Simulation Research On Control Strategies Of Electric Power Steering System

Electric Power Steering System (EPS) is a new high-tech which follows the development of modern automobile.It has the advantages of saving fuel, producing less pollutions, improving vehicle's handling stability, driving comfort and security. As a new kind of power steering system, EPS has become the focus of research of power steering technology in today, which pursues the high security, the high comfortableness,the highly effective and energy conservation.The paper selected SX3042GP vehicle which had been modified as the equipped target models of electric power steering system of commercial vehicle, according to the characteristics of target vehicle, choosed the key components and completed EPS design. A detailed study of EPS system from perspective of assist characteristic and control strategies was carried out. In order to get the target current of the motor,designed the fuzzy controller. It produced the assist characteristic curves at different velocity and torque input of steering wheel. According to the EPS system designed,established two-degree-of-freedom vehicle model, EPS dynamics model, proposed PID control and fuzzy control strategy, and established the MATLAB/Simulink simulation model combined with two-degree-of-freedom vehicle model, EPS dynamics model. Then analyzed the yaw angular velocity response with torque step input of steering wheel. The simulation results showed that the overshoot and the adjustment time of vehicle equipped with EPS had been remarkably improved, which proved that EPS system can improve vehicle's handling stability and steering easiness. Compared to PID control strategy, fuzzy control strategy had the merits of faster response. The steering return ability response characteristic curves proved that after joining the return control, the steering wheel can quickly returned to the middle position,and avoid the steering wheel's vibration in the middle position.