Model-based evaluation of railway pneumatic suspensions

On classical passenger trains, the secondary Suspension is commonly ensured by airsprings which are integrated in a pneumatic circuit. In addition to the pneumatic bellows. the circuit contains various pneumatic components such as tanks, pipes, orifices, levelling valves. etc., the purpose of the latter being, to maintain a costant height between the carbody and the bogie. These elements can be connected in several ways leading, to many existing suspension topologies. This paper deals with multidisciplinary modelling of a vehicle equipped with such a suspension taking into account both multibody and pneumatic aspects. First, it depicts in more detail the various elements of a pneumatic; suspension. Then, many criteria that influence the suspension morphology are presented: the kind of bogie, the use of an auxiliary tank, the position of this tank relative to the bellows, the kind of levelling system, the use of all additional anti-roll bar, the use of an additional hydraulic damper, etc. The description of the complete pneumatic Circuit implies the use of thermodynamic models which take into account the airflow through the pipes and the valves, the pressure in the bellows, etc, Several pipe models are presented, the choice depending on the length of the pipe: an algebraic model is sufficient for short pipes, while a differential model is needed to take into account the dynamics of longer pipes. The pneumatic model is then coupled with a SIMPACK multibody model in order to analyse the behaviour of the complete vehicle. Two-point and four-point configurations are compared for Delta Q/Q and curve entry tests.