| Commercial vehicles electronically controlled pneumatic brake system(ECPBS)utilizes compressed air as the power source and uses automatic pressure regulating valve to regulate the brake chamber pressure with electronic control signal dynamically in real-time,which ensures driving stability and riding comfort on the premise of safety.ECPBS is a new commercial vehicle brake system that inherits the advantages of the traditional pneumatic brake system and complies with the rapid development of the intelligent vehicle,driving automation,and other technologies.The automatic pressure regulating valve is the core and basic component to realize the brake and the adjustment of the driving condition of commercial vehicles.The brake pressure control of automatic pressure regulating valve in commercial vehicles ECPBS is the base to perform brake and hence is one of the core technologies to ensure vehicle active safety,driving automation and intelligent brake.At present,there is an urgent need for a suitable control method for the intelligent brake.Therefore,this thesis focused on the brake pressure control method of automatic pressure regulating valve in commercial vehicle ECPBS.With the issues of low control accuracy and compensation of nonlinearity taken into consideration,an appropriate control method available for engineering is proposed to enrich the brake control theory,break through the barrier of technology and lay a foundation in theory and technique to develop self-controlled commercial vehicle driving automation system.The main research work and innovative achievements of this thesis are as follows:(1)Focusing on different driving automation levels commercial vehicle ECPBS and the analysis of the structure,principle and characteristics of automatic pressure regulating valve,the research on the performance of the pressure regulating of commercial vehicle ECPBS and the control problem of brake pressure has been carried out.Based on the research work of driving automation technology,the commercial vehicle intelligent brake is defined.The brake conditions and modes of commercial vehicle pneumatic brake system under different driving automation levels are concluded.Commercial vehicle ECPBS for different driving automation levels is designed.Aiming at the intelligent brake,an improved automatic pressure regulating valve is proposed through analysis of comparative experiments.Based on the research of domestic and foreign standards and the research on vehicle functional systems,the pressure regulation performance requirements of commercial vehicles are proposed,and the issues of pressure control of automatic pressure regulating valve in commercial vehicle ECPBS are revealed to lay the engineering basis of the research work of the thesis.(2)Based on the analysis of the above system control problems,a detailed linear parameter-varying(LPV)mathematical model for the brake pressure control of the commercial vehicle ECPBS automatic pressure regulating valve is conducted.The mathematical model of each main component in commercial vehicle ECPBS is established to simulate the process from the input of electronic control signal and the output pressure of brake chamber.The overall mathematical model of automatic pressure regulating valve is as well established to simulate the pressure control process.Aiming at the high order nonlinearity characteristics of the system,to realize the online realization of the model,the linearization method which is suitable for time-varying and nonlinear system,q-Markov covariance equivalent realization(q-Markov cover)is adopted.The LPV pressure control model of automatic pressure regulating valve in commercial vehicle ECPBS is established.The established nonlinear mathematical model,the linear mathematical model under certain target pressure and the LPV mathematical model are validated through both simulation and bench test.(3)In the process of pressure tracking control of automatic pressure regulating valve in commercial vehicle ECPBS,there are the problems of the immeasurable state variables and the controller selection with the uncertain target pressure changes randomly.To solve these issues above,the immeasurable state variables are estimated through the Kalman filter.And the issues of the controller selection with uncertainty and randomness of target pressure are solved by designing an interpolator.Based on the theory of optimal tracking control,the control strategy of linear quadratic tracking(LQT)in the infinite time domain is improved,and the dynamic tracking control method for brake pressure control of automatic pressure regulating valve in commercial vehicle ECPBS including LQT control algorithm and its realization technology is proposed.The control method designed is verified through simulation and experiments,then the application characteristics are analyzed.Therefore,it is indicated that the control method can realize the transient and steady tracking control of brake pressure of automatic pressure regulating valve in commercial vehicle ECPBS in the whole parameter range with high performance.(4)Aiming at the nonlinearity compensation issue of brake pressure control of automatic pressure regulating valve in commercial vehicle ECPBS,based on the established LPV mathematical model,the gain-scheduled model predictive control(GSMPC)method is adopted to realize the real-time,stable and precise adjustment of the brake pressure of the commercial vehicle ECPBS automatic pressure regulating valve.Considering the time-varying control characteristics,an interpolation control algorithm is designed and a gain-scheduled model predictive control method which includes the GSMPC algorithm and its realization technology is proposed to control the brake pressure of automatic pressure regulating valve in commercial vehicle ECPBS.Then the correctness of the method is verified through simulation and experiments,and the application characteristics are analyzed.Hence it is indicated that the control method can realize the optimal tracking control of brake pressure of automatic pressure regulating valve in commercial vehicle ECPBS in the whole parameter range,and has a good nonlinearity compensation and a good consistency in cycles.The control methods of PID,LQT and GSMPC are analyzed and compared through experiments and simulations,then the characteristics and the proper application of each control method are revealed.(5)To verify the brake pressure control method of automatic pressure regulating valve in commercial vehicle ECPBS and its usability,the HIL test method of automatic pressure regulating valve in commercial vehicle ECPBS is proposed based on HIL test theory.The d SPACE real-time control system,IPG/ Truckmaker and MATLAB/ Simulink are adopted jointly to simulate the real-time driving condition of commercial vehicles.Combined with the pneumatic brake system,the test bench for the validation is built.Then the test conditions are designed.The application characteristics of the proposed control method in the vehicle environment are analyzed and verified for correctness,and the influence on driving performance in different conditions are analyzed.In summary,accurate brake pressure control is realized by a systematic methodology,during which theoretic methods are used for the system modeling and control design.The theoretical and technical basis will be provided to the intelligent brake of commercial vehicle ECPBS and driving automation of commercial vehicles to improve vehicle pneumatic brake control technology. |
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