Control characteristics of a continuously variable ER damper

A continuously variable ER (electro-rheological) damper for a passenger vehicle is proposed and its control characteristics are investigated. First, the field-dependent yield stress of arabic gum-based ER fluid is obtained using a couette type electroviscometer. The Bingham model with the yield stress is then incorporated into the governing equation of motion of the ER damper, which is derived from a bond graph model. After verifying that the damping force of the ER damper can be continuously tuned by the intensity of the electric field, a skyhook control algorithm is formulated to achieve the desired damping forces. Subsequently, control performances to track the desired damping force are evaluated through both computer simulation and experimental realization. In addition, time response characteristics of the ER damper to a high frequency control voltage are presented.