Magnetorheological Elastomer Isolator Research Articles

Model-free fuzzy control of a magnetorheological elastomer vibration isolation system: analysis and experimental evaluation

This paper addresses the problem of micro-vibration control of a precision vibration isolation system with a magnetorheological elastomer (MRE) isolator and fuzzy control strategy. Firstly, a polyurethane matrix MRE isolator working in the shear-compression mixed mode is introduced. The dynamic characteristic is experimentally tested, and the range of the frequency shift and the model parameters of the MRE isolator are obtained from experimental results. Secondly, a new semi-active control law is proposed, which uses isolation structure displacement and relative displacement between the isolation structure and base as the inputs. Considering the nonlinearity of the MRE isolator and the excitation uncertainty of an isolation system, the designed semi-active fuzzy logic controller (FLC) is independent of a system model and is robust. Finally, the numerical simulations and experiments are conducted to evaluate the performance of the FLC with single-frequency and multiple-frequency excitation, respectively, and the experimental results show that the acceleration transmissibility is reduced by 54.04% at most, which verifies the effectiveness of the designed semi-active FLC. Moreover, the advantages of the approach are demonstrated in comparison to the passive control and ON-OFF control.

Simulation study of electromagnetic circuit design in laminated magnetorheological elastomer isolator

This paper presents a simulation study of magnetic flux density distribution in a laminated magnetorheological elastomer (MRE) isolator. The performance of laminated MRE isolator depends on the particular magnetic properties of materials. Therefore, the electromagnetic simulation using Finite Element Method Magnetic (FEMM) had been carried out in designing and optimizing the MRE isolator. It is apparent that the capability of magnetic flux penetrated through the MRE depends on the design parameters approach including the selection of the materials, shape of MRE, thickness of MRE and steel sheet.

Development of a novel multi-layer MRE isolator for suppression of building vibrations under seismic events

Protecting civil engineering structures from uncontrollable events such as earthquakes while maintaining their structural integrity and serviceability is very important; this paper describes the performance of a stiffness softening magnetorheological elastomer (MRE) isolator in a scaled three storey building. In order to construct a closed-loop system, a scaled three storey building was designed and built according to the scaling laws, and then four MRE isolator prototypes were fabricated and utilised to isolate the building from the motion induced by a scaled El Centro earthquake. Fuzzy logic was used to output the current signals to the isolators, based on the real-time responses of the building floors, and then a simulation was used to evaluate the feasibility of this closed loop control system before carrying out an experimental test. The simulation and experimental results showed that the stiffness softening MRE isolator controlled by fuzzy logic could suppress structural vibration well.

Frequency control of smart base isolation system employing a novel adaptive magneto-rheological elastomer base isolator

In the past decades, base isolation techniques have become increasingly popular for seismic protection of civil structures owing to its capability of decoupling buildings from harmful ground motion. However, it has been recognised recently that the traditional passive base isolation technique could encounter a serious problem during earthquakes due its incapability in adjusting the isolation frequency to cope with the unpredictability and diversity of earthquakes. To address this challenge, a great deal of research efforts have been conducted to improve traditional base isolation systems, most of which focused on hybrid supplementary devices (passive, active and semi-active types) for the isolators to control displacement or to dissipate seismic energy. On the other hand, the most effective approach to address the aforementioned challenge should lay on varying isolator stiffness in real-time to achieve real-time spontaneous decoupling. A recent advance of the development of an adaptive magneto-rheological elastomer base isolator has brought such idea to reality as the new magneto-rheological elastomer base isolator is capable to alter its stiffness significantly in real-time. In this article, an innovative smart base isolation system employing such magneto-rheological elastomer isolator is proposed and a novel frequency control algorithm is developed to shift the fundamental frequency of the structure away from the dominant frequency range of earthquakes. Such design enables the building to avoid resonant state in real-time according to the on-coming spectrum of the earthquakes. Extensive simulation has been conducted using a five-storey benchmark model with the isolation system, and testing results indicate that the proposed control system is able to significantly suppress both the floor accelerations and inter-storey drifts simultaneously under different earthquakes.

Nonparametric modeling of magnetorheological elastomer base isolator based on artificial neural network optimized by ant colony algorithm

Laminated magnetorheological elastomer base isolator is regarded as one of the most promising candidates for realizing adaptive base isolation for civil structures. However, the intrinsic hysteretic and nonlinear behavior of magnetorheological elastomer base isolators imposes challenge for adopting the device to accomplish high-accuracy performance in structural control. Therefore, it is essential to develop an accurate model for symbolizing this unique characteristic before designing a feedback controller. So far, some classical parametric models, such as Bouc–Wen, Dahl, and LuGre, have been proposed to depict the hysteretic response of magnetorheological devices, that is, magnetorheological damper, which may also be used for describing the nonlinear behavior of magnetorheological elastomer base isolator. However, the parameter identification is difficult to implement due to the nonlinear differential equations existing in these models. Considering this problem, this article proposes a nonparametric model, that is, an artificial neural network–based model with 3 input neurons, 18 hidden neurons, and 1 output neuron, to predict the magnetorheological elastomer isolator behavior. In this model, the ant colony algorithm is employed for model training to obtain the optimal weights based on the force–displacement/velocity data sampled from the magnetorheological elastomer isolator. Finally, experimental data are used to validate the effectiveness of the proposed artificial neural network–based model with the good forecasting results.

Horizontal vibration reduction of a seat suspension using negative changing stiffness magnetorheological elastomer isolators

Magnetorheological elastomers (MREs) are being used more and more for the development of isolators and absorbers to attenuate vibrations. In this study, four innovative multilayer MRE isolators with negative changing stiffness characteristics are prototyped for horizontal vibration reduction of a seat. For each MRE isolator, a magnetic system consisting of two permanent magnets and an electromagnetic coil was designed to realise negative changing stiffness. This performance of the MRE isolators was verified by the experimental results which indicate that the MRE isolators exhibit a controllable negative changing stiffness characteristic; and this was further verified by the measured natural frequency shift of the MRE isolators. An experimental platform was also developed to test the vibration suppression of the MRE isolators for a real truck seat suspension. The test results demonstrate that the ride comfort of the MRE isolator based seat suspension is significantly better than passive seat suspension.

A Feasibility Study of Magnetorheological Elastomer Base Isolator

Magnetorheological elastomer (MRE) is a controllable smart material that demonstrates changes in rheological properties depending on the magnetic field strength. This paper presents thedevelopment of a new concept of MRE isolator in terms of design and magnetic simulation. All features of geometry parameters were considered and altered expeditiously in order to provide ample and uniform magnetic field. Finite Element Method Magnetics (FEMM) was used to design the electromagnetic circuit to generate magnetic fluxes penetrate through the MRE. The study, eventually, leads to the conclusion of different design parameters approach; selection of materials, diameter of the shaft, shape of MRE, length of shaft and thickness of housing.

A novel magnetorheological elastomer isolator with negative changing stiffness for vibration reduction

Magneto-rheological elastomers (MREs) have attracted notable credits in the development of smart isolators and absorbers due to their controllable stiffness and damping properties. For the purpose of mitigating unwanted structural and/or machinery vibrations, the traditional MRE-based isolators have been generally proven effective because the MR effect can increase the stiffness when the magnetic field is strengthened. This study presents a novel MRE isolator that experienced reduced stiffness when the applied current was increased. This innovative work was accomplished by applying a hybrid magnet (electromagnet and permanent magnets) onto a multilayered MRE structure. To characterise this negative changing stiffness concept, a multilayered MRE isolator with a hybrid magnet was first designed, fabricated and then tested to measure its properties. An obvious reduction of the effective stiffness and natural frequency of the proposed MRE isolator occurred when the current was continuously adjusted. This device could also work as a conventional MRE isolator as its effective stiffness and natural frequency also increased when a negative current was applied. Further testing was carried out on a one-degree-of-freedom system to assess how effectively this device could isolate vibration. In this experiment, two cases were considered; in each case, the vibration of the primary system was obviously attenuated under ON-OFF control logic, thus demonstrating the feasibility of this novel design as an alternative adaptive vibration isolator.

A new magnetorheological elastomer isolator in shear–compression mixed mode

A new magnetorheological elastomer isolator in shear–compression mixed mode is designed in this article. Two pieces of magnetorheological elastomer fabricated with different dimensions are utilized in the isolator. One magnetorheological elastomer operates on shear mode, and the other operates on compression mode. Next, a finite element method magnetic package is used to analyze the designed magnetic circuit system, and a test system is established to obtain the frequency response of magnetorheological elastomer isolator with mixed mode. It is found that the natural frequency of magnetorheological elastomer isolator changes greatly with variable current applied, and the amplitude of vibration is attenuated widely. Compared with the natural frequency of 0 A, the increment of natural frequency is up to 103% with applied current reaches to 1.5 A. Finally, the dynamic model of isolator system is established, and the stiffness and damping coefficients of magnetorheological elastomer isolator are identified by the experimental method. Meanwhile, the variable range for stiffness and damping of magnetorheological elastomer isolator with mixed mode is greater than that of single mode, which has been proved in theory and experiments.

Elastic band gaps of magnetorheological elastomer vibration isolators

Multi-layered two- and three-component magnetorheological elastomer (MRE) isolators were designed using a one-dimensional phononic crystal (PC) model. The elastic wave propagation properties of the two kinds of structures were studied using the transfer matrix method. Results show that the elastic band gap (EBG) position can be regulated by an external magnetic field and that the width of EBGs can be adjusted by varying component thickness. The three-component structure, which includes lead, can better tune the EBGs of MRE vibration isolators.

Research on new type MRE isolator and its mechanical model

A new type of seismic isolator with adjustable stiffness is proposed, based on the smart material of magnetorheological elastomers (MREs). This paper specifies the working principle of the isolator, analyses magnetic induction distribution of three different types of MRE isolators, which are unicoil magnetic energy input, twin coil magnetic energy input, and laminated steel plate coiling magnetic energy input respectively. The research shows that the third type of input produces relatively greater magnetic induction in the elastomer area, compared with the first two, and the magnetic field is evenly distributed in MRE area, therefore, it is the best structure. Eventually, the mechanical model of MRE isolator made of two steel slices and one elastomer slice is established together with the mechanical model made of multi-steel slices and multi-elastomer laminated structure. Furthermore, the numerical analysis is completed and the results show that MRE isolators have content adjustable behaviour.

Tunable Stiffness and Damping Vibration Control Strategy Based on Magnetorheological Elastomer Isolator

The combined variable stiffness and damping on-off control strategy is investigated using a magnetorheological elastomer (MRE) isolator. A one-degree-of-freedom system has been adopted to assess the efficiency of different control strategies under sinusoidal and random and pulse excitations. The obtained results illustrate that a single tunable stiffness control with maximal damping values under both excitations can simultaneously performs better control of displacement than using minimal damping if the relative displacement and relative velocity of load are in contrary directions . Moreover, on-off variable stiffness control plays a more important role than damping control, therefore it is feasible to only control magnetic field to change MRE elastic and damping property for simplicity.

Research on Hybrid Isolation System for Micro-Nano-Fabrication Platform

In order to obtain better vibration suppression effect, this paper designs a semiactive/fully active hybrid isolator by using magnetorheological elastomer (MRE) and piezoelectric material. Combined with multimode control scheme, full frequency vibration suppression is achieved. Firstly, series type structure is determined for the hybrid isolator, and the structure of hybrid isolator is designed. Next, the dynamic model of hybrid isolator is derived, the dynamic characteristics measurement for MRE isolator and piezoelectric stack actuator (PSA) is established, and parameters such as voltage-displacement coefficient, stiffness and damping constant are identified from the experimental results, respectively. Meanwhile, the switch frequency is determined by experimental results of PSA and MRE isolator. Lastly, influence of the stiffness of MRE, control voltage of PSA, and intermediate mass on hybrid isolator system is analyzed by simulations, and the results show that the hybrid isolator proposed is effective.

Experimental study and modeling of a novel magnetorheological elastomer isolator

This paper reports an experimental setup aiming at evaluating the performance of a newly designed magnetorheological elastomer (MRE) seismic isolator. As a further effort to explore the field-dependent stiffness/damping properties of the MRE isolator, a series of experimental testing were conducted. Based upon the analysis of the experimental responses and the characteristics of the MRE isolator, a new model that is capable of reproducing the unique MRE isolator dynamics behaviors is proposed. The validation results verify the model’s effectiveness to portray the MRE isolator. A study on the field-dependent parameters is then provided to make the model valid with fluctuating magnetic fields. To fully explore the mechanism of the proposed model, an investigation relating the dependence of the proposed model on every parameter is carried out.

A highly adjustable magnetorheological elastomer base isolator for applications of real-time adaptive control

Inspired by its controllable and field-dependent stiffness/damping properties, there has been increasing research and development of magnetorheological elastomer (MRE) for mitigation of unwanted structural or machinery vibrations using MRE isolators or absorbers. Recently, a breakthrough pilot research on the development of a highly innovative prototype adaptive MRE base isolator, with the ability for real-time adaptive control of base isolated structures against various types of earthquakes including near- or far-fault earthquakes, has been reported by the authors. As a further effort to improve the proposed MRE adaptive base isolator and to address some of the shortcomings and challenges, this paper presents systematic investigations on the development of a new highly adjustable MRE base isolator, including experimental testing and characterization of the new isolator. A soft MR elastomer has been designed, fabricated and incorporated in the laminated structure of the new MRE base isolator, which aims to obtain a highly adjustable shear modulus under a medium level of magnetic field. Comprehensive static and dynamic testing was conducted on this new adaptive MRE base isolator to examine its characteristics and evaluate its performance. The experimental results show that this new MRE base isolator can remarkably change the lateral stiffness of the isolator up to 1630% under a medium level of magnetic field. Such highly adjustable MRE base isolator makes the design and implementation of truly real-time adaptive (e.g. semi-active or smart passive) seismic isolation systems become feasible.

Development and simulation evaluation of a magnetorheological elastomer isolator for seat vibration control

Driver fatigue is one of the leading factors contributing to road crashes. Environmental stress, such as unwanted seat vibration, is a key contributor to fatigue. This article presents the design and development of a magnetorheological elastomer isolator for a seat suspension system. By altering the magnetorheological elastomer isolator’s stiffness through a controllable magnetic field and selecting suitable control strategy, the system’s natural frequency can be changed to avoid resonance, which consequently reduce the vehicle’s vibration energy input to seat, and thus suppress the seat’s response. Experimental results show that the developed magnetorheological elastomer isolator is able to reduce vibration more when compared with the passive isolation system, indicating the significant potential of its application in vehicle seat vibration control.

Semi-active variable stiffness vibration control of vehicle seat suspension using an MRelastomer isolator

This paper presents a study on continuously variable stiffness control of vehicle seatsuspension using a magnetorheological elastomer (MRE) isolator. A concept design for anMRE isolator is proposed in the paper and its behavior is experimentally evaluated. Anintegrated seat suspension model, which includes a quarter-car suspension and a seatsuspension with a driver body model, is used to design a sub-optimal controller for an active isolator. The desired control force generated by this active isolatoris then emulated by the MRE isolator through its continuously variable stiffness propertywhen the actuating condition is met. The vibration control effect of the MRE isolator isevaluated in terms of driver body acceleration responses under both bump andrandom road conditions. The results show that the proposed control strategyachieves better vibration reduction performance than conventional on–off control.

The Finite Element Analysis Based on ANSYS- Magnetorheological Elastomer Isolator

Use multiphysics module in finite element analysis software ANSYS to analyse Magnetorheological elastomer isolator of Static magnetic field and modal. Thus making a comprehensive evaluation to The design of the isolator whether it can meet the performance requirements and stability in the actual work.

Design and Vibration Characteristics Analysis of Magnetorheological Elastomer Isolators

Magnetorheological(MR) elastomer is a new branch of magnetorheological materials.It is an interesting candidate for active-passive hybrid vibration control of structural systems because it has both advantages of magnetorheological fluid and elastomer material.Based on the squeezing mode,a MR elastomer isolator is designed and manufactured.Vibration responses of the isolator are experimentally tested under different applied electric currents and excited frequencies.The influences of applied electric current and excited frequency on the dynamic response characteristics and vibration-isolation effects are studied.Experimental results show the amplitudes and frequencies of vibration response peaks can be changed by the applied electric current and the vibration-isolation effect can be improved by an external electric current.It is demonstrated that the MR elastomer isolator has the adaptive ability of shifting its natural frequency and decreasing the vibration amplitudes when a control current is applied,and can be used in structure active-passive hybrid vibration isolation system.

Performance Comparison between an MRF Damper and an MRE Isolator Incorporated with a Building Structure

As an important member of smart materials, magnetorheological elastomers (MREs) exhibit characteristics that their modulus can be controlled by an external magnetic field. Based on these experimental results, a viscoelastic solid model with four parameters was proposed to predict the performance of MRE. A building model, three stories high, was constructed using MATLAB SIMULINK to evaluate the performance of an MRE device in structural control. In addition, the performance of an MRF damper and an MRE device in structural control, where the resultant peak force was selected as a criterion in the evaluation process, was compared and discussed. Two controllers, passive on and passive off control strategy were used to compare the response of structure. The effectiveness of an MRE bearing in structural control was well justified.