Robust control of active suspension to improve ride comfort with structural constraints

This paper proposes the robust H2 controller with constraints for the active suspension using the half car model. The purpose of this study is to improve the ride comfort with satisfying the structural constraints. According to International Organization for Standardization 2631, there exist the uncomfortable frequency bands of the human body. The uncomfortable frequency bands are 4–8[Hz] for the vertical acceleration and 0.63–0.8[Hz] for the pitch angular acceleration. In this paper, the acceleration in the specific frequency bands is suppressed by using frequency shaping. On the other hand, the active suspension has the structural constraints which are constraints on the vertical force of the wheel, the suspension stroke, and the control input. They are expressed as the time-domain constraints. In addition, the robust stability for the perturbation of the front and rear weights of the car body is guaranteed. The perturbation of the weights of the car body affects the pitch motion of the car body and the vertical force of the wheels. The robust stability for the perturbation is guaranteed by using the polytopic representation. The robust H2 controller is designed by solving a finite set of LMIs to achieve the purposes. The effectiveness of proposed controller is evaluated by simulations and experiments.