Modeling And Simulation Of Electric Power Steering System

Vehicle Steering System is a pivotal part 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 in energy saving,environmental protecting,drive safety,making higher steering performance, better road feeling,has shown its tremendous focus.The development of the computer technology and the application of the software ADAMS and MATLAB help us to do more researches about the EPS.This thesis simulates and analyzes a multi-body dynamic model equipped with EPS of based on ADAMS simulation software and MATLAB control analysis software.Firstly,the structure,operating principle,critical component,categorization and features as well as the current development of EPS are interpreted.Then theory of the mufti-body dynamics,ADAMS simulation software and MATLAB control analysis software are introduced.Based on the mufti-body dynamics,using the ADAMS/CAR,the vehicle model including the front and rear suspension system,the steering system,the tires system the power train,the brake system and corresponding road files are built.A new way to add the assist power on the steering system is applied and the files which are used in the simulation are written.The thesis introduces request and classification of assist-characteristic and makes sure a set of straight-line assist characteristic according to the virtual experiments.The goal of EPS control was put forward,and the way of achieve control objectives was analyzed,the boundary conditions of the basic control mode choice was researched.H_∞control theory was applied on the research of EPS assist-control,H_∞assist-control mode was designed,and the arithmetic of return control mode,damping control mode and compensate control mode was researched. At last motor mode was built in MATLAB.Co-simulation technology is also used in this paper to link the control model established in MATLAB to the mechanical model established in ADAMS.Assist force is the input of mechanical model,and it is also used as the output of control model.The outputs of mechanical model,wheel torque and signal of vehicle speed, are used as the inputs of control model.The Co-simulation results prove that EPS built in this thesis has more retum-ability and handiness,and the EPS with H_∞control has better robust capability.In last chapter,the main work of this thesis was summed up,and introduced the prospects of the future work.