Semi-active vibration isolation using magnetorheological isolators

An experimental and theoretical analysis of a vibration isolation system that uses magnetorheological (MR) fluid-based semi-active isolators is presented. In doing so, a vibration isolator that uses MR fluids is designed, manufactured, and experimentally evaluated. Typically, a Bingham-plastic model, with its accompanying zero speed force step discontinuity, would be used to model an MR isolator. A new nonlinear model, with simple low-speed hysteresis characteristics, is proposed to describe the hysteresis force characteristics of the MR isolator. The damping forces of the MR isolator with different excitation frequency and current input are measured and compared with that resulting from the hysteresis model for the verification of the theoretical analysis. A vibration isolation system with the MR isolator is constructed, and its dynamic equation of motion is derived. A simple skyhook controller is formulated to attenuate the vibration of the system. Controlled performances of the vibration isolation system are experimentally and theoretically evaluated in the frequency and time domains. A key conclusion is that a simple model of the low-speed force vs low-speed velocity hysteresis characteristics is necessary for successful prediction of open- and closed-loop performance in both the time and frequency domains.