Study On EPS Road Excitation Suppression And Handling Stability Based On Sliding Mode And Predictive Control

With the development of automobile design and manufacturing industry and the continuous improvement of people's material living conditions,electric power steering system(EPS)has become the most important safety component in automobile steering system.The reliability of its working performance has a direct impact on the service life of the automobile and the life and property safety of the people in the vehicle.The actual road conditions of vehicles are complex,and the road undulation excitation will be transmitted to the steering wheel through the steering system,which will cause the torque fluctuation of the steering wheel,and also have adverse effects on the vehicle handling stability.In recent years,the transmission mode of force characteristics of road excitation in the steering system is studied to reduce the adverse impact of road excitation on the performance of EPS system,improve the return performance of EPS system products,and determine the hardware thermal protection control strategy of EPS system.When the temperature of EPS system controller increases,the assist current of EPS system can be reduced smoothly,and the vehicle handling stability and EPS system performance are improved The reliability of system controller hardware is an urgent problem in the development of EPS system technology.This paper focuses on the theme of EPS system and vehicle handling stability,starting from improving the real-time response of EPS system under uneven excitation road,studies the motor control strategy and vehicle handling stability of EPS system,puts forward the sliding mode predictive control algorithm based on EPS system,and designs the thermal optimization strategy of EPS system hardware layout based on Tabu search algorithm.The main research work of this paper is as follows:(1)From the point of view of vehicle steering dynamics,this paper studies the influence of EPS system on the characteristics of vehicle steering control torque and driving stability,considers the friction,damping,clearance and other factors in EPS system dynamics modeling,and adds friction compensation into EPS system control strategy;and designs the correction and damping control strategy to improve the performance of the system,aiming at the excitation conditions of EPS system on the road Next,a steering system identification algorithm based on ARX model is proposed.The transfer function from road excitation to steering wheel torque is established.The correctness of the system identification,the reliability of the friction compensation strategy and the correction control strategy are verified by simulation.(2)Aiming at the problem of steering wheel jitter caused by road excitation,a motor control strategy of EPS system based on fast terminal sliding mode control algorithm is proposed.Because of the jitter in the sliding mode control algorithm when the system approaches the sliding mode surface,the system stability is reduced.In order to eliminate the jitter in the sliding mode control algorithm,a new approach law is designed.At the same time,in order not to reduce the robustness of the system,a new approach law is designed The sliding mode observer enhances the robustness of the system.Through simulation and experiment,the effect of the system is verified.(3)Based on the ideal yaw rate of the vehicle,a nonlinear discrete model of the whole vehicle with EPS system is established by using the predictive control algorithm based on the state equation.The optimal solution of the system is transformed into a quadratic programming solution by taking the yaw rate of the whole vehicle as the optimization object.By limiting the output current of the auxiliary motor and adjusting the yaw rate of the vehicle in real time,different ideal yaw angles are analyzed Under speed condition,the influence of predictive time domain and control time domain in predictive control model on boost current and vehicle yaw rate is studied,and the online adjustment algorithm of system parameters is designed to improve vehicle handling stability.(4)In order to improve the service life of electric power steering system controller under the condition of high current,the hardware circuit optimization algorithm and thermal protection control strategy of ECU controller based on Tabu search algorithm are proposed.Firstly,the power loss model of the main power devices of ECU controller is established;then the temperature flow state equation of temperature field is established,and the temperature sensor inside MCU is used to monitor the real-time temperature of ECU controller;the hardware layout of ECU controller is optimized by designing the Tabu condition of Tabu search algorithm,and the thermal protection control of controller is designed with the upper limit of ECU controller 120? Strategy.At last,the thermal analysis software of Flotherm is used to analyze the ECU controller before and after optimization,and the effect of layout optimization before and after is determined by experiment comparison.