities under flywheel motion input is developed, and the powertrain transient event is validated with a vehicle start-up experiment. Second, the role of the nonlinear torsional path on the transient event is investigated in the time and time-frequency domains; interactions between the clutch damper and the transmission transients are estimated by using two metrics. Third, the harmonic balance method is applied to examine the nonlinear characteristics of clutch damper during a slowly varying non-stationary process in a simplified and validated single-degree-of-freedom powertrain system model. Finally, analytical formulas are successfully developed and verified to approximate the nonlinear amplification level for a rapidly varying process.

  13. Measuring the performance of underplatform dampers for turbine blades by rotating laser Doppler Vibrometer

    NASA Astrophysics Data System (ADS)

    Zucca, S.; Di Maio, D.; Ewins, D. J.

    2012-10-01

    Underplatform friction dampers are commonly used to control the vibration level of turbine blades in order to prevent high-cycle fatigue failures. Experimental validation of highly non-linear response predictions obtained from FEM bladed disk models incorporating underplatform dampers models has proved to be very difficult so as the assessment of the performance of a chosen design. In this paper, the effect of wedge-shaped underplatform dampers on the dynamics of a simple bladed disk under rotating conditions is measured and the effect of the excitation level on the UPDs performances is investigated at different number of the engine order excitation nearby resonance frequencies of the 1st blade bending modes of the system. The measurements are performed with an improved configuration of a rotating test rig, designed with a non-contact magnetic excitation and a non-contact rotating SLDV measurement system.

  14. Vibration suppression of advanced space cryocoolers: an overview

    NASA Astrophysics Data System (ADS)

    Ross, Ronald G., Jr.

    2003-07-01

    Mechanical cryocoolers represent a significant enabling technology for precision space instruments by providing cryogenic temperatures for sensitive infrared, gamma-ray, and x-ray detectors. However, the vibration generated by the cryocooler's refrigeration compressor has long been identified as a critical integration issue. The key sensitivity is the extent to which the cooler's vibration harmonics excite spacecraft resonances and prevent on-board sensors from achieving their operational goals with respect to resolution and pointing accuracy. To reduce the cryocooler's vibration signature to acceptable levels, a variety of active vibration suppression technologies have been developed and implemented over the past 15 years. At this point, nearly all space cryocoolers have active vibration suppression systems built into their drive electronics that reduce the peak unbalanced forces to less than 1% of their original levels. Typical systems of today individually control the vibration in each of the cryocoolers lowest drive harmonics, with some controlling as many as 16 harmonics. A second vibration issue associated with cryocoolers is surviving launch. Here the same pistons and coldfingers that generate vibration during operation are often the most critical elements in terms of surviving high input acceleration levels. Since electrical power is generally not available during launch, passive vibration suppression technologies have been developed. Common vibration damping techniques include electrodynamic braking via shorted motor coils and the use of particle dampers on sensitive cryogenic elements. This paper provides an overview of the vibration characteristics of typical linear-drive space cryocoolers, outlines their history of development, and presents typical performance of the various active and passive vibration suppression systems being used.

  15. Design and characterization of axial flux permanent magnet energy harvester for vehicle magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Dong, Xiaomin

    2016-01-01

    An axial flux permanent magnet energy harvester (AFPMEH) is proposed and analyzed for a vehicle magneto-rheological (MR) damper. The relationship between the output voltage and the input excitations are analytically developed. Under different constant rotation speeds and sinusoidal excitations, the harvesting energy is numerically computed for different loads of pure resistance and coil in the MR damper. To check the performance of the proposed AFPMEH for the MR damper, the AFPMEH and MR damper are fabricated individually. Experiments are performed to measure the harvesting energy of the AFPMEH and the damping characteristics of the MR damper under different excited conditions. The excited conditions include three constant rotation speeds and sinusoidal inputs. Load inputs of the pure resistance and the coil of the MR damper are considered. The results show that the time history of the generated voltage of the AFPMEH in experiment is agreed well with that of the AFPMEH in simulation. Under constant rotation speeds, the root mean square (rms) of loaded voltage will increase with the increment of load, whereas the rms of power will be affected by the amplitude of load. The MR damper powered by the AFPMEH can almost obtain the similar damping characteristics of that external power supply. Under sinusoidal inputs, the rms of loaded voltage will increase with the increment of external loads, whereas the rms of power will be almost kept as a constant. The damping range of the MR damper can also be enlarged over 30% comparing to off-state damping force. A quarter car model with an MR damper powered by the AFPMEH is developed to investigate the control performance. The on-off skyhook control is adopted to tune the input current of the MR damper. The vibration performance of the MR suspension is investigated under different roads and vehicle speeds. The numerical results show that the MR suspension with the AFPMEH under on-off skyhook control can achieve better ride comfort

  16. Note: A three-dimension active vibration isolator for precision atom gravimeters

    SciTech Connect

    Zhou, Min-Kang; Xiong, Xin; Chen, Le-Le; Cui, Jia-Feng; Duan, Xiao-Chun; Hu, Zhong-Kun

    2015-04-15

    An ultra-low frequency active vibration isolator, simultaneously suppressing three-dimensional vibration noise, is demonstrated experimentally. The equivalent natural period of the isolator is 100 s and 12 s for the vertical and horizontal direction, respectively. The vibration noise in the vertical direction is about 50 times reduced during 0.2 and 2 Hz, and 5 times reduced in the other two orthogonal directions in the same frequency range. This isolator is designed for atom gravimeters, especially suitable for the gravimeter whose sensitivity is limited by vibration couplings.

  17. Molecular vibration-activity relationship in the agonism of adenosine receptors.

    PubMed

    Chee, Hyun Keun; Oh, S June

    2013-12-01

    The molecular vibration-activity relationship in the receptor-ligand interaction of adenosine receptors was investigated by structure similarity, molecular vibration, and hierarchical clustering in a dataset of 46 ligands of adenosine receptors. The resulting dendrogram was compared with those of another kind of fingerprint or descriptor. The dendrogram result produced by corralled intensity of molecular vibrational frequency outperformed four other analyses in the current study of adenosine receptor agonism and antagonism. The tree that was produced by clustering analysis of molecular vibration patterns showed its potential for the functional classification of adenosine receptor ligands. PMID:24465242

  18. Molecular Vibration-Activity Relationship in the Agonism of Adenosine Receptors

    PubMed Central

    Chee, Hyun Keun

    2013-01-01

    The molecular vibration-activity relationship in the receptor-ligand interaction of adenosine receptors was investigated by structure similarity, molecular vibration, and hierarchical clustering in a dataset of 46 ligands of adenosine receptors. The resulting dendrogram was compared with those of another kind of fingerprint or descriptor. The dendrogram result produced by corralled intensity of molecular vibrational frequency outperformed four other analyses in the current study of adenosine receptor agonism and antagonism. The tree that was produced by clustering analysis of molecular vibration patterns showed its potential for the functional classification of adenosine receptor ligands. PMID:24465242

  19. Active vibration control for high speed train bogies

    NASA Astrophysics Data System (ADS)

    Peiffer, Alexander; Storm, Stefan; Röder, Arno; Maier, Rudolf; Frank, Paul-Gerhard

    2005-02-01

    This report deals with the design of an active vibration control (AVC) system integrated into the primary suspension of the bogie of a German high-speed train (ICE). As a design case a prototype bogie (WU92) for the ICE2 was taken. This paper comprises all parts and stages of the development of an AVC system. First, a transfer path analysis was performed in order to identify the main paths of propagation and to determine the boundary conditions at the actuator contact points. A detailed FE-analysis performed on the basis of an already existing FE-model serves as a support to investigate the actuator performance and evaluate several actuator concepts. However, the evaluation of a multifold of varying configurations of actuator, error sensor and monitor sensor positions is obviously not possible in the experiment, but is in the simulation. Based on the simulations and the experiments the control system is implemented on a digital signal processor (DSP) system. The structure borne noise level was determined during running tests at the ICE3 and measurements at the WU92 installed in the test rig. The design of the actuator system includes the layout of the specific system as well as the selection of the piezoelectric elements. A specifically developed amplifier drives the actuators. Finally the system is integrated into one axle of the WU92 and tested during roller-rig measurements.

  20. Development of a Practical Broadband Active Vibration Control System

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Perey, Daniel F.; Cabell, Randolph H.

    2011-01-01

    The goal of this work is to develop robust, lightweight, and low-power control units that can be used to suppress structural vibration in flexible aerospace structures. In particular, this paper focuses on active damping, which is implemented using compact decentralized control units distributed over the structure. Each control unit consists of a diamond-shaped piezoelectric patch actuator, three miniature accelerometers, and analog electronics. The responses from the accelerometers are added together and then integrated to give a signal proportional to velocity. The signal is then inverted, amplified, and applied to the actuator, which generates a control force that is out of phase with the measured velocity. This paper describes the development of the control system, including a detailed description of the control and power electronics. The paper also presents experimental results acquired on a Plexiglas window blank. Five identical control units installed around the perimeter of the window achieved 10 dB peak reductions and a 2.4 dB integrated reduction of the spatially averaged velocity of the window between 500 and 3000 Hz.

  1. Variable stiffness and damping semi-active vibration control technology based on magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Zhao, Shiyu; Deng, Huaxia; Zhang, Jin; Sun, ShuaiShuai; Li, Weihua; Wang, Lei

    2013-10-01

    Vibration is a source to induce uncertainty for the measurement. The traditional passive vibration control method has low efficiency and limited working conditions. The active vibration control method is not practical for its power demanding, complexity and instability. In this paper, a novel semi-active vibration control technology based on magnetorheological (MR) fluid is presented with dual variable stiffness and damping capability. Because of the rheological behavior depending on the magnetic field intensity, MR fluid is used in many damping semi-active vibration control systems. The paper proposed a structure to allow the both overall damping and stiffness variable. The equivalent damping and stiffness of the structure are analyzed and the influences of the parameters on the stiffness and damping changing are further discussed.

  2. Activities of the Institute of Sound and Vibration Research

    NASA Astrophysics Data System (ADS)

    Research in fluid dynamics and acoustics, vehicle noise, audiology and human effects, industrial noise, and noise and vibration control is summarized. Aircraft noise, underwater acoustics, damping of fiber reinforced materials and finite element methods are discussed.

  3. Passive and Active Vibrations Allow Self-Organization in Large-Scale Electromechanical Systems

    NASA Astrophysics Data System (ADS)

    Buscarino, Arturo; Fortuna, Carlo Famoso Luigi; Frasca, Mattia

    2016-06-01

    In this paper, the role of passive and active vibrations for the control of nonlinear large-scale electromechanical systems is investigated. The mathematical model of the system is discussed and detailed experimental results are shown in order to prove that coupling the effects of feedback and vibrations elicited by proper control signals makes possible to regularize imperfect uncertain large-scale systems.

  4. Development and performance evaluation of an MR squeeze-mode damper

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan; Gołdasz, Janusz

    2015-11-01

    In this paper the authors present results of a magnetorheological (MR) damper prototype development and performance evaluation study. The damper is a device functioning in the so-called squeeze-mode of MR fluid flow regime of operation. By principle, in a squeeze-mode damper the control (working) gap height varies according to the prescribed displacement or force input profile. Such hardware has been claimed to be well suited to small-amplitude vibration damping applications. However, it is still in its infancy. Its potential seems appealing yet unclear. Accordingly, the authors reveal performance figures of the damper complemented by numerical finite-element simulations of the electro-magnetic circuit of the device. The numerical results are presented in the form of maps of averaged magnetic flux density versus coil current and gap height as well as magnetic flux, inductance, and cogging force calculations, respectively. The simulated data are followed by experimental evaluation of the damper performance incorporating plots of force versus piston displacement (velocity) across a prescribed range of excitation inputs. Moreover, some insight into transient (unsteady) characteristics of the device is provided through testing results involving transient currents.

  5. Damper design for improving S/N ratio of the seismocardiogram monitoring in the OpenMRI-guided operating theater.

    PubMed

    Naemura, K; Iseki, H

    2004-01-01

    The final goal of this study is to establish a method of measuring precisely the seismocardiogram (SCG) of a patient who lying in an open magnetic resonance imaging (openMRI) machine for myocardial ischemia monitoring during surgery. Vibration isolation from the gantry vibration during MRI scan is essential for clinical use. Authors previously reported the comparison between the SCG and the gantry vibration. A damper to decrease vibration below 30 Hz should be designed. In this paper, authors fabricated a damper model to check the feasibility of the damping effect, and compared with the patient bed mat. Experiment using a vibrator showed 1) the viscosity damping coefficient of the current damper was 2 kN s/m, 2) owing to the damper, peak ratio between input and output amplitude decreased from 2.5 to 1.2, and 3) natural frequency decreased from 12 Hz to 5 Hz. Damping below 30 Hz was successfully achieved. The maximum S/N ratio was calculated 6, improving from 1.8. Simulation showed that the maximum S/N would be 75 under the viscosity damping coefficient of 1 N s/m. PMID:17271021

  6. On the computation of damped wind-excited vibrations of overhead transmission lines

    NASA Astrophysics Data System (ADS)

    Hagedorn, P.

    1982-07-01

    In the calculation of wind-excited overhead transmission line vibrations with Stockbridge dampers the damper behaviour is usually represented by its impedance corresponding to a vertical translatory damper clamp motion. The moments introduced by the damper clamp into the cable are normally disregarded. In this paper the dampers are characterized by means of a 2×2 complex impedance matrix which can be experimentally determined in the laboratory and which includes the effects of the rotatory motion of the clamp. The energy balance method is then adapted to this case and the bending strains in the cable are calculated at the dangerous points. It turns out that the moments introduced by the damper into the cable are of little or no importance with regard to the energy absorbed. They may however affect strongly the local bending strains in the cable at the damper clamp.

  7. Improved syncom-type fluid damper

    NASA Technical Reports Server (NTRS)

    Evans, J.

    1974-01-01

    Two efficient types of fluid nutation dampers that are simple, reliable, and inexpensive have been developed. In use, either damper may be mounted on a spinning body, parallel to the spin axis of the body and radially displaced from it, to eliminate nutation.

  8. The Tevatron bunch by bunch longitudinal dampers

    SciTech Connect

    Cheng-Yang Tan and James Steimel

    2002-09-25

    We describe in this paper the Tevatron bunch by bunch dampers. The goal of the dampers is to stop the spontaneous longitudinal beam size blowup of the protons during a store. We will go through the theory and also show the measured results during the commissioning of this system. The system is currently operational and have stopped the beam blowups during a store.

  9. Damper mechanism for nuclear reactor control elements

    DOEpatents

    Taft, William Elwood

    1976-01-01

    A damper mechanism which provides a nuclear reactor control element decelerating function at the end of the scram stroke. The total damping function is produced by the combination of two assemblies, which operate in sequence. First, a tapered dashram assembly decelerates the control element to a lower velocity, after which a spring hydraulic damper assembly takes over to complete the final damping.

  10. Docking-mechanism attenuator with electromechanical damper

    NASA Technical Reports Server (NTRS)

    Syromyatnikov, V. S.

    1971-01-01

    Theoretical and practical problems involved in the application of electromechanical damping for spacecraft docking-mechanism attenuation are discussed. Some drawbacks of hydraulic dampers used for the purpose are pointed out. The basic scheme of the attenuator with the electromechanical damper is given.

  11. Active Control of Panel Vibrations Induced by a Boundary Layer Flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1998-01-01

    In recent years, active and passive control of sound and vibration in aeroelastic structures have received a great deal of attention due to many potential applications to aerospace and other industries. There exists a great deal of research work done in this area. Recent advances in the control of sound and vibration can be found in the several conference proceedings. In this report we will summarize our research findings supported by the NASA grant NAG-1-1175. The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to study the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. The vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings will be presented in the next three sections. In Section II we shall describe our results on the boundary control of nonlinear panel vibration, with or without flow excitation. Section III is concerned with active control of the vibration and sound radiation from a nonlinear elastic panel. A detailed description of our work on the parametric vibrational control of nonlinear elastic panel will be presented in Section IV. This paper will be submitted to the Journal

  12. Multi-objective evolutionary optimization design of vehicle magnetorheological fluid damper

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Wang, Yang; Gao, Fang

    2007-07-01

    Structure design and parameters selection are crucial steps in developing magnetorheological fluid (MRF) damper for vehicle semi-active suspension system. Most traditional methods for deciding structure parameters by experiential expressions are unilateral and imprecise. In this paper, a multiobjective evolutionary optimization approach will be used to solve the optimization design problem. Based on Bingham fluid models, a structure design for MRF damper with shearing valve mode is completed for vehicle suspension. To reduce the dynamic response time and to enlarge the range the controllable damping force are taken as the optimization objectives. Three crucial parameters, including gap width, effective axial pole length and coil turns number are taken as optimization variables, a hybrid evolutionary algorithm combining particle swarm optimization (PSO) and crossover is employed to search for the Pareto solutions, According to the optimized results, a new type MRF damper design is accomplished for a pickup truck suspension system. The proposed method and analysis present a beneficial reference for MRF damper design.

  13. Stability Analysis of a High-Speed Seal Test Rotor With Marginal and Extended Squeeze-Film Dampers: Theoretical and Experimental Results

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Gunter, Edgar J.

    2007-01-01

    A case study of a high-speed seal test rotor shows how rotor dynamic analysis can be used to diagnose the source of high vibrations and evaluate a proposed remedy. Experimental results are compared with the synchronous and non-synchronous whirl response analysis of a double overhung, high-speed seal test rotor with ball bearings supported in 5.84- and 12.7-mm-long, un-centered squeeze-film oil dampers. Test performance with the original damper of length 5.84 mm was marginal. Non-synchronous whirling occurred at the overhung seal test disk and there was a high amplitude synchronous response near the drive spline above 32,000 rpm. Nonlinear synchronous unbalance and time transient whirl studies were conducted on the seal test rotor with the original and extended damper lengths. With the original damper design, the nonlinear synchronous response showed that unbalance could cause damper lockup at 33,000 rpm. Alford cross-coupling forces were also included at the overhung seal test disk for the whirl analysis. Sub-synchronous whirling at the seal test disk was observed in the nonlinear time transient analysis. With the extended damper length of 12.7 mm, the sub-synchronous motion was eliminated and the rotor unbalance response was acceptable to 45,000 rpm with moderate rotor unbalance. Seal test rotor orbits and vibration levels with the extended squeeze film dampers showed smooth operation to 40,444 rpm.

  14. Acute Effects of Whole-Body Vibration on Trunk and Neck Muscle Activity in Consideration of Different Vibration Loads

    PubMed Central

    Perchthaler, Dennis; Hauser, Simon; Heitkamp, Hans-Christian; Hein, Tobias; Grau, Stefan

    2015-01-01

    The intention of this study was to systematically analyze the impact of biomechanical parameters in terms of different peak-to-peak displacements and knee angles on trunk and neck muscle activity during whole-body vibration (WBV). 28 healthy men and women (age 23 ± 3 years) performed four static squat positions (2 peak-to-peak displacements x 2 knee angles) on a side alternating vibration platform with and without vibration stimulus. Surface electromyography (EMG) was used to record the neuromuscular activity of the erector spinae muscle, the rectus abdominis muscle, and of the splenius muscle. EMG levels normalized to maximal voluntary contractions ranged between 3.2 – 27.2 % MVC during WBV. The increase in muscle activity caused by WBV was significant, particularly for the back muscles, which was up to 19.0 % MVC. The impact of the factor ‘condition’ (F-values ranged from 13.4 to 132.0, p ≤ 0.001) and of the factor ‘peak-to-peak displacement’ (F-values ranged from 6.4 to 69.0 and p-values from < 0.001 to 0.01) were statistically significant for each muscle tested. However, the factor ‘knee angle’ only affected the back muscles (F-value 10.3 and 7.3, p ≤ 0.01). The results of this study should give more information for developing effective and safe training protocols for WBV treatment of the upper body. Key points The maximum levels of muscle activity were significantly reached at high amplitudes at a vibration frequency of 30 Hz. WBV leads to a higher muscle activation of the lower back muscles than of the abdominal muscles. Both knee angles of 30° and 45° have similar effects on the vibration load and represent safe positions to prevent any actual harm. Certain combinations of the biomechanical variables have similar effects on the level of muscle activity. PMID:25729303

  15. Active Outer Hair Cells Affect the Sound-Evoked Vibration of the Reticular Lamina

    NASA Astrophysics Data System (ADS)

    Jacob, Stefan; Fridberger, Anders

    2011-11-01

    It is well established that the organ of Corti uses active mechanisms to enhance its sensitivity and frequency selectivity. Two possible mechanisms have been identified, both capable of producing mechanical forces, which can alter the sound-evoked vibration of the hearing organ. However, little is known about the effect of these forces on the sound-evoked vibration pattern of the reticular lamina. Current injections into scala media were used to alter the amplitude of the active mechanisms in the apex of the guinea pig temporal bone. We used time-resolved confocal imaging to access the vibration pattern of individual outer hair cells. During positive current injection the the sound-evoked vibration of outer hair cell row three increased while row one showed a small decrease. Negative currents reversed the observed effect. We conclude that the outer hair cell mediated modification of reticular lamina vibration patterns could contribute to the inner hair cell stimulation.

  16. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    PubMed Central

    Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok

    2013-01-01

    In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water. PMID:23389344

  17. Dynamic performance and control of squeeze mode MR fluid damper rotor system

    NASA Astrophysics Data System (ADS)

    Wang, J.; Meng, G.; Feng, N.; Hahn, E. J.

    2005-08-01

    By using magnetorheological (MR) fluid in place of lubricating oil in a traditional squeeze film damper (SFD), one can build a variable-damping SFD, thereby controlling the vibration of a rotor by controlling the magnetic field. Assuming a Bingham model, the Reynolds equation for an MR fluid squeeze film is developed and solved to provide expressions for the velocity, the pressure distribution and the damping force. Electromagnetic theory is used to calculate the magnetic pull force between the magnetic poles in the damper. The mechanical properties of the squeeze film and the unbalance response characteristics of an MR fluid SFD-rigid rotor system are analyzed theoretically. An MR fluid SFD is designed and manufactured, and the unbalance response properties and control method of a flexible rotor supported on the damper are studied experimentally. The study shows that the magnetic pull force can decrease both the first critical speed and the critical amplitude; the film damping force can decrease the amplitude at the undamped critical speeds, but increase the amplitude in a speed range between two undamped critical speeds. The damper may have the best control effect to minimize the vibration within the range of all working speed by using the on-off control method.

  18. Numerical investigation of effectiveness of two seismic dampers on a benchmark structure

    NASA Astrophysics Data System (ADS)

    Qu, J. T.; Yang, W. L.

    2011-07-01

    The passive energy dissipation devices have been widely applied in seismic control of new constructions and reinforcement of seismic damage structures. The technique of passive energy dissipation has been written into the China Seismic Code for Buildings, which can give an impulse to the use and development of this technique. With the international common performance evaluation platform of structural vibration control - the third stage of benchmark, using three models and some performance evaluation indices of nonlinear vibration control, the control results of buildings with displacement-based and velocity-based dampers were compared. Combining the passive control of structures with the modern control theory, using MATLAB/SIMULINK to establish simulation models of the structures with displacement-based and velocity-based dampers, the responses of three benchmark structure models were calculated under far- and near-field earthquakes. Control effect is compared for different types of dampers on different structures through different evaluation indices, which can provide a certain criterion of reference for the application and design of the passive energy dissipation dampers.

  19. Vibration Control in Turbomachinery Using Active Magnetic Journal Bearings

    NASA Technical Reports Server (NTRS)

    Knight, Josiah D.

    1996-01-01

    The effective use of active magnetic bearings for vibration control in turbomachinery depends on an understanding of the forces available from a magnetic bearing actuator. The purpose of this project was to characterize the forces as functions shaft position. Both numerical and experimental studies were done to determine the characteristics of the forces exerted on a stationary shaft by a magnetic bearing actuator. The numerical studies were based on finite element computations and included both linear and nonlinear magnetization functions. Measurements of the force versus position of a nonrotating shaft were made using two separate measurement rigs, one based on strain gage measurement of forces, the other based on deflections of a calibrated beam. The general trends of the measured principal forces agree with the predictions of the theory while the magnitudes of forces are somewhat smaller than those predicted. Other aspects of theory are not confirmed by the measurements. The measured forces in the normal direction are larger than those predicted by theory when the rotor has a normal eccentricity. Over the ranges of position examined, the data indicate an approximately linear relationship between the normal eccentricity of the shaft and the ratio of normal to principal force. The constant of proportionality seems to be larger at lower currents, but for all cases examined its value is between 0.14 and 0.17. The nonlinear theory predicts the existence of normal forces, but has not predicted such a large constant of proportionality for the ratio. The type of coupling illustrated by these measurements would not tend to cause whirl, because the coupling coefficients have the same sign, unlike the case of a fluid film bearing, where the normal stiffness coefficients often have opposite signs. They might, however, tend to cause other self-excited behavior. This possibility must be considered when designing magnetic bearings for flexible rotor applications, such as gas

  20. Damping Control of Liquid Container by Swing-type Active Vibration Reducer on Mobile Robot

    NASA Astrophysics Data System (ADS)

    Hamaguchi, Masafumi; Taniguchi, Takao

    This paper proposes a damping control of sloshing in a cylindrical container with a swing-type active vibration reducer on a wheeled mobile robot (WMR). The WMR runs along a straight path on a horizontal plane. The container is mounted on the active vibration reducer. A laser displacement sensor is used to observe the liquid level in the container. The container can be tilted in the running direction by the active vibration reducer. A sloshing model is obtained from a spherical pendulum-type sloshing model, which approximately expresses (1, 1)-mode sloshing. The sloshing model is used to design a damping control system. The control system of the active vibration reducer is designed with an inverse model of sloshing and an optimal regulator with a Kalman filter. The WMR is driven by an acceleration pattern designed with an input shaping method. The usefulness of the proposed method is demonstrated through simulation and experimental results.

  1. Electromechanical simulation and test of rotating systems with magnetic bearing or piezoelectric actuator active vibration control

    NASA Technical Reports Server (NTRS)

    Palazzolo, Alan B.; Tang, Punan; Kim, Chaesil; Manchala, Daniel; Barrett, Tim; Kascak, Albert F.; Brown, Gerald; Montague, Gerald; Dirusso, Eliseo; Klusman, Steve

    1994-01-01

    This paper contains a summary of the experience of the authors in the field of electromechanical modeling for rotating machinery - active vibration control. Piezoelectric and magnetic bearing actuator based control are discussed.

  2. Effect of vertical active vibration isolation on tracking performance and on ride qualities

    NASA Technical Reports Server (NTRS)

    Dimasi, F. P.; Allen, R. E.; Calcaterra, P. C.

    1972-01-01

    An investigation to determine the effect on pilot performance and comfort of an active vibration isolation system for a commercial transport pilot seat is reported. The test setup consisted of: a hydraulic shaker which produced random vertical vibration inputs; the active vibration isolation system; the pilot seat; the pilot control wheel and column; the side-arm controller; and a two-axis compensatory tracking task. The effects of various degrees of pilot isolation on short-term (two-minute) tracking performance and comfort were determined.

  3. Suppressing Vertical Vibration in Railway Vehicles through Primary Suspension Damping Force Control

    NASA Astrophysics Data System (ADS)

    Sugahara, Yoshiki; Takigami, Tadao; Sampei, Mitsuji

    Suppression of the vertical bending vibration of carbodies has recently become essential in improving the riding comfort of railway vehicles. In many cases, the resonant frequency of the system (consisting of a bogie frame and axle springs) is close to that of the first mode bending vibration of the carbody, so suppressing the vibration of bogie frames near their resonant frequency effectively reduces carbody vibration. In this paper, we propose a method of suppressing such vibration by controlling the damping force of axle dampers installed between bogie frames and wheel sets. The design of the semi-active controller applied to determine the optimal damping force is based on the sky hook control theory. Numerical simulations using a vehicle model with 16 degrees of freedom as well as excitation tests using a carbody with variable axle dampers at a rolling stock test plant were carried out. The results show that this control method effectively reduces the power spectral density (PSD) of acceleration on the floor and that the riding comfort level (LT) can be improved by about 3 dB.

  4. Dynamic response time of a metal foam magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Yan, Yao X.; Hui, Liu X.; M, Yu; J, Fu; Dong, Liao H.

    2013-02-01

    Magneto-rheological (MR) dampers are a promising type of semi-active control device for various dynamic systems. Recently, low-cost MR dampers without any sealing structure have been required. Motivated by the desire to overcome the need for the costly dynamic seals of conventional MR dampers, a new type of metal foam MR damper is proposed in this study and the dynamic response performance is also investigated. The metal foam is firmly adhered to a working cylinder to store the unexcited MR fluids. In the action of a magnetic field, MR fluids will be extracted from the metal foam and fill up the shear gap to produce the MR effect. Three time parameters related to response time are introduced to further describe the dynamic response process. The results show that, due to the period required for extracting the MR fluids out from the metal foam, the time to produce the damper force of the metal foam MR damper is longer than for conventional fluid-filled MR dampers. The response time of the metal foam MR damper will change with different currents and shear rates. Given a constant shear rate, in a small range of currents (0-1.5 A), the response time decreases rapidly as the operating current increases; however, there is a slower change rate in larger ranges. To evaluate the effect of shear rate on response time, shear rates ranging from 2 to 10 s-1 are tested, and the results demonstrate that with increasing shear rates the response time decreases.

  5. Experimental analysis of large capacity MR dampers with short- and long-stroke

    NASA Astrophysics Data System (ADS)

    Zemp, René; de la Llera, Juan Carlos; Weber, Felix

    2014-12-01

    The purpose of this article is to study and characterize experimentally two magneto-rheological dampers with short- and long-stroke, denoted hereafter as MRD-S and MRD-L. The latter was designed to improve the Earthquake performance of a 21-story reinforced concrete building equipped with two 160 ton tuned pendular masses. The MRD-L has a nominal force capacity of 300 kN and a stroke of ±1 m; the MRD-S has a nominal force capacity of 150 kN, and a stroke of ±0.1 m. The MRD-S was tested with two different magneto-rheological and one viscous fluid. Due to the presence of Eddy currents, both dampers show a time lag between current intensity and damper force as the magnetization on the damper changes in time. Experimental results from the MRD-L show a force drop-off behavior. A decrease in active-mode forces due to temperature increase is also analyzed for the MRD-S and the different fluids. Moreover, the observed increase in internal damper pressure due to energy dissipation is evaluated for the different fluids in both dampers. An analytical model to predict internal pressure increase in the damper is proposed that includes as a parameter the concentration of magnetic particles inside the fluid. Analytical dynamic pressure results are validated using the experimental tests. Finally, an extended Bingham fluid model, which considers compressibility of the fluid, is also proposed and validated using damper tests.

  6. A programmable broadband low frequency active vibration isolation system for atom interferometry.

    PubMed

    Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng

    2014-09-01

    Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment. PMID:25273709

  7. Active control of panel vibrations induced by a boundary layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1995-01-01

    The problems of active and passive control of sound and vibration has been investigated by many researchers for a number of years. However, few of the articles are concerned with the sound and vibration with flow-structure interaction. Experimental and numerical studies on the coupling between panel vibration and acoustic radiation due to flow excitation have been done by Maestrello and his associates at NASA/Langley Research Center. Since the coupled system of nonlinear partial differential equations is formidable, an analytical solution to the full problem seems impossible. For this reason, we have to simplify the problem to that of the nonlinear panel vibration induced by a uniform flow or a boundary-layer flow with a given wall pressure distribution. Based on this simplified model, we have been able to consider the control and stabilization of the nonlinear panel vibration, which have not been treated satisfactorily by other authors. Although the sound radiation has not been included, the vibration suppression will clearly reduce the sound radiation power from the panel. The major research findings are presented in three sections. In section two we describe results on the boundary control of nonlinear panel vibration, with or without flow excitation. Sections three and four are concerned with some analytical and numerical results in the optimal control of the linear and nonlinear panel vibrations, respectively, excited by the flow pressure fluctuations. Finally, in section five, we draw some conclusions from research findings.

  8. Transmission of whole-body vibration and its effect on muscle activation.

    PubMed

    Tankisheva, Ekaterina; Jonkers, Ilse; Boonen, Steven; Delecluse, Christophe; van Lenthe, G Harry; Druyts, Hans L J; Spaepen, Pieter; Verschueren, Sabine M P

    2013-09-01

    The aim of current study was to measure the transmission of whole-body vibration through the entire body and to relate this to body posture and induced muscular activation. Eight clinically healthy subjects performed 3 static body postures-high squat (135°), deep squat (110°), and erect stance, whereas vibration transmission was assessed over a wide range of accelerations (from 0.33 to 7.98 g) and frequencies (from 30 to 50 Hz). To assess the vibration transmission, 9 triaxial accelerometers were attached from the ankle up to the head and the root mean square of acceleration signal of each site-specific body point was calculated. Additionally, muscle activity from 7 lower limb muscles was recorded. The results showed a significant attenuation of the platform accelerations transmitted from the feet to the head. Compared with erect stance, knee bent posture significantly diminished vibration transmission at the hip, spine, and the head (p < 0.05). Vibration transmission to the spine was significantly lower in deep vs. high squat (p < 0.05), suggesting that further knee bending may reduce the risk of overloading the spine. Vibration increased the muscle activity in most leg and hip muscles during both squat postures, although, on average, no clear dose-response relationship between the acceleration and/or frequency and muscle response was found. The muscular activation of vastus medialis and rectus femoris showed clear negative correlation to the vibration transmission at the sternum. The specific vibration parameters used in the present study can be considered as safe and suitable for a training program. Moreover, the present results contribute to optimize the most advantageous whole-body vibration protocol and to determine the beneficial effects on muscle and bone. PMID:23222086

  9. Digital control system for space structural dampers

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1984-01-01

    A recently developed concept for a damper was improved by adding a small taper to the proof-mass, and using a proximeter to determine position. Also, an experimental damper was built using a three-inch stroke in place of the standard one-inch stroke. The analog controller initially used was replaced by an independent digital controller slaved to a TRS-80 Model I computer, which also serves as a highly effective, low-cost development system. An overall system concept for the use of proof-mass dampers is presented.

  10. Hom dampers for ALS storage ring RF cavities

    SciTech Connect

    Kwiatkowski, S.; Baptiste, K.; Byrd, J.; DeSantis, S.; Julian, J.; Low, R.; Lyn, L.; Plate, D.

    2003-05-08

    The main source of narrowband impedance in the Advanced Light Source (ALS) are higher order modes (HOMs) of the two main RF and three third harmonic cavities. These HOMs drive longitudinal and transverse coupled bunch instabilities, which are controlled using active beam feedback systems. The dominant longitudinal HOMs in both systems are TM011-like modes with the R/Q factor an order of magnitude higher than all other longitudinal modes. To reduce the growth rates within the range of the longitudinal feedback system (LFB), these modes were tuned away from beam resonances by means of cooling water temperature control (main rf system), and the combination of two tuners (third harmonic system). To improve the reliability of the longitudinal dampening system, we have built and installed E-type HOM dampers for the fundamental and harmonic cavities. We present the design, commissioning and performance of the HOM dampers in this paper.

  11. Proportional-plus-integral semiactive control using magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Aguirre, N.; Ikhouane, F.; Rodellar, J.

    2011-05-01

    Magnetorheological (MR) dampers are a promising alternative to structural active actuators as they provide adjustable damping over a wide range of frequencies without large power requirements. However, the complex dynamics that characterizes these devices makes it difficult to formulate control laws based on the MR damper model. Instead, many semiactive control strategies proposed in the literature have been based on the idea of "clipping" the voltage signal so that the MR damper force "tracks" a desired active control force which is computed on-line. With this idea many algorithms have been proposed using, among others, techniques such as optimal control, H∞ control, sliding mode control, backstepping and QFT. This work presents a semiactive control strategy based on the same idea of "clipping" the voltage signal but using a simpler PI design. The proportional and integral gains of the controller are calculated so that the controller guarantees stability, minimization of the closed loop response and robustness against modeling errors. Effectiveness of the control strategy is compared to some others techniques and passive cases as well. Simulation results shows that this simple strategy can effectively improve the structural responses and achieve performance index comparable to that of more complex algorithms.

  12. Passive damping concepts for free and forced member and grillage vibration

    NASA Technical Reports Server (NTRS)

    Razzaq, Zia; Najjar, Bassam

    1988-01-01

    The performance of potential passive damping concepts is investigted for a long tubular aluminum alloy member, and a two-bar grillage structure. The members are restrained partially at the ends and are of the type being considered by NASA for possible use in the construction of a future space station. Four different passive damping concepts are studied and include nylon brush, wool swab, copper brush, and silly putty in chamber dampers. Both free and forced vibration tests are conducted. It is found that the silly putty in chamber damper concept provides considerably greater passive damping as compared to that of the other three concepts. For the grillage natural vibration, a five wool swab damper configuration provides greater damping than the five silly putty dampers in chamber configuration. Due to the constrained motion imposed by the vibrator used in the tests, the effectiveness of the passive dampers could not be adequately evaluated for the individual member. However, it is found that for the grillage under forced vibration, the five silly putty dampers in chamber damper configuration provides very effective passive damping although only at and around the resonant frequency. At resonance, these dampers provide a 51 percent reduction in the dynamic magnification factor for this case.

  13. An active control system for helicopter vibration reduction by higher harmonic pitch

    NASA Technical Reports Server (NTRS)

    Taylor, R. B.; Farrar, F. A.; Miao, W.

    1980-01-01

    An analytical study defining the basic configuration of an active control system to reduce helicopter vibrations is presented. Theoretical results for a nonlinear four-bladed single rotor helicopter simulation are discussed, showing that vibration reductions on the order of 80-90% for airspeeds up to 150 kn can be expected when using a higher harmonic pitch in an active feedback control system. The rotor performance penalty associated with this level of vibration reduction is about 1-3% and the increase in rotor blade stresses is considered to be low. The location of sensor accelerometers proved to be significant for vibration reductions, and it is noted that the RTSA controller is tolerant of sensor signal noise.

  14. A novel triple-actuating mechanism of an active air mount for vibration control of precision manufacturing machines: experimental work

    NASA Astrophysics Data System (ADS)

    Kim, Hyung-Tae; Kim, Cheol-Ho; Choi, Seung-Bok; Moon, Seok-Jun; Song, Won-Gil

    2014-07-01

    With the goal of vibration control and isolation in a clean room, we propose a new type of air mount which consists of pneumatic, electromagnetic (EM), and magnetorheological (MR) actuators. The air mount is installed below a semiconductor manufacturing machine to reduce the adverse effects caused by unwanted vibration. The proposed mechanism integrates the forces in a parallel connection of the three actuators. The MR part is designed to operate in an air spring in which the EM part is installed. The control logic is developed with a classical method and a switching mode to avoid operational mismatch among the forces developed. Based on extended microprocessors, a portable, embedded controller is installed to execute both nonlinear logic and digital communication with the peripherals. The pneumatic forces constantly support the heavy weight of an upper structure and maintain the level of the air mount. The MR damper handles the transient response, while the EM controller reduces the resonance response, which is switched mutually with a threshold. Vibration is detected by laser displacement sensors which have submicron resolution. The impact test results of three tons load weight demonstrate practical feasibility by showing that the proposed triple-actuating mechanism can reduce the transient response as well as the resonance in the air mount, resulting in accurate motion of the semiconductor manufacturing machine.

  15. Squeeze-film dampers for turbomachinery stabilization

    NASA Technical Reports Server (NTRS)

    Mclean, L. J.; Hahn, E. J.

    1984-01-01

    A technique for investigating the stability and damping present in centrally preloaded radially symmetric multi-mass flexible rotor bearing systems is presented. In general, one needs to find the eigenvalues of the linearized perturbation equations, though zero frequency stability maps may be found by solving as many simultaneous non-linear equations as there are dampers; and in the case of a single damper, such maps may be found directly, regardless of the number of degrees of freedom. The technique is illustrated for a simple symmetric four degree of freedom flexible rotor with an unpressurized damper. This example shows that whereas zero frequency stability maps are likely to prove to be a simple way to delineate multiple solution possibilities, they do not provide full stability information. Further, particularly for low bearing parameters, the introduction of an unpressurized squeeze film damper may promote instability in an otherwise stable system.

  16. Fermilab Recycler damper requirements and design

    SciTech Connect

    Crisp, J.; Hu, M.; Tupikov, V.; /Fermilab

    2005-05-01

    The design of transverse dampers for the Fermilab Recycler storage ring is described. An observed instability and analysis of subsequent measurements where used to identify the requirements. The digital approach being implemented is presented.

  17. A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity

    PubMed Central

    Cidem, Muharrem; Karacan, İlhan; Diraçoğlu, Demirhan; Yıldız, Aysel; Küçük, Suat Hayri; Uludağ, Murat; Gün, Kerem; Özkaya, Murat; Karamehmetoğlu, Şafak Sahir

    2014-01-01

    Background: Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. Aims: The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. Study Design: A prospective, randomised, controlled, double-blind, parallel-group clinical trial. Methods: Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. Results: In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15

  18. Investigation of a model vertical motion liquid damper: comparing numerical simulation and experimental evidence

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Chris; Tabatabai, Habib; Buechel, Craig

    2005-05-01

    Tuned Liquid Dampers (TLD) are used to limit horizontal vibrations in structures, and offer practical alternatives to Tuned Mass Dampers (TMD). However, to our knowledge, liquid damping systems have not been developed to reduce vertical vibrations. In this work, we develop a model for a Vertical Motion Liquid Damper (VMLD), idealized as a discrete, two degree of freedom system. One degree of freedom represents the 'target' structure that is to be damped, and the other represents the approximate, one-dimensional motion of a liquid in a U-shaped tube. Internal losses due to the fluid oscillation serve to limit and control motions of the target structure. The U-shaped tube has a flexible joint such that one vertical portion and the horizontal portion of the tube remain fixed, and the remaining vertical portion of the tube is affixed to the vibrating structure, allowing the liquid to become excited. The equations of motion are derived using Lagrange's Equations, and are integrated using Runge-Kutta algorithms that are available in Matlab. An experimental model was built in the laboratory, consisting of a mass attached to the end of a cantilevered beam (corresponding to the target structure), and a U-tube made from PVC pipe. The various damping and stiffness parameters of the system were calibrated independently based on experimental data. Measured data from the experimental model show reasonable agreement with numerical simulations.

  19. Results from the AGS Booster transverse damper

    SciTech Connect

    Russo, D.; Brennan, M.; Meth, M.; Roser, T.

    1993-01-01

    To reach the design intensity of 1.5 [times] 10[sup 13] protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s[sup [minus]1] have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.

  20. Results from the AGS Booster transverse damper

    SciTech Connect

    Russo, D.; Brennan, M.; Meth, M.; Roser, T.

    1993-06-01

    To reach the design intensity of 1.5 {times} 10{sup 13} protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s{sup {minus}1} have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.

  1. Investigation of squeeze-film dampers

    NASA Technical Reports Server (NTRS)

    Holmes, R.; Dogan, M.

    1982-01-01

    Squeeze film dampers are a means of curing instabilities in rotating shaft assemblies. Their efficiency depends very much on the condition of the oil, which in turn depends on inlet and outlet arrangements, on damper geometry and on the flexibility of the rotor and surrounding structure. Rig investigations in which structural flexibility is included experimentally are discussed. Comparisons are made between measured and predicted results.

  2. Dampers for Natural Draft Heaters: Technical Report

    SciTech Connect

    Lutz, James D.; Biermayer, Peter; King, Derek

    2008-10-27

    Energy required for water heating accounts for approximately 40percent of national residential natural gas consumption in California. With water heating contributing such a substantial portion of natural gas consumption, it is important to pay attention to water heater efficiencies. This paper reports on an investigation of a patented, buoyancy-operated flue damper. It is an add-on design to a standard atmospherically vented natural-draft gas-fired storage water heater. The flue damper was expected to reduce off-cycle standby losses, which would lead to improvements in the efficiency of the water heater. The test results showed that the Energy Factor of the baseline water heater was 0.576. The recovery efficiency was 0.768. The standby heat loss coefficient was 10.619 (BTU/hr-oF). After the damper was installed, the test results show an Energy Factor for the baseline water heater of 0.605. The recovery efficiency was 0.786. The standby heat loss coefficient was 9.135 (BTU/hr-oF). The recovery efficiency increased 2.3percent and the standby heat loss coefficient decreased 14percent. When the burner was on, the baseline water heater caused 28.0 CFM of air to flow from the room. During standby, the flow was 12.4 CFM. The addition of the damper reduced the flow when the burner was on to 23.5 CFM. During standby, flow with the damper was reduced to 11.1 CFM. The flue damper reduced off-cycle standby losses, and improved the efficiency of the water heater. The flue damper also improved the recovery efficiency of the water heater by restricting on-cycle air flows through the flue.With or without the flue damper, off-cycle air flow upthe stack is nearly half the air flow rate as when the burner is firing.

  3. Suppression of the Work-Piece Vibrations in Milling Using Active Clamp System

    NASA Astrophysics Data System (ADS)

    Parus, A.; Hoffmann, M.; Okulik, T.

    The machining is always accompanied by vibration. In certain cases the level of vibration is very high and may cause shortening of the tool life, poor quality of machined surface. Operational speed and machined surface depend on dynamic stability of three components of the machine tool-cutting system: the cutting tool, the machine tool structure, the work-piece and the clamping system. To assure stable machining, parameters of the cutting process have to be tuned and frequently the machining productivity is decreased. For this reasons different types of systems are developed for suppressing the work-piece vibration. In some cases an additional modification of the work-piece is allowed and mounting the vibration absorber is possible. The paper describes a modification of the work-piece dynamic properties using active clamp system. In comparison to the vibration absorbers this solution has a great advantageous - adaptation of the work-piece is not necessary. In the paper the simulation results of different variants of milling process with work-piece mounted using the active clamp are presented. Piezo actuators are used in order to assure active influence on the work-piece. The aim of the state space feedback control system is to minimize the amplitude of the vibration during machining process.

  4. Over-driven control for large-scale MR dampers

    NASA Astrophysics Data System (ADS)

    Friedman, A. J.; Dyke, S. J.; Phillips, B. M.

    2013-04-01

    As semi-active electro-mechanical control devices increase in scale for use in real-world civil engineering applications, their dynamics become increasingly complicated. Control designs that are able to take these characteristics into account will be more effective in achieving good performance. Large-scale magnetorheological (MR) dampers exhibit a significant time lag in their force-response to voltage inputs, reducing the efficacy of typical controllers designed for smaller scale devices where the lag is negligible. A new control algorithm is presented for large-scale MR devices that uses over-driving and back-driving of the commands to overcome the challenges associated with the dynamics of these large-scale MR dampers. An illustrative numerical example is considered to demonstrate the controller performance. Via simulations of the structure using several seismic ground motions, the merits of the proposed control strategy to achieve reductions in various response parameters are examined and compared against several accepted control algorithms. Experimental evidence is provided to validate the improved capabilities of the proposed controller in achieving the desired control force levels. Through real-time hybrid simulation (RTHS), the proposed controllers are also examined and experimentally evaluated in terms of their efficacy and robust performance. The results demonstrate that the proposed control strategy has superior performance over typical control algorithms when paired with a large-scale MR damper, and is robust for structural control applications.

  5. Large-scale ER-damper for seismic protection

    NASA Astrophysics Data System (ADS)

    McMahon, Scott; Makris, Nicos

    1997-05-01

    A large scale electrorheological (ER) damper has been designed, constructed, and tested. The damper consists of a main cylinder and a piston rod that pushes an ER-fluid through a number of stationary annular ducts. This damper is a scaled- up version of a prototype ER-damper which has been developed and extensively studied in the past. In this paper, results from comprehensive testing of the large-scale damper are presented, and the proposed theory developed for predicting the damper response is validated.

  6. Vibration damping for the Segmented Mirror Telescope

    NASA Astrophysics Data System (ADS)

    Maly, Joseph R.; Yingling, Adam J.; Griffin, Steven F.; Agrawal, Brij N.; Cobb, Richard G.; Chambers, Trevor S.

    2012-09-01

    The Segmented Mirror Telescope (SMT) at the Naval Postgraduate School (NPS) in Monterey is a next-generation deployable telescope, featuring a 3-meter 6-segment primary mirror and advanced wavefront sensing and correction capabilities. In its stowed configuration, the SMT primary mirror segments collapse into a small volume; once on location, these segments open to the full 3-meter diameter. The segments must be very accurately aligned after deployment and the segment surfaces are actively controlled using numerous small, embedded actuators. The SMT employs a passive damping system to complement the actuators and mitigate the effects of low-frequency (<40 Hz) vibration modes of the primary mirror segments. Each of the six segments has three or more modes in this bandwidth, and resonant vibration excited by acoustics or small disturbances on the structure can result in phase mismatches between adjacent segments thereby degrading image quality. The damping system consists of two tuned mass dampers (TMDs) for each of the mirror segments. An adjustable TMD with passive magnetic damping was selected to minimize sensitivity to changes in temperature; both frequency and damping characteristics can be tuned for optimal vibration mitigation. Modal testing was performed with a laser vibrometry system to characterize the SMT segments with and without the TMDs. Objectives of this test were to determine operating deflection shapes of the mirror and to quantify segment edge displacements; relative alignment of λ/4 or better was desired. The TMDs attenuated the vibration amplitudes by 80% and reduced adjacent segment phase mismatches to acceptable levels.

  7. Selected topics on the active control of helicopter aeromechanical and vibration problems

    NASA Technical Reports Server (NTRS)

    Friedmann, Peretz P.

    1994-01-01

    This paper describes in a concise manner three selected topics on the active control of helicopter aeromechanical and vibration problems. The three topics are as follows: (1) the active control of helicopter air-resonance using an LQG/LTR approach; (2) simulation of higher harmonic control (HHC) applied to a four bladed hingeless helicopter rotor in forward flight; and (3) vibration suppression in forward flight on a hingeless helicopter rotor using an actively controlled, partial span, trailing edge flap, which is mounted on the blade. Only a few selected illustrative results are presented. The results obtained clearly indicate that the partial span, actively controlled flap has considerable potential for vibration reduction in helicopter rotors.

  8. Active Suppression of Drilling System Vibrations For Deep Drilling

    SciTech Connect

    Raymond, David W.; Blankenship, Douglas A.; Buerger, Stephen; Mesh, Mikhail; Radigan, William Thomas; Su, Jiann-Cherng

    2015-10-01

    The dynamic stability of deep drillstrings is challenged by an inability to impart controllability with ever-changing conditions introduced by geology, depth, structural dynamic properties and operating conditions. A multi-organizational LDRD project team at Sandia National Laboratories successfully demonstrated advanced technologies for mitigating drillstring vibrations to improve the reliability of drilling systems used for construction of deep, high-value wells. Using computational modeling and dynamic substructuring techniques, the benefit of controllable actuators at discrete locations in the drillstring is determined. Prototype downhole tools were developed and evaluated in laboratory test fixtures simulating the structural dynamic response of a deep drillstring. A laboratory-based drilling applicability demonstration was conducted to demonstrate the benefit available from deployment of an autonomous, downhole tool with self-actuation capabilities in response to the dynamic response of the host drillstring. A concept is presented for a prototype drilling tool based upon the technical advances. The technology described herein is the subject of U.S. Patent Application No. 62219481, entitled "DRILLING SYSTEM VIBRATION SUPPRESSION SYSTEMS AND METHODS", filed September 16, 2015.

  9. Sizing of active piezoelectric struts for vibration suppression on a space-based interferometer

    NASA Technical Reports Server (NTRS)

    Sirlin, S. W.; Laskin, R. A.

    1991-01-01

    The present paper concerns itself with the active suppression of mechanical vibrations on a representative future spaceborne optical interferometer. This is accomplished by the incorporation of a set of piezoelectric struts into the truss structure of the interferometer and the use of these active struts to modify the damping and stiffness characteristics of the truss. It is shown that vibration propagation can be significantly reduced through the use of very simple control laws. It is further shown that the force and stroke requirements for the active struts for this application are rather modest and fall well within the capabilities already demonstrated by prototype hardware in ground testing.

  10. Variable force, eddy-current or magnetic damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E. (Inventor)

    1985-01-01

    An object of the invention is to provide variable damping for resonant vibrations which may occur at different rotational speeds in the range of rpms in which a rotating machine is operated. A variable force damper in accordance with the invention includes a rotating mass carried on a shaft which is supported by a bearing in a resilient cage. The cage is attached to a support plate whose rim extends into an annular groove in a housing. Variable damping is effected by tabs of electrically conducting nonmagnetic material which extend radially from the cage. The tabs at an index position lie between the pole face of respective C shaped magnets. The magnets are attached by cantilever spring members to the housing.

  11. Parametric study of pounding tuned mass damper for subsea jumpers

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Li, L.; Patil, D.; Singla, M.; Li, H.-N.; Mo, Y. L.; Song, G.

    2016-01-01

    In previous study, a pounding tuned mass damper (PTMD) was proposed to reduce the undesired vibration of a subsea jumper. Both experimental and numerical results verified the effectiveness of the PTMD. This paper aims to enhance the understanding of the PTMD through a parametric study. The jumper is subjected to sinusoidal forces of different frequencies. The reduction ratio is defined for evaluation of the mitigation performance. Three parameters are considered in this study: the pounding stiffness, the gap between the delimiter and the mass block, and the mass ratio. The parametric studies show that the PTMD system is not so sensitive to the small variations of the pounding stiffness and the gap. The reduction ratio is significantly increased with the mass ratio increased up to 2%. Afterwards, it is not so economic or practically feasible to enlarge the mass ratio.

  12. Active vibration suppression through positive acceleration feedback on a building-like structure: An experimental study

    NASA Astrophysics Data System (ADS)

    Enríquez-Zárate, J.; Silva-Navarro, G.; Abundis-Fong, H. F.

    2016-05-01

    This work deals with the structural and dynamic analysis of a building-like structure consisting of a three-story building with one active vibration absorber. The base of the structure is perturbed using an electromagnetic shaker, which provides forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. One beam-column of the structure is coupled with a PZT stack actuator to reduce the vibrations. The overall mechanical structure is modeled using Euler-Lagrange methodology and validated using experimental modal analysis and Fine Element Method (FEM) techniques. The active control laws are synthesized to actively attenuate the vibration system response via the PZT stack actuator, caused by excitation forces acting on the base of the structure. The control scheme is obtained using Positive Acceleration Feedback (PAF) and Multiple Positive Acceleration Feedback (MPAF) to improve the closed-loop system response. Some experimental results are included to illustrate the overall system performance.

  13. Experimental Comparison of two Active Vibration Control Approaches: Velocity Feedback and Negative Capacitance Shunt Damping

    NASA Technical Reports Server (NTRS)

    Beck, Benjamin; Schiller, Noah

    2013-01-01

    This paper outlines a direct, experimental comparison between two established active vibration control techniques. Active vibration control methods, many of which rely upon piezoelectric patches as actuators and/or sensors, have been widely studied, showing many advantages over passive techniques. However, few direct comparisons between different active vibration control methods have been made to determine the performance benefit of one method over another. For the comparison here, the first control method, velocity feedback, is implemented using four accelerometers that act as sensors along with an analog control circuit which drives a piezoelectric actuator. The second method, negative capacitance shunt damping, consists of a basic analog circuit which utilizes a single piezoelectric patch as both a sensor and actuator. Both of these control methods are implemented individually using the same piezoelectric actuator attached to a clamped Plexiglas window. To assess the performance of each control method, the spatially averaged velocity of the window is compared to an uncontrolled response.

  14. Analytical study on damping performances of magnetorheological grease damper based on disk squeeze mode and experimental test

    NASA Astrophysics Data System (ADS)

    Zhao, Danxia; Liao, Changrong; Liu, Qiong; Luo, Jing

    2011-09-01

    In this paper, a small displacement-type magnetorheological grease (MRG) damper based on disk squeeze mode is proposed. The squeeze flow differential equation is obtained. The Navier slip condition is considered on the surfaces and the boundary compatible condition is established. The radial velocity profiles and the radial pressure distributions are derived respectively, and the mathematical stress expression is calculated. To verify rationality of analytical method, the MRG damper is designed and fabricated according to the technical requirements of an engine vibration isolation system. The experimental damping force from MTS870 Electrohydraulic Servo with sine wave excitation shows that the proposed analytical method is feasible and provides the reference value for designing MRG damper based on disk squeeze mode.

  15. Influence of vibration on mechanical power and electromyogram activity in human arm flexor muscles.

    PubMed

    Bosco, C; Cardinale, M; Tsarpela, O

    1999-03-01

    The aim of this study was to evaluate the influence of vibration on the mechanical properties of arm flexors. A group of 12 international level boxers, all members of the Italian national team, voluntarily participated in the experiment: all were engaged in regular boxing training. At the beginning of the study they were tested whilst performing forearm flexion with an extra load equal to 5% of the subjects' body mass. Following this. one arm was given the experimental treatment (E; mechanical vibration) and the other was the control (no treatment). The E treatment consisted of five repetitions lasting 1-min each of mechanical vibration applied during arm flexion in isometric conditions with 1 min rest between them. Further tests were performed 5 min immediately after the treatment on both limbs. The results showed statistically significant enhancement of the average power in the arm treated with vibrations. The root mean square electromyogram (EMGrms) had not changed following the treatment but, when divided by mechanical power, (P) as an index of neural efficiency, it showed statistically significant increases. It was concluded that mechanical vibrations enhanced muscle P and decreased the related EMG/P relationship in elite athletes. Moreover, the analysis of EMGrms recorded before the treatment and during the treatment itself showed an enormous increase in neural activity during vibration up to more than twice the baseline values. This would indicate that this type of treatment is able to stimulate the neuromuscular system more than other treatments used to improve neuromuscular properties. PMID:10090628

  16. Active twist control methodology for vibration reduction of a helicopter with dissimilar rotor system

    NASA Astrophysics Data System (ADS)

    Pawar, Prashant M.; Jung, Sung Nam

    2009-03-01

    In this work, an active vibration reduction of hingeless composite rotor blades with dissimilarity is investigated using the active twist concept and the optimal control theory. The induced shear strain on the actuation mechanism by the piezoelectric constant d15 from the PZN-8% PT-based single-crystal material is used to achieve more active twisting to suppress the extra vibrations. The optimal control algorithm is based on the minimization of an objective function comprised of quadratic functions of vibratory hub loads and voltage control harmonics. The blade-to-blade dissimilarity is modeled using the stiffness degradation of composite blades. The optimal controller is applied to various possible dissimilarities arising from different damage patterns of composite blades. The governing equations of motion are derived using Hamilton's principle. The effects of composite materials and smart actuators are incorporated into the comprehensive aeroelastic analysis system. Numerical results showing the impact of addressing the blade dissimilarities on hub vibrations and voltage inputs required to suppress the vibrations are demonstrated. It is observed that all vibratory shear forces are reduced considerably and the major harmonics of moments are reduced significantly. However, the controller needs further improvement to suppress 1/rev moment loads. A mechanism to achieve vibration reduction for the dissimilar rotor system has also been identified.

  17. Active control of payload fairing noise using distributed active vibration absorbers

    NASA Astrophysics Data System (ADS)

    Charpentier, Arnaud; Johnson, Marty E.; Fuller, Chris R.

    2003-04-01

    High sound pressure inside a launch vehicle fairing during lift-off can damage the payload. Interior levels of up to 140 dB between 60 and 250 Hz are mostly due to exhaust plume noise combined with the limited transmission loss of lightweight composite fairings and little acoustic damping in the fairing volume. Past work using passive and hybrid passive/reactive noise control devices has shown that their limitations are mostly due to packaging volume and weight penalty. The objective of this work is to design a lightweight, compact, and low electrical power active noise control system to reduce the fairing interior sound level. Hybrid active/passive actuators such as Smart Foam (Couche and Fuller, Proceedings of Active 1999, Ft. Lauderdale, FL, pp. 609-620) and Distributed Active Vibration Absorbers (Marcotte, Fuller, and Johnson, Proceedings of Active 2002, ISVR, Southampton, England, pp. 535-546) are optimized for fairing noise control. The latter have been used to increase the transmission loss of the fairing. Active noise control test results on a sub-scale, sandwich composite fairing are presented. The global interior acoustic response due to airborne exterior excitation is minimized using an adaptive multiple-input, multiple-output feedforward controller. [Work supported by the Air Force Research Laboratory, Space Vehicles Directorate (AFRL).

  18. DOWNHOLE VIBRATION MONITORING AND CONTROL SYSTEM

    SciTech Connect

    Martin E. Cobern

    2003-04-01

    The project continues to advance approximately per the revised (14-month) schedule. Tasks 1-3 (Modeling, Specification and Design) are all essentially complete. Work has begun on designing the test equipment for the Test and Evaluation (Tasks 4 & 5.) One of the intents of this project is to not only dampen vibration above the damper, but to also dampen vibrations below the damper. This is accomplished by smoothing out the discontinuities as the bit drills ahead. The model has the capability to simulate the drilling looking at the depth of cut along the discontinuities. It can also look at the amount of time that the bit is in contact with the formation. It is found that under some conditions the vibrations increased the discontinuities due to resonant conditions. In the ideal situation, the damper reduces the discontinuities and smooths out the drilling. APS looked at a wide range of spring stiffness and damping properties to determine the optimum damper. Spring rates of 10,000 lb/in to 60,000 lbs/in were analyzed. The best compromise is at 30,000 lb/in for the 6 3/4 inch tool. Low spring rates would require large displacements for the damper, while stiff springs do not provide enough motion for the damper. Several damping concepts were analyzed: (1) The first thought was to have a damper providing high damping in the upward direction and low damping in the downward direction. It was found that this increased the vibration by wallowing out the troughs of the discontinuities leading to increased displacements at the bit. (2) Another method investigated was having increased damping at high acceleration levels and less damping at lower acceleration levels. This gave improved results. (3) Constant damping so far provides the damping situation. With the proper damping level the damper can smooth out the discontinuities and provide smooth drilling. However, the damping values are different for different drilling conditions. Different WOB and ROP require different damping

  19. Good vibrations, bad vibrations: Oscillatory brain activity in the attentional blink

    PubMed Central

    Janson, Jolanda; Kranczioch, Cornelia

    2011-01-01

    The attentional blink (AB) is a deficit in reporting the second (T2) of two targets (T1, T2) when presented in close temporal succession and within a stream of distractor stimuli. The AB has received a great deal of attention in the past two decades because it allows to study the mechanisms that influence the rate and depth of information processing in various setups and therefore provides an elegant way to study correlates of conscious perception in supra-threshold stimuli. Recently evidence has accumulated suggesting that oscillatory signals play a significant role in temporally coordinating information between brain areas. This review focuses on studies looking into oscillatory brain activity in the AB. The results of these studies indicate that the AB is related to modulations in oscillatory brain activity in the theta, alpha, beta, and gamma frequency bands. These modulations are sometimes restricted to a circumscribed brain area but more frequently include several brain regions. They occur before targets are presented as well as after the presentation of the targets. We will argue that the complexity of the findings supports the idea that the AB is not the result of a processing impairment in one particular process or brain area, but the consequence of a dynamic interplay between several processes and/or parts of a neural network. PMID:22253672

  20. Experimental verification of sensing capability of an electromagnetic induction system for an MR fluid damper-based control system

    NASA Astrophysics Data System (ADS)

    Jung, H. J.; Jang, D. D.; Cho, S. W.; Koo, J. H.

    2009-02-01

    This paper investigates the sensing capability of an Electromagnetic Induction (EMI) system that is incorporated in a vibration control system based on MR fluid dampers. The EMI system, consisting of permanent magnets and coils, converts reciprocal motions (kinetic energy) of MR damper into electrical energy (electromotive force or emf). According to the Faraday's law of electromagnetic induction, the emf signal, produced from the EMI, is proportional to the velocity of the motion. Thus, the induced voltage (emf) signal is able to provide the necessary measurement information (i.e., relative velocity across the damper). In other words, the EMI can act as a sensor in the MR damper system. In order to evaluate the proposed concept of the EMI sensor, an EMI system was constructed and integrated into an MR damper system. The emf signal is experimentally compared with the velocity signal by conducting a series of shaking table tests. The results show that the induced emf voltage signal well agreed with the relative velocity.

  1. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 3 2010-10-01 2010-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  2. Application of torque margin ratios for Eddy Current Dampers

    NASA Astrophysics Data System (ADS)

    Starin, Scott; Rodriguez, Tony

    2003-09-01

    Eddy Current Dampers (ECDs) offer higher robustness, torque capacity and linearity than Fluid Dampers. One of the perceived disadvantages of ECDs when compared to Fluid Dampers is the magnitude of zero speed Coulomb torque. However, the magnitude of total Coulomb torque must be analyzed and considered when applying torque margin ratios, depending on the construction of the ECD and method of reaction torque generation.

  3. A novel self-powered MR damper: theoretical and experimental analysis

    NASA Astrophysics Data System (ADS)

    Xinchun, Guan; Yonghu, Huang; Yi, Ru; Hui, Li; Jinping, Ou

    2015-10-01

    This paper presents a novel magnetorheological (MR) damper with a self-powered capability, which is proposed to have energy harvesting and MR damping technologies integrated into a single device. Vibration energy harvesting mechanisms were adopted, based on ball-screw mechanisms and a rotary permanent magnet dc generator, to convert the external vibration energy into electrical energy to power the MR damping unit. The configuration and operating principles of the proposed self-powered MR damper were presented. Considering the core loss effect on the magnetic field, a theoretical analysis of the proposed MR damper was carried out and a mechanical model was developed. Finally, a prototype with a capacity of 10 kN was fabricated and experimentally investigated in both the direct-supply mode and the supply-with-rectifier mode. The results indicated that the proposed configuration is feasible and that both modes can realize good self-adaptability of the MR damping force. However, the direct-supply mode has a sag effect in the force-displacement curve and provides a lower energy-dissipating capacity than the direct-supply mode does under the same conditions.

  4. Rectification of SEMG as a tool to demonstrate synchronous motor unit activity during vibration.

    PubMed

    Sebik, Oguz; Karacan, Ilhan; Cidem, Muharrem; Türker, Kemal S

    2013-04-01

    The use of surface electromyography (SEMG) in vibration studies is problematic since motion artifacts occupy the same frequency band with the SEMG signal containing information on synchronous motor unit activity. We hypothesize that using a harsher, 80-500 Hz band-pass filter and using rectification can help eliminate motion artifacts and provide a way to observe synchronous motor unit activity that is phase locked to vibration using SEMG recordings only. Multi Motor Unit (MMU) action potentials using intramuscular electrodes along with SEMG were recorded from the gastrocnemius medialis (GM) of six healthy male volunteers. Data were collected during whole body vibration, using vibration frequencies of 30 Hz, 35 Hz, 40 Hz or 50 Hz. A computer simulation was used to investigate the efficacy of filtering under different scenarios: with or without artifacts and/or motor unit synchronization. Our findings indicate that motor unit synchronization took place during WBV as verified by MMU recordings. A harsh filtering regimen along with rectification proved successful in demonstrating motor unit synchronization in SEMG recordings. Our findings were further supported by the results from the computer simulation, which indicated that filtering and rectification was efficient in discriminating motion artifacts from motor unit synchronization. We suggest that the proposed signal processing technique may provide a new methodology to evaluate the effects of vibration treatments using only SEMG. This is a major advantage, as this non-intrusive method is able to overcome movement artifacts and also indicate the synchronization of underlying motor units. PMID:23098913

  5. IIR filtering based adaptive active vibration control methodology with online secondary path modeling using PZT actuators

    NASA Astrophysics Data System (ADS)

    Boz, Utku; Basdogan, Ipek

    2015-12-01

    Structural vibrations is a major cause for noise problems, discomfort and mechanical failures in aerospace, automotive and marine systems, which are mainly composed of plate-like structures. In order to reduce structural vibrations on these structures, active vibration control (AVC) is an effective approach. Adaptive filtering methodologies are preferred in AVC due to their ability to adjust themselves for varying dynamics of the structure during the operation. The filtered-X LMS (FXLMS) algorithm is a simple adaptive filtering algorithm widely implemented in active control applications. Proper implementation of FXLMS requires availability of a reference signal to mimic the disturbance and model of the dynamics between the control actuator and the error sensor, namely the secondary path. However, the controller output could interfere with the reference signal and the secondary path dynamics may change during the operation. This interference problem can be resolved by using an infinite impulse response (IIR) filter which considers feedback of the one or more previous control signals to the controller output and the changing secondary path dynamics can be updated using an online modeling technique. In this paper, IIR filtering based filtered-U LMS (FULMS) controller is combined with online secondary path modeling algorithm to suppress the vibrations of a plate-like structure. The results are validated through numerical and experimental studies. The results show that the FULMS with online secondary path modeling approach has more vibration rejection capabilities with higher convergence rate than the FXLMS counterpart.

  6. The Raman and vibronic activity of intermolecular vibrations in aromatic-containing complexes and clusters

    SciTech Connect

    Maxton, P.M.; Schaeffer, M.W.; Ohline, S.M.; Kim, W.; Venturo, V.A.; Felker, P.M. )

    1994-11-15

    Theoretical and experimental results pertaining to the excitation of intermolecular vibrations in the Raman and vibronic spectra of aromatic-containing, weakly bound complexes and clusters are reported. The theoretical analysis of intermolecular Raman activity is based on the assumption that the polarizability tensor of a weakly bound species is given by the sum of the polarizability tensors of its constituent monomers. The analysis shows that the van der Waals bending fundamentals in aromatic--rare gas complexes may be expected to be strongly Raman active. More generally, it predicts strong Raman activity for intermolecular vibrations that involve the libration or internal rotation of monomer moieties having appreciable permanent polarizability anisotropies. The vibronic activity of intermolecular vibrations in aromatic-rare gas complexes is analyzed under the assumption that every vibronic band gains its strength from an aromatic-localized transition. It is found that intermolecular vibrational excitations can accompany aromatic-localized vibronic excitations by the usual Franck--Condon mechanism or by a mechanism dependent on the librational amplitude of the aromatic moiety during the course of the pertinent intermolecular vibration. The latter mechanism can impart appreciable intensity to bands that are forbidden by rigid-molecule symmetry selection rules. The applicability of such rules is therefore called into question. Finally, experimental spectra of intermolecular transitions, obtained by mass-selective, ionization-detected stimulated Raman spectroscopies, are reported for benzene--X (X=Ar, --Ar[sub 2], N[sub 2], HCl, CO[sub 2], and --fluorene), fluorobenzene--Ar and --Kr, aniline--Ar, and fluorene--Ar and --Ar[sub 2]. The results support the conclusions of the theoretical analyses and provide further evidence for the value of Raman methods in characterizing intermolecular vibrational level structures.

  7. The spectral analysis of an aero-engine assembly incorporating a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Holmes, R.; Dede, M. M.

    1989-01-01

    Aero-engine structures have very low inherent damping and so artificial damping is often introduced by pumping oil into annular gaps between the casings and the outer races of some or all of the rolling-element bearings supporting the rotors. The thin oil films so formed are called squeeze film dampers and they can be beneficial in reducing rotor vibration due to unbalance and keeping to reasonable limits the forces transmitted to the engine casing. However, squeeze-film dampers are notoriously non-linear and as a result can introduce into the assembly such phenomena as subharmonic oscillations, jumps and combination frequencies. The purpose of the research is to investigate such phenomena both theoretically and experimentally on a test facility reproducing the essential features of a medium-size aero engine. The forerunner of this work was published. It was concerned with the examination of a squeeze-film damper in series with housing flexibility when supporting a rotor. The structure represented to a limited extent the essentials of the projected Rolls Royce RB401 engine. That research demonstrated the ability to calculate the oil-film forces arising from the squeeze film from known motions of the bearing components and showed that the dynamics of a shaft fitted with a squeeze film bearing can be predicted reasonably accurately. An aero-engine will normally have at least two shafts and so in addition to the excitation forces which are synchronous with the rotation of one shaft, there will also be forces at other frequencies from other shafts operating on the squeeze-film damper. Theoretical and experimental work to consider severe loading of squeeze-film dampers and to include these additional effects are examined.

  8. Regular physical activity reduces the effects of Achilles tendon vibration on postural control for older women.

    PubMed

    Maitre, J; Serres, I; Lhuisset, L; Bois, J; Gasnier, Y; Paillard, T

    2015-02-01

    The aim was to determine in what extent physical activity influences postural control when visual, vestibular, and/or proprioceptive systems are disrupted. Two groups of healthy older women: an active group (74.0 ± 3.8 years) who practiced physical activities and a sedentary group (74.7 ± 6.3 years) who did not, underwent 12 postural conditions consisted in altering information emanating from sensory systems by means of sensory manipulations (i.e., eyes closed, cervical collar, tendon vibration, electromyostimulation, galvanic vestibular stimulation, foam surface). The center of foot pressure velocity was recorded on a force platform. Results indicate that the sensory manipulations altered postural control. The sedentary group was more disturbed than the active group by the use of tendon vibration. There was no clear difference between the two groups in the other conditions. This study suggests that the practice of physical activities is beneficial as a means of limiting the effects of tendon vibration on postural control through a better use of the not manipulated sensory systems and/or a more efficient reweighting to proprioceptive information from regions unaffected by the tendon vibration. PMID:24853711

  9. Vibration isolation

    NASA Technical Reports Server (NTRS)

    Bastin, Paul

    1990-01-01

    Viewgraphs on vibration isolation are presented. Techniques to control and isolate centrifuge disturbances were identified. Topics covered include: disturbance sources in the microgravity environment; microgravity assessment criteria; life sciences centrifuge; flight support equipment for launch; active vibration isolation system; active balancing system; and fuzzy logic control.

  10. Dynamic behavior of the mercury damper

    NASA Technical Reports Server (NTRS)

    Crout, P. D.; Newkirk, H. L.

    1971-01-01

    The dynamic behavior of the mercury nutation damper is investigated. Particular attention is paid to the eccentric annular mercury configuration, which is the final continuous ring phase that occurs in the operation of all mercury dampers. In this phase, damping is poorest, and the system is closely linear. During the investigation, the hydrodynamic problem is treated as three dimensional, and extensive use is made of a variational principle of least-viscous frictional power loss. A variational principle of least-constraint is also used to advantage. Formulas for calculating the behavior of the mercury damper are obtained. Some confirmatory experiments were performed with transparent ring channels on a laboratory gyroscope. Selected movie frames taken during wobble damping are shown along with the results of film measurements.

  11. An integrated approach for friction damper design

    NASA Technical Reports Server (NTRS)

    Cameron, T. M.; Griffin, J. H.; Hoosac, T. M.; Kielb, R. E.

    1987-01-01

    A procedure is outlined for determining the optimal design of friction dampers for high speed turbomachinery blading. The procedure includes: an integration of bench test results with finite element analysis and a single mode blade model to ensure accuracy of the analytical model and improve reliability of the friction damper design; an extension of the single mode blade model to predict the engine behavior of friction dampers; and a new way of viewing analytical and experimental results to determine optimal design parameters when the levels of excitation and damping in the system are unknown. Analysis and experiments are performed on a test disk in order to demonstrate and verify the accuracy of the design procedure.

  12. Performance of a high-force controllable MR fluid damper-liquid spring suspension systems

    NASA Astrophysics Data System (ADS)

    Raja, Pramod; Wang, Xiaojie; Gordaninejad, Faramarz

    2010-04-01

    In this study a compact compressible magneto-rheological (MR) fluid damper-liquid spring (CMRFD-LS) with high spring rate is designed, developed and tested. The proposed device consists of a cylinder and piston-rod arrangement, with an annular MR fluid valve. The internal pressures in the chambers on either side of the piston develop the spring force, while the pressure difference across the MR valve produces the damping force, when the fluid flows through the MR valve. A fluid mechanics-based model is conducted to predict the behavior of the damper device under sinusoidal input. The device is studied under oscillatory vibrations for various frequencies and applied magnetic fields. The experimental results are in good agreement with the theoretical predictions.

  13. Statistical modeling of a magneto-rheological fluid damper using the design of experiments approach

    NASA Astrophysics Data System (ADS)

    Shivaram, A. C.; Gangadharan, K. V.

    2007-08-01

    In this work, a through-rod-type magneto-rheological (MR) test damper has been designed and fabricated for experimental study. Various factors, such as the magnetic field strength, volume fraction of particles in the MR fluid, shearing gap between piston and cylinder, vibration frequency and amplitude, have been considered as input factors, and the root-mean-square (RMS) damping force as the output factor (response variable). These input factors are varied in two levels (low and high) during the initial phase of experimentation using 25 factorial design; the motivation is to identify the most influential factors. In the second phase of experimentation, the response surface method has been used to identify the modeling equation and to plot the response surfaces. Further, force versus displacement diagrams have been plotted at these factor levels; these give an insight into the damping behaviour of the MR damper.

  14. Preliminary results on passive eddy current damper technology for SSME turbomachinery

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1985-01-01

    Some preliminary results have been obtained for the dynamic response of a rotor operating over a speed range of 800 to 10,000 rpm. Amplitude frequency plots show the lateral vibratory response of an unbalanced rotor with and without external damping. The mode of damping is by means of eddy currents generated with 4 c shaped permanent magnets installed at the lower bearing of a vertically oriented rotor. The lower ball bearing and its damper assembly are totally immersed in liquid nitrogen at a temperature of -197 deg C (-320 deg F). These preliminary results for a referenced or base line passive eddy current damper assembly show that the amplitude of synchronous vibration is reduced at the resonant frequency. Measured damping coefficients were calculated to phi = .086; this compares with a theoretically calculated value of phi = .079.

  15. Fundamental study of lower limb muscle activity using an angled whole body vibration exercise instrument.

    PubMed

    Yu, Chang Ho; Kang, Seung Rok; Kwon, Tae Kyu

    2014-01-01

    This research was performed to assess the effects of angled whole body vibration on muscle activity of the lower limbs, by examining adults in their twenties during squat exercises, taking into account two variables of exercise intensity (vibration frequency and gradient). Twenty healthy males in their twenties with previous experience of more than 6 month's weight training and no past medical history were included in this study. The experiment was performed by participating in squat exercises which consisted of 3 sets (1 set = 5 seconds x 3 repetitions of exercise), and the muscle activities of the Rectus Femoris, Vastus Lateralis, Vastus Medialis were measured with variation in the gradients of 0°, 10°, and 20°, and vibration frequencies of 20, 30, and 40 Hz. At 30 and 40 Hz, the vastus lateralis showed the highest change in muscle activity, while activity of the vastus medialis also increased significantly. Analysis of muscle activity according to the gradient showed a significant increase of the vastus lateralis at 20°, while the highest muscle activity at 20° was observed for the vastus medialis. In comparison of the change in lower limb muscle activity according to simultaneous stimulation, at a gradient of 10°, high activity was shown in muscle, while at 20°, high muscle activities were produced at 40 Hz in the vastus lateralis, 40 Hz in the rectus femoris, and both 30 and 40 Hz in the vastus medialis. PMID:25226944

  16. The Influence of Whole-Body Vibration on Creatine Kinase Activity and Jumping Performance in Young Basketball Players

    ERIC Educational Resources Information Center

    Fachina, Rafael; da Silva, Antônio; Falcão, William; Montagner, Paulo; Borin, João; Minozzo, Fábio; Falcão, Diego; Vancini, Rodrigo; Poston, Brach; de Lira, Claudio

    2013-01-01

    Purpose: To quantify creatine kinase (CK) activity changes across time following an acute bout of whole-body vibration (WBV) and determine the association between changes in CK activity and jumping performance. Method: Twenty-six elite young basketball players were assigned to 3 groups: 36-Hz and 46-Hz vibration groups (G36 and G46, respectively)…

  17. A finite element method for active vibration control of uncertain structures

    NASA Astrophysics Data System (ADS)

    Morales, A. L.; Rongong, J. A.; Sims, N. D.

    2012-10-01

    This work introduces a fuzzy design method using the finite element procedure to simulate and analyze active vibration control of structures subjected to uncertain parameters. The purpose of this work is to provide a tool for studying the influence of uncertainty propagation on both stability and performance of a vibration control system, whilst avoiding the need for computationally expensive probabilistic methods or complex robust control techniques. The proposed procedure applies a general and efficient strategy for computing fuzzy results to a sequence of finite element calculations. Finally, the applicability of the methodology is illustrated through some realistic case studies related to structural control where spillover instability may arise.

  18. Measuring of object vibration using sinusoidal-modulation laser-diode active interferometer

    NASA Astrophysics Data System (ADS)

    Ai, Yong; Cao, Qinfeng; Lu, Su

    1996-09-01

    Using the character that the emitting optical frequency of the laser diode is controlled by the injected current, the ability of eliminating environmental disturbance of the sinusoidal modulation laser diode active interferometer will be raised by more than one hundred times through putting the disturbed interference signal produced by the environment into the interferometer. When vibrating frequency of objects is different from that of the sinusoidol modulation, 'beat- frequency' will be produced in the interfere signal, which can be analyzed to get the vibrating frequency of objects. This paper described the operation principle and theoretical delusion of the 'beat-frequency' method.

  19. An active optimal control strategy of rotor vibrations using external forces

    NASA Technical Reports Server (NTRS)

    Zhu, W.; Castelazo, I.; Nelson, H. D.

    1989-01-01

    An active control strategy for lateral rotor vibrations using external forces is proposed. An extended state observer is used to reconstruct the full states and the unbalance distribution. An optimal controller which accommodates persistent unbalance excitation is derived with feedback of estimated states and unbalances. Numerical simulations were conducted for two separate four degree of freedom rotor systems. These simulations indicated that the proposed strategy can achieve almost complete vibration cancellation. This was shown to be true even when the number of external control forces was less than the system order so long as coordinate coupling was present. Both steady state and transient response at a constant speed are presented.

  20. Semi-active magnetorheological refueling probe systems for aerial refueling events

    NASA Astrophysics Data System (ADS)

    Choi, Young-Tai; Wereley, Norman M.

    2013-09-01

    This study analyzes the feasibility of applying a semi-active magnetorheological (MR) damper to a naval hose-drogue based aerial refueling system to minimize undesirable hose-drogue vibrations. The semi-active smart aerial refueling probe system consists of a probe, a coil spring, and a MR damper. The dynamics of the smart refueling probe system were derived and incorporated into an analysis of the coupled hose-drogue dynamics, so as to evaluate the load reduction of the refueling hose at the drogue position effected by the MR damper. The simulated responses of the smart refueling probe system using a MR damper were conducted at different maximum closure velocities of 1.56 and 5 ft s-1 and different tanker flight speeds of 185 and 220 knots. The simulations demonstrate that the smart refueling probe system using a MR damper enables large reductions in probe-and-drogue motions, as well as preventing the onset of large and undesirable hose-drogue motions resulting from tension loads during engagement of the probe.

  1. Inverse eigenvalue problems in vibration absorption: Passive modification and active control

    NASA Astrophysics Data System (ADS)

    Mottershead, John E.; Ram, Yitshak M.

    2006-01-01

    The abiding problem of vibration absorption has occupied engineering scientists for over a century and there remain abundant examples of the need for vibration suppression in many industries. For example, in the automotive industry the resolution of noise, vibration and harshness (NVH) problems is of extreme importance to customer satisfaction. In rotorcraft it is vital to avoid resonance close to the blade passing speed and its harmonics. An objective of the greatest importance, and extremely difficult to achieve, is the isolation of the pilot's seat in a helicopter. It is presently impossible to achieve the objectives of vibration absorption in these industries at the design stage because of limitations inherent in finite element models. Therefore, it is necessary to develop techniques whereby the dynamic of the system (possibly a car or a helicopter) can be adjusted after it has been built. There are two main approaches: structural modification by passive elements and active control. The state of art of the mathematical theory of vibration absorption is presented and illustrated for the benefit of the reader with numerous simple examples.

  2. Improvements for rotary viscous dampers used in spacecraft deployment mechanisms

    NASA Technical Reports Server (NTRS)

    Stewart, Alphonso; Powers, Charles; Lyons, Ron

    1998-01-01

    During component level thermal-vacuum deployment testing of eight rotary viscous dampers for the Tropical Rainfall Measuring Mission (TRMM) satellite, all the dampers failed to provide damping during a region of the deployment. Radiographic examination showed that air in the damping fluid caused the undamped motion when the dampers were operated in a vacuum environment. Improvements in the procedure used to fill the dampers with damping fluid, the installation of a Viton vacuum seal in the damper cover, and improved screening techniques eliminated the problem.

  3. Active Vibration Isolation of Microgravity Experiments with Spring Umbilicals Using an Electrodynamic Actuator

    NASA Technical Reports Server (NTRS)

    Banerjee, B. B.; Allaire, P. E.; Grodsinsky, C. M.

    1996-01-01

    Microgravity experiments will require active vibration isolation in the low to mid frequency range of 0.1 Hz to 10 Hz. Approximately two orders of acceleration reduction (40 dB) will be required. Previous works have reported results for accelerations transmitted through the umbilical. This paper describes experimental and theoretical results for vibration isolation in one dimension (horizontal) where the simulated experiment is connected to the spacecraft by a spring umbilical. The experiment consisted of a spacecraft (shaker), experiment (mass), umbilical, accelerometer, control electronics, and Lorentz actuator. The experiment mass was supported in magnetic bearings to avoid any stiction problems. Acceleration feedback control was employed to obtain the vibration isolation. Three different spring umbilicals were employed. Acceleration reductions on the order of 40 dB were obtained over the frequency range of 0.1 Hz to 10 Hz. Good agreement was obtained between theory and experiment.

  4. Active control of bending vibrations in thick bars using PZT stack actuators

    SciTech Connect

    Redmond, J.; Parker, G.; Barney, P.; Rodeman, R.

    1995-07-01

    An experimental investigation into active control of bending vibrations in thick bar and plate-like structural elements is described. This work is motivated by vibration problems in machine tools and photolithography machines that require greater control authority than available from conventional surface mounted PZT patches or PVDF films. Focus of this experiment is a cantilevered circular steel bar in which PZT stacks are mounted in cutouts near the bar root. Axially aligned and offset from the neutral axis, these actuators control the bending vibrations by generating moments in the bar through their compressive loads. A Positive Feedback control law is used to significantly augment the damping in the first bending mode. Implications of the experimental results for machine tool stability enhancement are discussed.

  5. Active vibration control of a flexible cantilever beam using shape memory alloy actuators

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; Kagawa, Y.

    2010-08-01

    This paper demonstrates the feasibility of using shape memory alloys (SMAs) as actuators to control the vibration of a flexible cantilever beam. In a tendon mechanism, SMAs are controlled in a push-pull fashion based on H-infinity theory and taking into account the uncertainty in the actuator performance. Using this mechanism, the four vibrational modes (three bending and one torsional) of the cantilever beam can be simultaneously damped. To control bending and torsional vibrational modes of a flexible beam, we install SMAs obliquely in a beam-SMA structure, then measure and theoretically model the properties of an actuator consisting of an SMA and a spring. Using the properties of the actuator, we introduce the state equations based on the dynamic model of the proposed beam-SMA structure and design the active control system according to H-infinity theory. Finally, we experimentally verify the functioning of the system.

  6. Whole-body vibration increases upper and lower body muscle activity in older adults: potential use of vibration accessories.

    PubMed

    Marín, Pedro J; Santos-Lozano, Alejandro; Santin-Medeiros, Fernanda; Vicente-Rodriguez, German; Casajús, Jose A; Hazell, Tom J; Garatachea, Nuria

    2012-06-01

    The current study examined the effects of whole-body vibration (WBV) on upper and lower body muscle activity during static muscle contractions (squat and bicep curls). The use of WBV accessories such as hand straps attached to the platform and a soft surface mat were also evaluated. Surface electromyography (sEMG) was measured for the medial gastrocnemius (MG), vastus lateralis (VL), and biceps brachii (BB) muscles in fourteen healthy older adults (74.8±4.5 years; mean±SD) with a WBV stimulus at an acceleration of 40 m s(-2) (30 Hz High, 2.5 mm or 46 Hz Low, 1.1 mm). WBV increased lower body (VL and MG) sEMG vs baseline (no WBV) though this was decreased with the use of the soft mat. The addition of the bicep curl with hand straps had no effect on lower body sEMG. WBV also increased BB sEMG vs baseline which was further increased when using the hand straps. There was no upper body effect of the soft mat. This study demonstrates WBV increases both lower and upper body muscle activity in healthy older adults. Moreover, WBV accessories such as hand straps attached to the platform or a soft surface mat may be used to alter exercise intensity. PMID:22406015

  7. Experimental study on using electromagnetic devices on bridge stay cables for simultaneous energy harvesting and vibration damping

    NASA Astrophysics Data System (ADS)

    Shen, Wenai; Zhu, Songye; Zhu, Hongping

    2016-06-01

    Flexible bridge stay cables are often vulnerable to problematic vibrations under dynamic excitations. However, from an energy perspective, such excessive vibrations denote a green and sustainable energy source to some electronic devices (such as semi-active dampers or wireless sensors) installed on the same cables. This paper presents an experimental study on a novel dual-function system called electromagnetic damper cum energy harvester (EMDEH). The proposed EMDEH, consisting of an electromagnetic device connected to an energy-harvesting circuit (EHC), simultaneously harvests cable vibration energy and provides sufficient damping to the cables. A fixed-duty-cycle buck–boost converter is employed as the EHC, which emulates a resistive load and provides approximately optimal damping and optimal energy harvesting efficiency when operating in discontinuous conduction mode. A 5.85 m long scaled stay cable installed with a prototype EMDEH is tested in the laboratory under a series of harmonic and random excitations. The EMDEH can achieve a control performance comparable to passive viscous dampers. An average electrical power of 31.6 and 21.51 mW is harvested under harmonic and random vibrations, respectively, corresponding to the efficiency of 16.9% and 13.8%, respectively. Moreover, this experimental study proves that optimal damping and energy harvesting can be achieved simultaneously, which answers a pending question regarding such a dual-objective optimization problem. Self-powered semi-active control systems or wireless sensor networks may be developed for bridge stay cables in the future based on the proposed concept in this study.

  8. Active vibration control for flexible rotor by optimal direct-output feedback control

    NASA Technical Reports Server (NTRS)

    Nonami, K.; Dirusso, E.; Fleming, D. P.

    1989-01-01

    Experimental research tests were performed to actively control the rotor vibrations of a flexible rotor mounted on flexible bearing supports. The active control method used in the tests is called optimal direct-output feedback control. This method uses four electrodynamic actuators to apply control forces directly to the bearing housings in order to achieve effective vibration control of the rotor. The force actuators are controlled by an analog controller that accepts rotor displacement as input. The controller is programmed with experimentally determined feedback coefficients; the output is a control signal to the force actuators. The tests showed that this active control method reduced the rotor resonance peaks due to unbalance from approximately 250 microns down to approximately 25 microns (essentially runout level). The tests were conducted over a speed range from 0 to 10,000 rpm; the rotor system had nine critical speeds within this speed range. The method was effective in significantly reducing the rotor vibration for all of the vibration modes and critical speeds.

  9. Active vibration control for flexible rotor by optimal direct-output feedback control

    NASA Technical Reports Server (NTRS)

    Nonami, Kenzou; Dirusso, Eliseo; Fleming, David P.

    1989-01-01

    Experimental research tests were performed to actively control the rotor vibrations of a flexible rotor mounted on flexible bearing supports. The active control method used in the tests is called optimal direct-output feedback control. This method uses four electrodynamic actuators to apply control forces directly to the bearing housings in order to achieve effective vibration control of the rotor. The force actuators are controlled by an analog controller that accepts rotor displacement as input. The controller is programmed with experimentally determined feedback coefficients; the output is a control signal to the force actuators. The tests showed that this active control method reduced the rotor resonance peaks due to unbalance from approximately 250 micrometers down to approximately 25 micrometers (essentially runout level). The tests were conducted over a speed range from 0 to 10,000 rpm; the rotor system had nine critical speeds within this speed range. The method was effective in significantly reducing the rotor vibration for all of the vibration modes and critical speeds.

  10. Design and modeling of energy generated magneto rheological damper

    NASA Astrophysics Data System (ADS)

    Ahamed, Raju; Rashid, Muhammad Mahbubur; Ferdaus, Md Meftahul; Yusof, Hazlina Md.

    2016-02-01

    In this paper an energy generated mono tube MR damper model has been developed for vehicle suspension systems. A 3D model of energy generated MR damper is developed in Solid Works electromagnetic simulator (EMS) where it is analyzed extensively by finite element method. This dynamic simulation clearly illustrates the power generation ability of the damper. Two magnetic fields are induced inside this damper. One is in the outer coil of the power generator and another is in the piston head coils. The complete magnetic isolation between these two fields is accomplished here, which can be seen in the finite element analysis. The induced magnetic flux densities, magnetic field intensities of this damper are analyzed for characterizing the damper's power generation ability. Finally, the proposed MR damper's energy generation ability was studied experimentally.

  11. Direct voltage control of magnetorheological damper for vehicle suspensions

    NASA Astrophysics Data System (ADS)

    Du, Haiping; Lam, James; Cheung, K. C.; Li, Weihua; Zhang, Nong

    2013-10-01

    The paper presents a study on the direct voltage control of a magnetorheological (MR) damper for application in vehicle suspensions. As MR damper dynamics is highly nonlinear, the direct control system design for an MR damper is difficult. Representing an MR damper by a Takagi-Sugeno (TS) fuzzy model enables the linear control theory to be directly applied to design the MR damper controller. In this paper, first the MR damper dynamics is represented by a TS fuzzy model, and then an H∞ controller that considers the suspension performance requirements and the constraint on the input voltage for the MR damper is designed. Furthermore, considering the case that not all the state variables are measurable in practice, the design of an H∞ observer with immeasurable premise variables and the design of a robust controller are proposed, respectively. Numerical simulations are used to validate the effectiveness of the proposed approaches.

  12. Activities report of the Institute of Sound and Vibration Research

    NASA Astrophysics Data System (ADS)

    Research concerning fluid dynamics and acoustics; audiology and human effects; structures and machinery; and signal processing and control is summarized. Aircraft noise; underwater acoustics; silencers; biomechanics; noise measurement; hearing; structural dynamics; laser technology; automotive engineering; and active control are discussed.

  13. Active vibration damping of the Space Shuttle remote manipulator system

    NASA Technical Reports Server (NTRS)

    Scott, Michael A.; Gilbert, Michael G.; Demeo, Martha E.

    1991-01-01

    The feasibility of providing active damping augmentation of the Space Shuttle Remote Manipulator System (RMS) following normal payload handling operations is investigated. The approach used in the analysis is described, and the results for both linear and nonlinear performance analysis of candidate laws are presented, demonstrating that significant improvement in the RMS dynamic response can be achieved through active control using measured RMS tip acceleration data for feedback.

  14. An analytical study of a six degree-of-freedom active truss for use in vibration control

    NASA Technical Reports Server (NTRS)

    Wynn, Robert H., Jr.; Robertshaw, Harry H.; Horner, C. Garnett

    1990-01-01

    An analytical study of the vibration control capabilities of three configurations of an active truss is presented. The truss studied is composed of two bays of an octahedral-octahedral configuration. The three configurations of the active truss studies are: all six battens activated (6 DOF), the top three battens activated (3 DOF), and the bottom three battens activated (3 DOF). The closed-loop vibration control response of these three configurations are studied with respect to: vibration attenuation, energy utilized, and the effects of motor drive amplifier saturation non-linearities.

  15. The Effects of Vibration Stimuli Applied to the Shoulder Joint on the Activity of the Muscles Around the Shoulder Joint

    PubMed Central

    Lee, Su-kyoung

    2013-01-01

    [Purpose] The present study compared the muscle activity of the upper trapezius with those of the serratus anterior and the lower trapezius when slings, unstable surfaces, were laterally vibrated, to examine the effects of vibration during sling exercises on shoulder stabilization muscles. [Methods] The subjects performed push-up exercises on a sling and maintained isometric contraction in the final stage, while vibration was manually administered to the rope of the sling during the isometric-contraction stage. Vibration within a range of 10 cm was delivered for five seconds at a frequency of 1 Hz in time with a metronome. Vibrations were applied for five seconds at 3 Hz and 3.5 Hz, respectively. [Results] The serratus anterior showed a significant differences between isometric contraction with vibration of 3 Hz and isometric contraction with vibration of 3.5 Hz. [Conclusion] The upper trapezius and the lower trapezius showed prominent changes in muscle activity at 3.5 Hz, and the serratus anterior showed prominent changes in muscle activity at 3 Hz and 3.5 Hz. Therefore, as vibration frequency increased, making the load-bearing surface more unstable, the recruitment of the upper trapezius, the lower trapezius, and the serratus anterior increased. To perform exercises that selectively strengthen the serratus anterior, the exercises should be performed at a vibration frequency of 3 Hz. PMID:24396199

  16. Resonance modeling and control via magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Letelier, Mario F.; Siginer, Dennis A.; Stockle, Juan S.

    2016-08-01

    A method to model and minimize resonant structural oscillations using magnetorheological dampers is presented. The response of the magnetorheological fluid flowing in a circular tube under a pressure gradient to the applied variable magnetic field is tailored to determine the optimum stress field in the fluid to mitigate resonance effects.

  17. A magnetorheological damper with an integrated self-powered displacement sensor

    NASA Astrophysics Data System (ADS)

    Wang, Dai-Hua; Bai, Xian-Xu

    2013-07-01

    In this paper, aiming at self-powering the integrated relative displacement sensor (IRDS) and the corresponding electronic system of an integrated relative displacement self-sensing magnetorheological (MR) damper (IRDSMRD) based semi-active system, the principle of an MR damper with an integrated self-powered displacement sensor is proposed and realized. The prototype of the MR damper with an integrated self-powered displacement sensor is designed and fabricated. In this MR damper, a coil evenly wound on the piston simultaneously acts as the exciting coil for the MR fluid and the IRDS, while a coil evenly wound on the cylinder simultaneously acts as the induction coil (i.e., pick-up coil) for the IRDS and the pick-up coil for the energy harvesting device. On one hand, both the MR fluid and the IRDS are simultaneously magnetized by a mixed signal, in which the carrier signal for the IRDS and the current for the MR fluid with different frequencies are superposed by a superposition circuit. That is, the exciting coil is frequency division multiplexed. On the other hand, when the exciting coil of the MR damper is energized by the carrier signal for the IRDS and the current for the MR fluid, the induced voltage in the pick-up coil not only can be harvested by the energy harvesting circuit to power the IRDS and the corresponding electronic system of the IRDSMRD, but also can be demodulated to obtain the relative displacement of the piston relative to the cylinder. That is, the induction coil for the IRDS and the pick-up coil for the energy harvesting device are functionally multiplexed. The characteristics of the fabricated MR damper with an integrated self-powered displacement sensor, including the energy harvested by the pick-up coil, the relative displacement sensed by the IRDS, and the controllable damping force, are modeled, analyzed, and tested. The feasibility and capability of the proposed principle are validated theoretically and experimentally.

  18. Active control of sound radiation from a vibrating rectangular panel by sound sources and vibration inputs - An experimental comparison

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.; Hansen, C. H.; Snyder, S. D.

    1991-01-01

    Active control of sound radiation from a rectangular panel by two different methods has been experimentally studied and compared. In the first method a single control force applied directly to the structure is used with a single error microphone located in the radiated acoustic field. Global attenuation of radiated sound was observed to occur by two main mechanisms. For 'on-resonance' excitation, the control force had the effect of increasing the total panel input impedance presented to the nosie source, thus reducing all radiated sound. For 'off-resonance' excitation, the control force tends not significantly to modify the panel total response amplitude but rather to restructure the relative phases of the modes leading to a more complex vibration pattern and a decrease in radiation efficiency. For acoustic control, the second method, the number of acoustic sources required for global reduction was seen to increase with panel modal order. The mechanism in this case was that the acoustic sources tended to create an inverse pressure distribution at the panel surface and thus 'unload' the panel by reducing the panel radiation impedance. In general, control by structural inputs appears more effective than control by acoustic sources for structurally radiated noise.

  19. A Study of Vibration Reduction of Rolling Piston Type Rotary Compressor

    NASA Astrophysics Data System (ADS)

    Yoshimura, Takao; Koyama, Takashi; Morita, Ichiro; Kobayashi, Masanori; Uetuji, Toshio

    In general,the vibration of rolling piston type rotary compressors is greater than that of reciprocating compressors because the compressor-motor unit is fixed to the shell. It is therefore necessary that refrigerators utilizing rotary compressors incorporated a vibration-proof design. This paper refers to the experimental vibration reduction study of rotary compressors (horizontally installed) for household refrigerators and other appliances. The vibration of rotary compressors consists of the rotational vibration caused by the speed variation of the shaft and of the imbalance vibration caused by the mass imbalance in the rotation system. There are various methods for reducing the rotational vibration. This study researched the dynamic damper. It will be shown that the dynamic damper,using a helical extension spring applied to the outside of the shell,is effective in reducing vibration. In regards to the imbalance vibration,this paper researched the influence of the number of correction planes and the accuracy of the balancing.

  20. Effectiveness of a passive-active vibration isolation system with actuator constraints

    NASA Astrophysics Data System (ADS)

    Sun, Lingling; Sun, Wei; Song, Kongjie; Hansen, Colin H.

    2014-05-01

    In the prediction of active vibration isolation performance, control force requirements were ignored in previous work. This may limit the realization of theoretically predicted isolation performance if control force of large magnitude cannot be supplied by actuators. The behavior of a feed-forward active isolation system subjected to actuator output constraints is investigated. Distributed parameter models are developed to analyze the system response, and to produce a transfer matrix for the design of an integrated passive-active isolation system. Cost functions comprising a combination of the vibration transmission energy and the sum of the squared control forces are proposed. The example system considered is a rigid body connected to a simply supported plate via two passive-active isolation mounts. Vertical and transverse forces as well as a rotational moment are applied at the rigid body, and resonances excited in elastic mounts and the supporting plate are analyzed. The overall isolation performance is evaluated by numerical simulation. The simulation results are then compared with those obtained using unconstrained control strategies. In addition, the effects of waves in elastic mounts are analyzed. It is shown that the control strategies which rely on unconstrained actuator outputs may give substantial power transmission reductions over a wide frequency range, but also require large control force amplitudes to control excited vibration modes of the system. Expected power transmission reductions for modified control strategies that incorporate constrained actuator outputs are considerably less than typical reductions with unconstrained actuator outputs. In the frequency range in which rigid body modes are present, the control strategies can only achieve 5-10 dB power transmission reduction, when control forces are constrained to be the same order of the magnitude as the primary vertical force. The resonances of the elastic mounts result in a notable increase

  1. Active Monitoring With The Use Of Seismic Vibrators: Experimental Systems And The Results Of Works

    NASA Astrophysics Data System (ADS)

    Kovalevsky, V.; Alekseev, A.; Glinsky, B.; Khairetdinov, M.; Seleznev, V.; Emanov, A.; Soloviev, V.

    2004-12-01

    Active methods of geophysical monitoring with the use of powerful seismic vibrators play an important role in the investigation of changes in the medium's stressed-deformed state in seismic prone zones for problems of seismic hazard prediction. In the last three decades, this scientific direction has been actively developed at institutes of Siberian Branch of Russian Academy of Sciences. In this period, experimental systems for the active monitoring of the medium, which include powerful vibrational sources with computer control systems, mobile specialized complexes for the precision recording of vibrational seismic signals, and data processing systems have been created. A review of various constructions of resonant vibrational seismic sources with a vibrational force of 100 tons in the frequency range from 5 to 15 Hz and the principles of creation of precision computer control systems and low-frequency three-component recording systems VIRS-M, VIRS-K, and ROSA is presented. A method for the active monitoring of the medium with the use of wideband sweep signals and narrow-band harmonic signals radiated by seismic vibrators has been developed. To determine the sensitivity of the active monitoring system, some experiments to detect the influence of the Earth's crust tidal deformations (of the order of 10-7) on seismic wave velocities have been performed. A 100-ton seismic vibrator and recording systems were located at a distance of 356 km. The radiation sessions of harmonic and sweep signals were repeated every 3 hours during 8 days. This made it possible to construct the time series of variations in the amplitudes and phases of the signals and wave arrival times. Both 12-hour and 24-hour periodicities correlated with the earth's tides were distinguished in the spectrum of variations of the recorded signals. The experiment has shown that the active monitoring system makes it possible to detect relative variations of the seismic wave velocities of the order of 10

  2. A fully dynamic magneto-rheological fluid damper model

    NASA Astrophysics Data System (ADS)

    Jiang, Z.; Christenson, R. E.

    2012-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.

  3. Experimental characterization of commercially practical magnetorheological fluid damper technology

    NASA Astrophysics Data System (ADS)

    Kelso, Shawn P.

    2001-06-01

    As technologies for magnetorheological (MR) fluid hardware further evolve towards commercial adoption, the appeal for simpler, more cost-effective solutions becomes evident. While the skills involved in methods of manufacturing and cost-reduction efforts for mass production lie with the manufacturing community, practical and cost-effective MR technologies must first exist. As part of a 'whole approach' MR solution, the MR damper technology presented in this paper illustrates the development of a fast-response, low-power, cost-effective solution. Fundamentally, a competitive 'whole approach' active or semi-active MR solution can be viewed as system of separate components: parameter sensing, intelligent control, power delivery, and MR hardware technology. The development of any one single component should not successfully evolve without the addressing the cost efficiency and commercialization concerns of the other three. The MR hardware component should be predictable in performance behavior, capable of high damping force at minimal power, and fast in time response to complement simplified control schemes. The design effort is further challenged to meet these requirements within a simple, cost-effective package that holds commercial development appeal. This research includes the characterization of a new prototype MR damper including a description of the device technology, characterization test results and current work. It is evident by these results that this MR technology, comprising simple, commercial-off-the-shelf (COTS) components where possible, presents an attractive, practical and cost effective component of the 'whole approach' MR solution.

  4. H ∞ control of a suspension with a magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Félix-Herrán, L. C.; Mehdi, D.; Rodríguez-Ortiz, J. de J.; Soto, R.; Ramírez-Mendoza, R.

    2012-08-01

    This research work presents an H ∞ controller based on a Takagi-Sugeno (T-S) fuzzy model for a two-degrees-of-freedom (2-DOF) one-quarter-vehicle semi-active suspension with a magnetorheological damper where the actuator dynamics are included in the control synthesis. These dynamics enclose nonlinear damper phenomena, avoided in many other studies, and that can improve the suspension system by means of a more accurate model. The objective is to obtain a semi-active suspension that considerably improves the passive suspension efficiency based on some frequency domain performance criteria. The advantage of having the T-S system as a reference is that each piecewise linear system can be exposed to the well-known control theory. Besides, the proposed solution is compared with the recent reported work to highlight its advantages. A case of study is included and simulation work supports the results. The methodology applied herein can be extended to a half-vehicle model, and to the four wheels to have a global chassis control in order to maximise passenger comfort and vehicle stability.

  5. Elastic ring deformation and pedestal contact status analysis of elastic ring squeeze film damper

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Ding, Qian

    2015-06-01

    This paper investigates the dynamic parametric characteristic of the elastic ring squeeze film damper (ERSFD). Firstly, the coupled oil film Reynolds equations and dynamic equations of an ERSFD supported rotor system are established. The finite differential method and numerical simulation are used to analyze the oil film pressure distribution, bearing capacity of ERSFD, oil film stiffness and damping characteristics during a vibration period. Then, based on the oil film pressure results, the deformation of elastic ring is revealed by the finite element method. Finally, pedestal contact status is analyzed according to the change of oil film thickness during a vibration period. The results reveal that the oil film pressure is sectionally continuous, the deformation of elastic ring is complex under the compression of inner and outer oil film, and different pedestal contacts occur in a vibration period. The level of nonlinearity of the bearing capacity, oil film stiffness and damping can be effectively lightened by application of the elastic ring.

  6. Active control of panel vibrations induced by boundary-layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1991-01-01

    Some problems in active control of panel vibration excited by a boundary layer flow over a flat plate are studied. In the first phase of the study, the optimal control problem of vibrating elastic panel induced by a fluid dynamical loading was studied. For a simply supported rectangular plate, the vibration control problem can be analyzed by a modal analysis. The control objective is to minimize the total cost functional, which is the sum of a vibrational energy and the control cost. By means of the modal expansion, the dynamical equation for the plate and the cost functional are reduced to a system of ordinary differential equations and the cost functions for the modes. For the linear elastic plate, the modes become uncoupled. The control of each modal amplitude reduces to the so-called linear regulator problem in control theory. Such problems can then be solved by the method of adjoint state. The optimality system of equations was solved numerically by a shooting method. The results are summarized.

  7. Experimental studies on active vibration control of a smart composite beam using a PID controller

    NASA Astrophysics Data System (ADS)

    Jovanović, Miroslav M.; Simonović, Aleksandar M.; Zorić, Nemanja D.; Lukić, Nebojša S.; Stupar, Slobodan N.; Ilić, Slobodan S.

    2013-11-01

    This paper presents experimental verification of the active vibration control of a smart cantilever composite beam using a PID controller. In order to prevent negative occurrences in the derivative and integral terms in a PID controller, first-order low-pass filters are implemented in the derivative action and in the feedback of the integral action. The proposed application setup consists of a composite cantilever beam with a fiber-reinforced piezoelectric actuator and strain gage sensors. The beam is modeled using a finite element method based on third-order shear deformation theory. The experiment considers vibration control under periodic excitation and an initial static deflection. A control algorithm was implemented on a PIC32MX440F256H microcontroller. Experimental results corresponding to the proposed PID controller are compared with corresponding results using proportional (P) control, proportional-integral (PI) control and proportional-derivative (PD) control. Experimental results indicate that the proposed PID controller provides 8.93% more damping compared to a PD controller, 14.41% more damping compared to a PI controller and 19.04% more damping compared to a P controller in the case of vibration under periodic excitation. In the case of free vibration control, the proposed PID controller shows better performance (settling time 1.2 s) compared to the PD controller (settling time 1.5 s) and PI controller (settling time 2.5 s).

  8. Optimal placement of piezoelectric plates for active vibration control of gas turbine blades: experimental results

    NASA Astrophysics Data System (ADS)

    Botta, F.; Marx, N.; Gentili, S.; Schwingshackl, C. W.; Di Mare, L.; Cerri, G.; Dini, D.

    2012-04-01

    It is well known that the gas turbine blade vibrations can give rise to catastrophic failures and a reduction of the blades life because of fatigue related phenomena[1]-[3] . In last two decades, the adoption of piezoelectric elements, has received considerable attention by many researcher for its potential applicability to different areas of mechanical, aerospace, aeronautical and civil engineering. Recently, a number of studies of blades vibration control via piezoelectric plates and patches have been reported[4]-[6] . It was reported that the use of piezoelectric elements can be very effective in actively controlling vibrations. In one of their previous contributions[7] , the authors of the present manuscript studied a model to control the blade vibrations by piezoelectric elements and validated their results using a multi-physics finite elements package (COMSOL) and results from the literature. An optimal placement method of piezoelectric plate has been developed and applied to different loading scenarios for realistic configurations encountered in gas turbine blades. It has been demonstrated that the optimal placement depends on the spectrum of the load, so that segmented piezoelectric patches have been considered and, for different loads, an optimal combination of sequential and/or parallel actuation and control of the segments has been studied. In this paper, an experimental investigation carried out by the authors using a simplified beam configuration is reported and discussed. The test results obtained by the investigators are then compared with the numerical predictions [7] .

  9. Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

    NASA Technical Reports Server (NTRS)

    Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.

    2014-01-01

    This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

  10. Refinement and evaluation of helicopter real-time self-adaptive active vibration controller algorithms

    NASA Technical Reports Server (NTRS)

    Davis, M. W.

    1984-01-01

    A Real-Time Self-Adaptive (RTSA) active vibration controller was used as the framework in developing a computer program for a generic controller that can be used to alleviate helicopter vibration. Based upon on-line identification of system parameters, the generic controller minimizes vibration in the fuselage by closed-loop implementation of higher harmonic control in the main rotor system. The new generic controller incorporates a set of improved algorithms that gives the capability to readily define many different configurations by selecting one of three different controller types (deterministic, cautious, and dual), one of two linear system models (local and global), and one or more of several methods of applying limits on control inputs (external and/or internal limits on higher harmonic pitch amplitude and rate). A helicopter rotor simulation analysis was used to evaluate the algorithms associated with the alternative controller types as applied to the four-bladed H-34 rotor mounted on the NASA Ames Rotor Test Apparatus (RTA) which represents the fuselage. After proper tuning all three controllers provide more effective vibration reduction and converge more quickly and smoothly with smaller control inputs than the initial RTSA controller (deterministic with external pitch-rate limiting). It is demonstrated that internal limiting of the control inputs a significantly improves the overall performance of the deterministic controller.

  11. Modelling and study of active vibration control for off-road vehicle

    NASA Astrophysics Data System (ADS)

    Zhang, Junwei; Chen, Sizhong

    2014-05-01

    In view of special working characteristics and structure, engineering machineries do not have conventional suspension system typically. Consequently, operators have to endure severe vibrations which are detrimental both to their health and to the productivity of the loader. Based on displacement control, a kind of active damping method is developed for a skid-steer loader. In this paper, the whole hydraulic system for active damping method is modelled which include swash plate dynamics model, proportional valve model, piston accumulator model, pilot-operated check valve model, relief valve model, pump loss model, and cylinder model. A new road excitation model is developed for the skid-steer loader specially. The response of chassis vibration acceleration to road excitation is verified through simulation. The simulation result of passive accumulator damping is compared with measurements and the comparison shows that they are close. Based on this, parallel PID controller and track PID controller with acceleration feedback are brought into the simulation model, and the simulation results are compared with passive accumulator damping. It shows that the active damping methods with PID controllers are better in reducing chassis vibration acceleration and pitch movement. In the end, the test work for active damping method is proposed for the future work.

  12. Origin invariance in vibrational resonance Raman optical activity.

    PubMed

    Vidal, Luciano N; Egidi, Franco; Barone, Vincenzo; Cappelli, Chiara

    2015-05-01

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them. PMID:25956084

  13. Origin invariance in vibrational resonance Raman optical activity

    NASA Astrophysics Data System (ADS)

    Vidal, Luciano N.; Egidi, Franco; Barone, Vincenzo; Cappelli, Chiara

    2015-05-01

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

  14. Origin invariance in vibrational resonance Raman optical activity

    SciTech Connect

    Vidal, Luciano N. Cappelli, Chiara; Egidi, Franco; Barone, Vincenzo

    2015-05-07

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

  15. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

    NASA Astrophysics Data System (ADS)

    Premkumar, S.; Jawahar, A.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin

    2015-06-01

    The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

  16. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

    SciTech Connect

    Premkumar, S.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin; Jawahar, A.

    2015-06-24

    The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material.

  17. An overview of possible and not-so-possible tasks for active control of sound and vibration

    NASA Astrophysics Data System (ADS)

    von Flotow, Andreas H.

    1991-05-01

    While such passive approaches to helicopter sound and vibration control as vibration isolation/acoustic blocking, damping/acoustic absorption, and tuned absorbers, can be actively implemented and enhanced, active control methods transcend these possibilities. A survey is presently conducted of the literature generated by active-control research in recent years, with a view to emerging opportunities that do not risk instability, excessive development and production costs, and undue complexity.

  18. Vibration reduction in helicopter rotors using an active control surface located on the blade

    NASA Technical Reports Server (NTRS)

    Millott, T. A.; Friedmann, P. P.

    1992-01-01

    A feasibility study of vibration reduction in a four-bladed helicopter rotor using individual blade control (IBC), which is implemented by an individually controlled aerodynamic surface located on each blade, is presented. For this exploratory study, a simple offset-hinged spring restrained model of the blade is used with fully coupled flap-lag-torsional dynamics for each blade. Deterministic controllers based on local and global system models are implemented to reduce 4/rev hub loads using both an actively controlled aerodynamic surface on each blade as well as conventional IBC, where the complete blade undergoes cyclic pitch change. The effectiveness of the two approaches for simultaneous reduction of the 4/rev hub shears and hub moments is compared. Conventional IBC requires considerably more power to achieve approximately the same level of vibration reduction as that obtained by implementing IBC using an active control surface located on the outboard segment of the blade. The effect of blade torsional flexibility on the vibration reduction effectiveness of the actively controlled surface was also considered and it was found that this parameter has a very substantial influence.

  19. Active vibration control of a smart pultruded fiber-reinforced polymer I-beam

    NASA Astrophysics Data System (ADS)

    Song, Gangbing; Qiao, Pizhong; Sethi, Vineet; Prasad, A.

    2002-06-01

    Advanced and innovative materials and structures are increasingly used in civil infrastructure applications. By combining the advantages of composites and smart sensors and actuators, active or smart composite structures can be created and be efficiently adopted in practical structural applications. This paper presents results of active vibration control of a pultruded fiber-reinforced polymer (FRP) composites thin-walled I-beams using smart sensors and actuators. The FRP I-beams are made of E-glass fibers and polyester resins. The FRP I-beam is in a cantilevered configuration. PZT (Lead zirconate titanate) type of piezoelectric ceramic patches are used as smart sensors and actuators. These patches are surface-bonded near the cantilevered end of the I-beam. Utilizing results from modal analyses and experimental modal testing, several active vibration control methods, such as position feedback control, strain rate feedback control and lead compensator, are investigated. Experimental results demonstrate that the proposed methods achieve effective vibration control of FRP I-beams. For instance, the modal damping ratio of the strong direction first bending mode increases by more than 1000 percent with a positive position feedback control.

  20. Active vibration control of a smart pultruded fiber-reinforced polymer I-beam

    NASA Astrophysics Data System (ADS)

    Song, G.; Qiao, P.; Sethi, V.; Prasad, A.

    2004-08-01

    Advanced and innovative materials and structures are increasingly used in civil infrastructure applications. By combining the advantages of composites and smart sensors and actuators, active or smart composite structures can be created and be efficiently adopted in practical structural applications. This paper presents results on active vibration control of pultruded fiber-reinforced polymer (FRP) composite thin-walled I-beams using smart sensors and actuators. The FRP I-beams are made of E-glass fibers and polyester resins. The FRP I-beam is in a cantilevered configuration. The PZT (lead zirconate titanate) type of piezoelectric ceramic patches are used as smart sensors and actuators. These patches are surface bonded near the cantilevered end of the I-beam. Utilizing results from modal analyses and experimental modal testing, several active vibration control methods, such as position feedback control, strain rate feedback control and lead compensation, are investigated. Experimental results demonstrate that the proposed methods achieve effective vibration control of FRP I-beams. For instance, the modal damping ratio of the strong direction first bending mode increases by more than 1000% with positive position feedback control.

  1. Active vibration control on a quarter-car for cancellation of road noise disturbance

    NASA Astrophysics Data System (ADS)

    Belgacem, Walid; Berry, Alain; Masson, Patrice

    2012-07-01

    In this paper, a methodology is presented for the cancellation of road noise, from the analysis of vibration transmission paths for an automotive suspension to the design of an active control system using inertial actuators on a suspension to reduce the vibrations transmitted to the chassis. First, experiments were conducted on a Chevrolet Epica LS automobile on a concrete test track to measure accelerations induced on the suspension by the road. These measurements were combined with experimental Frequency Response Functions (FRFs) measured on a quarter-car test bench to reconstruct an equivalent three dimensional force applied on the wheel hub. Second, FRFs measured on the test bench between the three-dimensional driving force and forces at each suspension/chassis linkage were used to characterize the different transmission paths of vibration energy to the chassis. Third, an experimental model of the suspension was constructed to simulate the configuration of the active control system, using the primary (disturbance) FRFs and secondary (control) FRFs also measured on the test bench. This model was used to optimize the configuration of the control actuators and to evaluate the required forces. Finally, a prototype of an active suspension was implemented and measurements were performed in order to assess the performance of the control approach. A 4.6 dB attenuation on transmitted forces was obtained in the 50-250 Hz range.

  2. Active vibration and noise control of vibro-acoustic system by using PID controller

    NASA Astrophysics Data System (ADS)

    Li, Yunlong; Wang, Xiaojun; Huang, Ren; Qiu, Zhiping

    2015-07-01

    Active control simulation of the acoustic and vibration response of a vibro-acoustic cavity of an airplane based on a PID controller is presented. A full numerical vibro-acoustic model is developed by using an Eulerian model, which is a coupled model based on the finite element formulation. The reduced order model, which is used to design the closed-loop control system, is obtained by the combination of modal expansion and variable substitution. Some physical experiments are made to validate and update the full-order and the reduced-order numerical models. Optimization of the actuator placement is employed in order to get an effective closed-loop control system. For the controller design, an iterative method is used to determine the optimal parameters of the PID controller. The process is illustrated by the design of an active noise and vibration control system for a cavity structure. The numerical and experimental results show that a PID-based active control system can effectively suppress the noise inside the cavity using a sound pressure signal as the controller input. It is also possible to control the noise by suppressing the vibration of the structure using the structural displacement signal as the controller input. For an airplane cavity structure, considering the issue of space-saving, the latter is more suitable.

  3. Optimal design of magnetic system for the magnetorheological intelligent damper

    NASA Astrophysics Data System (ADS)

    Mei, De-Qing; Kong, Tian-Rong; Chen, Zi-Chen

    2005-12-01

    In the structure of Magnetorheological (MR) intelligent damper, the magnetic system is a pivotal part. It has direct influence on the damper's performance. In order to optimize damper's magnetic system, the parameter model of magnetic system was established, which included many factors such as radius of piston rod, radius of piston, number of coil, thickness of piston cylinder, gap length of the annular orifice, and effectual length of the annular orifice. Then the optimal model of magnetic system was established, which was based on the characteristic equation of MR fluid, the mechanical model of damper, the restrained dimension of damper's structure and the parameter model of magnetic system. And the optimal model was solved based on the large-scale optimizing algorithm. The optimized result was validated by FEM analysis. The results show that the optimizing method of magnetic system for MR intelligent damper is accurate and effective.

  4. Active vibration reduction by optimally placed sensors and actuators with application to stiffened plates by beams

    NASA Astrophysics Data System (ADS)

    Daraji, A. H.; Hale, J. M.

    2014-10-01

    This study concerns new investigation of active vibration reduction of a stiffened plate bonded with discrete sensor/actuator pairs located optimally using genetic algorithms based on a developed finite element modeling. An isotropic plate element stiffened by a number of beam elements on its edges and having a piezoelectric sensor and actuator pair bonded to its surfaces is modeled using the finite element method and Hamilton’s principle, taking into account the effects of piezoelectric mass, stiffness and electromechanical coupling. The modeling is based on the first order shear deformation theory taking into account the effects of bending, membrane and shear deformation for the plate, the stiffening beam and the piezoelectric patches. A Matlab finite element program has been built for the stiffened plate model and verified with ANSYS and also experimentally. Optimal placement of ten piezoelectric sensor/actuator pairs and optimal feedback gain for active vibration reduction are investigated for a plate stiffened by two beams arranged in the form of a cross. The genetic algorithm was set up for optimization of sensor/actuator placement and feedback gain based on the minimization of the optimal linear quadratic index as an objective function to suppress the first six modes of vibration. Comparison study is presented for active vibration reduction of a square cantilever plate stiffened by crossed beams with two sensor/actuator configurations: firstly, ten piezoelectric sensor/actuator pairs are located in optimal positions; secondly, a piezoelectric layer of single sensor/actuator pair covering the whole of the stiffened plate as a SISO system.

  5. Enzyme activation and catalysis: characterisation of the vibrational modes of substrate and product in protochlorophyllide oxidoreductase.

    PubMed

    Sytina, Olga A; Alexandre, Maxime T; Heyes, Derren J; Hunter, C Neil; Robert, Bruno; van Grondelle, Rienk; Groot, Marie Louise

    2011-02-14

    The light-dependent reduction of protochlorophyllide, a key step in the synthesis of chlorophyll, is catalyzed by the enzyme protochlorophyllide oxidoreductase (POR) and requires two photons (O. A. Sytina et al., Nature, 2008, 456, 1001-1008). The first photon activates the enzyme-substrate complex, a subsequent second photon initiates the photochemistry by triggering the formation of a catalytic intermediate. These two events are characterized by different spectral changes in the infra-red spectral region. Here, we investigate the vibrational frequencies of the POR-bound and unbound substrate, and product, and thus provide a detailed assignment of the spectral changes in the 1800-1250 cm(-1) region associated with the catalytic conversion of PChlide:NADPH:TyrOH into Chlide:NADP(+):TyrO(-). Fluorescence line narrowed spectra of the POR-bound Pchlide reveal a C=O keto group downshifted by more than 20 cm(-1) to a relatively low vibrational frequency of 1653 cm(-1), as compared to the unbound Pchlide, indicating that binding of the chromophore to the protein occurs via strong hydrogen bond(s). The frequencies of the C=C vibrational modes are consistent with a six-coordinated state of the POR-bound Pchlide, suggesting that there are two coordination interactions between the central Mg atom of the chromophore and protein residues, and/or a water molecule. The frequencies of the C=C vibrational modes of Chlide are consistent with a five-coordinated state, indicating a single interaction between the central Mg atom of the chromophore and a water molecule. Rapid-scan FTIR measurements on the Pchlide:POR:NADPH complex at 4 cm(-1) spectral resolution reveal a new band in the 1670 cm(-1) region. The FTIR spectra of the enzyme activation phase indicate involvement of a nucleotide-binding structural motif, and an increased exposure of the protein to solvent after activation. PMID:21103538

  6. Function Test of an Automatic Locking and Unlocking System for Passive Damper by using Parabolic Flight

    NASA Astrophysics Data System (ADS)

    Sakurai, M.; Yoshihara, S.; Ohnishi, M.; Watanabe, K.; Sekiya, T.

    2002-01-01

    existence of residual acceleration has been reported.The acceleration is called "g-jitter".In a lot of experiments carried out in space, the adverse influence of the g-jitter on their results has been found out.To understand the effect of g-jitter on fluid phenomena, we are making preparation to orbital experiment as a post-JUSTSAP. In the experiment, the information to understand the influence of the g-jitter on diffusion phenomena will be obtained by comparing diffusion process in two containers. One container is isolated from the g-jitter using a passive damper and the other is not. To avoid the strong accelerations during launch giving damage to the passive damper, an automatic locking and unlocking system for the passive damper must be applied to the experimental apparatus. To increase flight opportunity of the experiment, the apparatus is designed as a small, light, self-controlled and self-powered system.In order to test the function of the apparatus, we have carried out parabolic flight experiments as preparations for the orbital experiment. mol/l), ethanol (0.7%) and NaCl (0.02 mol/l) is set on the upper base plate, which has the passive damper and the locking-unlocking system.The other container is directly set on the lower base plate.The passive damper comprises of flexible membranes and thin-metal plate and connecting rods. The damping is performed under micro-gravity condition by utilizing the non-linear elasticity of flexible membranes. The CPU unit on the upper base plate has 8 channels of A/D converter to measure 3-dimensional vibrations and 8 relays to control all experimental procedures, that is, locking, unlocking, heating, recording and so on. The power unit provides electricity to the CPU unit, the locking-unlocking system and heaters. A digital camera records diffusion of color in both cells simultaneously. color between pH8.3 and pH10. airplane vibrations were directly translated to the experimental container.During a parabolic flight, a

  7. Characterization and design of tuned liquid dampers with floating roof considering arbitrary tank cross-sections

    NASA Astrophysics Data System (ADS)

    Ruiz, R. O.; Taflanidis, A. A.; Lopez-Garcia, D.

    2016-04-01

    A recently proposed new type of liquid mass damper, called Tuned Liquid Damper with Floating Roof (TLD-FR), is the focus of this paper. The TLD-FR consists of a traditional TLD (tank filled with liquid) with the addition of a floating roof. The sloshing of the liquid within the tank counteracts the motion of the primary structure it is placed on, offering the desired energy dissipation in the vibration of the latter, while the roof prevents wave breaking phenomena and introduces an essentially linear response. This creates a dynamic behavior that resembles other types of linear Tuned Mass dampers (TMDs). This investigation extends previous work of the authors to consider TLDs-FR with arbitrary tank cross-sections, whereas it additionally offers new insights on a variety of topics. In particular, the relationship between the tank geometry and the resultant vibratory characteristics is examined in detail, including the impact of the roof on these characteristics. An efficient mapping between these two is also developed, utilizing Kriging metamodeling concepts, to support the TLD-FR design. It is demonstrated that the overall behavior can be modeled through introduction of only four variables: the liquid mass, the frequency and damping ratio of the fundamental sloshing mode of the TLD-FR, and the efficiency index, which is related to the portion of the total mass that participates in this mode. Comparisons between TLDs-FR and other types of mass dampers are established through the use of the latter index. A design example is presented considering the dynamic response of a structure under stationary excitation. It is illustrated in this example that for complex tank cross-sectional geometries there exists a manifold of tank configurations leading to the same primary vibratory characteristics and therefore same efficiency of the TLD-FR. Considerations about excessive displacements of the roof can be then incorporated to indicate preference towards some of these

  8. BVI induced vibration and noise alleviation by active and passive approaches

    NASA Astrophysics Data System (ADS)

    Liu, Li

    This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

  9. Probing the Raman-active acoustic vibrations of nanoparticles with extraordinary spectral resolution

    NASA Astrophysics Data System (ADS)

    Wheaton, Skyler; Gelfand, Ryan M.; Gordon, Reuven

    2015-01-01

    Colloidal quantum dots, viruses, DNA and all other nanoparticles have acoustic vibrations that can act as ‘fingerprints’ to identify their shape, size and mechanical properties, yet high-resolution Raman spectroscopy in this low-energy range has been lacking. Here, we demonstrate extraordinary acoustic Raman (EAR) spectroscopy to measure the Raman-active vibrations of single isolated nanoparticles in the 0.1-10 cm-1 range with ˜0.05 cm-1 resolution, to resolve peak splitting from material anisotropy and to probe the low-frequency modes of biomolecules. EAR employs a nanoaperture laser tweezer that can select particles of interest and manipulate them once identified. We therefore believe that this nanotechnology will enable expanded capabilities for the study of nanoparticles in the materials and life sciences.

  10. Active vibration control of flexible cantilever plates using piezoelectric materials and artificial neural networks

    NASA Astrophysics Data System (ADS)

    Abdeljaber, Osama; Avci, Onur; Inman, Daniel J.

    2016-02-01

    The study presented in this paper introduces a new intelligent methodology to mitigate the vibration response of flexible cantilever plates. The use of the piezoelectric sensor/actuator pairs for active control of plates is discussed. An intelligent neural network based controller is designed to control the optimal voltage applied on the piezoelectric patches. The control technique utilizes a neurocontroller along with a Kalman Filter to compute the appropriate actuator command. The neurocontroller is trained based on an algorithm that incorporates a set of emulator neural networks which are also trained to predict the future response of the cantilever plate. Then, the neurocontroller is evaluated by comparing the uncontrolled and controlled responses under several types of dynamic excitations. It is observed that the neurocontroller reduced the vibration response of the flexible cantilever plate significantly; the results demonstrated the success and robustness of the neurocontroller independent of the type and distribution of the excitation force.

  11. BNL 56 MHz HOM damper prototype fabrication at JLAB

    SciTech Connect

    Huque, N.; McIntyre, G.; Daly, E. F.; Clemens, W.; Wu, Q.; Seberg, S.; Bellavia, S.

    2015-05-03

    A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

  12. BNL 56 MHz HOM Damper Prototype Fabrication at JLab

    SciTech Connect

    Huque, Naeem A.; Daly, Edward F.; Clemens, William A.; McIntyre, Gary T.; Wu, Qiong; Seberg, Scott; Bellavia, Steve

    2015-09-01

    A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider's (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

  13. Vibration control via stiffness switching of magnetostrictive transducers

    NASA Astrophysics Data System (ADS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-04-01

    In this paper, a computational study is presented of structural vibration control that is realized by switching a magneto-strictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magneto-strictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magneto-strictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magneto-strictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magneto-strictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

  14. Vibration Control via Stiffness Switching of Magnetostrictive Transducers

    NASA Technical Reports Server (NTRS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-01-01

    In this paper, a computational study is presented of structural vibration control that is realized by switching a magnetostrictive transducer between high and low stiffness states. Switching is accomplished by either changing the applied magnetic field with a voltage excitation or changing the shunt impedance on the transducer's coil (i.e., the magnetostrictive material's magnetic boundary condition). Switched-stiffness vibration control is simulated using a lumped mass supported by a damper and the magnetostrictive transducer (mount), which is represented by a nonlinear, electromechanical model. Free vibration of the mass is calculated while varying the mount's stiffness according to a reference switched-stiffness vibration control law. The results reveal that switching the magnetic field produces the desired change in stiffness, but also an undesired actuation force that can significantly degrade the vibration control. Hence, a modified switched-stiffness control law that accounts for the actuation force is proposed and implemented for voltage-controlled stiffness switching. The influence of the magneto-mechanical bias condition is also discussed. Voltage-controlled stiffness switching is found to introduce damping equivalent to a viscous damping factor up to about 0.13; this is shown to primarily result from active vibration reduction caused by the actuation force. The merit of magnetostrictive switched-stiffness vibration control is then quantified by comparing the results of voltage- and shunt-controlled stiffness switching to the performance of optimal magnetostrictive shunt damping. For the cases considered, optimal resistive shunt damping performed considerably better than both voltage- and shunt-controlled stiffness switching.

  15. Shunted Piezoelectric Vibration Damping Analysis Including Centrifugal Loading Effects

    NASA Technical Reports Server (NTRS)

    Min, James B.; Duffy, Kirsten P.; Provenza, Andrew J.

    2011-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue problems which require damping treatments to mitigate vibration levels. One method is the use of piezoelectric materials as passive or active dampers. Based on the technical challenges and requirements learned from previous turbomachinery rotor blades research, an effort has been made to investigate the effectiveness of a shunted piezoelectric for the turbomachinery rotor blades vibration control, specifically for a condition with centrifugal rotation. While ample research has been performed on the use of a piezoelectric material with electric circuits to attempt to control the structural vibration damping, very little study has been done regarding rotational effects. The present study attempts to fill this void. Specifically, the objectives of this study are: (a) to create and analyze finite element models for harmonic forced response vibration analysis coupled with shunted piezoelectric circuits for engine blade operational conditions, (b) to validate the experimental test approaches with numerical results and vice versa, and (c) to establish a numerical modeling capability for vibration control using shunted piezoelectric circuits under rotation. Study has focused on a resonant damping control using shunted piezoelectric patches on plate specimens. Tests and analyses were performed for both non-spinning and spinning conditions. The finite element (FE) shunted piezoelectric circuit damping simulations were performed using the ANSYS Multiphysics code for the resistive and inductive circuit piezoelectric simulations of both conditions. The FE results showed a good correlation with experimental test results. Tests and analyses of shunted piezoelectric damping control, demonstrating with plate specimens, show a great potential to reduce blade vibrations under centrifugal loading.

  16. Damping properties of stay cable-passive damper system with effects of cable sag and damper stiffness

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zhang, Guangqiao

    2013-04-01

    The present paper derivate the asymptotic solution of modal damping of one taut stay cable attached with one passive damper including damper stiffness and viscous damping. The effect of the damper stiffness on the modal damping of the stay cable-passive system was analytical investigated. On the basis of the asymptotic solution of modal damping of one stay cable attached with one passive damper with the effect of cable stiffness and by using the decay factor of damper stiffness and the decay factor of cable sag, maximum modal damping ratio and corresponding optimal damping coefficient, which indicates the relationships of the characteristics of the damper and the cable sag was theoretically analyzed. Numerical analysis of parameters on the effect of dynamic performance of the controlled stay cable was conducted.

  17. The partially filled viscous ring damper.

    NASA Technical Reports Server (NTRS)

    Alfriend, K. T.

    1973-01-01

    The problem of a spinning satellite with a partially filled viscous ring damper is investigated. It is shown that there are two distinct modes of motion, the nutation-synchronous mode and spin-synchronous mode. From an approximate solution of the equations of motion a time constant is obtained for each mode. From a consideration of the fluid dynamics several methods are developed for determining the damping constant.

  18. Analytical design and evaluation of an active control system for helicopter vibration reduction and gust response alleviation

    NASA Technical Reports Server (NTRS)

    Taylor, R. B.; Zwicke, P. E.; Gold, P.; Miao, W.

    1980-01-01

    An analytical study was conducted to define the basic configuration of an active control system for helicopter vibration and gust response alleviation. The study culminated in a control system design which has two separate systems: narrow band loop for vibration reduction and wider band loop for gust response alleviation. The narrow band vibration loop utilizes the standard swashplate control configuration to input controller for the vibration loop is based on adaptive optimal control theory and is designed to adapt to any flight condition including maneuvers and transients. The prime characteristics of the vibration control system is its real time capability. The gust alleviation control system studied consists of optimal sampled data feedback gains together with an optimal one-step-ahead prediction. The prediction permits the estimation of the gust disturbance which can then be used to minimize the gust effects on the helicopter.

  19. Buck-boost converter for simultaneous semi-active vibration control and energy harvesting for electromagnetic regenerative shock absorber

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zhang, Chongxiao; Kim, Junyoung; Yu, Liangyao; Zuo, Lei

    2014-04-01

    Regenerative semi-active suspensions can capture the previously dissipated vibration energy and convert it to usable electrical energy for powering on-board electronic devices, while achieve both the better ride comfort and improved road handling performance at the same time when certain control is applied. To achieve this objective, the power electronics interface circuit connecting the energy harvester and the electrical loads, which can perform simultaneous vibration control and energy harvesting function is in need. This paper utilized a buck-boost converter for simultaneous semi-active vibration control and energy harvesting with electromagnetic regenerative shock absorber, which utilizes a rotational generator to converter the vibration energy to electricity. It has been found that when the circuit works in discontinuous current mode (DCM), the ratio between the input voltage and current is only related to the duty cycle of the switch pulse width modulation signal. Using this property, the buck-boost converter can be used to perform semi-active vibration control by controlling the load connected between the terminals of the generator in the electromagnetic shock absorber. While performing the vibration control, the circuit always draw current from the shock absorber and the suspension remain dissipative, and the shock absorber takes no additional energy to perform the vibration control. The working principle and dynamics of the circuit has been analyzed and simulations were performed to validate the concept.

  20. Evaluating Attenuation of Vibration Response using Particle Impact Damping for a Range of Equipment Assemblies

    NASA Technical Reports Server (NTRS)

    Knight, Brent; Parsons, David; Smith, Andrew; Hunt, Ron; LaVerde, Bruce; Towner, Robert; Craigmyle, Ben

    2013-01-01

    Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from a series of acoustically excited tests to determine the effectiveness of these dampers for equipment mounted to a curved orthogrid panel for a launch vehicle application. Vibration attenuation trends are examined for variations in particle damper fill level, component mass, and excitation energy. A significant response reduction at the component level was achieved, suggesting that comparatively small, strategically placed, particle damper devices might be advantageously used in launch vehicle design. These test results were compared to baseline acoustic response tests without particle damping devices, over a range of isolation and damping parameters. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.