Research Of Control Strategy Of Electric Power Steering System Based On Compensation

EPS has advantages of environment protection,energy saving,good road feeling,and being able to realize the vehicle integration control.What’s more,it conforms to the development trend of today’s intelligent and networking car.So EPS becomes the ideal choice of vehicle power steering systems.The basic assist control can be realized by controlling the motor power torque.However,the dynamic property of steering system can’t be improved only by the basic control.Compensation control strategy should be designed.In this paper,the compensation control strategy is designed based on the basic assist control.The results of simulation and bench test validate that the control strategy has good effect.Firstly,the dynamic model of steering system is established by MATLAB /Simulink and vehicle model is established by CarSim.Then the Co-simulation platform of CarSim and Simulink is established,which lays the foundation for the following research of EPS control strategy.Secondly,the curve-typed assistance curve based on the road feeling is designed.Also the effects of assist control strategy based on PID control and fuzzy PID control are analyzed and compared.At the same time,in order to improve the dynamic characteristics of EPS,the torque compensation scheme and the motor compensation scheme are designed,which include the torque phase compensation,the torque differential compensation,the inertia compensation and the damping compensation.And the effectiveness of the compensation control strategy is validated by simulation.Thirdly,on the basis of analyzing the friction characteristics of mechanical servo system,LuGre model is selected,and the steering system friction model is established on LuGre model.And adaptive neural network friction compensation control strategy based on backstepping is designed.It’s proved stable by Lyapunov stability theorem.And the friction compensation control strategy is proved correct and effective by simulation.Finally,the hardware and software architecture of EPS controller are introduced.The designed control strategy is tested on hardware-in-the-loop test bench,including fast turning test,step steering angle test,torque impact test,steering portability test and return-to-center performance test.The test results show that the dynamic characteristics of EPS,the steering portability and the return-to-center performance have obvious promotion,which can verify that the design of compensation control strategy is effective.