Research On Fault-tolerant Control Of Four-wheel Independent Driven Electric Vehicle Based On Optimal Allocation

The revolution of the automotive industry has promoted the development of the global economy.And it also contributed to the problems of energy crisis and environmental pollution.In order to cope with the dual pressures of energy and environment,the electric vehicle has become a hot spot of research.And among them,the four-wheel independent drive(4WID)electric vehicles(EVs)have recently attracted more and more attention from researchers because of its incomparable advantages in energy saving and environmental protection.A 4WID electric vehicle employs four in-wheel motors to drive the four wheels,and the driving or braking torque of each wheel can be controlled independently.That significantly improves the vehicle controllability.However,due to the increase in the number of actuators,the probability of failure increases greatly in 4WID EVs.When an in-wheel motor fault occurs,if there is no corresponding control strategy,the vehicle will deviation or even lose stability,which will threaten the safety of the driver seriously.Thus,the fault-tolerant control(FTC)strategy is needed.In this paper,a FTC strategy based on optimal allocation control algorithm is proposed to redistribute torque of each wheel when fault occurs,in order to ensure the stability of the vehicle.Firstly,the present situation and characteristics of 4WID EV,the status of torque distribution and the status of FTC are introduced.The seven degrees of freedom(7DOF)vehicle model for 4WID EV is established.By simplifying the 7DOF vehicle model,the 2DOF vehicle model is built.And the output reference values are analyzed.Secondly,Design the FTC with double layers structure,based on analyzing the effect of the yaw rate to vehicle stability.The upper layer controller adopts the nonsingular fast terminal sliding mode(NFTSMC)to follow the reference yaw rate.The lower layer controller employs quadratic programming control algorithm to realize the redistribution of torque,in order to ensure the stability of the vehicle even when fault occurs.And according to the actuator whether overrun designed two kinds of fault allocation strategies.The overall design of fault-tolerant control is completed.Then,The FTC simulations are carried out under several different conditions based on Simulink and the CarSim vehicle dynamics simulation software.The results show the correctness of proposed FTC strategy.Finally,the test platform for 4WID EV is constructed.Based on the hardware in the loop simulation system dSPACE,the FTC test is carried out.The simulation results and the experimental results show effectiveness of the proposed FTC in dealing with actuator faults.