Study On Vehicle Body Height Adjustment And Ride Comfort Of ECAS Automobile

With the increasing demand for vehicle ride comfort and the performance of vehicles,electronically controlled air suspension(ECAS)has been widely used because of its good performance.Compared with the traditional mechanical suspension,the ECAS can be used for air spring charging and discharging to realize the height adjustment of the vehicle body.Furthermore,it can also be used to realize the damping adjustment of the shock absorber to reduce the body vibration and improve the ride comfort.Visible,ECAS will be the main trend of the future development of automotive suspension and the hot attention that automotive designers focus on.In view of the overshoot phenomenon in the process of ECAS vehicle body height adjustment,a new ECAS air supply system and a new method of vehicle body height adjustment are designed by this article.At the same time,after the vehicle body height adjustment,the vehicle dynamic driving,,a H_?robust controller is designed to improve vehicle ride comfort,and the simulation analysis is carried out.The main contents of this paper are as follows:Firstly,the structure and working principle of the new type ECAS air supply system are introduced,and the system is simplified as an air path composed of a gas storage tank,an electromagnetic valve,a flow meter and an air sprin.Establishing the mathematical model of the air suspension system based on the thermodynamic theory and the dynamic equation of the air suspension system.Secondly,according to the vehicle driving conditions,three types of body height are set up: high,middle and low,and the modular design of the vehicle body height adjustment control strategy is carried out.In order to study the phenomenon of overshoot in the process of adjusting the height of the vehicle body,the influence of different structural parameters of the air suspension system on the height of the vehicle body is analyzed by simulation.The simulation results show that the structure parameters such as length,diameter,damping coefficient,spring mass and gas tank pressure will affect the overshoot size of the vehicle body height adjustment,so the parameters of pipeline should be taken into account in the vehicle body heightadjustment of the air suspension.Then,the road simulation model is built and the air spring mass model is established either.According to the vehicle body height adjustment in the process of overshoot phenomenon,put forward a new method of adjusting the height of the vehicle body,also known as the gas quality control about vehicle body height,and using this method to simulate and analyze the static and dynamic adjustment of vehicle body height.The simulation results show that this method is feasible and effective to solve the problem of the vehicle body height changes caused by the change of the static load.At the same time,it can improve the accuracy of the vehicle body height adjustment under the vehicle dynamic driving,so as to avoid the problem of over charge or over discharge of the air spring.Finally,the vibration model of air suspension system is established,and the H_?controller is designed to reduce the vertical acceleration of the vehicle body.Using Matlab/simulink software to simulate and verify in different road conditionsand speed.The simulation results show that the H_?controller designed has better ride comfort compared with the passive suspension under various conditions.Simulation analysis is carried out in order to investigate the influence of the structural parameters of the suspension system on the performance of the controller,the results show that the controller has good robustness to the system parameter perturbation.