Showing papers on "Magnetorheological damper published in 2013"

Magnetorheological Damper Utilizing an Inner Bypass for Ground Vehicle Suspensions

Abstract: This study presents the design, fabrication, and test of a magnetorheological (MR) damper utilizing an inner bypass that can simultaneously produce large dynamic range (ie, ratio of field-on to field-off stroking load) and low field-off stroking load at high piston velocity These two damper properties, large dynamic range and low field-off stroking load, are critical to achieving high performance in ground vehicle suspensions The MR damper is comprised of a pair of concentric tubes, a movable piston-shaft arrangement, and an annular MR fluid flow gap between the concentric tubes The inner tube serves as the piston guide, the inner surface of the annular flow gap, and the bobbin for the five electromagnetic coils used in this design The outer tube serves as the flux return and the outer surface of the annular flow gap The annular flow gap is an inner bypass annular valve where the rheology of the MR fluids, and hence the stroking load of the damper, is controlled The MR damper is analyzed using a Bingham-plastic nonlinear fluid mechanics model To experimentally validate the analysis of the MR damper with the inner bypass, and to illustrate its advantages over the MR damper with the conventional annular orifice, the prototype damper is tested in terms of controllable damping force or stroking load, dynamic range, and equivalent damping as a function of shaft/piston velocity

Design and Characterization of a Small-Scale Magnetorheological Damper for Tremor Suppression

Abstract: This paper explores the design methodology and effectiveness of small-scale magnetorheological dampers (MRDs) in applications that require variable damping. Previously, applications of MRD have been chiefly limited to vehicle shock absorbers and seismic vibration attenuators. There has been recent biomedical interest in active-damping technology, however, particularly in the field of rehabilitation robotics. The topic at hand is the feasibility of developing MRDs that would be functionally and cosmetically adequate for actuation of an upper limb tremor suppression orthosis. A Bingham plastic model is used to determine MRD's functional characteristics, and experimental data are presented to validate the mathematical model. The feasibility of applying the developed small-scale MRDs to attenuation of tremorous motion is explored.

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

Abstract: 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.

Design, performance test and analysis on magnetorheological damper for earthquake mitigation

Abstract: SUMMARY As a semi-active control device, magnetorheological (MR) dampers have been paid more attention because of their high controllability, fast response and low power requirement When MR dampers are used for vibration mitigation, some challenge topics must be taken into account, such as design method, performance study and intelligent control algorithm In this paper, a detailed design process of MR damper involving the geometry design and magnetic circuit design is carried out, and a multistage shear-valve mode MR damper is designed and manufactured Then the MR damper is tested to investigate the influence of control current, displacement amplitude and excitation frequency on the damper's mechanical behavior and energy dissipation performance At the same time, the design target values are compared with experimental results Comparison results show that the proposed design method holds promise in designing and optimizing the MR damper Finally, a modified Sigmoid model is proposed Comparison results between the experimental data and the numerical data indicate that the modified Sigmoid model can accurately describe the behaviors of the MR damper Copyright © 2012 John Wiley & Sons, Ltd

Direct voltage control of magnetorheological damper for vehicle suspensions

Abstract: 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.

Comparative Studies of Semiactive Control Strategies for MR Dampers: Pure Simulation and Real-Time Hybrid Tests

Abstract: This paper presents comparisons of the performances of three semiactive control algorithms for use with multiple magnetorheological (MR) dampers. The three controllers are (1) the clipped-optimal controller, (2) the decentralized output feedback polynomial controller, and (3) the simple passive controller. These controllers use different types of inputs to calculate control signals for the MR dampers, based on different control mechanisms. To investigate the advantages of each controller, a three-degree-of-freedom steel moment-resisting frame, designed using a performance-based design methodology, was developed. The performance was investigated by using four different earthquakes utilized during the design of the building frame. Comparisons of the controllers’ performance were carried out in terms of reduction in the maximum interstory drifts, displacements, absolute accelerations, and control forces. Real-time hybrid tests were carried out to validate these comparisons.

Magnetorheological fluid composites synthesized for helicopter landing gear applications

Abstract: Magnetorheological fluid composites were formulated in this study to investigate their performance for potential use in landing gear hydraulic systems, such as shock struts. The magnetorheological fluids synthesized here utilized three hydraulic oils certified for use in landing gear, two average diameters of spherical magnetic particles, and a lecithin surfactant. The magnetorheology of these fluids was characterized, including (a) magnetorheology (yield stress and viscosity) as a function of magnetic field, (b) sedimentation analysis using an inductance-based sensor, (c) cycling of a small-scale magnetorheological damper undergoing sinusoidal excitations at frequencies of 2.5 and 5 Hz, and (d) impact testing of an magnetorheological damper for a range of magnetic field strengths and velocities using a free-flight drop tower facility. The goal of this research is to analyze the performance of these magnetorheological fluid composites, compare their behavior to standard commercial magnetorheological fluid...

Fuzzy Control for Semi-Active Vehicle Suspension

Abstract: In this paper semi-active control of the suspension of an all-terrain vehicle is considered. A seven degree of freedom suspension model is presented first. A fuzzy approach for controller synthesis is then proposed. Expert knowledge is stored in the form of IF-THEN rules. The Takagi-Sugeno inference system is employed, with triangle membership functions. The fuzzy system output is the damper coefficient. In contrary to many other control algorithms, the presented fuzzy algorithm does not require inverse modelling of the magnetorheological damper. Instead, some scaling parameters are set. They can be chosen experimentally, or a bio-inspired strategy can be applied. The fuzzy control is then compared with the Skyhook control in simulations, in terms of road holding and driving comfort indicators. Obtained results are similar. However, lack of necessity to use an MR inverse model allows the fuzzy system to provide successful performance in case of different operating conditions, what is an important benefit.

Principle, modeling, and testing of an annular-radial-duct magnetorheological damper

Abstract: Aiming at improving the efficiency of magnetorhelogical (MR) dampers, the principle of an annular-radial-duct MR damper (ARDMRD), in which annular-radial ducts in series in MR fluid flow channel are integrated, is presented and the prototype of the ARDMRD is designed and fabricated. The mathematical model of the ARDMRD considering the nonlinear flow effect of the MR fluid in the flow channel is established. The finite element analysis (FEA) is utilized to validate the principle of the ARDMRD and obtain the magnetic properties of its magnetic circuit. The controllable damping force and equivalent damping of the ARDMRD are tested on the established experimental setup based on MTS 849 shock absorber test system and compared with the theoretical results based on the mathematical model and FEA. The tested controllable damping force of the ARDMRD under excitation velocity of 0.19 m/s is as high as 3149 N and the tested damping force range of the ARDMRD under excitation velocities of 0.025–0.19 m/s is 140–3149 N. The research results show that the designed magnetic circuit structure of the ARDMRD is beneficial to improving the efficiency of the MR damper and the established mathematical model of the ARDMRD can describe and predict its damping force performance accurately.

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

Abstract: 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.

Vibration Control of Buildings Using Magnetorheological Damper: A New Control Algorithm

Abstract: This paper presents vibration control of a building model under earthquake loads. A magnetorheological (MR) damper is placed in the building between the first floor and ground for seismic response reduction. A new control algorithm to command the MR damper is proposed. The approach is inspired by a quasi-bang-bang controller; however, the proposed technique gives weights to control commands in a fashion that is similar to a fuzzy logic controller. Several control algorithms including decentralized bang-bang controller, Lyapunov controller, modulated homogeneous friction controller, maximum energy dissipation controller, and clipped-optimal controller are used for comparison. The new controller achieved the best reduction in maximum interstory drifts and maximum absolute accelerations over all the control algorithms presented. This reveals that the proposed controller with the MR damper is promising and may provide the best protection to the building and its contents.

A magnetorheological damper with an integrated self-powered displacement sensor

Abstract: 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.

Seismic performance of structures incorporating magnetorheological dampers with pseudo‐NEGATIVE STIFFNESS

Abstract: SUMMARY Pseudo-negative stiffness control is a control scheme that is aimed to track, in a passive energy dissipation fashion, a target spring force with negative stiffness when possible. In this study, it is proved that systems with pseudo-negative stiffness control have the property of homogeneity even though they are nonlinear systems. The harmonic response analyses reveal that the pseudo-negative stiffness reduces the resonant frequency of the system. Seismic response spectrum analyses show that both acceleration and displacement can be reduced with the pseudo-negative stiffness control when the structural period is long and damping level is not high. Pseudo-negative stiffness control of a five-story base-isolated structure incorporating magnetorheological damper is studied through analytical and real-time hybrid test methods. The results show that displacement and acceleration responses with pseudo-negative stiffness control are lower than those with passive-off control and isolator alone, whereas the displacement response with pseudo-negative stiffness is greater than the passive-on control. Copyright © 2011 John Wiley & Sons, Ltd.

Optimal Magnetorheological Damper Configuration Using the Taguchi Experimental Design Method

Abstract: Magnetorheological (MR) dampers have attracted the interest of suspension designers and researchers because of their variable damping feature, mechanical simplicity, robustness, low power consumption and fast response. This study deals with the optimal configuration of an MR damper using the Taguchi experimental design approach. The optimal solutions of the MR damper are evaluated for the maximum dynamic range and the maximum damper force separately. The MR dampers are constrained in a cylindrical container defined by radius and height. The optimal damper configurations obtained from this study are fabricated and tested for verification. The verification tests show that the dampers provide the specified damper force and dynamic range.

On the Chaotic Suppression of Both Ideal and Non-ideal Duffing Based Vibrating Systems, Using a Magnetorheological Damper

Abstract: In this paper the dynamics of the ideal and non-ideal Duffing oscillator with chaotic behavior is considered. In order to suppress the chaotic behavior and to control the system, a control signal is introduced in the system dynamics. The control strategy involves the application of two control signals, a nonlinear feedforward control to maintain the controlled system in a periodic orbit, obtained by the harmonic balance method, and a state feedback control, obtained by the state dependent Riccati equation, to bring the system trajectory into the desired periodic orbit. Additionally, the control strategy includes an active magnetorheological damper to actuate on the system. The control force of the damper is a function of the electric current applied in the coil of the damper, that is based on the force given by the controller and on the velocity of the damper piston displacement. Numerical simulations demonstrate the effectiveness of the control strategy in leading the system from any initial condition to a desired orbit, and considering the mathematical model of the damper (MR), it was possible to control the force of the shock absorber (MR), by controlling the applied electric current in the coils of the damper.

A new magnetorheological damper for seismic control

Abstract: 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.

Promptness and dissipative capacity of MR dampers: Experimental investigations

Abstract: SUMMARY The experimental analyses of response time and dissipative capability of two prototype magnetorheological semi-active dampers are presented herein. These activities have been conducted during an Italian research project on devices manufactured in Germany. A detailed report of the response time analysis based on experimental data is presented and commented. It is shown how the control delays are strongly dependent on the effectiveness of the electric part of the control hardware, generally being less than 10 ms if special care is paid in designing the whole control chain. The dissipative capacity of the devices is further analyzed under the action of different imposed displacement laws, investigating a large range of displacement amplitudes, frequencies, and feeding currents. Interesting comparisons in terms of energy are finally drawn between magnetorheological damper used in a passive (constant current) and in a semi-active mode (variable current commanded by an energy-based control logic). Copyright © 2013 John Wiley & Sons, Ltd.

Multiphysics modeling of magnetorheological dampers

Abstract: The dynamics of a small scale magnetorheological damper were modeled and analyzed using multiphysics commercial finite element software to couple the electromagnetic field distribution with the non-Newtonian fluid flow. The magnetic flux lines and field intensity generated within the damper and cyclic fluid flow in the damper under harmonic motion were simulated with the AC/DC and CFD physics modules of COMSOL Multiphysics, respectively. Coupling of the physics is achieved through a modified Bingham plastic definition, relating the fluid’s dynamic viscosity to the intensity of the induced magnetic field. Good agreement is confirmed between simulation results and experimentally observed resistance forces in the damper. This study was conducted to determine the feasibility of utilizing magnetorheological dampers in a medical orthosis for pathological tremor attenuation. The implemented models are thus dimensioned on a relatively small scale. The method used, however, is not specific to the damper’s size or geometry and can be extended to larger-scale devices with little or no complication.

Unsteady analysis for oscillatory flow of magnetorheological fluid dampers based on Bingham plastic and Herschel–Bulkley models

Abstract: It is known that a quasi-static analysis without considering fluid inertia is usually used for magnetorheological damper design. However, fluid inertia terms need to be incorporated into the governing Navier–Stokes equation in practical application for oscillatory or unsteady fluid flow. In this article, an unsteady flow of magnetorheological fluids within flow mode magnetorheological dampers was theoretically investigated under sinusoidal displacement excitation. Based on the governing Navier–Stokes equation, incorporating the boundary and initial conditions, central numerical velocity solutions of magnetorheological fluids within magnetorheological damping channel were developed and used to confirm the damping force using both Bingham plastic and Herschel–Bulkley models of magnetorheological fluids. To simplify the governing equation of Herschel–Bulkley flow, an approximation method replacing Herschel–Bulkley model velocity with Bingham plastic model velocity during calculating effective viscosity shear...

Analysis of a magnetorheological damper incorporating temperature dependence

Abstract: Aside from external environmental heating, a magnetorheological (MR) damper may internally self-heat due to both resistive heating by the electromagnetic coil and to a greater extent, by dissipating mechanical energy into thermal energy. Temperature can significantly alter damper behaviour, as the fluid viscosity and accumulator gas pressure are highly dependent on temperature. Therefore, to improve the understanding of the behaviour of a linear stroke MR damper, a damper designed for a ground vehicle seat suspension, its performance is characterised over temperatures ranging from 0 to 100°C. A hydro-mechanical analysis is used to represent MR damper behaviour when it is subjected to large temperature perturbations and captures contributions from fluid viscosity, fluid inertia and pneumatic compressibility. The effect of damper self-heating on the identified model parameters is presented and the connection of these parameters to physical properties is also discussed.

Linear magnetorheological brake with serpentine flux path as a high force and low off-state friction actuator for haptics

Abstract: In robotics and haptics, actuators that are capable of high force output with compact size are desired for stable and stiff interfaces. Magnetorheological brakes are viable options for such impleme...

System Identification and Semiactive Control of a Squeeze-Mode Magnetorheological Damper

Abstract: The main goal of this investigation is to establish modeling of a squeeze-mode magnetorheological (MR) damper and to design a semiactive fuzzy controller for vibration reduction. To model the MR damper, the Bouc-Wen model has been used in many past studies. However, using the Bouc-Wen model to characterize the squeeze-mode MR damper needs a lookup table of system parameters for the application with various amplitudes and frequencies. Therefore, a biviscosity model is proposed to describe this squeeze-mode MR damper. In addition, genetic-algorithm-based optimization is used to evaluate the parameters of the system. To reduce the vibration of the structure, a semiactive fuzzy controller using the MR damper is presented for the structure vibration at various frequencies. To check the consistency of the proposed fuzzy controller, the real-time implementation validated the performance of the controller.

Design and Performance Evaluation of a Rotary Magnetorheological Damper for Unmanned Vehicle Suspension Systems

Abstract: We designed and validated a rotary magnetorheological (MR) damper with a specified damping torque capacity, an unsaturated magnetic flux density (MFD), and a high magnetic field intensity (MFI) for unmanned vehicle suspension systems. In this study, for the rotary type MR damper to have these satisfactory performances, the roles of the sealing location and the cover case curvature of the MR damper were investigated by using the detailed 3D finite element model to reflect asymmetrical shapes and sealing components. The current study also optimized the damper cover case curvature based on the MFD, the MFI, and the weight of the MR damper components. The damping torques, which were computed using the characteristic equation of the MR fluid and the MFI of the MR damper, were 239.2, 436.95, and 576.78 N·m at currents of 0.5, 1, and 1.5 A, respectively, at a disk rotating speed of 10 RPM. These predicted damping torques satisfied the specified damping torque of 475 N·m at 1.5 A and showed errors of less than 5% when compared to experimental measurements from the MR damper manufactured by the proposed design. The current study could play an important role in improving the performance of rotary type MR dampers.

Viscoelastic plastic continuous physical model of a magnetorheological damper applied in the high speed train

Abstract: In the preliminary design stage of high-speed train smart suspension, a simple, yet accurate magnetorheological (MR) damper model whose parameters have clear physical meaning is needed. Based on the working mechanism analysis and the dynamic behavior study of the MR damper, a new consecutive viscoelastic plastics (VEP) model is proposed. A methodology to find the parameters of the proposed model directly has been proposed. The comparison with experimental results indicates that the proposed model could adequately characterize the intrinsic nonlinear behavior of the MR damper, including the hysteretic behavior, roll-off phenomenon, and the variation of the hysteresis width in terms of the frequency and magnitude of excitation. The results of experimental testing prove that the accuracy of the proposed model is higher than that of the phenomenological model while only containing four undetermined parameters with clear physical meaning. Moreover, based on the proposed VEP model, a nonlinear stiffness VEP (nkVEP) model is developed with higher precision in the hysteretic region. The nkVEP model, which can reproduce the behavior of the damper with fluctuating input current, is developed. The proposed model could predict accurately the response of the MR damper in a wide range of frequency and displacement.

Semi-active control of aircraft landing gear system using H-infinity control approach

Abstract: The landing of an aircraft is one of the most critical operations because it directly affects the passenger safety and comfort. During landing, the aircraft fuselage undergoes excessive vibrations that cause the safety and the comfort problem and hence need to be suppressed quickly. A semi-active control system of a landing gear suspension by using Magnetorheological damper can solve the problem of excessive vibrations effectively. In this paper, a switching technique is developed in the simulation of the landing procedure which enables the system to switch from the single degree of freedom to three degrees of freedom system in order to simulate the sequential touching of the two wheels of the main landing gears and the nose landing gear wheels with the ground. A semi-active Magnetorheological damper is developed using two different controllers namely linear quadratic regulator and the H∞. Spencer model is used to predict the dynamic behavior of the Magnetorheological damper. The results of the designed controllers are compared to study the performance of the controllers in reducing the overshoot of the bounce response as well as the bounce rate response. The simulation results validated the improved performance of the robust controller compared to the optimal control strategy when the aircraft is subjected to the disturbances during landing.

Force control of a magnetorheological damper using an elementary hysteresis model-based feedforward neural network

Abstract: An inverse controller is proposed for a magnetorheological (MR) damper that consists of a hysteresis model and a voltage controller. The force characteristics of the MR damper caused by excitation signals are represented by a feedforward neural network (FNN) with an elementary hysteresis model (EHM). The voltage controller is constructed using another FNN to calculate a suitable input signal that will allow the MR damper to produce the desired damping force. The performance of the proposed EHM-based FNN controller is experimentally compared to existing control methodologies, such as clipped-optimal control, signum function control, conventional FNN, and recurrent neural network with displacement or velocity inputs. The results show that the proposed controller, which does not require force feedback to implement, provides excellent accuracy, fast response time, and lower energy consumption.

Experimental calibration of forward and inverse neural networks for rotary type magnetorheological damper

Abstract: This paper presents a systematic design and training procedure for the feed-forward back- propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

A novel adaptive base isolator utilising magnetorheological elastomer

Abstract: Base isolation is the most popular seismic protection technique for civil structures. However, research has revealed that the traditional base isolation system is vulnerable to both kinds of earthquakes, i.e. the near-fault and far-fault earthquakes, due to its passive nature. A great deal of effort has been dedicated to improve the performance of the traditional base isolation system for these two types of earthquakes. Controllable supplementary and energy-dissipation members, such as magnetorheological damper, friction damper or hydraulic fluid damper, have been proposed to reduce the seismic response of the building structures. However, with the introduction of additional control devices, the system complexity increases which results in difficulty in the system implementation and control system design. It would be ideal if a certain level of adaptability could be introduced into the base isolator while maintaining the traditional outfit. This paper addresses the challenge facing the current base isolation practice and proposes a novel adaptive base isolator as solution to the problem. A smart rubber, namely, magnetorheological elastomer (MRE), is utilised in this research for its magnetic field-sensitive material property as the main element in the novel device. The tradition base isolation design for a large-scale structure with laminated steel and MRE layers is adopted. To verify and characterise the performance of the MRE base isolator, experimental testing was conducted on UTS shake table facility. Experimental results show that after being energised with magnetic field, the maximum force and the stiffness of the novel device can increase by up to approximately 45% and 37%, respectively. With the field-dependent stiffness and damping, the proposed adaptive base isolator is very promising in meeting the challenges associated with the base isolation encountered in practice. of the building structures. Yang (Yang, Danielians and Liu, 1991) presented a hybrid control system in which a passive or active mass damper, connected with base isolation system, is used to alleviate the deformation of seismic isolators. Although numerical results showed that the proposed system worked effectively, the hybrid system is less practical since it is difficult to implement a mass damper, either passive or active, on the seismic isolators. Destructive potential of near-source earthquakes to flexible structures still remains a challenge and has received considerable attention within the earthquake engineering community. Another effort to augment the adaptability of base isolation system has been to combine passive isolators with semi-active or active actuators to develop hybrid base isolation systems. Spencer (Ramallo, Johnson and Spencer, 2002) proposed a smart base isolation system, composed of conventional low-damping elastomeric isolators and smart controllable dampers, such as MR damper, to protect structures against extreme earthquakes. Wongprasert (Wongprasert and Symans, 2005) experimentally evaluated a smart base isolation system consisting of spherical sliding bearings and variable fluid dampers for a multi-storey building frame. In the above-mentioned research, the proposed base isolation systems proved to be more effective than the traditional passive ones. However, those systems, termed hybrid systems, are either a combination of passive bearings/isolators (such as low-damping bearing or spherical sliding bearings) and semiactive actuators (MR damper or piezoelectric friction damper) or a mixture of passive bearings/isolators and active actuating system. The separated passive and semi-active/active actuator increases the complexity of the base isolation system, leading to many problems, such as instability, reliability, and the increasing difficulty in system installation. Moreover, the need for large power in active hybrid base isolation systems restricts their implementation in largescale structures. The advent of a kind of smart material, magnetorheological elastomer, offers a way forward to develop more effective and efficient semi-active base isolators than traditional passive ones, and will further lead to the development of intelligent selfadaptive base isolation systems. Magnetorheological elastomer (MRE) is a new generation of MR materials whose stiffness and damping can be changed by magnetic field in real-time. In the absence of magnetic field, MRE is similar to that of a soft rubber. While under magnetic field, MRE turns to be very stiff. The maximum relative change of the modulus of the MRE can be from about 50% (stiffer rubber carrier) to beyond 300% (soft rubber carrier, such as silicone gel) (Davis, 1999). Damping ratio of the MRE can differ from 10% to 32% depending on the types of rubber matrix and iron particles, and is more affected by the magnetic field when the MRE is driven at a lower frequency (Chen, Gong and Li, 2008). Other merits of MREs are their low power requirement and rapid response to the magnetic field. Normally, magnetic coils will be designed and utilised to supply the currents for the energisation and control of the MREs. The power supply needed by the magnetic coil is only 20-40 volts which can be easily achieved by normal batteries and accumulators. MREs also have rapid response to magnetic fields and the time of response is less than 10 ms (Li, Zhang, Du and Chen, 2006.). Although the research and development in MRE material has been emerging in recent years, research on MRE applications can rarely be found. Majority of research on new MRE devices are reported in mechanical engineering. Ginder (Ginder, Scholotter and Nichols, 2001) piloted a pioneer theoretical work that utilised MREs as variable-spring-rate elements to develop an adaptive tuned vibration absorber. Deng (Deng and Gong, 2008) developed an adaptive tuned vibration absorber. Experimental results indicated that its natural frequency can be tuned from 27.5Hz to 40Hz. In civil engineering, however, the idea of using MRE as the fundamental material to develop adaptive MRE seismic isolators is quite new and novel. Hwang (Hwang, Lim, and Lee, 2006) carried out a conceptual study on the application of MREs to base isolation system for building structures. Usman (Usman, et al, 2009) numerically evaluated the dynamic performance of a smart base isolation system employing MR elastomer, and the results show that the proposed system outperforms the conventional system in reducing the responses of the structures during seismic excitations. Despite the two publications addressing the potential of MRE based base isolation system, the critical question on how to incorporate MREs into the base isolation system is yet to be addressed. This paper aims to design and develop an adaptive base isolator using the new smart material, MR elastomer, for its controllable material properties, including shear modulus and damping. A novel MRE base isolator with similar laminated structure of passive rubber base isolator is prototyped with the aim to comply with the requirement in the base isolation practice. Experiments were designed and conducted to examine the adaptive performance of the MRE base isolator. 2 MR ELASTOMER AND THE ADAPTIVE BASE ISOLATOR