Analysis And Research On Robust Control Of Electric Power-steering System

Along with the high-speed development of automobile industry, more and more requirements about automobile active safety, usage economy, environmental protection and etc. have been put forward. As important control equipments of its route and direction, automobile steering system affects its manipulate ability and stability directly. Besides work safety credibility, easy manipulation, good maneuverability, efficiently saving energy, more new requirements are put forward for automobile steering system, and it must provide the best road feeling under various conditions (such as straight drive, normal steering, fast steering and etc.) according to various drive velocities and road performances. Now the electric power-steering system (EPS) is paid more attention to by automobile industry, because it integrates the functions such as environmental protection, usage economy, drive safety and comfortable function...etc. In this thesis, according to the characteristics of EPS, the author researches its robust controller by means of classic control theory and H_∞control theory, and simulates its close loop system accord to MATAB.The following results are obtained:(1) After analyzing the following EPS components: assist motor, torque sensor, rack pinion shaft, steering wheel and so on, the dynamic EPS model is established, and according to the further transformation, the proper state-space model is obtained also. During the modeling process, it is put forward that there are modeling errors existed for the real object such as nonlinear factor and parametric uncertainty.(2) With the viewpoint of the model uncertainty, sensor noise, road disturbance and so on in EPS system, the H_∞control theory is introduced to EPS's control strategy, and the general state-space model is established with the selected suitable weight function. The advantages of H_∞controller can be shown accord to MATLAB simulation.(3) The robust controller design of EPS with parametric uncertainty is considered under the nonlinear condition. The state feedback controller is designed by means of modern control theory, and close loop EPS system is simulated according to MATLAB. Simulating results show that the close loop EPS system with parametric uncertainties can be kept stable and has good responsiveness by this controller.(4) As parametric uncertainty and the failures of executers or sensors are inevitable in EPS system, their effects for the control system should be considered. The failure -tolerant controller is robust to the parametric uncertainty and can tolerate the failures of sensors. According to MATLAB, close loop EPS system is also simulated.