| Vehicle Steering System is a pivotal parts which has big influence on vehicle's control stability, drive safety and comfort. Electric Power Steering, is a new high-tech which follows the development of modern automobile, has advantages both in energy saving, environmental protecting, drive safety, making higher steering performance, better road feeling, has shown its tremendous direction.Based on the structure and the dynamic characteristics of electric power steering system (EPS), the control strategy and algorithm of electric power steering system is analyzed and the mathematical model the state space model is established. Through the further research based on other domestic university, this paper bring forward PID control and Fuzzy-PID control, combined with three freedom full vehicle model (considered drift angular) and Fiala tire model, and the EPS simulation model is finally established.Through the model we established, the dynamic characteristics of EPS was conducted due to disturbance of the road condition, such as the variety of the tire load during steering, the variety of longitudinal and latitude acceleration, the factors, such as the vehicle speed, the stiffness of the steering system which influence steering system, is also analyzed. Also, the simulation results is carried out by system model applied with PID and Fuzzy-PID control strategy respectively, the Characteristic of Steering Wheel's return to center response is analyzed by transient response with angle step input, and the results show that vehicle equipped with EPS has faster response and better stabilization, System equipped with Fuzzy-PID controller has better dynamic performance such as faster response, less over-altitude, better stabilization and so on.
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