Design Of Distributed Four-wheel Drive Vehicle Motor Torque Control Strategy With Differential Assisted Steering

At present,pure electric vehicles have some problems to be solved,such as short endurance,slow charging,also,the reliability of motor,battery and electric control system needs more data to prove.As the subsidy policy for electric vehicles gradually declines,the industry will soon face a big test.It is urgent to improve the performance of electric vehicles.To optimize the performance of electric vehicles,we should not only improve the endurance and upgrade the charging and replacement technology to alleviate the endurance pressure,but improve the driving ability and take advantage of the accurate and controllable response of the motor torque.Distributed drive electric vehicles are equipped with independent drive motors for each wheel,with less mechanical structure constraints,and have good performance potential,which is a research hotspot in the electric vehicle industry.This article is aimed at a vehicle equipped with wheel-side motors on all four wheels.Firstly,the ideal yaw angular velocity and centroid side slip angle calculated by the two-degree-offreedom vehicle model are used as control targets,according to the requirements of handling stability.Both fuzzy controller and sliding mode controller are used to design the compensation yaw moment formulation modules.The objective function is established based on the friction circle theory,and the driving torque is distributed to each wheel in combination with the constraints of other hardware parameters.Also,a variable parameter PI controller is designed to realize the anti-skid function.For low-speed cornering driving conditions,the necessary condition for the dual-axle wheeled distributed drive electric vehicle to achieve in-situ differential steering is that the tread is greater than the wheelbase,which is not suitable for the vehicle selected in this paper.Based on the Akaman steering model,a differential assisted steering control strategy is designed to distribute driving torque based on the vertical load ratio of the left and right wheels.Using MATLAB / Simulink to build the control strategy modules,CarSim to build the test vehicle model.Six typical conditions are designed to simulate and test the control strategy.The simulation results show that for roads with good adhesion conditions,when the vehicle speed reaches 80km/h,the direct yaw moment control strategy can effectively improve the vehicle's handling stability.Among them,the sliding mode controller shows better performance than the fuzzy controller;Under the low-speed condition designed in this paper,when the steering wheel angle is 540°,the turning radius is reduced by 6.73% compared with the control group in which the driving torque is equally divided.Using NI's real-time controller to build a rapid control prototype test platform.The running time of the main program of the controller is stable within 20 ms,showing good real-time performance and practical value.Designing real-vehicle tests such as right-angle turns,snakes,and fixed-length circles to test the performance of the controller.The experimental data shows highly consistent with the simulation results under same operating conditions.