Research On Fault-Tolerant Control Strategy Of Four-Wheel-Hubdriven Electric Vehicle

In view of the problems such as the continuous reduction of mineral resources and the increasing destruction of the ecological environment on the earth,various countries in the world have put forward the concept of green development in order to protect the homeland of human survival,which has become a very important development trend.As a representative product of the green development of the automotive industry,new energy vehicles have gradually become an important indicator for the future development of automobile enterprises.The four-wheel-drive electric vehicle has attracted the attention and research of engineers and scholars in new energy vehicles because of its simple mechanical structure,environmental protection and high transmission efficiency.Moreover,each wheel hub motor can be independently controlled due to the four-wheel hub drive electric vehicle.Therefore,the stability of the vehicle is completely dependent on the operating condition of the hub motor.Consequently,when one or more hub motors fail,if the control system does not respond accordingly,the vehicle will have a great possibility of rollover and deviation.Such phenomena are a serious threat to the safety of drivers and passengers.Thus,in view of this problem,this paper studies the fault-tolerant control strategy of four-wheel drive electric vehicle drive in order to ensure the stability of vehicle operation.The main contents are as follows:(1)In order to understand the dynamic characteristics of the four-wheel-drive electric vehicle,the dynamics theory analysis of the simplified seven-degree-of-freedom vehicle model is carried out,and the vehicle tire simulation model is built on the basis of the magic formula;The stability and steering characteristics are also established.The linear two-degree-of-freedom vehicle reference model is used to obtain the reference value of the yaw rate and the centroid angle of the vehicle during stable operation,and the simulation analysis is carried out in Simulink.(2)The DTC system is studied for the selected brushless DC hub motor.The real-time torque of the motor is calculated by the combination of Hall signal and phase current.A voltage vector selection of two-tube conduction zero vector is proposed.The method and the simulation and analysis of the DTC system composed by the above method are carried out,and the experimental verification based on DSP2812 is the main control board.The effectiveness and feasibility of the control system are verified by simulation and experiment.(3)A two-layer control strategy with motion control layer and fault-tolerant control layer is designed for the four-wheel hub driven electric vehicle drive fault-tolerant system.The motion control layer mainly adopts the variable universe fuzzy PI algorithm to increase the expectation of the vehicle when it is running stably.The pendulum torque is tracked and calculated;the fault-tolerant control layer uses the fuzzy algorithm to actively detect the motor fault and the sequence quadratic programming algorithm to optimize the distribution of the desired torque and the motor state factor based on the active fault detection to restart the fault after the driving torque Optimize distribution.Based on the fault-tolerant control strategy,the joint simulation model of Carsim and Simulink was built,and the omnidirectional simulation verification of the fault motor of different speeds,different time,different sections and different positions under different driving conditions was carried out.The simulation results were verified.The effectiveness of the drive fault-tolerant control strategy designed in this paper can control the running stability of the vehicle under different motor fault conditions.(4)Based on the STM32F407ZGT6 development board as the vehicle controller,a four-wheel hub-driven electric vehicle experimental prototype was built,and the drive fault-tolerant experiment under linear conditions was carried out on the basis of the experimental prototype.The experimental analysis results show that the drive fault-tolerant control strategy designed in this paper can maintain the stable operation of the vehicle after the failure of the hub motor,thus ensuring the safety of the driver and passenger.