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.

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Magnetorheological (MR) and electrorheological (ER) dampers are known to exhibit nonlinear behaviour which can make it difficult to predict their performance, particularly when they are integrated into engineering structures. As a result it can be impossible to properly assess the feasibility of using such semi-active devices to solve practical engineering problems. In this paper, a new model format is proposed which represents an extension of earlier work by the authors. The proposed model is more general and yet maintains the physical significance of key parameters. A novel model updating (or system identification) technique is developed so that the model can account for the behaviour of various configurations of device without the need for prior knowledge of the fluid properties. The technique relies upon the iterative adjustment of the model’s stiffness parameter so that the quasi-steady behaviour of the device can be estimated. Correlation between a bi-viscous model and the estimated quasi-steady behaviour is used as the criterion for choosing the most suitable value of stiffness. The modelling technique is completed by establishing empirical shape relationships between the pre-yield parameters, post-yield parameters, yield force and the applied excitation conditions. The modelling and identification procedures are applied to an MR damping device and the results are validated by comparing predicted and experimental responses under both non-sinusoidal and broadband excitation conditions.

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A smart fluid comprises a suspension of micrometre-sized particles in a dielectric carrier liquid. The application of a suitable stimulus -either electrical or magnetic -causes a significant increase in the resistance to flow of the fluid. Current and future developments in smart fluids are reviewed, paying particular attention to electro-rheological (ER) and magneto-rheological (MR) fluids. ER fluids have been the focus of intense academic interest over several decades. However, not until the re-discovery of MR fluids did commercial exploitation finally occur. Both microscopic and macroscopic models of smart fluids will be described. The link with industrial applications is established by introducing the three modes of operation through which smart fluids are harnessed. Insight into the behaviour of smart fluids is obtained through the development of relatively simple quasi-steady and dynamic models. A concise summary of the latest industrial applications is provided. Future trends are then considered under the headings of smart fluid technology, modelling of smart fluids and, finally, engineering devices.MST/6012