Robust Optimal Control for the Vehicle Suspension System With Uncertainties

The suspension system is an important unit that affects vehicle performance, including handling stability and riding comfort. In order to improve vehicle performances, a novel robust optimal control strategy for the active suspension system in vehicles is proposed. To handle the parameter uncertainties and external random disturbances, the proposed optimal control strategy is designed by using the combination of the linear quadratic regulator (LQR) optimal control and sliding-mode control. First, by using the nominal model of the active suspension system without the uncertain parameters and the external random disturbances, an optimal control performance index is given, and the initial optimal controller is designed by using the LQR control strategy. Then, to handle the parameter uncertainties and the external disturbances, a robust optimal integral sliding-mode control strategy based on the initial optimal controller is designed, which not only can achieve the optimal control objective but also has good robustness to the uncertain parameters and external disturbances. By using the Lyapunov stability theory, stability analysis of the proposed robust optimal integral sliding-mode control strategy is performed. Finally, the collaborative simulation platform based on the Carsim and MATLAB/Simulink is developed. The simulation results illustrate the advantage of the proposed robust optimal control strategy for the suspension system.

I. Introduction

In vehicles, the suspension system is applied to transmit the force and torsion between the wheel and the vehicle frame, and buffer the impact force transmitted from the uneven road surface [1]. The suspension system has the ability to isolate the vibrations and shocks from the road excitations, and keep the tire in good contact with the ground. A good suspension system can effectively suppress the acceleration amplitude of the vehicle body, and reduce tire deflection. Hence, the suspension system plays a significant role in influencing the vehicle’s running performances. The suspension system can improve the vehicle’s handling stability in an effective way and, at the same time, provide as much comfort as possible for the passengers by isolating passengers from the shocks and vibrations induced by the external road excitations.