Analysis of dynamic behaviour of an active pantograph in multiple composition

The sliding contact between pantograph and catenary is used to collect the current fed by the electrical trains for running. A good quality of current collection, i.e. a sliding contact with a low percentage of contact losses, is then essential to assure the regular run of the electrical railway vehicles. In some cases, multiple pantographs to collect current for a railway vehicle are used: this configuration represents a critical condition, even to relatively low vehicle speeds, due to the dynamic interaction among the contact wire motion produced by the first pantograph passage and the trailing pantographs that are subject to an high probability of contact loss between the collector strip and the contact wire. This paper deals with an active control acting on the articulated frame of a pantograph by means of its pneumatic spring in order to study the effect on the current collection quality, when a double pantograph configuration with a close distance is used. Experimental tests aimed at the definition of the transfer function between the air pressure of the pneumatic spring acting on the articulated frame, and the contact force have been carried out in order to define the possibility to use the air spring as actuator for control at low frequency. Finally the numerical simulation of two pantographs in standard configuration and with the application of active control has been performed to preliminarily verify the advantages on the current collection quality.