Design And Simulation Of Control Strategy For Electro-Mechanical Braking System

At present,the intelligent and electronic technology is deeply integrated with the automobile industry,and the electronic mechanical braking system(EMB)has become the development focus of the automobile braking industry.Embs replace traditional hydraulic lines with signal transmission lines and related electrical integrated components,use electronic pedal sensors to induce demand braking,and the controller outputs braking force through the control motor.The compact structure is easy to integrate into vehicle communication technology,and easy to combine with anti-lock braking system(ABS).As an active safety device,ABS mainly controls wheel slip rate at present.By controlling motor,ABS based on EMB actively regulates wheel brake pressure to maintain the optimal slip rate,so as to continuously obtain peak longitudinal adhesion and large lateral adhesion,shorten braking distance and improve braking stability.In this paper,an EMB actuator is designed in terms of EMB structure.In terms of control,the overall framework of the control system based on EMB is designed.The control strategy of EMB braking intention recognition,EMB response control and ABS control based on EMB are designed in detail.This paper uses theoretical analysis,modeling simulation and experimental verification to conduct in-depth research on the above key theories and technologies.The main research contents are as follows:(1)Overall design and modeling simulation of EMB actuator.EMB actuator is designed according to the overall requirements of vehicle braking,including the selection of torque motor,deceleration and torque increase device and motion conversion device.Working parameters of EMB actuator are designed according to hydraulic brake parameters of target models in the laboratory,including maximum braking force,brake clearance,time to eliminate brake clearance,etc.On this basis,the selection and design of ball screw,planetary gear reducer and permanent magnet brushless DC torque motor were completed,the physical model of EMB actuator was established,the three-dimensional model was simulated and analyzed by finite element in ANSYS/Workbench,and the mathematical model of EMB actuator was established.The maximum brake clamping force and the time to eliminate brake gap were simulated and verified in MATLAB/Simulink.(2)Overall framework design of the control system based on EMB.According to the working principle of EMB,the overall framework of EMB control system integrating braking intention recognition,response control and ABS control is established,and the ideal braking control process based on EMB is designed.Then the vehicle dynamics system is modeled,including the vehicle single wheel model,tire model and EMB actuator model.The relationship between slip rate and adhesion coefficient is analyzed.(3)Design of EMB braking intention recognition control strategy.According to the analysis of braking driving behavior,three variables,electronic pedal displacement,electronic pedal speed and vehicle speed,were taken as the input parameters of EMB braking intention recognition based on the premise of considering the driver’s braking comfort.Firstly,the braking intention intensity was divided according to the electronic pedal speed value,and then the identification parameters were quantified by storing table.The linear proportional coefficient between the electronic pedal displacement and the output braking force was determined according to the speed and vehicle speed of the electronic pedal,and the relationship between the displacement and the output force was established.(4)EMB response control strategy design.According to the overall design idea of EMB response control,PID controller principle analysis and tuning PID controller parameter theory,the three closed-loop response control system of EMB actuator based on PID control is established.The overall model is built in MATLAB/Simulink according to relevant models,and the simulation design verification of current ring,speed ring and clamping force ring is carried out.At the same time,the optimal parameters of PID controller required by each ring are set.(5)Design and simulation of ABS control strategy based on EMB.According to the principle of ABS control,PID controller,fuzzy controller and self-tuning fuzzy PID controller based on fixed slip rate control are designed respectively.All the above ABS controllers adopt the control strategy based on wheel optimal slip rate,and realize real-time online closed-loop control of optimal slip rate and brake pressure by controlling the current variation of EMB executive motor.According to the vehicle dynamics model,the overall simulation model is established in MATLAB/Simulink,respectively in three typical road surface,namely high adhesion,medium adhesion,low adhesion road simulation to verify the advantages and disadvantages of ABS controller.In addition,an online identification system for the optimal slip rate of pavement was established,and an improved PSO-BP-PID controller based on the optimal slip rate control was designed,which was consistent with the above control mode and modeling environment.Simulation was carried out under single and variable working conditions based on the above three typical pavement types.The feasibility and effectiveness of the online identification system and ABS controller for optimal pavement slip rate are verified.(6)Verification of EMB hardware in loop test.According to the simulation results above,the EMB hardware-in-the-loop test bench is designed and built,and the hardware system composed of the main engine,DSpace real-time simulation system,controller,EMB actuator and various sensors is built.At the same time,the software system composed of vehicle model building,controller control strategy development,computing main engine monitoring and data recording function is designed.The maximum clamping force was verified according to the test bench,and the ABS test was simulated,and the corresponding simulation results were compared and analyzed to verify the function of the designed EMB actuator and the effectiveness of the established self-tuning fuzzy PID controller.