Magnetorheological Elastomer Isolator Research Articles

Investigation of a semi-active suspension system for high-speed trains based on magnetorheological isolator with negative stiffness characteristics

As the operation speed of high-speed train increases, trains with fixed suspension stiffness will encounter dramatical vibrations, especially when its lateral resonance occurs. This greatly affects the ride comfort and safety of the trains. Based on this motivation, a novel stiffness variable suspension system using magnetorheological elastomer (MRE) isolator with negative stiffness is proposed. The controllable stiffness can make the train avoid lateral resonance while the negative stiffness characteristics can provide an actuating force similar to the active control, which further improve the vibration attenuation performance of the suspension. The new MRE isolator was firstly fabricated and tested to verify its stiffness variability, especially negative stiffness characteristics. Four different suspension systems were then tested on a 6-DOF vibration platform for the performance comparison. The experimental results show that this new semi-active lateral suspension system has improved vibration attenuation performance than the passive system and the traditional MRE isolation system without negative stiffness. The vibration attenuation performance of the new suspension system is even comparable to that of some of the existing active suspensions while avoiding the disadvantages of the active control.

Development of a Novel Magneto-Rheological Elastomer-Based Semi-Active Seat Suspension System

Human operators in the transportation sector are exposed to whole-body vibration (WBV) while driving. Occupational exposure to WBV, predominant at low frequencies (<20 Hz), has been linked to spinal injuries and reduced functioning. This study aims at the design development of a novel semi-active seat suspension system featuring magneto-rheological elastomers (MREs) to mitigate the WBV. The proposed suspension system allows a greater range of strokes, while ensuring the MRE remains within an acceptable level of deformation. Several MRE samples were fabricated and characterized under shear mode. Afterward, a field- and frequency-dependent phenomenological model was developed to predict the viscoelastic properties of MREs as functions of both the excitation frequency and applied magnetic field. The MRE material model was subsequently used to design and optimize an adaptive seat suspension system incorporating a C-shaped MRE-based isolator in parallel and series with passive springs. The proposed adaptive seat suspension system demonstrated a frequency shift of 29% by increasing the applied current from 0 to 2 A. Finally, a 6-DOF lumped parameter model of a seated human subject combined with the proposed semi-active suspension system featuring the MRE isolator has been formulated to investigate the vibration transmissibility from the floor to the subject’s head.

Modeling and design of magnetorheological elastomer isolator system for an active control solution to reduce the vibration transmission in elevator context

The attenuation of the structure-borne sound caused by elevator systems in residential buildings is a priority for manufacturers. This work develops a model of an active control isolation system for the vibrations produced by the elevator drive machine. This solution proposes the substitution of conventional passive isolators by new ones made of a magnetorheological elastomer (MRE), a smart material whose modulus can be modified by applying a magnetic field. To guide the design process, MRE isolators are fabricated and experimentally tested statically and dynamically in compression mode. Subsequently, the parameters of the MRE are fitted to build a nonlinear material sub-model that accounts for the frequency, amplitude, and magnetic field dependency. Afterward, a global model of the elevator drive machine vibration isolation system is developed, which incorporates the drive machine, structure, and MRE-based isolator. To enhance vibration isolation, two active control strategies are designed and assessed. Simulation results predict that active control systems based on MRE isolators improve vibration isolation as compared to traditional passive systems. The excitation amplitude and frequency, along with the control strategy and magnetization of the MRE isolators are shown to be critical parameters when designing an active control solution.

Modeling and semi-active control performance analysis of MRE isolator based on BPNN optimized by GA using different evaluation indexes

The utilization of isolation systems employing Magnetorheological Elastomer (MRE) devices holds significant promise for structural vibration applications due to their customizable stiffness and damping characteristics. However, the nonlinear dynamics inherent in MRE isolators present formidable obstacles for the establishment of accurate models and development of effective control strategies for practical implementation. In this work, the dynamic properties of a self-made MRE isolator under different loading conditions are tested and analyzed. Then the nonparametric forward model and inverse model of MRE isolator based on BPNN (back propagation neural network) are established respectively, and the GA (genetic algorithm) is used to optimize the neural structure of BPNN. The precision and accuracy of the forward and inverse model is verified by comparing the predicted and experimental data. Simulation and experimental results show that the BPNN optimized by GA can efficiently and accurately model the nonlinear behavior of MRE isolators. Based on this, we take an eight-story shear frame building based on the proposed MRE vibration isolator model as the research object and numerically studied the vibration suppression effect under the control of three typical control algorithms, that is, LQR, FC, and FC-PID. In the process of evaluating the effect of vibration isolation control, in addition to utilizing the traditional displacement amplitude, layer distance and acceleration as evaluation indexes, we also propose a new comprehensive evaluation index which has weighting coefficients and considers the input cost. It is shown that the newly proposed comprehensive index can more conveniently compare the advantages and disadvantages of different control algorithms, and the fuzzy PID is the most suitable among the three control algorithms.

Robustness analysis of magnetorheological elastomer-based vibration isolation system with optimal fuzzy controller

Due to adjustable stuffiness with applied magnetic fields, magnetorheological elastomer (MRE)-based vibration isolation method has attracted more attention in vibration engineering fields, such as precision-fabrication or precision-measurement platform for high-tech facilities, civil structure. However, there exists parameter uncertainty in dynamic model of control system, such as variation load mass in different working conditions, increasing or decreasing stiffness due to the rubber aging induced by the temperature and humidity of the environment. So it is necessary to investigate and evaluate quantitatively the robustness of MRE-based vibration isolation control system. This paper addresses that. Firstly, the dynamic model of MRE vibration isolation system with consideration of uncertain stiffness of the isolator and load mass is established. Then, a fuzzy controller (FC) is designed under the certain amplitude and frequency excitation, the parameters of FC are optimized by genetic algorithm. On this basis, RI (robustness index) is proposed to divide the robustness of the system under variation of parameters (stiffness of MRE isolator and load mass) as ‘good’, ‘fair’ and ‘poor’ level. Lastly, simulation and experiments are carried out to evaluate quantitatively the robustness performance of MRE vibration control system with designed optimal FC, respectively. The results show that the designed optimal FC has greater RI than experienced-based FC for different variation range stiffness of MRE isolator and load mass, and demonstrates outstanding robustness.

Analysis and design of a semi-active X-structured vibration isolator with magnetorheological elastomers

This paper proposes a semi-active X-shaped vibration isolation (XSVI) system with magnetorheological elastomer (MRE) based on its field-controlled variable properties. The conceptual design of the proposed system is constructed by embedding an MRE-based device into a X-shaped structure, instead of the original XSVI’s linear spring. The proposed system could fulfill tuning capability stiffness for effective vibration mitigation in random low-frequency excitations. The theoretical modeling is developed and the static analysis of the proposed MRE-based XSVI system is studied. The dynamic equation of proposed isolation system is established and solved by harmonic balance method. The influence of key geometrical parameters and field strength on the proposed system characteristics are detailly studied and discussed, and the tunable frequency-shift properties are presented. Under the harmonic excitations in a single frequency, the displacement of the isolated objective can be reduced by 22.5% with the field strength of 0.7 T. In the presence of double-tone (2 Hz mixed with 5 Hz) external loading, the reduction ratio of excited and isolated objectives’ displacements by semi-active control are respectively 63.95% and 18.77% by comparing the passive-off state. Additionally, compared with the original XSVI system and MRE isolator, the proposed MRE-based XSVI system in semi-active controller presents outstanding isolation performances. This study indicates that the proposed MRE-based XSVI system could provide a potential method for vibration isolation tuning in wide-band low-frequency range.

Developing the viscoelastic model and model-based fuzzy controller for the MRE isolator for the wide frequency range vibration isolation

The ability to mitigate the vibrations by a magnetorheological elastomer (MRE) isolator varies with the amplitude of the excitation and the magnetic field. To implement semi-active vibration control, a mathematical model representing the dynamic response over a wide frequency range is crucial. In the present study, an attempt was made to develop a mathematical model for the designed MRE isolator over a wide frequency range under different operating conditions. A model-based fuzzy controller was developed to implement semi-active control attributes over a broadband frequency. The methodology entails that the MRE isolator operating in shear mode was designed. The performance of the isolator was evaluated over a frequency range of 15–80 Hz with varying input currents and excitation amplitudes. The transmissibility response of MRE isolator was mathematically represented using viscoelastic constitutive relations. The isolator system was represented in state-space form, and its parameters were determined by minimizing the mean square error between experimental and model responses. A polynomial function was used to generalize variations in viscoelastic model parameters with respect to the input current. Based on the controller stopping frequency, a relationship was established between the current input to the MRE isolator and the excitation amplitude. Using the mathematical equations, a model-based fuzzy controller was developed and tested in simulation and real-time conditions. The results show that the controller effectively isolates the vibration amplitude at various excitation amplitudes and frequencies.

Modeling and validation of multifield coupled self-sensing characteristics of magnetorheological elastomer for vibration isolators

In this paper, a multifield coupled self-sensing model for magnetorheological elastomer (MRE) isolators is proposed. By dispersing carbonyl iron particles and multiwalled carbon nanotubes in polydimethylsiloxane, an MRE with improved force-sensing capability is fabricated as a further effort to explore its comprehensive sensing effect. Then, the model is developed based on magnetic dipole analysis and tunneling theory. In addition, the conductive mechanism and vibrational operating state of the MRE are analyzed, while the effects of input force and current are investigated. The experimental results show that the resistance of the MRE decreases with increasing force or current, which is consistent with the theoretical model. For instance, the resistance decreases from 1.55 kΩ to 0.55 kΩ as the force changes from 0 N to 160 N, and the dynamic resistance responses show a very good match with the force input curve and the response curve present continuous, stable, and perfectly reversible signals. The validation results demonstrate that the proposed model can reproduce experimental results well without causing significant differences. In summary, the proposed model provides an accurate approach to estimating the conductivity of MREs for self-sensing actuator applications.

Investigation of a new metamaterial magnetorheological elastomer isolator with tunable vibration bandgaps

Semi-active isolators with laminated magnetorheological elastomer (MRE) structures draw increasing attentions for vibration control because of their resonance-frequency-shift property. Their vibration attenuation capacity can be further improved by integrating the acoustic metamaterial characteristics with tunable vibration bandgaps at designed frequencies. On this basis, a novel metamaterial MRE isolator with controllable vibration bandgaps was designed and prototyped. The mechanism of the formation of vibration bandgaps was analysed theoretically using the method of mass-spring model. Both infinite and finite periodic structures were discussed respectively. The equivalent negative stiffness of the metamaterial MRE isolator was studied. The evaluation experiments were conducted to study bandgaps of the metamaterial MRE isolator and its vibration isolation capacity. Results demonstrate that the new metamaterial MRE isolator possesses controllable bandgaps and can provide improved vibration isolation performance.

A hybrid MRE isolation system integrated with ball-screw inerter for vibration control

Magnetorheological elastomer (MRE), as a field-dependent smart material, has been widely applied on base isolation for vibration reduction. However, the MRE isolation system often experiences large drift during a strong earthquake, which may cause mechanical failure. Additionally, its performance among the low-frequency range is still limited. To tackle these problems, this paper proposes a hybrid vibration isolation system which is composed of four stiffness softening MRE isolators and a passive ball-screw inerter. A simulation was developed to prove the effectiveness of the hybrid isolation system before the earthquake tests. A scaled three-storey building was developed based on the scaling laws as the isolated objective in earthquake experiments. Besides, a linear quadratic regulation controller was utilised to control the mechanical properties of the hybrid MRE isolation system. Finally, the evaluation experiments of the building under a scaled Kobe earthquake excitation were conducted. The experimental results show that the simulation and the experimental results were in agreement, validating that the hybrid isolation system could provide a better vibration mitigation performance, in the meanwhile, reduce the displacement amplitude of the isolation system.

Nonlinear characterization of magnetorheological elastomer-based smart device for structural seismic mitigation

ABSTRACT Magnetorheological elastomer (MRE) has been demonstrated to be effective in structural vibration control because of controllable stiffness and damping properties with the effect of external magnetic fields. To achieve a high performance of MRE device-based vibration control, a robust and accurate model is necessary to describe nonlinear dynamics of MRE device. This article aims at realising this target via nonlinear modeling of an innovative MRE device, i.e. MRE vibration isolator. First, the field-dependent properties of MRE isolator were analysed based on experimental data of the isolator in various dynamic tests. Then, a phenomenal model was developed to account for these unique characteristics of MRE-based device. Moreover, an improved PSO algorithm was designed to estimate model parameters. Based on identification results, a generalised model was proposed to clarify the field-dependent properties of the isolator due to varied currents, which was then validated by random and earthquake-excited test data. Based on the proposed model, a frequency control strategy was designed for semi-active control of MRE devices-incorporated smart structure for vibration suppression. Finally, using a three-storey frame model and four benchmark earthquakes, a numerical study was conducted to validate the performance of control strategy based on the generalised current-dependent model with satisfactory results.

Modelling and experimental characterisation of a compressional adaptive magnetorheological elastomer isolator

This article proposes a simple physical-based model to describe and predict the performance of axially compressed magnetorheological elastomer cylinders used as vibration and shock absorbers. The model describes the magnetorheological elastomer macroscopic stiffness changes because of an externally applied magnetic field from a microscopic composite cell of silicone rubber and carbonyl iron particle. Despite neglecting the material hyperelasticity, anisotropy and adjacent magnetic interaction, the model describes effectively the effect of the magnetic field on the macroscopic modulus of elasticity. The changes in the mechanical properties with the induced magnetic field are measured on samples of different particle concentration based on volume percentage, that is, 10 and 30 percent concentration of iron particles in a silicone rubber matrix. The manufacturing process of the samples is detailed, as well as the experimental validation of the effective stiffness change under a magnetic field in terms of transmissibility and mobility testing. However, the prediction seems to be limited by the linear elastic material model. Predictions and measurements are compared, showing that the model is capable of predicting the tunability of the dynamic/shock absorber and that the proposed devices have a possible application in the reduction of mechanical vibrations.

A hybrid skyhook active force control for impact mitigation using magneto-rheological elastomer isolator

This paper presents control characteristic of an impact isolator featuring a magneto-rheological elastomer isolator device (MREID). The developed MREID is analysed in term of its magnetic intensity to produce a large of MR effect that controlled by the input current. In order to control the input current, the hybrid skyhook active force control (HySAFC) is proposed. The HySAFC is used to track the signal based on the force obtained from the feedback of the force sensor and accelerometer. However, the control output of the HySAFC is desired force of the current generator which is designed using the inverse adaptive neuro-fuzzy inference system (ANFIS). Then, the selection of the input current using the IF–THEN rules depend on desired force and impact energy for current generator. Next, for the development of control structure, the impact isolation system is formulated and the impact isolation test rig is used to perform the experimental validation process. The validation assessment of HySAFC is experimentally realized, and the control responses, namely such as jerk, accelerations and transmitted forces as well as the impact isolation system are presented in the time domain. Finding of this study, the HySAFC is able to improve the MREID performance for impact loading application in simulation and experiment and capable in providing fast response when impact occurred.

Improved magnetic circuit analysis of a laminated magnetorheological elastomer device featuring both permanent magnets and electromagnets

As an essential and critical step, magnetic circuit modelling is usually implemented in the design of efficient and compact magnetorheological (MR) devices, such as MR dampers and MR elastomer isolators. Conventional magnetic circuit analysis simplifies the analysis by ignoring the magnetic flux leakage and magnetic fringing effect. These assumptions are sufficiently accurate in dealing with less complicated designs, featuring short magnetic path lengths such as in an MR damper. However, when dealing with MR elastomer devices, such simplification in magnetic circuit analysis results in inaccuracy of dimensioning and performance estimation of the devices due to their sophisticated design and complex magnetic paths. Modelling permanent magnets also imposes challenges in the magnetic circuit analysis. This work proposes an improved approach to include magnetic flux fringing effect in magnetic circuit analysis for MR elastomer devices. An MRE-based isolator containing multiple MRE layers and both a permanent magnet and an exciting coil was designed and built as a case study. The results of the proposed method are compared to those of conventional magnetic circuit modelling, finite element analysis and experimental measurements to demonstrate the effectiveness of the proposed approach.

A novel bi-directional shear mode magneto-rheological elastomer vibration isolator

In this article, a novel bi-directional shear mode magneto-rheological elastomer–based vibration isolator has been designed, fabricated, and characterized to improve the dynamic response and identification of this class of “intellectual” mechanical devices. A heuristic embodiment has been realized in order to design such an isolator wherein both the vertical and horizontal directions can be operated only in the shear mode not only individually but also simultaneously. Two fixtures have been designed for performing the characterization of the magneto-mechanical behavior of the proposed magneto-rheological elastomer isolator in the vertical and horizontal shear modes under wide ranges of strain amplitude (4%–32%), excitation frequency (1–8 Hz), and magnetic flux density (0–220 mT). Experimental results revealed maximum relative magneto-rheological effects of 35% and 27 % in the vertical and horizontal shear modes, respectively. Furthermore, basic mathematical models of single-degree-of-freedom systems, employing the magneto-rheological elastomer–based isolator in the vertical and horizontal shear modes, have been established. The proposed magneto-rheological elastomer isolator in the vertical mode exhibited natural frequency shift of 6.1% by a small increment in the magnetic flux density which approves the potential of the proposed bi-directional shear mode magneto-rheological elastomer–based vibration isolator for vibration control applications, such as seat suspension systems.

Design and application of an improved vulcanization apparatus for magnetorheological elastomer

Magnetorheological elastomer is a new intelligent material, which shows a promising application prospect in the intelligent control area. In the molding of magnetorheological elastomer, vulcanization under magnetic field condition is the critical step. However, the traditionally used vulcanization apparatus cannot be applied in the preparation of magnetorheological elastomer directly for the unavailable magnetic field, uneven pressure, and serious heat dissipation. An improved vulcanization apparatus with magnetic field generator, support device, and temperature control device was designed. To ensure the rationality of the designs, magnetic circuit simulation, thermal simulation, and stiffness consistency test were conducted. Experimental tests showed that the vulcanization apparatus we designed applied well in the preparation of magnetorheological elastomers and magnetorheological elastomer isolator.

Semi-Active Control for Benchmark Building Using Innovative TMD with MRE Isolators

Tuned Mass Damper (TMD) with magneto-rheological elastomer isolators (MRE-TMD) is a novel control device for suppressing structural vibration caused by earthquakes. It is a nonlinear hybrid vibration absorber and the stiffness & damping can be controlled by changing the current of isolators’ coil. Using MRE-TMD as an adaptive frequency TMD to mitigate vibration and treating it as only a passive damper is the focus of most nowadays researches. In this paper, semi-active control theory is introduced to the MRE-TMD-structure system which means that the control force can be obtained through variable stiffness & damping technology, and MRE-TMD is a semi-active damper instead of a passive one. A control system sketch, as well as principles and control strategies of a semi-active MRE-TMD-structure system for vibration control is designed. An improved limited sliding (ILSL) algorithm based on linear quadratic optimal theory is also introduced. Numeric simulations of a five-story benchmark building model equipped with semi-active MRE-TMD subjected to several benchmark earthquake records are conducted to investigate the control performance of the proposed semi-active MRE-TMD. Control force characteristics of the structural MRE-TMD systems are also evaluated. The results indicate that semi-active MRE-TMD can provide control force to the system and it shows superior ability to suppress the structural vibrations of comparing to the passive MRE-TMD.

Vibration suppression of tunnel boring machines using non-resonance approach

Tunnel boring machines (TBM) are efficient tunnel excavation equipment, and the number of TBM in many countries is increasing rapidly. TBM works in a harsh geological environment and long-term vibration will cause tremendous damages, including loosening the pipeline and damaging the mechanical system on the main frame of TBM. In this paper, a variable stiffness magnetorheological elastomer (MRE) isolator is installed under the main frame in order to control its resonance frequency to avoid the vibration resonance to reduce the high-level vibration of TBM, this is called non-resonance control approach. A multi-degree-of-freedom dynamics model of the TBM is established as the first step. The performance of the MRE isolator on vibration control of TBM is numerically evaluated. Then a scaled TBM is built for experimental evaluation and a laminated MRE isolator is designed, prototyped according to the requirement of the scaled TBM; its properties are tested by a shaking table, including its current-dependency, frequency-dependency, and amplitude-dependency features. In the end, the MRE is installed on the scaled TBM platform to evaluate its vibration reduction effectiveness. The experimental test results demonstrate that the displacement amplitude of the TBM vibration could be reduced by up to 20.18% and 14.52% under harmonic sweep excitation and nonsynchronous excitation, respectively.

Integration of an omnidirectional self-powering component to an MRE isolator towards a smart passive isolation system

Base isolator is one of the most adopted and effective means of mitigating unwanted and harmful vibrations to protect buildings and other key civil infrastructure from seismic events. For this reason, the base isolation technology has advanced greatly in recent years, especially the magnetorheological elastomer (MRE) isolator. However, the operation of such an MRE isolator needs external power supply to be activated, which may fail due to the power outage caused by the seismic movement. To this end, this work developed an MRE base isolation system with self-powering capability. This characteristic enables the isolation system self-sufficient without relying on external power. The self-powering component is an innovative omnidirectional element and can collect vibration energy from all horizontal directions. In addition, the self-powered isolation system performs rate-dependent softening behaviour which overcomes the conflicting requirements that the stiffness is required to be hard during daily operation but soft when the earthquake happens. For this reason, this new isolation system has been built and tested, including its MRE isolator and self-powering components. Its vibration reduction capability for building is also investigated on a scaled building. The theoretical analysis and verification is also performed and the conclusions coincide with the experimental results. The experimental and simulation results demonstrate that this new isolation system is capable of generating electricity which is sufficient to power itself when it is subjected to ground motions, and that it shows a high effectiveness in reducing the floor accelerations and the relative displacement.

A physical model of magnetorheological elastomer isolator and its dynamic analysis

Magnetorheological elastomers have been paid increasing attention in the fields of vibration mitigation. One of the challenging aspects of utilizing magnetorheological elastomer–based device is to develop dynamic models that could accurately describe their unique characteristics. In this work, a comprehensive physical model including viscoelasticity, hysteresis, and frictional effects is proposed by exploring the unique dissipated energy mechanisms of magnetorheological elastomer isolator. And, a particle swarm optimization–genetic algorithm hybrid algorithm is utilized for model parameter identification. The parameter sensitivity analysis is also conducted. The effectiveness of the proposed model is validated by comparing the predicted force and experimental force. Furthermore, a semi-active fuzzy controller is designed to evaluate the performance of magnetorheological elastomer isolator for vibration mitigation. Numerical results show that the displacement and acceleration of a magnetorheological elastomer isolated system could be reduced, which indicates potential for structural vibration attenuation.