Response time of magnetorheological dampers to current inputs in a semi-active suspension system: Modeling, control and sensitivity analysis

Abstract

Abstract A new magnetorheological (MR) damper has been recently developed that delivers a very fast response to the input current (or magnetic field). This study investigates the effect of the MR-damper response time on the vibration control of a full-car semi-active suspension system subjected to parameter uncertainties. After briefly reviewing the response-time characteristics of the fast-response MR damper, a full-car suspension model with seven degrees of freedom (DOF) is derived by considering the time constant of the actuator. Subsequently, a robust sliding mode controller is formulated for achieving effective vibration control of the suspension system for three different motions: heave, pitch, and roll. For the synthesis of the controller, the sprung mass is considered the uncertain parameter, and the stability of the overall control system is proved via Lyapunov stability. By evaluating the performance at a random road profile, it is shown that both ride comfort and road holding (steering stability) can be enhanced by utilizing the fast-response MR damper. In addition, to analyze the control results, the nonlinear suspension model is linearized. Using the linearized model, the state outputs from the road input are observed, and the sensitivities of the closed loop feedback system considering response time of MR dampers are analyzed in the Nyquist domain.