| Electric power steering is the feture of automible steering technology and true of auomobile technology electrization. Electric power steering (EPS) is a kind of new motor driven steering technology. EPS has the advantage of simpler structure, easier installation and maintenance, lower consumption, better environmental protection and contol nicety. It is more important that EPS can realize adjusting steering assisting force according to vehicle speed and ensure the drive obtaining the enough road information. In current, EPS is used in the front tire steering of the car. Therefore, it is of great importance to study and develop this kind of steering system.The article studies the vehicle landscape dynamics interrelated with the steering, and builds the model of the vehicle landscape dynamics from the handling stability of the vehicle. The lateral force and the return moment influencing are studied from the tire pressure, vertical load and the road surface status, etc. The tire model is built based the analysis. At last, the tire model and the vechile model are linked. The vechile simulation plate is structured for developing electric power steering. The simulation test is finished on the plate.The mechanical parts and electric parts of EPS are respectively studied and parameterized. The two degree mechnical model of steering system is built which is based on the sports and force analysis about the electric power steering. The motor model is built after analyzing the motor structure.The electric control unit (ECU) model is also built by the study of control module in ECU. The mechnical model, the motor model and ECU model are linked by the relationship of them, and the EPS model is finished. Based on the vehicle model and the tire model, the whole electric power system dynamic model is developed and simulated.According to the need of the vehicle and the driver on steering control, the basic assist characteristic is confirmed. The assist control, the compensate control, the damp control and the return control are adopted in the EPS. In the study of the assist control, three kinds of assist curve are compared, and the basic assist control strategy is selected. In the return control, the active steering return control is used to achieve rapid retum. The damp control is also introduced to prevent the surge of the steering wheel. In order to ensure the handling safety of the driver, the way is provided to solve the road information absences in EPS.After considering the ideal process in the dynamic analysis of EPS, uncertain control object model with the variety of load in the used vehicle, sensor noise and the disturb from the oad information, the generalized plant of the electric power steering is built. All kinds of weight functions are analyzed and determined. The Robust Controller is designed based on multi-sensitive way of H∞control theory in order to satisfy the performances of the steering sensitivity, obtaining road information and stability with Matlab robust control toolbox. Further, The electric power steering with the controller is simulated and verified for Robust.Through the theory analysis, The electric control unit (ECU) of EPS is designed. The input process circuit is designed respectively according to the characteristic of vehicle speed, engine rotate speed and steering torque. The steering torque controls the assist direction by the window comparision. The assist motor is the direct circuit motor. It is driven by H bridge included four N-MOS transistors with PWM control. PID is used to finish the feedback control of the assist motor circuit. The monitor is provided to protect the safety of controller and steering.At last, by designing the test project of the electric power steering, simulating the actual input signals to ECU from the vehicle with the instrurnents and the steering resistance torque with magnetism brake, the offline test desktop of EPS is built. The assist performance test is finished when ECU is in EPS, and ECU is not in EPS. The result implies the actual assit is basically consistent with the ideal assit.
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