Distributed Electric Vehicle Path Tracking Control Based On Electronic Differential

The increase of car ownership leads to the frequent occurrence of traffic accidents,which further makes the driving environment more complicated and increases fatigue of drivers.Therefore,more intelligent and safe vehicles become an effective way to solve this problem.The development of intelligent vehicle requires its platform has reliable security and highly efficient and flexible control,and emerging distributed-drive electric vehicle can independently control the driving force of each wheel,and can realize torque and rotational speed of response of each wheel quickly and accurately,can provide flexible chassis drive form,which is the ideal development platform.Meanwhile,differential control of vehicle is a key technical difficulty of distributed driven electric vehicles.This paper will conduct an in-depth study on this issue and further study on the path tracking of intelligent vehicles based on the realization of differential control.This paper mainly carries out the following research work:(1)Establish the vehicle dynamics simulation platform.According to the unique vehicle dynamic characteristics of distributed-drive electric vehicle,a nonlinear eight-degree-of-freedom vehicle model was established,including the longitudinal,yaw,roll and lateral movement of the vehicle body and the rotation of four wheels.The Gim tire model and the hub motor driving system were established as simulation auxiliary models.The effectiveness and rationality of the vehicle dynamics simulation platform were verified by comparing the result of condition simulation of established simulation platform with the Car Sim vehicle dynamics model.(2)Ackermann steering principle optimization and electronic differential steering research.Based on the analysis of tire lateral distortion characteristics,it is found that the tire lateral deviation will lead to the understeering of the vehicle,which proves the limitation of the ideal Ackermann steering principle which ignores the influence of tire side deviation.The ideal Ackermann steering principle was optimized by introducing the tire slip Angle correction coefficient,and the differential steering model of distributed-drive electric vehicle was established based on Ackermann-Jeantand steering model.(3)Study of vehicle electronic differential control strategy.Using the hierarchical control thought to design vehicle differential overall control strategy of distributed electronic vehicle.The upper controller is ideal quasi sliding mode controller to track the vehicle motion,the middle controller is the nonlinear quadratic programming controller to optimize and distribute the drive force of four wheels,the bottom controller is BP neural network PID controller combining with the particle swarm optimization to follow ideal rotate speed of four wheels.Sinusoidal conditions under different road adhesion are designed to verify the effectiveness and stability of the electronic differential control strategy and the adaptability and superiority of the PSO-BPNN-PID controller.(4)Path tracking control based on optimized Ackermann steering.The path tracking model and the linear time-varying vehicle dynamics model were established to design the path tracking controller.The vehicle steering control variable was obtained by solving the path tracking objective function and constraint conditions.Considering the influence of tire cornering on vehicle steering,the steering wheel control variable is taken as the input variable of electronic differential control based on optimized Ackermann steering modle,thus,the steering Angle control variable of Inside and outside steering road wheels of front-axle to control vehicle path tracking is obtained.The simulation results show that the tire slip Angle does cause understeer,and the expected trajectory tracking error will increase with the increase of vehicle speed and steering Angle.The tracking accuracy of the vehicle path will be greatly improved by modifying the Ackermann steering.In this paper,the optimized ackermann steering principle with tire slip angle correction coefficient is proposed,and the electronic differential strategies control and path tracking control strategies have some reference significance based on that for whole control and intelligent control of distributed electric vehicles.