Research On Anti-Lock Braking Control Of Wheel-Driven Electric Vehicle

In recent years,with the increase in the share of pure electric vehicles in the automotive market,the safety of electric vehicles are being put more attention.As one of the vehicle active safety systems,the electric vehicle anti-lock braking system(ABS)is an important element of vehicle braking safety.The hydraulic brake reliability is a key consideration when the ABS is activated by emergency braking;after motor brake engagement,and it is the most important to coordinate the control of the hydraulic and motor brakes in the design of the anti-lock control strategy.In this paper,two emergency braking anti-lock control strategies are designed for four-wheel hub drive electric vehicles,one is a pure hydraulic ABS control without motor brake participation during emergency braking,and the other is a layered motor-hydraulic composite ABS control.And a joint simulation platform is built to simulate and test the two control strategies.The main research elements are as follows.(1)The forces on the wheels and vehicle during the anti-lock braking process were analyzed,and the Burckhardt tire model with high accuracy of longitudinal friction fitting was selected to establish the mathematical relationship between the road adhesion coefficient and the wheel slip rate.The hydraulic system of the brake actuator and the wheel motor were mathematically modeled,and the corresponding Simulink simulation control model was established on the basis of the mathematical model.(2)The PID control algorithm based on the slip rate was proposed,and the particle swarm optimization algorithm(PSO)was used to dynamically adjust the inertia weights to adjust the controller parameters to meet the requirements of ABS under different operating conditions.And a joint simulation platform of Car Sim vehicle model and Simulink pure hydraulic ABS control model was built to verify the effect of pure hydraulic anti-lock control.(3)A hierarchical control strategy for electric-hydraulic composite anti-lock control was proposed.Firstly,the upper layer used the optimal control to calculate the total braking torque of the front and rear wheels,and the output braking torque of the optimal control was constrained according to the estimated wheel braking torque,and the lower layer controller distributes the total braking torque.Secondly,the fuzzy control algorithm was used to determine the motor effective braking proportionality coefficient and calculate the motor effective braking torque value,then the demand hydraulic braking torque was calculated based on the road adhesion constraints and the effective braking torque of the motor,and the motor braking torque was compensated the total braking torque output within the effective range.Thirdly,a joint simulation platform between the Car Sim vehicle model and Simulink motor-hydraulic composite ABS control model was built to verify the effect of electric-hydraulic composite anti-lock control.