Research On The Control Strategy Of Electronically Controlled Air Suspension Height Adjustment For Electric Bus

The suspension can connect the body and the whee elastically so that slowing down the impact and the oscillations caused by external excitations in the process of running and guaranteeing that vehicle has good driving performance in a variety of conditions.At the same time,enhancing the stability and safety of vehicle movement and guaranteeing good trafficability and the integrity of the goods in complex road conditions.With the progress of science and technology and the increasing demand for vehicle comfort,air spring has been widely used because of its outstanding performanceThe height regulating of the vehicle body according to the road condition is an important function of the electronically controlled air suspension.It should not only ensure the accuracy of vehicle body height regulating during parking,but also realize the precise control of vehicle body height when there is a random road excitation.The main contents of this thesis are as follows:1.Studying on characteristics of air spring.The stiffness and frequency characteristics of the nonlinear system of air spring were studied.The mass flow rate,the pressure gradient equation and the static equilibrium position of the gas in the process of inflation/deflation were studied according to the knowledge of thermodynamics and fluid mechanics.2.According to the vertical dynamic equation of car body,a two DOF vehicle body model was built and the stiffness characteristics of the air spring were simulated by using AMESim.In view of the phenomenon of overshoot in the process of height regulating in the absence of road excitation,the Fuzzy-PID controller was designed to generate the PWM signals to control the on-off time of the solenoid valve so as to realize the height regulating of the vehicle body.3.In view of the existing road excitation,the state observer was designed and the unscented Kalman filtering algorithm was uswed to obseve the pneumatic suspension static equilibrium position.And this provided the basis for accurate and effective regulation of the vehicle body and design of the vehicle regulating control strategy.4.Seven degrees of freedom vehicle model was established and the TruckSimAMESim-Simulink simulation platform was built.The Fuzzy-PID controller and the unscented Kalman filter algorithm were used to regulate the front and rear bus body height and the function of kneeling in the process of parking in the city.In view of the existence of random road excitation,a reasonable control strategy was designed to meet the actual driving requirements and achieve accurate control of vehicle body height.