Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external ...Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.展开更多
Sandwich structures are widespread in engineering applications because of their advantageous mechanical properties.Recently,their acoustic performance has also been improved to enable attenuation of low-frequency vibr...Sandwich structures are widespread in engineering applications because of their advantageous mechanical properties.Recently,their acoustic performance has also been improved to enable attenuation of low-frequency vibrations induced by noisy environments.Here,we propose a new design of sandwich plates(SPs)featuring a metamaterial core with an actively tunable low-frequency bandgap.The core contains magnetorheological elastomer(MRE)resonators which are arranged periodically and enable controlling wave attenuation by an external magnetic field.We analytically estimate the sound transmission loss(STL)of the plate using the space harmonic expansion method.The low frequency sound insulation performance is also analyzed by the equivalent dynamic density method,and the accuracy of the obtained results is verified by finite-element simulations.Our results demonstrate that the STL of the proposed plate is enhanced compared with a typical SP analog,and the induced bandgap can be effectively tuned to desired frequencies.This study further advances the field of actively controlled acoustic metamaterials,and paves the way to their practical applications.展开更多
In order to improve the screening efficiency of vibrating screen and make vibration process smooth,a new type of magnetorheological (MR) damper was proposed. The signals of displacement in the vibration process during...In order to improve the screening efficiency of vibrating screen and make vibration process smooth,a new type of magnetorheological (MR) damper was proposed. The signals of displacement in the vibration process during the test were collected. The trispectrum model of autoregressive (AR) time series was built and the correlation dimension was used to quantify the fractal characteristics during the vibration process. The result shows that,in different working conditions,trispectrum slices are applied to obtaining the information of non-Gaussian,nonlinear amplitude?frequency characteristics of the signal. Besides,there is correlation between the correlation dimension of vibration signal and trispectrum slices,which is very important to select the optimum working parameters of the MR damper and vibrating screen. And in the experimental conditions,it is found that when the working current of MR damper is 2 A and the rotation speed of vibration motor is 800 r/min,the vibration screen reaches its maximum screening efficiency.展开更多
Magnetorheological (MR) dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal...Magnetorheological (MR) dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal output control force based on the responses of jacket platforms. A typical jacket platform in Mexico Gulf was selected as the numerical example to investigate the effectiveness of the proposed control method. Furthermore, a model experiment was performed to validate the results of the numerical simulation. The experimental model of the jacket platform was designed based on dynamical similarity criterion by the scale of 1:50. Both of the numerical and experimental results show that the semi-active control system with the MR damper can reduce vibrations of jacket platforms effectively and at the same time the control effect is stable.展开更多
The methodology for adaptive control of helicopter ground resonance with magnetorheological (MR) damper is presented. The adaptive inverse control method is used to control the output damping force of MR damper and ...The methodology for adaptive control of helicopter ground resonance with magnetorheological (MR) damper is presented. The adaptive inverse control method is used to control the output damping force of MR damper and the range of the damping force is given. Through the adaptive inverse control, the damping force of MR damper is fit to a desired damping force. With the background of applying MR damper to control of helicopter ground resonance, a model of loss force and an adaptive arithmetic for stabilization of the coupled rotor/fuselage system are presented. The simulation shows that the controller presented in this paper can stabilize the rotor/fuselage coupling system quickly and control the helicopter ground resonance effectively.展开更多
The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid(MRF)damper.A dynamic model of the MRF damper-rotor system was built ...The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid(MRF)damper.A dynamic model of the MRF damper-rotor system was built and simulated in Matlab/Simulink to analyze the rotor vibration characteristics and the vibration reduction effect of the MRF damper.Based on the numerical simulation analysis,an optimizing control strategy using pattern search method was proposed and designed.The control system was constructed on a test rotor bench and experiment validations on the effectiveness of the proposed control strategy were conducted.Experimental results show that rotor vibration caused by unbalance can be well controlled whether in resonance region(70%)or in non-resonance region(30%).An irregular vibration amplitude jump can be suppressed with the optimization strategy.Furthermore,it is found that the rapidity of transient response and efficiency of optimizing technique depend on the pattern search step.The presented strategies and control system can be extended to multi-span(more than two or three spans)rotor system.It provides a powerful technical support for the extension and application in target and control for shafting vibration.展开更多
A generalized model is synthesized to characterize the asymmetric hysteresisforce-velocity (F-v) properties of the magneto-rheological (MR) fluids damper. The model isrepresented as a function of the command current, ...A generalized model is synthesized to characterize the asymmetric hysteresisforce-velocity (F-v) properties of the magneto-rheological (MR) fluids damper. The model isrepresented as a function of the command current, excitation frequency, and displacement amplitude,based on the symmetric and asymmetric sigmoid functions. The symmetric hysteresis damping propertiesof the controllable MR-damper and properties of the conventional passive hydraulic damper can alsobe described by the proposed model. The validity of the model is verified by experiments, which showthat the results calculated from the model are consistent with the measured data. In addition, itis shown that the model applies to a wide vibration frequency range. The proposed model haspotential application in vehicle suspension design employing the symmetry MR-damper, and also indeveloping the asymmetry MR-damper especially for the vehicle suspension attenuation.展开更多
This paper investigates the problem of controlling half-vehicle semi-active suspension system involving a magnetorheological(MR)damper.This features a hysteretic behavior that is presently captured through the nonline...This paper investigates the problem of controlling half-vehicle semi-active suspension system involving a magnetorheological(MR)damper.This features a hysteretic behavior that is presently captured through the nonlinear Bouc-Wen model.The control objective is to regulate well the heave and the pitch motions of the chassis despite the road irregularities.The difficulty of the control problem lies in the nonlinearity of the system model,the uncertainty of some of its parameters,and the inaccessibility to measurements of the hysteresis internal state variables.Using Lyapunov control design tools,we design two observers to get online estimates of the hysteresis internal states and a stabilizing adaptive state-feedback regulator.The whole adaptive controller is formally shown to meet the desired control objectives.This theoretical result is confirmed by several simulations demonstrating the supremacy of the latter compared to the skyhook control and passive suspension.展开更多
Isolator systems on ships should ideally be able to simultaneously reduce low frequency vibration response and high frequency shock response. Conventional isolator systems are unable to do so To solve the problem, a n...Isolator systems on ships should ideally be able to simultaneously reduce low frequency vibration response and high frequency shock response. Conventional isolator systems are unable to do so To solve the problem, a new style isolator system was created. This isolator system consists of a steel coil spring component and a magnetorheological (MR) damper component working in parallel. Experiments on this isolator system were carried out, including tests of vibration reduction and shock resistance. The vibration load frequencies were set from 1-15 Hz, and force amplitudes from 2.94-11.76kN. The maximum shock input acceleration was 20 g, and impulse width was lores. Both the vibration and shock loads were applied using MTS Systems Corporation's hydraulic actuators. The experimental results indicated that the isolator system performs well on system vibration response, with resonance humps of the vibration response obviously reduced after using the MR damper. For the shock experiment, the attenuation of shock response was much faster with increased MR damping. The MR damper's effect on shock moments was very different from its performance in vibration mode. The correlation between MR force and control current was not as evident as it was during vibration loads.展开更多
Magnetorheological (MR) fluid is a kind of smart material whose rheological properties can be rapidly varied in magnetic field. To make full use of the advantages of MR fluid to devices, a model of double ended, shear...Magnetorheological (MR) fluid is a kind of smart material whose rheological properties can be rapidly varied in magnetic field. To make full use of the advantages of MR fluid to devices, a model of double ended, shear combined and valve typed MR damper is designed and manufactured, and the dynamic properties under sinusoidal excitations are experimentally studied. The experiment results show that the maximum damping force of the MR damper at the full magnetic intensity reaches about 20 kN while the maximum power required is less than 50 W, which predicts that the MR damper will be a powerful measurement for semi active vibration control of civil infrastructures.展开更多
Based on the Bingham parallel-plate model, a simplified design method of shear-valve magnetorheological (MR) dampers is proposed considering the magnetic circuit optimization. Correspondingly, a new MR damper with a...Based on the Bingham parallel-plate model, a simplified design method of shear-valve magnetorheological (MR) dampers is proposed considering the magnetic circuit optimization. Correspondingly, a new MR damper with a full-length effective damping path is proposed. The prototype dampers are also fabricated and studied numerically and experimentally. According to the test results, the Bingham parallel-plate model is further modified to obtain a damping force prediction model of the proposed MR dampers. This prediction model considers the magnetic saturation phenomenon. The study indicates that the proposed simplified design method is simple, effective and reliable. The maximum damping force of the proposed MR dampers with a full-length effective damping path is at least twice as large as those of conventional MR dampers. The dynamic range of damping force increases by at least 70%. The proposed damping force prediction model considers the magnetic saturation phenomenon and it can realize the actual characteristic of MR fluids. The model is able to predict the actual damping force of MR dampers precisely.展开更多
Recent developments have demonstrated that the brake pedal simulator(BPS)is becoming an indispensable apparatus for the break-by-wire systems in future electric vehicles.Its main function is to provide the driver with...Recent developments have demonstrated that the brake pedal simulator(BPS)is becoming an indispensable apparatus for the break-by-wire systems in future electric vehicles.Its main function is to provide the driver with a comfortable pedal feel to improve braking safety and comfort.This paper presents the development and control of an adjustable BPS,using a disk-type magnetorheological(MR)damper as the passive braking reaction generator to simulate the traditional pedal feel.A detailed description of the mechanical design of the MR damper-based BSP(MRDBBPS)is presented in this paper.Several basic performance experiments on the MRDBBPS prototype are conducted.A returnto-zero(RTZ)algorithm is proposed to avoid hysteresis and improve the repeatability of the pedal force.In addition,an RTZ algorithm-based real-time current-tracking controller(RTZRC)is designed in consideration of the response lag of the coil circuit.Finally,an experimental system is established by integrating the MRDBBPS prototype into a selfdeveloped automotive MR braking test bench(AMRBTB),and several control and braking experiments are performed.This research proposes a RTZRC control algorithm which can significantly increase the tracking accuracy of the brake pedal characteristic curve,particularly at a high pedal velocity.Additionally,the designed MRDBBPS prototype can achieve an effective and favorable control of the AMRBTB with a good repeatability.展开更多
A control system aims at vibration reduction in a two-span rotor system with two shear mode magnetorheological (MRF) dampers is designed. A finite element model of the MRF damper- rotor system is built and used to a...A control system aims at vibration reduction in a two-span rotor system with two shear mode magnetorheological (MRF) dampers is designed. A finite element model of the MRF damper- rotor system is built and used to analyze the rotor vibration characteristics. Based on Hooke and Jeeves algorithm and the numerical simulation analysis, an optimal appropriate controller is proposed and designed. Experimental results show that rotor vibration caused by unbalance is well controlled ( first critical speed region 37% , second critical speed region 42% ). To reflect advantages of optimi- zing strategy presented and validate the intelligent optimization control technology, detailed experi- ments were developed on a two-span rotor-vibration-control platform. The influence on accuracy, rapidity and stability of optimizing control for rotor vibration are analyzed. It provides a powerful technical support for the extension and application in target and control for shafting vibration.展开更多
Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is loc...Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among them.In this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems.Multi-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes.On each level,the displacement of MR dampers was taken into account.The responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures.According to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures.This method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.展开更多
In the dynamic characteristic experiment of magnetorheological( MR) damper, a strange feature which the improved Bouc-Wen model based on tanh function cannot accurately describe has been shown when MR damper is revers...In the dynamic characteristic experiment of magnetorheological( MR) damper, a strange feature which the improved Bouc-Wen model based on tanh function cannot accurately describe has been shown when MR damper is reversing or at a low speed. In order to describe this phenomenon,a new mechanicaldelay dynamic model based on the improved Bouc-Wen model has been proposed for MR damper. This new model comprehensively considers the coupling effect on the structural flexibility of MR damper and the MR effect of MR fluid. The identification results show that the new mechanical-delay dynamic model for MR damper has a good coherence with experiment whenever at low or high speed.展开更多
With many features,the magnetorheological fluid( MRF) damper is widely applied in the semiactive vibration control system. And sensitivity analysis is an important method to study the influence weight of various param...With many features,the magnetorheological fluid( MRF) damper is widely applied in the semiactive vibration control system. And sensitivity analysis is an important method to study the influence weight of various parameters on damping force characteristics. A mathematical model of the output damping force on the MRF damper is established by the mechanism modeling method,a first order output sensitivity equation is deduced and the expression of the first order output sensitivity function is obtained. The first-order sensitivity functions of ten design parameters are solved,and the influence degree of system parameters change on the output force of MRF damper is analyzed by comparing the sensitivity index of the parameters. Two sensitivities of vibration velocity and control current are obtained through experiment to prove the other parameters sensitivity analysis conclusion by analogy verification,which provides guidance for the structure optimization design of MRF damper.展开更多
Based on the performance of magnetorheological damper we have developed,a tremor suppression method using human limb nonrigid characteristic was presented.The tremor suppression machine was designed,and the measure pa...Based on the performance of magnetorheological damper we have developed,a tremor suppression method using human limb nonrigid characteristic was presented.The tremor suppression machine was designed,and the measure part and the tremor suppression part were separated.Subsequently,the mathematic models of fuzzy neural network and elbow nonrigid tremor were worked out.Using selected training data set,the off-line fuzzy neural network training was finished.Then the tremor suppression method was simulated in Matlab.From the simulation results,it is found that the tremor suppression method has presented suppresses tremor effectively,and the tremor amplitude and tremor suppression torque can be controlled with angle displacement sensor.展开更多
A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the...A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads. In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied ex-perimentally in order to investigate its isolation performance under the impact loads. A new me-chanical model of MRD was proposed according to the data obtained by impact test. A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads. It is also demon-strated that MRD can improve the acceleration and displacement response of the structure obvi-ously under impact loads.展开更多
A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook da...A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook damper system is chosen as the reference model to be followed, and the control law is so determined that the asymptotically stable error dynamics occurs between the controlled state and the reference model state. Numerical simulations are carried out to study the performance of the new sliding mode controller. The results show that the proposed controller yields almost perfect tracking to the reference model and has a high robustness against model parameter uncertainties and disturbances.展开更多
基金the National Natural Science Foundation of China(No.52003142).
文摘Magnetorheological elastomers(MREs)hold significant promise in various fields such as automotive engineering,and civil engineering,where they serve as intelligent materials.Depending on the application of an external magnetic field,these materials exhibit varying magnetorheological and viscoelastic properties,including shear stress,yield stress,dynamic moduli,and damping.In this work,a new type of MRE,termed self-healing MREs(SH-MREs),has been developed by adding a novel self-healing agent into existing MREs.The dynamic modulus and loss factor of SH-MREs with different compositions have been characterized under various conditions of frequency,temperature,and strain.The results show that as the strain value increases,the loss factor also increases.Moreover,the loss factor initially increases and then decreases with increasing magnetic field strength.Although higher concentrations of ferromagnetic particles increase the loss factor,they enhance the operational range due to their better responsiveness to magnetic fields.SH-MREs demonstrate improved damping capabilities,attributed to the formation of coordination bonds between ferromagnetic particles and the self-healing agent.The stable structure increases the viscosity of MREs.The results of the regression model suggest a direct proportionality between sensitivity to the magnetic field and the ferromagnetic particle concentration.
基金Project supported by the National Natural Science Foundation of China(Nos.12472007 and 12072084)the Fundamental Research Funds for the Central Universities of China。
文摘Sandwich structures are widespread in engineering applications because of their advantageous mechanical properties.Recently,their acoustic performance has also been improved to enable attenuation of low-frequency vibrations induced by noisy environments.Here,we propose a new design of sandwich plates(SPs)featuring a metamaterial core with an actively tunable low-frequency bandgap.The core contains magnetorheological elastomer(MRE)resonators which are arranged periodically and enable controlling wave attenuation by an external magnetic field.We analytically estimate the sound transmission loss(STL)of the plate using the space harmonic expansion method.The low frequency sound insulation performance is also analyzed by the equivalent dynamic density method,and the accuracy of the obtained results is verified by finite-element simulations.Our results demonstrate that the STL of the proposed plate is enhanced compared with a typical SP analog,and the induced bandgap can be effectively tuned to desired frequencies.This study further advances the field of actively controlled acoustic metamaterials,and paves the way to their practical applications.
基金Project(50975098) supported by the National Natural Science Foundation of ChinaProject(2008HZ0002-1) supported by the Major Scientific and Technological Program of Fujian Province,China
文摘In order to improve the screening efficiency of vibrating screen and make vibration process smooth,a new type of magnetorheological (MR) damper was proposed. The signals of displacement in the vibration process during the test were collected. The trispectrum model of autoregressive (AR) time series was built and the correlation dimension was used to quantify the fractal characteristics during the vibration process. The result shows that,in different working conditions,trispectrum slices are applied to obtaining the information of non-Gaussian,nonlinear amplitude?frequency characteristics of the signal. Besides,there is correlation between the correlation dimension of vibration signal and trispectrum slices,which is very important to select the optimum working parameters of the MR damper and vibrating screen. And in the experimental conditions,it is found that when the working current of MR damper is 2 A and the rotation speed of vibration motor is 800 r/min,the vibration screen reaches its maximum screening efficiency.
基金Supported by the National Natural Science Foundation of China (NSFC-5060900).
文摘Magnetorheological (MR) dampers have been proposed to control the vibration of offshore platforms in this paper. The semi-active control strategy based on fuzzy control algorithm was adopted to determine the optimal output control force based on the responses of jacket platforms. A typical jacket platform in Mexico Gulf was selected as the numerical example to investigate the effectiveness of the proposed control method. Furthermore, a model experiment was performed to validate the results of the numerical simulation. The experimental model of the jacket platform was designed based on dynamical similarity criterion by the scale of 1:50. Both of the numerical and experimental results show that the semi-active control system with the MR damper can reduce vibrations of jacket platforms effectively and at the same time the control effect is stable.
基金Foundation item: Aeronautical Science Foundation of China (04A52005)
文摘The methodology for adaptive control of helicopter ground resonance with magnetorheological (MR) damper is presented. The adaptive inverse control method is used to control the output damping force of MR damper and the range of the damping force is given. Through the adaptive inverse control, the damping force of MR damper is fit to a desired damping force. With the background of applying MR damper to control of helicopter ground resonance, a model of loss force and an adaptive arithmetic for stabilization of the coupled rotor/fuselage system are presented. The simulation shows that the controller presented in this paper can stabilize the rotor/fuselage coupling system quickly and control the helicopter ground resonance effectively.
基金Supported by the National Program on Key Basic Research Program(″973″Program)(2012CB026000)the Ph.D.Programs Foundation of Ministry of Education of China(20110010110009)
文摘The aim of this work is to analyze and design a control system for vibration reduction in a rotor system using a shear mode magnetorheological fluid(MRF)damper.A dynamic model of the MRF damper-rotor system was built and simulated in Matlab/Simulink to analyze the rotor vibration characteristics and the vibration reduction effect of the MRF damper.Based on the numerical simulation analysis,an optimizing control strategy using pattern search method was proposed and designed.The control system was constructed on a test rotor bench and experiment validations on the effectiveness of the proposed control strategy were conducted.Experimental results show that rotor vibration caused by unbalance can be well controlled whether in resonance region(70%)or in non-resonance region(30%).An irregular vibration amplitude jump can be suppressed with the optimization strategy.Furthermore,it is found that the rapidity of transient response and efficiency of optimizing technique depend on the pattern search step.The presented strategies and control system can be extended to multi-span(more than two or three spans)rotor system.It provides a powerful technical support for the extension and application in target and control for shafting vibration.
基金This project is supported by Senior Visiting Scholarship of Chinese Scholarship Council (No.20H05002), Provincial Natural Science Foundation of Education Commission of Jiangsu (No.03KJB510072) and Doctoral Scholarship of Concordia University in Canada.
文摘A generalized model is synthesized to characterize the asymmetric hysteresisforce-velocity (F-v) properties of the magneto-rheological (MR) fluids damper. The model isrepresented as a function of the command current, excitation frequency, and displacement amplitude,based on the symmetric and asymmetric sigmoid functions. The symmetric hysteresis damping propertiesof the controllable MR-damper and properties of the conventional passive hydraulic damper can alsobe described by the proposed model. The validity of the model is verified by experiments, which showthat the results calculated from the model are consistent with the measured data. In addition, itis shown that the model applies to a wide vibration frequency range. The proposed model haspotential application in vehicle suspension design employing the symmetry MR-damper, and also indeveloping the asymmetry MR-damper especially for the vehicle suspension attenuation.
文摘This paper investigates the problem of controlling half-vehicle semi-active suspension system involving a magnetorheological(MR)damper.This features a hysteretic behavior that is presently captured through the nonlinear Bouc-Wen model.The control objective is to regulate well the heave and the pitch motions of the chassis despite the road irregularities.The difficulty of the control problem lies in the nonlinearity of the system model,the uncertainty of some of its parameters,and the inaccessibility to measurements of the hysteresis internal state variables.Using Lyapunov control design tools,we design two observers to get online estimates of the hysteresis internal states and a stabilizing adaptive state-feedback regulator.The whole adaptive controller is formally shown to meet the desired control objectives.This theoretical result is confirmed by several simulations demonstrating the supremacy of the latter compared to the skyhook control and passive suspension.
文摘Isolator systems on ships should ideally be able to simultaneously reduce low frequency vibration response and high frequency shock response. Conventional isolator systems are unable to do so To solve the problem, a new style isolator system was created. This isolator system consists of a steel coil spring component and a magnetorheological (MR) damper component working in parallel. Experiments on this isolator system were carried out, including tests of vibration reduction and shock resistance. The vibration load frequencies were set from 1-15 Hz, and force amplitudes from 2.94-11.76kN. The maximum shock input acceleration was 20 g, and impulse width was lores. Both the vibration and shock loads were applied using MTS Systems Corporation's hydraulic actuators. The experimental results indicated that the isolator system performs well on system vibration response, with resonance humps of the vibration response obviously reduced after using the MR damper. For the shock experiment, the attenuation of shock response was much faster with increased MR damping. The MR damper's effect on shock moments was very different from its performance in vibration mode. The correlation between MR force and control current was not as evident as it was during vibration loads.
文摘Magnetorheological (MR) fluid is a kind of smart material whose rheological properties can be rapidly varied in magnetic field. To make full use of the advantages of MR fluid to devices, a model of double ended, shear combined and valve typed MR damper is designed and manufactured, and the dynamic properties under sinusoidal excitations are experimentally studied. The experiment results show that the maximum damping force of the MR damper at the full magnetic intensity reaches about 20 kN while the maximum power required is less than 50 W, which predicts that the MR damper will be a powerful measurement for semi active vibration control of civil infrastructures.
基金The National Basic Research Program of China(973 Program)under Grant No.2011CB013606the Major Research Plan of the National Natural Science Foundation of China under Grant No.91315301-06+2 种基金the National Natural Science Foundation of China under Grant No.51378343the Natural Science Foundation of Tianjin,China under Grant No.13JCZDJC35200the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20110032110042
文摘Based on the Bingham parallel-plate model, a simplified design method of shear-valve magnetorheological (MR) dampers is proposed considering the magnetic circuit optimization. Correspondingly, a new MR damper with a full-length effective damping path is proposed. The prototype dampers are also fabricated and studied numerically and experimentally. According to the test results, the Bingham parallel-plate model is further modified to obtain a damping force prediction model of the proposed MR dampers. This prediction model considers the magnetic saturation phenomenon. The study indicates that the proposed simplified design method is simple, effective and reliable. The maximum damping force of the proposed MR dampers with a full-length effective damping path is at least twice as large as those of conventional MR dampers. The dynamic range of damping force increases by at least 70%. The proposed damping force prediction model considers the magnetic saturation phenomenon and it can realize the actual characteristic of MR fluids. The model is able to predict the actual damping force of MR dampers precisely.
基金National Natural Science Foundation of China(Grant Nos.52175047 and 51505114)Anhui Provincial Natural Science Foundation of China(Grant No.2008085ME140).
文摘Recent developments have demonstrated that the brake pedal simulator(BPS)is becoming an indispensable apparatus for the break-by-wire systems in future electric vehicles.Its main function is to provide the driver with a comfortable pedal feel to improve braking safety and comfort.This paper presents the development and control of an adjustable BPS,using a disk-type magnetorheological(MR)damper as the passive braking reaction generator to simulate the traditional pedal feel.A detailed description of the mechanical design of the MR damper-based BSP(MRDBBPS)is presented in this paper.Several basic performance experiments on the MRDBBPS prototype are conducted.A returnto-zero(RTZ)algorithm is proposed to avoid hysteresis and improve the repeatability of the pedal force.In addition,an RTZ algorithm-based real-time current-tracking controller(RTZRC)is designed in consideration of the response lag of the coil circuit.Finally,an experimental system is established by integrating the MRDBBPS prototype into a selfdeveloped automotive MR braking test bench(AMRBTB),and several control and braking experiments are performed.This research proposes a RTZRC control algorithm which can significantly increase the tracking accuracy of the brake pedal characteristic curve,particularly at a high pedal velocity.Additionally,the designed MRDBBPS prototype can achieve an effective and favorable control of the AMRBTB with a good repeatability.
基金Supported by the National Program on Key Basic Research Project(973Program)(2012CB026000)Ph.D Programs Foundation of Ministry of Education of China(20110010110009)
文摘A control system aims at vibration reduction in a two-span rotor system with two shear mode magnetorheological (MRF) dampers is designed. A finite element model of the MRF damper- rotor system is built and used to analyze the rotor vibration characteristics. Based on Hooke and Jeeves algorithm and the numerical simulation analysis, an optimal appropriate controller is proposed and designed. Experimental results show that rotor vibration caused by unbalance is well controlled ( first critical speed region 37% , second critical speed region 42% ). To reflect advantages of optimi- zing strategy presented and validate the intelligent optimization control technology, detailed experi- ments were developed on a two-span rotor-vibration-control platform. The influence on accuracy, rapidity and stability of optimizing control for rotor vibration are analyzed. It provides a powerful technical support for the extension and application in target and control for shafting vibration.
文摘Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among them.In this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems.Multi-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes.On each level,the displacement of MR dampers was taken into account.The responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures.According to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures.This method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.
基金National Natural Science Foundations of China(Nos.10972065,11372083)
文摘In the dynamic characteristic experiment of magnetorheological( MR) damper, a strange feature which the improved Bouc-Wen model based on tanh function cannot accurately describe has been shown when MR damper is reversing or at a low speed. In order to describe this phenomenon,a new mechanicaldelay dynamic model based on the improved Bouc-Wen model has been proposed for MR damper. This new model comprehensively considers the coupling effect on the structural flexibility of MR damper and the MR effect of MR fluid. The identification results show that the new mechanical-delay dynamic model for MR damper has a good coherence with experiment whenever at low or high speed.
基金Supported by the National Natural Science Foundation of China(No.51375423,51505410)the National Key Basic Research Program(No.2014CB046400)
文摘With many features,the magnetorheological fluid( MRF) damper is widely applied in the semiactive vibration control system. And sensitivity analysis is an important method to study the influence weight of various parameters on damping force characteristics. A mathematical model of the output damping force on the MRF damper is established by the mechanism modeling method,a first order output sensitivity equation is deduced and the expression of the first order output sensitivity function is obtained. The first-order sensitivity functions of ten design parameters are solved,and the influence degree of system parameters change on the output force of MRF damper is analyzed by comparing the sensitivity index of the parameters. Two sensitivities of vibration velocity and control current are obtained through experiment to prove the other parameters sensitivity analysis conclusion by analogy verification,which provides guidance for the structure optimization design of MRF damper.
基金Doctoral Fund of Ministry of Education of China(No.20070213086)National Natural Science Foundation of China(No.60975067)
文摘Based on the performance of magnetorheological damper we have developed,a tremor suppression method using human limb nonrigid characteristic was presented.The tremor suppression machine was designed,and the measure part and the tremor suppression part were separated.Subsequently,the mathematic models of fuzzy neural network and elbow nonrigid tremor were worked out.Using selected training data set,the off-line fuzzy neural network training was finished.Then the tremor suppression method was simulated in Matlab.From the simulation results,it is found that the tremor suppression method has presented suppresses tremor effectively,and the tremor amplitude and tremor suppression torque can be controlled with angle displacement sensor.
基金Supported by National Natural Science Foundation of China (No.50638030,50525825)the National Science and Technology SupportProgram (No.2006BAJ13B02)
文摘A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads. In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied ex-perimentally in order to investigate its isolation performance under the impact loads. A new me-chanical model of MRD was proposed according to the data obtained by impact test. A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads. It is also demon-strated that MRD can improve the acceleration and displacement response of the structure obvi-ously under impact loads.
基金the Nature Science Foundation of China (No: 51035030) and the Applied and Basic Research Foundation of Chongqing University.
文摘A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook damper system is chosen as the reference model to be followed, and the control law is so determined that the asymptotically stable error dynamics occurs between the controlled state and the reference model state. Numerical simulations are carried out to study the performance of the new sliding mode controller. The results show that the proposed controller yields almost perfect tracking to the reference model and has a high robustness against model parameter uncertainties and disturbances.