Research On Electronic Differential Control Of Distributed Electric Vehicle

The distributed drive electric vehicle cancels the complicated mechanical transmission structure of the traditional internal combustion engine vehicle.It can achieve precise and independent control of each driving wheel,greatly improving the steering stability and driving reliability of the vehicle.However,due to the cancellation of the mechanical differential,how to ensure the coordination of the rotation speed and torque of the inner and outer driving wheels when the vehicle turns has become a major problem in the driving technology of distributed electric drive vehicles,that is,the electronic differential control technology.Therefore,this paper took the two-rear-wheel distributed independent drive electric vehicle as the research object,and carried out the following research work:(1)Discussed the development status of domestic and foreign distributed drive electric vehicles and the current research status of electronic differential control methods,summarized three different types of electronic differential control methods,compared their advantages and disadvantages,and finally the electronic differential control method based on torque adjustment was determined.(2)The performance of various motors were compared and analyzed,and combined with the actual research requirements of on-board motors,the three-phase permanent magnet synchronous motor was selected as the wheel motor of distributed drive electric vehicles.By analyzing the mathematical model of the motor and the double closed-loop PI vector control theory based on id=0,a simulation model of the motor driving system was built in Matlab/Simulink software,and the dynamic response ability and anti-interference ability of the system were verified.In view of the shortcomings of double closed-loop PI vector control,a vector control strategy based on improved approach rate was proposed and verified in the Matlab/Simulink model.The results show that the PMSM control system based on the improved approach law has better response performance and anti-interference performance.(3)According to the vehicle model parameters,based on Trucksim software and Matlab/Simulink software,a distributed drive electric vehicle model that can truly reflect the operating state of the vehicle was built,and a linear 2-DOF reference model of the vehicle was also established.The electric vehicle model,the linear 2-DOF reference model and the traditional vehicle model in Truck Sim were respectively simulated and verified under typical working conditions.The simulation results show that the established electric vehicle model has high accuracy,which can be used for the design,analysis and verification of the electronic differential control strategy.(4)A hierarchical electronic differential control strategy based on target torque secondary allocation was designed.The upper layer was the additional yaw moment control based on LQR,and the lower layer was the slip rate control of the driving wheel based on the slip rate correction coefficient.The LQR parameters were optimized and the target driving torque was allocated.In addition,the simulation experiments of traditional vehicles and distributed electric vehicles were carried out in typical working conditions on roads with different speeds and adhesion coefficients.The results show that the electronic differential control strategy can not only realize the differential function well,but also improve the vehicle handling stability to a certain extent.(5)On the basis of theoretical research and simulation analysis,a distributed drive electric vehicle test bench was designed from the aspects of drive motor selection,prototype design and development,and electrical architecture.Based on the Matlab /Simulink platform,the electronic differential control algorithm model which can automatically generate the code is established to verify the electronic differential in real vehicle,which proves the operability and effectiveness of the differential strategy.