Study On The Control Stability Of In-wheel Motord Riven Ev Based On The Coordination Of Steering System And Driving System

At present,the motorization of the traditional centralized fuel vehicle power source has achieved initial results.However,this simple inheritance of the conventional vehicle chassis structure has resulted in a limited improvement of the vehicle control effect.In contrast,distributed independent drive,steering,and braking in-wheel motor drive electric vehicles(inwheel motor drive electric vehicle,IWMDEV)are independently controllable in each wheel steering angle and drive torque,fundamentally changing the traction control method of the chassis.This distributed drive structure brings brand-new possibilities to vehicle movement and control,and has more advantages in active safety and dynamic quality.Therefore,it is hailed by the industry as the ultimate drive form of automobiles.However,the subversive changes in structure and dynamics has also made the handling stability of the vehicle a completely new problem.The lack of a certain constraint relationship between the wheels of IWMDEV,and thus the resulting differential steering effect will produce yaw moment interference,which will cause the current mainstream vehicle stability control system to lose control effect.Based on the National Natural Science Foundation of China(NO:51577120)and the basic research grants project of Shenzhen(NO: JCYJ20170302142107025),the coordinated control of steering system and drive system for four wheel IWMDEV have been carried out in this paper.This paper mainly deals with the movement conflict caused by fuzzy structural attribute of IWMDEV steering system and drive system.Focusing on the purpose of the study,the following work has been carried out.(1)Construction of test platform for X-by-Wire IWMDEVFor meeting the functional requirements of 4WIS/4WID/4WIB,the X-by-Wire(XBW)IWMDEV test platform is designed,assembled in this paper.In order to solve the adaptation problem between the suspension system and the electric wheel,a new central point steering suspension system was proposed,designed and analyzed.In addition,based on ADAMS/view,a vehicle virtual prototype of the test platform was established to complete the stability analysis of the test platform.(2)Development of XBW IWMDEV simulation platformThe development of the simulation platform mainly includes the abstraction of the dynamic model of the XBW IWMDEV,the dynamic modeling of the actuators and the modular design of the simulation platform structure.Aiming at the insufficiency of current research,a 19 DOFs nonlinear time variant coupled IWMDEV simulation platform considering vehicle vertical motion and considering the dynamic response characteristics of the actuator is built by modular design.(3)The design of the stability control strategy of the vehicleBased on the stability control theory,the stability control problem of XBW IWMDEV is analyzed.Based on this,for the system’s high redundancy and non-linear characteristics of control,the layered centralized stability control structure with the five-layer motion control as the core is determined,which reduces the difficulty of vehicle decoupling control.In addition,considering the demand of closed loop control of “human-vehicle-road”,a driver model of lateral acceleration dynamic feedback correction is established,and the special driving model of the vehicle is designed and simulated.(4)Research on the coordinated control of steering and drivingThe problem of steering and driving coordination is decomposed into motion tracking control and actuator allocation control.The motion tracking control is used to generate the total control force,thereby eliminating the motion conflict between the drive system and the steering system.The actuator allocation control focuses on the realization of the control force on the tire,so as to solve the over drive problem of the system actuator.In motion tracking control,motion controller is designed based on SMC theory,and driver behavior monitoring is completed based on vehicle state comprehensive stability domain.The tire force assignment problem is summed up as the LQP extreme optimization problem with multiple constraints.Furthermore,considering the problem of over constraints,a mixed solution strategy of tire force is designed in this paper.The above research contents preliminarily achieved stability control of XBW four wheel independent IWMDEV,and made basic work for subsequent research of the subject.