Study on Assist Coefficient and Disturbance Resistance for EPS

In this study, a nonlinear electric power steering (EPS) system dynamic model based on road disturbance and torque sensor noise is investigated. In this paper, a new method of determining assist coefficient is proposed to obtain good driverpsilas feel, which is only relative to vehicle velocity. Evaluation indexes and an augmented system combined with the state space model of EPS are obtained. Hinfin control theory is introduced to minimize road disturbance and sensor noise, and linear matrix inequalities (LMIs) method is employed to design an optimal Hinfin dynamic output feedback controller. Simulation results show that the controller has good robustness and can reduce the influence of disturbance. So it can maintain good driverpsilas feel and the systempsilas stability.