During 2005, the Italian railway Network Operator (RFI – Rete Ferroviaria Italiana) realized two ETR500 train sets completely dedicated to diagnostic operation on the new high speed lines being built in Italy. During 2006, these train were equipped with a complete acceleration measuring system for test activities on new Italian high speed line Turin – Novara and Rome – Neaples. A complete accelerometric measurement set up has been installed for track investigation. To this aim, the experimental set up is able to identify vertical profile of track geometry, without the limitation to 25 – 30 m, typical of the traditional measuring methods. On the other hand, a tool for predictive identification of hunting instability has been developed. For each run, it is possible to define a map, highlighting all the irregularity wavelengths involved as a function of the space: for high speed application wavelength over 100 m can become really important both for comfort and safety, because they are able to interest low frequency dynamic (around 0.8 – 1.5 Hz). Moreover, with the aim of identifying the beginning of hunting instability, a tool has been developed in order to identify yaw instability vibration mode and thus its non-dimensional damping, just by bogie yaw acceleration measurement. Both this tools have been developed by means of comparison between numerical multi body simulations and experimental measurements. Numerical simulation have been used to simulate a wide range of operating condition, that was of fundamental importance in tuning of such tools. Full evidence on these method will be given in the paper, together with an example of the obtained results.
Development of gravitational acceleration measurement set up based on laser beams
