Adaptive Fault-Tolerant Coordinated Control Of Distributed Redundant Drive System For 4WID Electric Vehicle

With the development of the economy,countries in the world paid more and more attention to traditional fossil energy.The depletion of global energy and the continuous deterioration of the environment have a great impact on the development of human society.As an indispensable means of transportation for social development,the development of traditional fuel vehicles is bound to be restricted,so people's traveling costs will greatly increase.In order to cope with such pressures,people have turned their attention to all kinds of new energy vehicles.Among them,Four-wheel-independent drive electric vehicle(4WID-EV)has attracted wide attention due to its unique driving form and potential dynamic control advantage.4WID-EV adopts four hub motors to constitute a distributed driving system.It abandons the traditional mechanical transmission system so that it has high driving efficiency and quick response.The dynamic characteristics of the vehicle can be greatly improved because it can realize independent control of each wheel's driving force and braking force.However,the addition of the drive motor will also bring a lot of new problems,that is,the increase in the number of vehicle driving motors leads to an increase in the probability of failure of the driving system.However,the increasing of the number of driving motors constitutes a system with redundant driving characteristics of the vehicle.When the output torque of a motor is reduced due to failure,the vehicle can still achieve safe operation through other driving motors.Therefore,it is of great significance to study fault-tolerant control strategy for this kind of drive system with redundant drive characteristics.This paper mainly discusses the adaptive fault tolerance of 4WID-EV redundant drive system,which is used to redistribute the output of the vehicle drive system after failure to meet the requirements of the vehicle dynamics control.(1)Firstly,this paper introduces the development history of electric vehicles and the emergence and research status of 4WID-EV,then the fault-tolerant control strategy proposed for 4WID-EV and the research status of vehicle stability are introduced.The dynamic analysis of 4WID-EV was carried out,and the actuator fault and its characterization were considered.Based on this,a two-degree-of-freedom model of the vehicle is established.(2)The dynamic control of the vehicle with a hierarchical structure is adopted.Firstly,a sideslip angle observer is designed considering the fact that it is difficult to measure directly the sideslip angle.Secondly,the non-singular fast terminal sliding mode(NTSMC)is used to design the upper controller to calculate the virtual control quantity needed to obtain the ideal trajectory,in which the variable-exponential approach law is introduced to reduce the influence of disturbance.(3)This paper makes full use of the independent control characteristics of each actuator of 4WID-EV which simulates the motor failure problem by adjusting the control distribution matrix without change the original control strategy.Based on this rule,the virtual quantity obtained from the control layer is taken as the input,and the driving signals of four driving motors are taken as the output.The control distribution strategy is designed to maximize the vehicle stability margin and the quadratic programming optimization algorithm,in which the motor failure is considered in order to realize the fault-tolerant control of the vehicle.(4)The driver's control factor is considered after the motor failure.Under low adhesion condition,the fault-tolerant control algorithm proposed above was simulated with Carsim software in the straight line and double shift line combined with the optimal curvature driver model for preview with different fault degrees.Finally,the 4WID-EV experimental platform was built,and the algorithm was experimentally verified based on the hardware in the loop simulation system dSPACE.Simulation and experimental results show that the fault-tolerant algorithm has a good control effect on the actor fault of 4WID-EV drive system.