Mathematical modelling of railway vehicles with secondary airspring suspension: safety and ride comfort

Aims of this paper are to define testing methods for airspring characterisation, and to investigate mathematical modelling approaches suitable to reproduce the behaviour of this type of suspension and their effect on the accuracy of rail vehicle dynamics multi-body simulation. Two different modelling approaches are considered for the airspring: a quasi-static one, suitable for vehicle dynamics simulations in curve and/or in presence of crosswinds, and a dynamic model which is used for the estimation of ride quality, in conjunction with a flexible carbody vehicle model. The results of these models are compared with those provided by simpler models, often used in multi-body simulations: it is demonstrated that the quasi-static modelling of the airspring can have a large effect on the simulation of load transfer effects in curve and in presence of crosswinds. Furthermore, it is shown that a dynamic model of the air spring is required to correctly asses ride comfort, especially when the pneumatic layout of the suspension includes a long pipe between the air spring and the reservoir.