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Analysis of the odometry algorithm performance (SSC/SCMT BL3) on board of VM370 vehicles

A collaboration between MDM Team and Alstom is in act on the testing of the performance of odometry algorithms for SSC/SCMT baseline3 systems, applied on VM370 vehicles, aimed at maintenance works on RFI network when the lines are not in service. The VM370 vehicles are equipped of a mechanical coupling between the axles, that not involves an independent behaviour of the two GITs mounted on each one. 

First a 2D model of the vehicle has been developed in LMS Amesim environment and the main parts concerning the transmission of the traction forces towards the axles, the geometry of wheelset, car body and the definition of the main forces acting on the vehicle movement, have been analysed and modelled in details. With the aim to reproduce more accurately the vehicle dynamic in the traction and braking phases, a 3D multibody model has been developed. The model has been validated in a preliminary phase, evaluating the stopping space and comparing it with that obtained with the braking couple obtained from the Fiche UIC 544-1. The odometry performance have been evaluated in different operating conditions concerning the friction coefficient of track, comparing the results with coupled and uncoupled axles. The scenarios used to test the odometry performances are those provided by RFI, and differ from each other for a different value of the track friction coefficient.

The performance have been analysed in terms of the accumulated estimation errors on the vehicle speed and position, making reference to the maximum error limits imposed by the requirements for the SSB and SST systems, defined for the SCMT system. More focused, a comparison among the obtained speed profiles, from the GIT computing and finally the speed profile estimated by the odometry algorithm has been carried out for each scenario.

The obtained results highlight estimation errors within the limits imposed by the SSB requirement, instead there is an overestimation of the travelled space if compared with limits imposed by the SST requirement. However, safety performances are guaranteed, despite a less service availability.

With the aim to consolidate the vehicle model, a wide experimental campaign has been planned to provide proofs of traction, braking  (when the adhesion is no lost) and coasting, in order to evaluate the transmission couple, the braking performances and the advancement resistances.

Has been planned an extension of the simulation campaign with other vehicle models of the VM370 platform.

 

[1] Trenitalia: Odometria SCMT Specifica requisiti funzionali n° 372574 esp.03

 

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