Research On Electric Power Steering System With Automatic Steering Function

In recent years,self-driving cars have become a research hotspot in the automotive field and a new driving force for industrial growth.At present,the automatic Steering control is mainly based on Electric Power Steering(EPS).Other forms of Steering systems,such as Active Front Steering(AFS)and Steering by Wire(SBW),have not been promoted on a large scale in self-driving vehicles.Therefore,in order to meet the development of automatic driving technology,it is increasingly important to develop EPS control system that integrates automatic steering function.EPS system and automatic steering control are integrated into the same controller to meet the needs of human driving and automatic driving.After years of development,Permanent Magnet Synchronous Motor(PMSM)has gradually become the first choice of EPS booster Motor due to its superior performance and increasingly perfect control strategy.The traditional current control of EPS with permanent magnet synchronous motor is based on the model.Inaccurate motor parameters or slow change of motor parameters caused by environmental factors such as temperature will affect the stability and control accuracy of EPS current control.EPS for above problems existing in the current control in permanent magnet synchronous motor,this paper established the model of EPS system test bench with all-digital fuzzy mathematical model,by the method of Kalman filter to estimate the power Angle signal is optimized,reduce torque current fluctuation,in order to improve the driver’s steering comfort,design of linear dynamical characteristics curve to meet the requirements of basic power.According to the theory of Model Reference Adaptive Control(MRAC),a Model Reference Adaptive current Control strategy with automatic steering function was designed and simulated in MATLAB/Simulink.Secondly,the control effect of the model reference adaptive current control strategy is verified by the electric power steering test bed.The results show that this control strategy can realize the accurate control of current in the automatic driving.In the power-assisted mode,the output torque of the power-assisted motor can track the target torque accurately and without delay,achieving the desired effect..The current automatic driving control is mainly realized based on EPS steering motor’s steering Angle control,which determines that the driver and the automatic driving system cannot interact with each other.Therefore,this paper proposes an automatic steering control strategy based on PMSM torque ring.Through the scheme of superposition of steering torque,the driver and the autopilot system share the steering control power,and the man-machine steering wheel interaction can be realized through the form of torque.Is established considering the man-machine torque input of steering model,vehicle dynamics model,vehicle kinematics model and road model,the second for the involvement of the driver’s steering torque and unknown disturbance problems brought by the steering resistance moment,disturbance can be divided into known time-varying disturbance and unknown time-varying bounded disturbance,and for the unknown time-varying adaptive law is designed by the bounded disturbances.Aiming at the problem of system nonlinearity and parameter change caused by the introduction of vehicle road model,a control strategy of automatic steering and self-adaptive back-push based on torque ring is designed,and a parameter self-adaptive law is designed for the parameters.The automatic steering lateral motion control strategy of the intelligent vehicle was simulated under the environment of Car Sim and MATLAB/Simulink.The simulation results show that the automatic steering control strategy designed based on the method in this paper can guarantee the more accurate lateral motion control of the intelligent vehicle at different adhesion coefficients and different speeds,and at the same time improve the robustness of the system to unknown disturbances and parameter changes.Finally,an automatic steering test bench based on NI-PXI and d SPACE was built,and the control algorithm was tested on the bench,and the real control effect was obtained.