Research On Stability Control Of Electro-Hydraulic Compound Braking For In-Wheel Motors Drive Electric Vehicle

The speed and torque of each drive wheel of a distributed drive electric vehicle can individually and accurately controlled,which facilitates the realization of vehicle dynamics control and braking energy feedback.This improves both the vehicle’s active safety and driving economy.However,in the process of regenerative braking of the vehicle,if one motor suddenly fails,the braking torque generated by other motors will form additional yaw moment to the whole vehicle,once one motor breaks down suddenly,resulting in vehicle instability.At the same time,the vehicle braking force will be attenuated and lost,which is not conducive to the safe driving of vehicles.In order to solve this problem,after by means of cutting off the break torque output from the motor on the opposite side,this paper proposes a brake fluid pressure compensation control method based on electric power assisted hydraulic brake system,and designs a vehicle stability controller based on model predictive control algorithm,so as to ensure the vehicle braking safety and stability effectively.The main research contents are as follows:(1)In view of the structural characteristics of the developed electric wheel drive test vehicle,the vehicle dynamics model and the hub motor model are established.According to the test results of the response characteristics of the hub motor,the instability characteristics of the electric wheel drive vehicle with one side feedback braking system failure and the shortcomings of motor torque truncation control are verified through simulation.(2)According to the working principle of the electric power hydraulic brake system,the model of the electric power hydraulic brake system is built;based on the actual working conditions and performance requirements of the electric power hydraulic brake system,the existing electric power hydraulic brake is modified,its controller is designed,and the accuracy of the model of the electric power hydraulic brake system is verified by the bench test of the principle prototype.(3)On the basis of the brake pedal opening,the brake strength is identified,and a reasonable braking torque distribution strategy is developed;aiming at the problem of unilateral regenerative braking system failure of electric wheel drive vehicle,complying with the torque truncation of the normal braking motor on the opposite side,the brake pressure compensation controller is designed,realizing the hydraulic brake compensation control effect simulation verification,and passing the real vehicle road test which verifies the correctness and practicability of the designed brake compensation controller.(4)In accordance with the model predictive control algorithm,the vehicle stability control strategy is proposed,and on the basis of the torque truncation control after the regenerative braking failure of one side motor,the vehicle stability control effect is verified by simulation.The accuracy and practicability of the designed vehicle stability controller are confirmed by real vehicle road test.