Application of LQR control theory to the design of modified skyhook control gains for semi-active suspension systems

The control objective in this paper is to improve the ride comfort and the road holding ability, while maintaining the constraint on suspension deflection, for the semi-active suspension system equipped with a MR damper and a suspension relative displacement sensor. Two optimal control strategies are investigated: First, the linear quadratic regulator (LQR) control is investigated from the perspective of finding what optimal control forces are needed. Second, a modified skyhook control law is investigated for a semi-active suspension equipped with an MR damper. The parameters of the modified skyhook control are determined by minimizing the difference between the modified skyhook control forces and the optimal forces obtained by the LQR control using a minimum norm criterion. Furthermore, the use of filters to estimate the state variables is proposed. Simulation results are provided.