Study On Vehicle Electric Power Steering System

As an important component of the car, steering system develops from mechanical steering system to hydraulic power steering system and electric power steering(EPS) system gradually. In the 21 st century, major research institutions of China are driven to deeply explore with EPS system. Thus the research of EPS system is becoming more and more popular in automobile industry. By contrast, the technology of EPS oversea is more mature than domestic. In this thesis, a large number of collection and studied of literature at home and abroad are discussed and how EPS system work and related research at home and abroad is informed. But as time is going along, by making use of PID control and robust control, the control strategy of EPS system is discussed and a new controller is designed. The work and achievements of this research are as follows:Based on the basic components of EPS system, how EPS system work and the main factors related the stability of EPS system is discussed. In addition, the function of every part of EPS system is performed.By analyzing EPS system at the moment, the mathematical model of EPS system is founded. According to the parameters and mathematical model of each module of EPS system, the simulation model of steering column and rack and pinion and motor are established in the MATLAB/Simulink. In the end, by comparing the simulation results and research findings, the truth of models is performed.Based on the assistance characteristic of the EPS system in the current position, the assistance characteristic of the EPS system is researched. According to the theoretical calculation, the relationship between steering force and vehicle speed and motor current is discussed. And the maximum current is given. By taking advantage of MATLAB, the coefficient of speed is decided. Finally, the sustainable assistance characteristics of the EPS system are given.The traditional control strategy is researched by analyzing power control mode. Besides, under Power-Assisted control and based on the modern control theory, PID control and H_∞ control are chosen. Then, corresponding controller model is founded and the truth of models is showed.Vehicle model is built in CarSim and done a co-simulation with EPS model in MATLAB/Simulink. In the comparison of the results of two different kinds of controllers, the efficiency of controller is proved.