Research On Electronic Differential Control Of Four-wheel Wheel-drive Electric Bus

The distributed drive car is a new type of electric vehicle,which eliminates the mechanical structure of the engine,transmission,drive shaft and differential.The drive motor is directly connected to the wheel or through the reducer connected to the wheel.This type of drive has a higher transfer efficiency than conventional cars and greater flexibility in control.However,it is necessary to design a reasonable electronic differential controller while canceling the mechanical differential.This paper mainly studies the application of the electronic differential control strategy in four-wheel wheel-driven electric buses.In this paper,the four-wheel wheel-drive electric bus is the research object,using the car as a prototype to build a trucksim vehicle model,and the electric vehicle co-simulation model is built with MATLAB/simulink,including the car body,tires and suspension KC.Modeling of sub-modules such as features,braking systems and steering systems.The vehicle model was tested with minimum turning radius,30km/h linear sliding distance,0-30km/h acceleration time,and compared with the actual vehicle data to verify the accuracy of the model.Based on the working principle of the traditional mechanical differential.The slip rate is used as the electronic differential evaluation index,and the electronic differential control strategy is proposed to make the driving wheel approach pure rolling.At the same time,the simulation experiment of distributed drive vehicle shows that the electronic differential strategy should adopt the torque control,and with the increase of the wheel slip rate,the appropriate torque control strategy must be adopted to achieve the electronic differential target.The electronic differential control strategy designed considers the vertical load transfer during steering,and establishes the left and right drive torque distribution module based on this.At the same time,considering the slip of the wheel during the limit steering,establishing the slip control module based on PID control,monitoring the wheel slip rate in real time to adjust the torque of the four drive motors to reduce the drive wheel slip rate.The steering off-line simulation experiment was carried out under the trucksim/simulink electric vehicle co-simulation platform.It was verified that the strategy can distribute the torque of each drive motor according to different steering conditions.Comparing the simulation results with electronic differential control strategy and no electronic differential control strategy,it is found that vehicles with electronic differential control strategy have better differential effect and steering stability than vehicles without strategy.Through the established wheel-drive electric vehicle co-simulation platform,studying the effect of centroid height,centroid to front axle distance,and sprung mass on electronic differential.And studying the impact of these parameters on the electronic differential control strategy.The control strategy is proved to have good stability and robustness.Performing real-time simulation experiments on The hardware-in-the-loop simulation platform based on the dSPACE and Infineon-TC1728,compares the real-time simulation results with the off-line simulation results,and verifies the real-time and effectiveness of the electronic differential control strategy.Based on the self-developed four-wheel wheel-drive electric bus,and the vehicle equipped with the electronic differential control strategy was installed on the actual vehicle to carry out the steering experiment,which verified the feasibility and effectiveness of the strategy in running on a real vehicle.