Research On Electronic Differential Control System Of Light Electric Vehicle

The increasingly serious environmental pollution and energy crisis promote the rapid development of new energy vehicles,among which the electric vehicles which are close to "zero pollution" are the research and development focus of the automobile industry.The short cruising range of electric vehicles and the decay of battery capacity limit consumers' desire to buy.The use of light-weight materials such as magnesium alloys and wheel motors can effectively reduce the quality of the entire vehicle.It helps improve the battery life of electric vehicles under the background of the slow development of battery technology mileage.However,light-weight vehicles are greatly affected by the quality of passengers.A safe and reliable electronic differential control system helps to improve the vehicle's handling and operating stability.In order to design the electronic control system for light vehicles,the following work has been done in this paper:Firstly,the vehicle dynamics is studied,and the relationship between the position of the mass center and the vertical load of the tire,as well as the vertical load change caused by the longitudinal and lateral movement of the vehicle are analyzed.According to the load change of tire,the 11 DOF vehicle model is established,and the tire model is analyzed.The longitudinal force and lateral force of tire are calculated by magic formula.Using Ackermann steering model to analyze the relationship between the rotation speed of each wheel when the vehicle is turning,the theoretical values of yaw rate and centroid sideslip angle are calculated according to the simplified two degrees of freedom.Secondly,according to the nonlinear mapping relationship between the sideslip angle and yaw rate of the vehicle and the vertical load,wheel speed and front wheel angle of the tire,the BP neural network algorithm is used to predict the sideslip angle and yaw rate of the vehicle in motion.The experimental data are obtained by the accelerated experiment under the condition of double moving lines in the Car Sim software.After the training of algorithm,some data are predicted,and the predicted value basically achieves the fitting of the experimental data.Then through the comparison of the characteristics of the motor,the hub motor with outer rotor permanent magnet synchronous motor is selected.According to the speed change of the vehicle when turning,the motor speed regulation strategy of fixed time super spiral vector control is designed,and the motor speed regulation model is built in Simulink for motor speed regulation experiment.The experimental results reduce the overshoot of the wheel motor and improve the robustness of the wheel motor control.Finally,a double-layer electronic differential controller is designed.In the first layer,the hub motor follows the target speed according to the Ackerman proportion coefficient.In the second layer,the accessory yaw moment is calculated according to the difference between the actual value and the theoretical value of the sideslip angle and the yaw rate,and distributed according to the vertical load proportion coefficient.The joint simulation experiment of Car Sim and Simulink is established to realize the following of the theoretical values of the sideslip angle and the yaw rate of the center of mass under the medium and high speed,and keep in its stable range all the time.