Study On Vertical Performance And Comfort Evaluation Of Vehicle Air Suspension In Vacuum Pipeline

Unlike the traditional transportation mode,the vacuum pipeline transportation system(ETT)is a new type of transportation mode,in which the moving carrier is suspended in a closed pipeline pumped into low pressure.This new type of transportation mode has the characteristics of fast,energy saving,zero pollution,high safety and so on.It can solve the current traffic dilemma facing human beings well.With the increase of vehicle speed,the vertical vibration of the vacuum pipeline air suspension system is gradually strengthened,and the interaction between the vehicle and the pipeline is more obvious.The vibration generated by the vehicle running will affect the physiology and psychology of passengers,and even endanger the health of passengers.The study of the vertical performance of the air suspension system and the vibration response of the vehicle is of great significance to the running stability and passenger comfort of the vehicle.Firstly,the dynamic mathematical model of air suspension is deduced and established.The dynamic performance of the air suspension is solved,and the equivalent stiffness and damping coefficient of the gas film are obtained.Several classical track spectra are briefly introduced,and the spectral power spectral density of ballastless track of high-speed railway in China is converted into time-domain samples by using inverse Fourier transform method as external excitation of vehicle-pipeline vertical coupling model.Secondly,the nodding and floating motion equations of car body and air suspension are deduced by using Lagrange motion equation,and the three-span continuous beam model is selected to establish the vertical coupling model of vehicle and pipeline.The equivalent stiffness and damping coefficient of the gas film are taken as one suspension system,and the value of the second suspension system is selected as the initial suspension.The vibration response of the system is solved by Newmark-beta integral method,and the vibration acceleration of the body and the first exhaust suspension and the vibration response of the beam are obtained when the velocity is between 300 km/h and 500 km/h.Finally,using Sperling index and weighted acceleration root mean square value as the evaluation criteria of stationarity and comfort,the different factors affecting passenger comfort were studied.The relationship between the parameters ofsecondary suspension,the vertical sensitive wavelength between 400 km/h and 800km/h,the different seat positions of vehicles and the comfort index was studied.After analysis and study,it is found that the passenger comfort can basically reach a good level after adding the second suspension.Within the selected parameters,the Sperling index increases with the increase of stiffness and damping coefficient of secondary spring;with the increase of driving speed,the range of vertical sensitive wavelength becomes larger and passengers' discomfort is strengthened;the seat position is strongly correlated with the weighted acceleration value,and the vibration response of the seats at both ends of the head and tail is stronger than that in the middle.The research on the factors affecting the comfort can provide reference for the parameter design,pipeline construction and maintenance of the secondary suspension as well as the seat arrangement position.