Research On EPS Control System Of Permanent Magnetic Synchronous Machine

The electric power steering system of automobile takes motor as the power unit,eliminates the whole set of hydraulic devices in the hydraulic power steering system,solves the problems of high energy consumption and easy oil leakage,and is widely used in the automobile steering system.At present,the development of EPS control system mainly depends on the torque sensor,but the existence of the torque sensor not only increases the cost of the system,but also increases the complexity of the mechanical part of the system.Especially,the torsion bar in the torque sensor reduces the stiffness of the steering column and affects the driver's road feeling.In order to solve the above problems,this paper focuses on the development of EPS system without torque sensor.The specific research contents are as follows.(1)The permanent magnet synchronous motor with stable operation,smooth torque,small pulsation and fast response is selected as the assisting motor of EPS system.Based on three-phase stationary coordinate system,two-phase static coordinate system and two-phase synchronous rotating coordinate system,the mathematical model of permanent magnet synchronous motor is established,and the vector control strategy of permanent magnet synchronous motor is analyzed.The closed-loop current control strategy of permanent magnet synchronous motor is designed based on sliding mode control.(2)Based on the voltage equation and electromagnetic torque equation of permanent magnet synchronous motor in two-phase synchronous rotating coordinate system,the dynamic model of EPS system and the steering resistance moment model and CarSim vehicle model are established.Finally,the steering wheel torque estimator is designed based on Sage-Husa adaptive Kalman algorithm,and the performance of the estimator is verified by simulation.(3)Based on the estimated torque signal,the basic control strategy of EPS is designed.Considering the influence of power motor and deceleration mechanism on the steering system,the control strategy of inertia damping compensation is designed.To solve the influence of the torque disturbance caused by frequent steering on the steering feel of the driver,the control strategy of moment differential compensation is designed.In order to solve the problems of insufficient of low-speed steering and overshoot of high-speed steering for EPS vehicles,a double closed-loop control strategy based on angular speed isdesigned.Finally,the control strategy is validated by Simulink/CarSim joint simulation.(4)The road condition is classified and recognized based on convolution neural network,and the reliability of the model is verified according to the accuracy of the classification results.Then,according to road adhesion coefficient and vehicle speed,a fuzzy compensation control strategy is designed based on fuzzy control.Finally,Simulilnk/CarSim joint simulation is used to verify the performance of the model and control strategy.