Electro-rheological (ER) fluids are now regarded as one of the most versatile of the materials available for building smart structures and machines. In principle, ER fluids promise an elegant means of providing continuously variable forces for the control of mechanical vibrations. In practice, the development of industrial devices has been hampered by the unavailability of suitable ER fluids. Prompted by recent advances in ER fluid development this paper provides a comprehensive survey of ER devices for vibration control. The key modes of operation are identified and progress towards a unified approach to visualizing the macroscopic behaviour is summarized before presenting a comprehensive survey which includes contributions to the identification of ER fluid dynamics and the application of feedback control. The discussion of results includes some thoughts on future trends.

https://iopscience.iop.org/article/10.1088/0964-1726/5/4/011/pdf

Applications of electro-rheological fluids in vibration control: a survey

A nonlinear dynamic model is presented that characterizes electrorheological material behavior in terms of its shear stress versus shear strain behavior. The ER fluid model is essentially a nonlinear combination of linear shear flow mechanisms. These linear shear flow mechanisms, a three-parameter viscoelastic fluid element and a viscous fluid element, are used to describe shear flow behavior in the pre-yield and the post-yield regimes, respectively. In order to capture the material behavior in the transition through the yield point, a nonlinear combination of these linear shear flow mechanisms is used. The model, which relates the shear strain input to the shear stress output, is represented by a simple network that consists of two parallel linear mechanisms whose outputs are combined using nonlinear weighting functions. The weighting functions are dependent on the strain rate in the material. A system identification technique is developed to estimate the model parameters from experimental data, which consists of shear stress versus shear strain hysteresis loops at different levels of electric field. The results of this system identification approach indicate that the model parameters are smooth monotonic functions of the electric field. The experimental hysteresis loops are reconstructed using the estimated model parameters and the results show that the model accurately predicts material response. It is shown that the Coulomb friction-like behavior at high field strengths, which is characteristic of ER fluids, can be captured by this nonlinear mechanism-based model.

https://iopscience.iop.org/article/10.1088/0964-1726/6/3/012/pdf

A nonlinear viscoelastic - plastic model for electrorheological fluids

Semi-actively controlled magnetorheological (MR) fluid dampers offer rapid variation in damping properties in a reliable fail-safe manner using very low power requirements. Their characteristics make them ideal for semi-active control in structures and vehicle applications in order to efficiently suppress vibration. To take advantage of their exceptional characteristics, a high fidelity model is required for control design and analysis. Perfect understanding of the dynamic characteristics of such dampers is necessary when implementing MR struts in applications. Different models have been proposed to simulate the hysteresis phenomenon of MR dampers. The Bouc–Wen model has been extensively used to simulate the hysteresis behavior of MR dampers. However, considerable differences still exist between the simulation and experimental results. Moreover, the characteristic parameters in the traditional Bouc–Wen model are not functions of the frequency, amplitude and current excitations; therefore, the estimated parameters can characterize the behavior of the tested MR damper under specific excitation conditions and must be re-evaluated if a different combination of excitation parameters is desired. This can be extremely cumbersome and computationally expensive. In this work, a new hysteresis model based on the Bouc–Wen model has been developed to better characterize the hysteresis phenomenon of the MR damper. The proposed model incorporates the frequency, amplitude and current excitation as variables and thus enables us to predict efficiently and accurately the hysteresis force for changing excitation conditions. The proposed modified Bouc–Wen model has been validated against the experimental results through graphical and quantitative analysis in time, displacement and velocity domains and an excellent correlation has been found.

https://iopscience.iop.org/article/10.1088/0964-1726/15/5/004/pdf

A new dynamic hysteresis model for magnetorheological dampers

The development of a powerful new magnetorheological fluid (MRF), together with recent progress in the understanding of the behavior of such fluids, has convinced researchers and engineers that MRF dampers are among the most promising devices for semi-active automotive suspension vibration control, because of their large force capacity and their inherent ability to provide a simple, fast and robust interface between electronic controls and mechanical components. In this paper, theoretical and experimental studies are performed for the design, development and testing of a completely new MRF damper model that can be used for the semi-active control of automotive suspensions. The MR damper technology presented in this paper is based on a completely new approach where, in contrast to in the conventional solutions where the coil axis is usually superposed on the damper axis and where the inner cylindrical housing is part of the magnetic circuit, the coils are wound in a direction perpendicular to the damper axis. The paper investigates approaches to optimizing the dynamic response and provides experimental verification. Both experimental and theoretical results have shown that, if this particular model is filled with an 'MRF 336AG' MR fluid, it can provide large controllable damping forces that require only a small amount of energy. For a magnetizing system with four coils, the damping coefficient could be increased by up to three times for an excitation current of only 2 A. Such current could be reduced to less than 1 A if the magnetizing system used eight small cores. In this case, the magnetic field will be more powerful and more regularly distributed. In the presence of harmonic excitation, such a design will allow the optimum compromise between comfort and stability to be reached over different intervals of the excitation frequencies.

https://iopscience.iop.org/article/10.1088/0964-1726/14/4/041/pdf

An innovative magnetorheological damper for automotive suspension: from design to experimental characterization

The twenty-first century could be called the 'Multifunctional Materials Age' The inspiration for multifunctional materials comes from nature, and therefore these are often referred to as bio-inspired materials Bio-inspired materials encompass smart materials and structures, multifunctional materials and nano-structured materials This is a dawn of revolutionary materials that may provide a 'quantum jump' in performance and multi-capability This book focuses on smart materials, structures and systems, which are also referred to as intelligent, adaptive, active, sensory and metamorphic The purpose of these materials from the perspective of smart systems is their ability to minimize life-cycle cost and/or expand the performance envelope The ultimate goal is to develop biologically inspired multifunctional materials with the capability to adapt their structural characteristics (such as stiffness, damping and viscosity) as required, monitor their health condition, perform self-diagnosis and self-repair, morph their shape and undergo significant controlled motion over a wide range of operating conditions

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Smart Structures Theory

This paper presents some of the results of an experimental and analytical study of a controllable electrorheological (ER) device configured to induce an adjustable amount of dynamic shear force in response to an applied voltage. Maps of the force-deformation characteristics of the aluminosilicate based ER material are developed over a relatively wide frequency range, and approximating analytical expressions are obtained for the force-deformation-frequency-voltage characteristics of the material. Subsequently, an evaluation is made of the efficiency of using online control of an electrorheological actuator to emulate the operation of an optimally tuned auxiliary mass damper attached to a primary system subjected to arbitrary dynamic environments. It is shown through numerical simulation studies that the proposed parameter control algorithm provides an efficient means for the online control of the primary system under a wide range of excitations. An experimental study is presented in which an ER device is used, in conjunction with a small laboratory building model, as a semiactive element in an online structural control approach using pulse control techniques.

https://iopscience.iop.org/article/10.1088/0964-1726/4/1A/015/pdf

S F Masri

Papers

Modeling and control of an electrorheological device for structural control applications