Research On The Control Strategy Of Four Wheel Independent Drive Vehicle

Four-wheel independent drive electric vehicle is one of the most important development directions of electric cars in the future.However,there are few studies on the control strategy of a four-wheel independent drive electric vehicle.This paper takes four-wheel independent drive electric vehicle as the research object,analyses and establishes the simulation and experimental platform of four-wheel independent drive electric vehicle.It combines the motor drive control and the whole vehicle stability control as the research focus,and studies the control strategy of the low speed four-wheel independent drive electric vehicle.Firstly,the vehicle is designed according to the research target,the vehicle shape and weight are determined,and the mathematical model of the vehicle is set up according to the design requirements.In order to ensure the correctness of the mathematical model and meet the requirements of the following vehicle simulation platform,the Carsim software is used to set up the vehicle model,and the simulation environment of the Matlab combined with Carsim software is set up,and the related tests are carried out to meet the needs of following simulation.Secondly,the wheel hub motor is selected according to the vehicle dynamic demand,and the drive control of the selected wheel hub motor is studied.Considering the accuracy and energy saving of the selected wheel hub motor control,the vector control scheme is adopted.However,a high precision rotor position angle estimation is needed for the low precision Hall position sensor,This paper improves on the basis of the first-order angle estimation to make the position angle estimation more accurate.The simulation and experimental results show that the algorithm is good in motor drive application,and can satisfy the following research.Thirdly,the four wheel independent drive control scheme is analyzed,and the control scheme is divided into speed and torque distribution control scheme according to the control mode of the motor.The torque distribution scheme is designed to increase the vehicle stability and reduce the vehicle slip rate as the control target.And on the basis of the traditional direct yaw moment control,improvements were made,and feedforward torque control was added to make the control performance more rapid.The vehicle controller calculates the torque required for each wheel according to the yaw torque control scheme,and assigns it to each motor controller.The speed distribution scheme is used to reduce the vehicle slip rate as the control target.The vehicle controller is based on the Ackermann vehicle rotation model,accurately calculates the target speed of each motor and assigns it to each motor controller.The algorithm is tested by the joint simulation platform and the correctness of the algorithm is verified through some experiments.Finally,1,Simulation and experiment of motor drive control algorithm in Matlab/Simulink are carried out.The results show that:the estimation performance of the rotor position angle is good to meet the needs of the following motor drive control,and the performance of the motor under the control mode of torque and speed can also meet the needs.2,Based on the comparison between the vehicle with torque distribution for each wheel and the ordinary vehicle,it shows that the yaw rate and the vehicle slip rate are less than that of the ordinary vehicle under the same condition.When the closed loop line is used,the tracking of vehicle tracks is more accurate,which meets the control objectives.Matlab and Carsim vehicle simulation platform are applied to carry out vehicle simulation analysis.Based on the simulation comparison between the vehicle with the rotational speed distribution for each wheel and the ordinary vehicle with average torque distribution control,the slip rate of the low attached pavement is less than that of the ordinary vehicle,and the stability is obviously strengthened to meet the control target.