Page 152 - 360.revista de Alta Velocidad - Nº 5

Hutchinson, Michael. Marais, Juliette. Masson, Émilie. Mendizabal, Jaizki. Meyer zu Hörste, Michael.

1. Introduction

The precise as well as reliable detection of the position and their safe communication play a
key role for the train operation control system. In recent years, the tendency to shift more
and more positioning equipment functionality for safety-critical applications from the track
side to the vehicle on-board-side could be observed. Train-borne positioning systems enable
a costeffective operation technology for railway lines with a low traffic density and a more
flexible operation than track-side positioning systems can offer for lines with a high traffic
density. For on-board positioning systems, such as satellite-based train positioning systems, the
mapmatching process is of particular importance, since then the data provided by different
positioning sensors, such as GALILEO receivers, Doppler radars, odometers and inertial sensors
are related to a digital map of the respective railway network. This implies that the digital map
is a key element in a positioning system for safety-critical applications.

2. State of the art

Train location is of main use in signalling applications. In Europe, the train position is traditionally
processed with the help of equipment on tracks. The typical equipment is a track circuit, i.e. a
simple electrical device used to detect the presence of a train on rail tracks. This equipment is
thus not devoted to locating the train specifically but to locating it indirectly on a track portion.
The location can also be determined with the help of detectors placed along the track, on which
the train protection relies. These sensors can be transponders (Balises), which communicate with
the train on-board equipment when the train runs over them. In order to harmonize European
solutions, Europe has developed the European Train Control System (ETCS) for the signalling,
control and train protection. In levels 1 and 2 of ETCS, a Balise or a group of Balises is installed
on tracks to give a passing train a position reference. The Balise initializes the odometer, and the
train position is computed by the odometer as a distance run since the last relevant Balise group.
The system composed of a Balise and odometer computes the position of the train interfaced
with the EVC (European Vital Computer) train-borne subsystem (cf. figure 1). In level 3 of ETCS,
the train location shall be sent by the train itself to the ground [UNISIG SUB026]. No line side
signals will be required for delivering movement authorities. All information will be exchanged
between the ETCS on-board system and the Radio Block Center (RBC) trackside system through
mobile networks. Two main pieces of information are communicated by the train to the RBC: its
location and the confirmation that the train did not lose any wagon (train integrity). Fig. 1 shows
the generic structure of the onboard train control system.

Figure 1: Overview of current setup of the localisation in the on-board train control

150 360.revista de alta velocidad