| Electric Power Steering system(EPS) is a new power steering system besides hydraulic pressure steering system. It is cmposed by torque sensor ,speed sensor, feedback signal, control, electromoter, clutch, speed-down system.Compared with hydraulic pressure steering system, the electric power steering system can be controlled. The traditional hydraulic pressure steering system is gradually substituted by EPS in the area of cars, and develop into trucks. Now EPS come to be one of newest subjects in the area of vehicle and has a good future.ECU is the key part of the EPS. Its function is to analyses the signal gathered by the torque sensor, speed sensor and control the engine and the clutch by the using the signal.Besides, ECU has the function of self-diagnose and safe protection. We can know whether the system is in danger by analyzing the engine signal. Once it is in danger, the system can low the power automatically. ECU is normally a single chip system which should has the ability of avoiding interference and adapting to the various environments. The control algorithms should be high velocity ,real-time and can achieve the ideal steering disciplinarian and characteristic effectively. I search the following parts on the basis of domestic and foreign current technology of the EPS:First: fully analyses the principle and the structure of the current EPS, and deeply research torque sensor which is a pivotal part in the system. Second: We do more research on the curve of the curvilinear power steering system and fix every point on the curve with the specific shape of the car; also I study out the power steering curve to the car. In order to realize the purpose that control the turning of the car steadily. Start with the analyses of linear two-degree automotive model, I research the necessary of landscape orientation acceleration feedback control from theory. I use the linear and non-linear area of the tyrp list characteristic as critical point of the landscape orientation acceleration and the active damp control. after that I study out the control style by curve. I systemically analyses theControl, damp control, compensate control of the EPS system. According to the angle of the steering wheel, angle speed, torque of the steering wheel,I find a new way in judgement which is demonstrated to be feasible by the last test. In order to make the electromotor tracking the objective current to achieve the good control effect, I design a PID controller to control electromotor current.Third: By the deeply research of the EPS, I design the ECU of the EPS and using TMS3202812 as the CPU. The controlling of the DC electromotor and the collecting of the signal collected by various sensor can be done by the hardware. We use the function PWM of the single chip itself which can generate a variable impulse to control the DC electromotor. The drive circuit is composed by power amplifier, a group of audion, resistance, capacitance which compose a correspond switch circuit. The function of the power amplifier which is the primary load is provided large current. Audions in the former of the power amplifier are switches. They are always saturated. The currency of the parts in the entire circuitry design is strong. Also, the parts have better capabilities , higher credibilities and lower cost .Four: Based on the foundational processes of the ECU,s hardware circuit and the EPS,s control, the modularizing design of the control system ,s software program is carried out. Also, the directional judgement of the motor,s rotor , the numeric sieving wave of the sensor signal, the start-up control of the motors and the choosing and counting function of the entire EPS,s control all are implemented.Five: for validating the correctness of the control tactics ,the trials of turning handiness in the same place, low speed turning handiness ,low speed returning ,middle speed returning and fixing corner are carried through. The purpose of the expecting designs are achieved seeing from the results of the experiments.
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