The suspension system is the main tool to achieve ride comfort and drive safety for a vehicle. Passive suspension systems have been designed to obtain a good compromise between these objectives, but intrinsic limitations prevent them from obtaining the best performances for both goals. In present work, a robust controller for the active suspension system has been designed to get the best performance of the
suspension system. The nonlinear robust controller is designed based on adding an integrator to a two-degree-of-freedom quarter-car model. The control action will decouple the upper sprung mass subsystem from the lower (unsprung mass) subsystem after a certain small period of time. As a result, by adjusting the control law parameters, the dynamical response for the sprung mass subsystem is freely specified (the damping ratio and the natural frequency for the sprung system after
decoupling). The simulation results, which are carried out by using Matlab/Simulink, proved the effectiveness of the proposed control law. The results confirmed that the sprung mass system is decoupled from the lower unsprung system and unaffected by the change in sprung mass and the road excitation disturbance. Additionally, the time history of the
sprung mass response is according to a mass spring system response with the desired damping ratio and the natural frequency.