Research On Vehicle Height Predictive Control For Bus With ECAS Based On Road Surface Recognition

With the increasing demand of people for ride comfort and the current situation of domestic transportation,electronic controlled air suspension system has become the best choice for future transportation vehicle configuration because of its controllability and road friendliness.However,as far as the domestic market of ECAS is concerned,there is not a company that has fully mastered the independent development technology.A large part of the ECAS-products and related core components are imported.Therefore,the relevant theoretical research and control performance experimental analysis of the system are of practical significance to get rid of technology introduction,promote technology and realize independent research and development in China as soon as possible.In this paper,based on the control requirements of the ECAS system of passenger cars,the high regulation system of passenger cars is taken as the research object,combined with the relevant road identification theory,and the main research contents are as follows:(1)Nonlinear dynamic modeling of ECAS vehicle high regulation system.Based on the thermodynamic theory and fluid mechanics theory of variable mass charging and discharging system,the nonlinear mathematical models of air spring,gas flow mass characteristics of solenoid valve and pipeline are established.On this basis,the nonlinear model of the high regulation system of the vehicle ECAS is established by combining with the 7-dof dynamic model of the vehicle ECAS,which provides a theoretical reference for the linearization of the vehicle model and the establishment of the MLD model.(2)Hybrid dynamic modeling of vehicle ECAS system.On the basis of nonlinear model,the model of ECAS vehicle height adjustment system is approximately linearized,and the error degree of the linear model is verified.This paper introduces the theory of hybrid system,analyzes the hybrid state of Vehicle Height Adjustment System,and establishes the MLD model of hybrid system based on the linear model according to the coupling constraint relationship between continuous dynamic process and discrete events.(3)Road level identification.Considering the importance of external excitation source of air suspension--Pavement excitation in suspension control for improving the overall performance of suspension,a pavement grade identification controller is proposed.Taking vehicle speed,vehicle body vertical acceleration and suspension dynamic deflection as input variables,BP neural network control algorithm is used to train data,and based on vehicle dynamic response,road grade information is output in reverse,realization of road information identification.(4)Controller design and simulation test of ECAS vehicle high regulation system.Based on the model predictive control(MPC)algorithm theory,an ECAS vehicle height adjustment controller is designed to accurately track the height adjustment of the whole vehicle.The body height dynamic control is divided into two parts: electromagnetic valve controller based on error band identification and magnetorheological damping force controller based on hybrid model predictive control.Finally,in view of the vehicle body height under the dynamic and static state movement characteristic,the coordination control strategy is carried out by combining the electromagnetic valve control strategy and the magnetorheological damping force control strategy,the control effects under static and dynamic conditions are simulated and analyzed through Matlab /Simulink.