| In the context of driving automation,the demand for the brake system includes diversified indicators such as safety,stability and smoothness.The accurate regulation of pressure during braking is becoming more and more important.Electronically controlled pneumatic brake system(ECPBS)is a new type of pneumatic brake system for commercial vehicles,which uses compressed air as the transmission medium and adjusts the brake chamber pressure in real time by an automatic pressure regulating valve to realize automatic and intelligent braking.Taking the automatic pressure regulating valve in commercial vehicle ECPBS as an object,this master dissertation collects its pressure regulation requirements.Based on PWM-PFM technology,the voltage regulation method is proposed and the voltage regulation characteristics are optimized.The main contents of the research are as follows:(1)According to the development of vehicle intelligent driving technology,based on the braking requirements of different driving automation levels,the functional requirements and pressure regulating requirements of the automatic pressure regulating valve in commercial vehicle ECPBS are proposed.The commercial vehicle ECPBS and its automatic pressure regulating valve are designed.The structure and working principle are expounded,and the theoretical analytical model of the pressure regulating characteristics of an automatic pressure regulating valve is established.The simulation model of the automatic pressure regulating valve is established by MATLAB/Simulink,which is the basis for studying the method of regulating pressure.(2)Based on the functional requirements,pressure regulating requirements and related standards of automatic pressure regulating valve,a test method for evaluating the pressure regulating characteristics of automatic pressure regulating valve is proposed in commercial vehicle ECPBS.The d SPACE real-time simulation system is used as the controller of automatic pressure regulating valve to develop a test system for the pressure regulating performance of automatic pressure regulating valve in commercial vehicle ECPBS,and the test steps are proposed.By comparing and analyzing the simulation and experimental data,the correctness of the analytical model and the simulation model of the automatic pressure regulating valve are verified.(3)Based on the experimental data of the pressure regulating characteristics of the automatic pressure regulating valve,the relationship between the frequency,duty cycle and the pressure response of the automatic pressure regulating valve are analyzed.The method of using PWM-PFM to improve the linearity of the outlet pressure-duty cycle curve of the automatic pressure regulating valve is proposed.Based on PWM-PFM technology,two pressure regulating methods for optimizing the pressure regulating characteristics of automatic pressure regulating valve are proposed.The first one is a feedforward PID pressure regulation method without considering the pressure change rate.The second is a regulating method that adds the pressure change rate as the regulating requirement and uses particle swarm optimization algorithm to adjust the PID controller parameters.The regulating method makes the automatic pressure regulator outlet pressure response meet the multivariate evaluation index.Through the method of combining experiment and simulation,the results of two automatic pressure regulating valve pressure regulating methods based on PWM-PFM control are compared and analyzed.The results show that the two pressure regulating methods of automatic pressure regulating valve are correct for the requirements of the commercial vehicle ECPBS and its automatic pressure regulating valve with different driving automation levels.Based on PWM-PFM control technology and the pressure regulating requirements of the automatic pressure regulating valve,the proposed pressure regulating method of automatic pressure regulating valve can be used as the theoretical basis and technical support to ensure the safety and smoothness of commercial vehicle braking process and the comfort of drivers and passengers,which is of great significance to the development of commercial vehicle driving automation and intelligent braking system. |
