Bahman Abdi - Research laboratory of vibration and mechatronic, Mechanical Engineering Department, Sahand University of Technolo
Mehdi Mirzaei
Sajjad Aghasizade

Magneto-rheological (MR) dampers are semi–active devices in vehicle suspension systems that pro-duce controllable forces dependent on the input current to the damper as well as the relative velocity of the sprung mass. In this paper, by the response prediction of nonlinear quarter–car model which in-cludes a nonlinear MR damper dynamics, a new optimal tracking controller is analytically designed for the semi–active suspension system. In order to develop a more accurate control law, a realistic nonlinear model of the spring force is also employed in the design model. In the proposed scheme, the control input is the input current to the MR damper and is determined by minimizing a pointwise per-formance index defined as a weighted combination of ride quality and control energy. Optimal prop-erty of the control law provides the possibility of limiting the input current to the MR damper, as the control input, to the physically admissible range. The performed analysis and the simulation results indicate that the proposed non–linear controller can improve the vehicle ride comfort using the re-duced input current to the MR damper without deteriorating the handling performance.

Semi–active suspension; nonlinear optimal control; MR damper; Prediction