Research Of A Vehicle Electric Power Steering (EPS) System

Electric Power Steering (EPS) system, which emerged in recent years, is a new type of vehicle steering system. Physical and mathematics model of EPS system is constructed and analyzed based on column EPS system in this thesis. The EPS control system cored in Digital Signal Processor is designed.The control strategy of EPS should be firstly concerned because of the importance of the control system's stability and comfort, and the control theory of three types of control is presented, which is assist control, return control and damp control. In the process of compiling program, some problems are resolved. The compensating method integration and method resolve the problem of dithering between motor and steering wheel. The digital adjuster can make assistance softness and the motor's overturning can be eliminated because of steering wheel faster turning. A novel software-filter, which can provide control system more exact sampling data, is brought forward and realized.Compared with DC motor, brushless DC (BLDC) motor has the unexampled advantage. The control method of BLDC motor substituting for DC motor is studied and designed in EPS system.A novel model is proposed and the simulation results show the correct control theory of BLDC motor. It can also test the feasibility of new method to promote the design of real system. Using TMS320LF2407 as control slug, we construct the control system of BLDC motor. At last, we do experiment and perfect results of both simulation and experiment demonstrate the control scheme is feasible.A novel Neural Network (NN)-Fuzzy PID control strategy is proposed. Through the constructed NN-Fuzzy PID controller, which can modify parameters value of proportion, integral and differential coefficient to adapt variety of control system, the better result reaches and the system is much more robust than that we get through PID controller. A sensorless BLDC motor system with novel rotor position detection method based on back electromotive force and zero crossing is presented. Experimental research is conducted and the results verify the control scheme is valid and its dynamic and stationary performance is very good.