Research On Control Strategy For Automotive Brake-by-wire System

With the increasing consumers’ demand for the automobile safety performance and the continuous development of automotive electronic control technology,the brake-by-wire(BBW)technology,represented by Electromechanical Brake(EMB),has become the future development direction of automobile braking technology.Compared with the traditional automobile braking system,the EMB system abandons many defects,and is more suitable for the future development trend of automotive,such as electric,intelligent,lightweight and integrated,and has broad application prospects.However,as a brand-new automotive braking system,the EMB system is still in the stage of research and development trials.Developing a safe,reliable,economical and efficient control system,and improving the control quality of the system has become the key issue to be solved urgently.This paper combines the research status of EMB systems in domestic and overseas,and focuses on the precise control of EMB actuators and the braking force’s synchronism control.The main research contents include:By analyzing the typical structural type of the EMB system,the mathematical model of the EMB actuator was established,and the three-stage closed-loop control strategy of EMB actuator was designed.The simulation model was established in Matlab/Simulink environment,and the feasibility of the EMB actuator control strategy was verified by the simulation with the conventional PID closed loop control algorithm.By analyzing the dynamic response characteristics of EMB actuators,the limitations of the conventional fixed gain PID closed loop control algorithm were recognized.In order to control the brake pressure accurately,the Active Disturbance Rejection Control(ADRC)algorithm based on model compensation was adopted to improve the accuracy,dynamic and static response characteristics of brake pressure control.The simulation results show that the control algorithm has better control performance and better adaptability to the target value of braking pressure compared with the conventional PID control.A hardware-in-the-loop experimental platform for EMB actuator was established,and the real-time simulation environment based on MicroautoboxII was built to realize the on-line monitoring and data recording of the real-time experiment.The experimental results verify the feasibility of the EMB brake,the feasibility of the three-stage closed-loop control strategy and the superiority of the ADRC algorithm based on the model compensation.For the vehicle equipped with EMB system,the influencing factors of the braking pressure’s asynchronism in the four wheel independent braking system was analyzed.Based on the CarSim and Simulink co-simulation platform,the influence of the non-synchronous braking force output caused by the inconsistent of brake disk performance parameters and the braking gap on the driving stability of the vehicle during braking,was simulated and analyzed.Focusing on the inconsistent factors of the performance parameters of the brake disc,the braking force Coupling Control algorithm based on wheel speed Deviation Compensation was proposed to realize synchronous response of the braking force for the BBW system,simulation results show that the control algorithm can effectively improve the braking stability of the vehicle.