Susanna Papini

A railway vehicle multibody model for real-time applications

Hardware in the loop (HIL) techniques are widely used for fast prototyping of control systems, electronic and mechatronic devices. In the railway field, several mechatronic on board subsystems are often tested and calibrated following the HIL approach. The accuracy of HIL tests depends on how the simulated virtual environment approximates the physical conditions. As the computational power available on real-time hardware grows, the demand for more complex and realistic models of railway vehicles for real-time application increases. In past research activities, the authors worked on the implementation of simplified real-time models for several applications and in particular for an HIL test rig devoted to the type approval of wheel slide protection systems. The activity has then been focused on the development of a three-dimensional model of the dynamics of a railway vehicle for more complex applications. The paper summarises the features and the results of the study.

Identification of a wheel--rail adhesion coefficient from experimental data during braking tests

The forces that occur in the wheel–rail interface significantly affect vehicle dynamics, especially in the longitudinal direction. Conventionally, the tangential component of the force exchanged between the rail and the wheel is expressed as the product of the normal component of the force, and the so-called adhesion coefficient. This ratio depends on several parameters that are usually summarized in the term ‘adhesion conditions’. When the adhesion conditions are degraded (for example, in cases of rain, fog, ice, dead leaves, etc.), and the vehicle is accelerating or braking, pure rolling conditions between the wheels and the rails do not hold any more, and macroscopic sliding occurs on one or more of the wheels. The aim of this work is to identify a relationship between adhesion coefficient and some parameters, namely wheel sliding and train speed, starting from a set of experimental measurements, obtained from test runs conducted with artificially degraded adhesion conditions.

Simulation of braking performance: The AnsaldoBreda EMU V250 application

This paper presents the development of a modular tool for the prediction of train braking performance. Particular attention is devoted to the accurate prediction of stopping distances, considering different loading and operating conditions, necessary to verify safety requirements prescribed by the European Technical Specifications for Interoperability of High Speed Trains (TSI-HS) and the corresponding EN regulations. Results are verified by considering, as a benchmark, the AnsaldoBreda EMU V250: a European train being developed for Belgium and The Netherlands’s high-speed lines. Technical information and experimental data were available for this train, directly recorded during preliminary supplier exercise. Validation results were encouraging, and allowed a more accurate identification of the pad friction factor influence on braking performance.