Research On Modeling And Control Method Of Integrated Electro-Hydraulic Brake System

In order to meet the requirements of new energy vehicles and autonomous vehicles on the braking system,this article selects the Integrated Electro-Hydraulic Brake System(I-EHB)as the research object.The system working principle and target braking force identification principle are designed,the system mathematical model is established,and the system model oriented to the feedforward controller design is derived.Design the hardware-in-the-loop test to study the system friction and verify the system model.A double closed-loop PID controller based on pressure and speed and a feedforward controller based on the system model are designed,and a hardware-in-the-loop test is performed to verify the "pressure feedforward + pressure and speed double closed-loop cascade PID" composite control method.Based on the working characteristics of the I-EHB system,an adaptive hill-start assisted control strategy was designed,and simulation verification was performed using the Simulink / Car Sim joint simulation platform.The specific research work is as follows:(1)The I-EHB system working method and target braking force identification method are designed.A mathematical model of the mechanical and hydraulic subsystems in the I-EHB system was established,and the system transfer function was derived.Based on the Padé order reduction method,the system transfer function is reduced to the second order,and a system model for feedforward controller design is obtained.(2)An I-EHB system test bench was constructed,and the I-EHB system hardware-in-theloop test method was analyzed.The classic friction model is used to analyze the system friction,and the effect of friction on the dynamic characteristics of the system is studied using the AMESim model.A parameter-oriented friction model is obtained through optimization and linearization.A hardware-in-the-loop test is designed and the parameter identification is completed.(3)A double closed-loop PID controller based on pressure and speed is designed,and a hardware-in-the-loop test of pressure tracking is performed.The actual pressure of the servo master cylinder basically follows the target pressure of the servo master cylinder,but the step pressure adjustment time exceeds 0.698 s.The maximum root mean square error of the sinusoidal pressure and the ramp pressure is close to 12 bar and 1.4 bar,respectively.Double closed-loop PID control can consider both response speed and steady-state error,but further optimization of the control structure is required.(4)The system model is verified,and a feedforward controller based on the system model is designed.The control structure of "pressure feedforward + pressure and speed double closedloop cascade PID" is formed,and the hardware-in-the-loop test of pressure follow is performed.The step pressure adjustment time is shortened by more than 500 ms and controlled within 0.2s;the root mean square error of the sinusoidal pressure and the slope pressure is less than 7bar and 1bar,and the performance improvement rate is about 20%-50%.Therefore,the effectiveness of pressure feedforward is verified.(5)A slope inclination correction method is derived based on the body posture.A car-slope model verification and correction method was constructed using Car Sim,and the correction rate can reach more than 85%.Based on the working characteristics of the I-EHB system,Based on the working characteristics of the I-EHB system,an adaptive hill-start assisted control strategy is proposed,and the strategy is simulated and verified using the Simulink / Car Sim joint simulation platform.