Magnetorheological (MR) damper is one type of semi-active devices that shows a great potential for vibration suppression and hazard mitigation of civil structures. One special advantage of the damper is that its damping characteristics can be adaptively and quickly altered by a varying magnetic field. A linear valve-mode MR damper was obtained from Lord Corporation for investigation. A phenomenological model based on Bouc-Wen hysteresis model was developed to emulate the highly nonlinear behavior of the MR damper. A simplified yet relatively accurate inverse dynamic model that can directly relate the damper force to the input voltage was then proposed. This inverse dynamic model can directly estimate voltage required to be commanded into the damper in order to produce a desired damping...[ Read more ]

Magnetorheological (MR) damper is one type of semi-active devices that shows a great potential for vibration suppression and hazard mitigation of civil structures. One special advantage of the damper is that its damping characteristics can be adaptively and quickly altered by a varying magnetic field. A linear valve-mode MR damper was obtained from Lord Corporation for investigation. A phenomenological model based on Bouc-Wen hysteresis model was developed to emulate the highly nonlinear behavior of the MR damper. A simplified yet relatively accurate inverse dynamic model that can directly relate the damper force to the input voltage was then proposed. This inverse dynamic model can directly estimate voltage required to be commanded into the damper in order to produce a desired damping force. Experiments demonstrate that MR damper using this inverse model can closely reproduce the prescribed forces. Two control algorithms, the classical pole placement technique and the linear-quadratic regulator (LQR) with output weighting method, were used to illustrate how this inverse model can be implemented in the applications. In an attempt to validate the effectiveness of the MR damper in controlling wind-induced response of a building model in wind tunnel, it is necessary to have a damper with a small force range so that it can be used to control the light-weight building model. In this study, a small-scale rotary type MR damper was designed, manufactured and tested. The damper uses shear mode behavior of the MR fluids and was designed based on the simple Bingham viscoplastic model. A prototype damper that can produce forces in the order of a few Newtons was made and tested in the laboratory. It was found that the Bouc-Wen model, which has been used to emulate the linear valve-mode MR dampers, can also portray the hysteretic behavior of the shear-mode rotary damper. An inverse dynamic model was also developed for this rotary MR damper. Experiments were also conducted to demonstrate the accuracy and implementation of this inverse dynamic model.