Research On The Control Of Vehicle Height For Bus With ECAS Based On Model Predictive Control

Electronically controlled air suspension system(ECAS),one of the advanced suspension system,through the active control the quality of the air bag,directly and effectively change the vehicle suspension stiffness and the height of the vehicle body,effectively improve the performance of vehicle ride comfort,handling stability and through.The advantage of the electrically control air suspension is not only the comfort of the low-frequency suspension,but also the characteristics of the electronic components used in the system,especially the stiffness of the suspension and the variability of height body.Electronically controlled air suspension is the branch of active control technology,there are larger gap about domestic and domestic ECAS controller technology,the current has been widely used abroad electronically controlled air suspension system on passenger cars,while the domestic passenger car market is only part of the configuration of electronically controlled air suspension system,and the domestic independent research and development of electronically controlled air suspension is rare and heavily dependent on imports.At present,the main reason for the popularity of electronically controlled air suspension on the domestic market is the lack of theory to product leaps and practice to explore,thus to electronically controlled air suspension system related theoretical research and engineering practice,as soon as possible the domestic independent research and development,stable and reliable air suspension controller has a certain engineering practice significance.Based on the control requirements of ECAS,the difficulties in control characteristics and the domestic demand,this paper studies the electric control air suspension system of the bus,and design algorithm and control strategy.The main research includes:1.The nonlinear model of single wheel air suspension is established and verifiedResearching on relationship between thermodynamics and dynamics under the height adjustment process,establish a nonlinear model of air spring,the air suspension model of single degree of freedom is deduced by using AMESim structures,using air suspension AMESim model of single wheel to the validation and contrast of air suspension Simulink model.2.Establishment of hybrid system of single-wheel air suspension modelSimplified nonlinear model of the electronically controlled air suspension to linear model,The model is compiled wih hybrid system language and the Mixed Logical Dytnamical equationis established.3.Prediction control of hybrid model of single wheel air suspension modelBased on model predictive control theory and the air suspension model MLD equation of single wheel,mixed model predictive control algorithm about air suspension of single wheel model,setting up the reference height as the control target,and the simulation experiments.Based on the algorithm and cost,the air spring pressure observer is proposed based on the sliding mode control theory,and the pressure value of the air spring is estimated in real time.4.Hybrid model prediction control of air suspensionsingle wheel model predictive control algorithm is respectively applied to the vehicle control,then puts forward the relevant problem of the roll and pitch anger of vehicle body being bigger,body height adjustment easy being overshoot,then puts forward based on the 7 degrees of freedom vehicle model of mixed model predictive control,respectively set up the reference height reference,reference roll angle and pitch angle as the control target,the constraint of control times about valve.5.Design of dynamic static control strategy for vehicle bodyDue to the low stiffness suspension body highly vulnerable to the road,under the vehicle dynamic driving,the height of vehicle is easily disturbed and changes,in order to stabilize the body height,the system should be timely identification of load change height changing and real-time adjustment,and to identify the road caused by the height changing,ensure performance of the smooth and stability of vehicle height.6.Design and verify the experimental scheme of vehicleDesigning bench experiment scheme and the real vehicle experiment scheme,using of air suspension bench experiment and real vehicle test mixed model predictive control algorithm and the effect of the control strategy of the dynamic and static control.