Description in details:
Using satellite techniques for the train control systems is derived from a promising demand from both international and European Community markets, which are setting new priorities on the ERTMS-ETCS technology roadmap.
The adoption of new satellite techniques for the train system is carrying on much faster in Australia, USA and Russia than in Europe, where most of the demands focus on the local-regional railway lines.
GNSS localization and new telecommunication techniques are going to be introduced into the ERTMS-ETCS platform.
Five main target market areas (Australia, USA, Russia, Europe) have been identified and for each of them user requirements have been derived. A standard platform should be defined, which can be customized for each of these five target market areas.
Depending on the specific market area, three existing satellite localization systems, i.e. GPS, GLONASS and GALILEO, can be used.
The proposed general architecture of the train control and management system is shown in the following figure:
The Space Segment includes:
The User Segment includes:
The Ground Segment includes:
The function of train positioning is performed by the following elements:
The main task of the space segment is to provide reference satellite signals needed for the computation of train positions, as well as to distribute real time corrections related to satellite ephemerides, clock offsets, propagation delays and Signal in Space (SIS) integrity. Additionally the satellite segment provides communication links between trains and remote control centers. The DLR Institute of Communications and Navigation is mainly involved in the satellite communications tasks, and in the design of a direct train-to-train collision avoidance system.
One of the major objectives and final outputs of the 3InSat project is a technology demonstration in Sardinia (Italy). The objective of the technology demonstration with respect to the telecommunications (TLC) component is to gather performance indicators related to delay, jitter, effective bitrate and packet loss rate.
During this trial, two TLC architectures will be demonstrated:
The LRS networks play a role similar to the EGNOS RIM subsystem. In fact, it will be mainly deployed only on those areas out of the EGNOS footprint. In essence, processing of satellite signals received at known locations allows to estimate the error sources affecting train positioning and to detect possible GNSS faults. Compared to the actual EGNOS, the major differences consist of a denser spatial deployment of the LRSs, compensating for milder requirements (and lower cost) on the GNSS receiver clocks and the use of the wireless network employed for train signaling even for augmentation data distribution.
To enhance the capabilities of systemic satellite fault detection, as well as to detect possible faults of LRSs themselves, their outputs are jointly processed by a Track Area LDS Safety (TALS) server.
In order to reduce the probability that any Misleading Information caused by hardware/software failure would produce a dangerous situation, the Location Determination System of the on-board unit adopts a multisensor solution that combines the information provided by the GNSS LDS subsystem with localization data provided by classical Odometric subsystem, denoted as ODO LDS, that processes tachometer data as well as inertial sensor packages.
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