Study On Height Control Of A Bus Equipped With HIS System And ECAS System

Due to its superior ride comfort performance,the air suspension and its combination with anti-roll bar have been widely adopted in large-size buses.One of the main drawbacks of this kind of suspension configuration is that the limited improvement of the handling stability while maintaining preferable the ride comfort.It is for the fact that a bus always has the higher center of gravity(C.G.)and vulnerable to rollover accident,causing great threat to people's life and property.In this paper,a new suspension configuration is proposed to balance the compromise between ride and handling performance for a tour bus,which consisted of Hydraulically Interconnected Suspension(HIS)system and Electronic Controlled Air Spring(ECAS)system.The suspension system could automatically change their mode according to the riding condition,and automatically change the height of the vehicle according to the driving conditions to improve passing ability of vehicle.First of all,based on the thermodynamic theory,the dynamic models of the main gas chamber,additional gas chamber and throttle orifice are constructed,and the vibration response characteristic of the air spring with additional air chamber is studied by numerical integral method in Simulink.The dynamic elastic characteristics of the front air spring under different initial pressure are simulated,the correctness of the model is verified by comparison with the experimental data,and the dynamic stiffness value of the air spring is obtained according to the model,and the influence of the key parameters on the dynamic stiffness of air spring is discussed.Then,based on the centroid theorem and the momentum moment theorem,the dynamic equation of the nine-DOF dynamic model of the vehicle is established.For HIS system,the mathematical models of the two-acting hydraulic cylinder,damper valve,pipeline,accumulator and other components of HIS system are established,and the air spring model and HIS model are coupled with the vehicle model through boundary conditions.The simulation of snake test is carried out between a ECAS vehicle with HIS system and the same vehicle with anti-roll bar,and the experimental data are compared to verify the model.the results show that HIS system can obviously improve vehicle's handling performance.Finally,the formulation of the height adjustment control strategy of ECAS system and the determination of the main switching parameters are carried out,so that the vehicle can adjust the height of the vehicle body according to the driving condition,and the results show that the vehicle can achieve the static and dynamic height adjustment with road interference.Based on the analysis of random road input,fishhook test,snake test and other test conditions,the influence of vehicle body height variation on vehicle ride comfort,and handling stability is discussed.In summary,this paper establishes nine-DOF dynamic model of the vehicle with HIS system and ECAS system.Using fuzzy control algorithm to control the gas charging and discharging process of ECAS system so as to adjust the height of the vehicle.Through the simulation analysis,the influence of the height change on ride comfort and handling performance are discussed.