Design of a vehicle height and body posture adjustment hybrid automaton of electronically controlled air suspension

The vehicle height and body posture adjustment of electronically controlled air suspension (ECAS) poses great challenges to hybrid control, since it involves discrete events of solenoid valve (SV) switching and dynamic evolutions of continuous variables. This article investigates in the modeling and verification of the vehicle height and body posture adjustment control system. A nonlinear mechanism model of the ECAS which considers the pneumatic characteristics of the SV is established. On the basis of mixed logical dynamical (MLD) modeling approach, a hybrid automaton describing on-off statuses transition equations of charging SV, discharging SV and four air spring SVs is established and then is compiled into the standard MLD model by using hybrid system descriptions language, realizing the coordinated control between the vehicle height and body posture by directly adjusting the SV on-off statuses. Simulation tests and bench tests are conducted and the results are presented to show how the designed hybrid automaton can be successfully applied to solve the difficulties that exist in the ECAS.