Research On ESC Control For Battery Electric Vehicle Under Extreme Conditions

As a new environmental means of transport,the battery electric vehicle has great potential for development.With the vehicle high-speed and the traffic intensive becoming more increasingly obvious,handling stability and driving safety of battery electric vehicle receive much concern.Under the extreme conditions that include the high speed large steering,the high speed lane-change and the cross wind disturbance,the battery electric vehicle tires easily work in nonlinear areas,vehicle sideslip angle increases rapidly,and the vehicle yaw rate response is nonlinear,which results in vehicle deviating from the desired track or even out of control.The vehicle Electronic Stability Control(ESC)system can control the vehicle yaw moment under extreme conditions and restrict the tire sideslip angle to a certain range,actively intervening the vehicle driving state to prevent the car out of control under extreme conditions with large lateral acceleration and sideslip angle.Therefore,taking to improve handling stability and driving safety of battery electric vehicle as the starting point,the ESC problem for battery electric vehicle under extreme conditions is studied in this paper,and the main research work is as follows:(1)The methods for modeling battery electric vehicle are analyzed.According to the needs of ESC control research for battery electric vehicle,considering the factors including accuracy and efficiency of modeling,speed and precision of simulation,etc.,based on the MATLAB/Simulink software platform,a 10-DOF vehicle dynamic model,a "magic formula" tire model,a driving motor model and its controller model along with 3-DOF vehicle reference model are established respectively by applying the theoretical modeling method.(2)On the basis of dynamics modeling of vehicle and key components,the ESC system control for battery electric vehicle is analyzed concretely.The control references of ESC system are determined,and the vehicle sideslip angle state observer based on EKF algorithm is designed.The control criteria of each control reference are respectively formulated to judge the running status of the vehicle.The differential braking method is selected as the control method of the ESC system in this paper.On this basis,the braking force distribution control of each wheel brake is realized by unilateral wheel braking.(3)Aiming at the yaw moment decision-making problem of ESC system,fuzzy control strategy,LQG control strategy and PID control strategy based on Seeker Optimization Algorithm(SOA)of ESC system are developed respectively based on fuzzy control theory,LQG optimal control theory,PID control method and SOA.Also,merits and drawbacks of the three control strategies for ESC system are compared and analyzed.(4)In order to verify the control effect of the ESC control strategies for the battery electric vehicle under extreme conditions,the steering wheel angle step input condition along with the ISO 3888 emergency double lane change condition are selected to conduct the offline simulation in MATLAB/Simulink.Also,under the sine with dwell test condition commonly used by the FMVSS126 regulation and the cross wind disturbance condition,the CarSim and MATLAB/Simulink is applied to conduct the co-simulation analysis.The simulation results demonstrate that the ESC control strategies can effectively control the yaw rate and the sideslip angle of the battery electric vehicle,and reasonably restrain the excessive steering state of the vehicle reducing the lateral displacement of the vehicle,to ensure good retentivity of track and lateral stability of the vehicle,which enhances the handling stability and driving safety of the battery electric vehicle under extreme conditions.