Research On Control Strategy Of Electronically Controlled Air Suspension Fixed On Rear Axle

The vehicle suspension system is the key components of the chassis system.The suspension system can absorb the vibration and shock from the road to improve the comfort and operability.With the demand of the vehicle driving experience increasing,the air suspension was used more widely because of its excellent performance.This research,based on the vehicle with Electronically Controlled Air Suspension fixed on rear axle,includes the key technologies during the height adjustment at rest,and the control strategy.First,the equation about stiffness characteristics,the frequency characteristic of the air bladder has been derived.And the various factors related to the characteristic of the air bladder.Then the results have been verified by AMESim software.The inflating and deflating procedure of air suspension is a complex nonlinear dynamic process.This paper researched the gas loop flowing characteristics,and derived the gas mass flowing equation and the model formula of the air spring.Then,according to the mechanics laws,a vehicle 1/4 model has been established in Simulink.It proved the superiority of air suspension by Contrastive Analysis between coil spring and air spring.Another full vehicle model has been established to show the balloon overshoot phenomenon.A two-input one-output controller was designed to solved the overshoot phenomenon,according to the fuzzy theory.The output,a PWM wave,is to control the solenoid valve opening and closing time.Another three-input one-output.Finally,the appropriate control strategy was developed to satisfy the project requirements.We completed the system structure design and PC program.The height adjustment in the real vehicle proved that the Electronically Controlled Air Suspension designed is effective.