Modeling and Control of a Full-Scale Roller-Rig for the Analysis of Railway Braking Under Degraded Adhesion Conditions

Currently, braking on board subsystems such as wheel slide protection (WSP) devices almost totally control the longitudinal train dynamics. In particular, the vehicle safety highly depends on the study and the development of these systems, especially at high speeds and under degraded adhesion conditions. Usually, to save time and to avoid expensive on-track tests, the performances of braking subsystems are tested on full-scale roller-rigs. Nevertheless, the analysis of the subsystem behavior under degraded adhesion conditions is still limited to a few applications on roller-rigs because large slidings among the rollers and wheelsets produce severe wear of the rolling surfaces. This circumstance is not acceptable due to the effects on the maintenance costs (the rollers have to be turned or substituted), on the system dynamical stability and on the safety. In this paper, the modeling and control of an innovative hardware in the loop (HIL) architecture to test braking on board subsystems on full-scale roller-rigs is described. The new approach permits to reproduce on the roller-rig a generic wheel-rail adhesion pattern and, in particular, degraded adhesion conditions. The presented strategy is also followed by the innovative full-scale roller-rig of the Railway Research and Approval Center of Firenze-Osmannoro (Italy); the new rollerrig has been built by Trenitalia and is owned by SIMPRO. At this initial phase of the research activity, to effectively validate the proposed approach, a complete model of the HIL system has been developed. The complete numerical model is based on the real characteristics of the components provided by Trenitalia. The results coming from the simulation model have been compared with the experimental data provided by Trenitalia and relative to on-track tests performed in Velim, Czech Republic, with a UIC-Z1 coach equipped with a fully working WSP system. The preliminary validation performed with the HIL model highlights the good performance of the HIL strategy in reproducing on the roller-rig, the complex interaction between the degraded adhesion conditions and railway vehicle dynamics during the braking maneuver.