Modelling of pneumatic suspensions


Multiphysics Modelling of Railway Pneumatic Suspensions


Most of passenger trains are equipped with pneumatic suspensions. Such a system allows to adapt the suspension height and stiffness to a varying payload and provides better comfort and sound insulation. However, in order to achieve these interesting properties, the air suspension involves a complete pneumatic circuit composed of auxiliary tanks, pipes, restriction orifices and several valves. These various components can be combined in many ways leading to an increasing design complexity. From an industrial point of view, resorting to a simulation tool could be very beneficial in designing more efficient suspensions.

Multibody dynamics is certainly a powerful way to model railway vehicles. Many developments were performed and railway specific features such as the wheel/rail contact problem were implemented in commercial multibody packages. They are now widely used in the industry to design vehicles and analyse their performances, for example, in terms of comfort and safety. However, suitable tools to study the behaviour of the overall pneumatic suspension circuit are still lacking. This research activity therefore aims at analysing the existing pneumatic suspension models and proposing a modelling approach that involves most of the pneumatic circuit elements and that can be coupled with multibody dynamics. The goal is both to be able to address industrial problems and to provide an in-depth understanding of the physical phenomena that occur in the system.

Pneumatic suspension modelling

Various modelling approaches for the pneumatic circuit has been compared on a given test case is described. A component oriented approach based on thermodynamics has been developed, focusing on pipes for which several methods have been investigated. It has been shown how the chosen equations affect the frequency response of the suspension.

Experimental illustration and validation

Then,  experiments have been carried out on a real suspension. A system composed of an air spring connected to an auxiliary tank has been submitted to various kinds of excitation and various configurations of the connecting pipe are tested. Afetr determining the model parameter of the suspension, the influence of heat transfer phenomena has received a particular attention. The dynamic response of the suspension has been tested and experimental measurements has been confronted to simulation results.



Railway modelling applications

Finally, thanks to the developped models, a complete metro car and its pneumatic circuit have been implemented. The complete vehicle performances has thus been analysed for tests in which components such as valves play an important role. In particular the impact of some suspension component failure has been investigated. Several pneumatic circuit morphology have been compared and novel topology have been proopsed.


Docquier N., Multiphysics Modelling of Multibody Systems: Application to Railway Pneumatic Suspensions, PhD thesis, Université catholique de Louvain, 2010.

Docquier N., Fisette P., Jeanmart H., Multiphysic modelling of railway vehicles equipped with pneumatic suspensions, Vehicle system Dynamics, 2007, 45, 6, pp. 505-524.

Docquier N., Fisette P., Jeanmart H., Model-based evaluation of railway pneumatic suspensions, Vehicle System Dynamics, 2008, 46 (SUPPL.1), pp. 481-493