The influence on vehicle dynamics of active lateral suspensions: experimental assessment

Increasing a railway vehicle's speed on existing track, its dynamic performances are negatively affected. To compensate for the deteriorated dynamic behaviour, a re-design of the suspension system has been carried out in the years. For trains which are operated at very high speed in combination with high cant deficiency, a purely passive solution is not always sufficient. Thus, an active solution offering better possibilities of improving the vehicle’s dynamic performances are sought for. Active suspensions in trains have been studied for a number of years. Two general categories can be identified: one improving running stability and wheelset guidance and another improving passenger ride comfort. However, due to relatively high implementation and maintenance costs, only few applications are being used in service operation. One of these active suspensions has recently been tested on V300Zefiro train, the new Italian high speed train. In fact, V300Zefiro is being homologated up to a speed of 350km/h with a high cant deficiency. The main target of active lateral suspensions on V300Zefiro train is to improve passenger ride comfort. In a conventional bogie, the carbody’s inertia forces in curves are transferred through the suspension and eventually through the bumpstops to the bogie frame. With an active lateral suspension, these inertia forces are transferred to the bogie frame through the lateral actuators in order to avoid bumpstop contact, and finally to the wheelsets resulting in a change in wheel-rail contact forces. This force transfer, together with the passenger comfort, should carefully be addressed in order to evaluate all consequences of the developed control logic with respect to the track. The present paper focuses on the dynamic characterization of the active lateral suspensions (with particular focus on V300Zefiro) based on the measurement of displacement and transmitted force in real working conditions, as well as on the influence of the active lateral suspensions on the centring capabilities of the carbody with respect to the bogie and on the resulting wheel-rail contact force components (being the instrumented active lateral suspensions mounted on bogies having load measurement wheelsets).