Modeling And Simulation Of Vehicle Electric Power Steering System

The steering system is used to control vehicle driving direction, its performance affects the comfort and safety of vehicle directly, so the research on steering system is one focus of the vehicle dynamics research. Electric Power steering system is a dynamic steering control system which can supply assist torque according to the state of motion and driver’s steering requirements on different road conditions. Vehicle equipped with EPS can meet the requirements of the higher maneuverability for low-speed steering and the better stability for high-speed steering.Therefore, it is of great importance to study and develop this kind of steering system.Vehicle dynamic model, which contains suspension, steering, chassis, tire, brake and road subsystems, is built in ADAMS. EPS control model is also built in MATLAB/Simulink,whicl includes steering model, assist character, current PID closed loop controller, PWM module and motor model. Co-simulation technology is used in this paper to link the control model established in MATLAB to the mechanical model established in ADAMS. Rack assis force is the input of mechanical model, and it is also the output of control model. The outputs of mechanical model, wheel steering torque, wheel steering angle and signal of vehicle speed,are used as the inputs of control model. Co-simulation results verify the control strategy is effective in improving maneuverability and stability.Through the steady state Steering Simulation Experiment of the vehicle model, The model showed obvious insufficiency of steering characteristic.After analysis, step test and snaking test results return ability test, we know that EPS system can effectively improve the vehicle handling stability, Thus, the rationality of the model is verified.It is feasible to use virtual prototyping software for dynamic simulation. It Can effectively improve the research speed and shorten the product development cycle.