| In this paper,the important components and structure of the Integrated Electro-Hydraulic Braking System(I-EHB)are designed.Firstly,the simplified linear system is modeled to derive the transfer function without considering the nonlinear disturbances,and the AMESim software is used to verify the correctness of the linear system.Secondly,building the I-EHB system test bench,and parameters of friction torque parameters in the static and dynamic friction stages of the system are identified by the Stribeck friction model,so as to obtain a more accurate friction model.Then,based on the friction-disturbed I-EHB system model,the pressure-speed-current three loop cascade PID controller are designed and add the feedforward controller,constitutes a "pressure feedforward compensation + pressure-speedcurrent three closed-loop cascade PID control" structure,followed by a bench test and make I-EHB system realized a faster and more stable stress response than that of traditional PID control.Finally,based on the working characteristics of I-EHB system,the regenerative braking energy recovery control strategy for two different system layout schemes are designed,the corresponding Matlab/Simulink simulation model is built,and the real vehicle test and simulation verification are carried out.The specific research work is as follows:(1)The working method of I-EHB system is designed.Under the premise of ignoring the influence of the nonlinear factors,the mathematical modeling of the mechanical subsystem and the hydraulic subsystem is carried out.After establishing the I-EHB system state equation,the system transfer function can be deduced.The corresponding simulation model is built by AMESim software,and the accuracy of the linearization model of I-EHB system is preliminarily verified without considering the influence of system friction.(2)The I-EHB system test bench is built,and several hardware in the loop tests are designed and their working principle are described.The friction Stribeck effect of I-EHB system is analyzed,and the effects of static friction moment and dynamic friction moment on the dynamic characteristics of the system are studied by using the AMESim model.The static and dynamic friction torques of the I-EHB system are identified by repeated tests,and a more accurate friction model of the I-EHB system based on the Stribeck effect is obtained.(3)Based on the fitted friction model of the I-EHB system,the open loop test of the motor active increase and decrease pressure is carried out,and the accuracy of the friction model is verified.Based on control object oriented designed I-EHB system model,a threeloop cascade PID controller considering servo master cylinder pressure,servo master cylinder piston speed and motor current is designed.A reduced order transformation is carried out by using the method of Lucas I-EHB system transfer function and joining the feed-forward compensation controller based on system load,obtaining for the overall structure of the feedforward compensation control.(4)The bench test of the I-EHB system with "three closed-loop cascade PID control" and "three closed-loop cascade PID control + feedforward compensation" control strategies are carried out respectively to test the actual response of the system under different target pressure input.The test results show that the adjustment time of the system in the step pressure response is shortened by about 0.1s under the input of different target hydraulic pressure signals,the root mean square errors of sinusoidal pressure response are all less than 5 bar,and the root mean square errors of slope pressure response are all less than 1 bar.The overall performance is improved by about 40%-50%,which ensured the I-EHB system with better braking stability and performance.(5)Based on the rapid and accurate braking hydraulic pressure response of I-EHB system,a rational regenerative braking energy distribution strategy is proposed based on the single-motor layout scheme,which only integrated one motor in the front axle driving wheel,and its function is verified by a real vehicle test platform.Then,a regenerative braking energy distribution strategy is proposed based on the four-wheel independent drive four-wheel side motor layout scheme,and the simulation verification and optimization analysis of the control strategy are carried out after building a Simulink simulation model. |
PDF Full Text Request