GNSS-based Enhanced Odometry for Rail
Background & Objectives
A number of train protection systems rely on speed control at singular spots along the track (end of sections, points, stations, etc). In ERTMS, train protection is based on the knowledge of train position with respect to a spot to be protected and the supervision of a braking curve. The spots to be protected are referred with respect to balises located on the track. This system implies the need for odometric systems providing current position and speed. One of the traditional odometry systems more widely used calculates the train speed from the number of turns of a wheel of the train with corrective mechanisms for avoiding slide and slip phenomena. The aim of the additional GNSS Enhanced Odometry Subsystem is to support the odometry with accurate position and speed. The GNSS Enhanced Odometry Subsystem could be used as a substitute for / complement of the current odometer sensors (tachometers, INS, Doppler radar etc.) in the ETCS odometry.
The objective of GRAIL-2 is to define, develop and validate a GNSS based ETCS application in High Speed Railway Lines. Starting from the work done in the GRAIL Project, GRAIL-2 goes further in the implementation and testing of this application so that a real validation of the application against user needs can be performed, thus achieving a system closer to a final product. The proposed system is based on Enhanced Odometry (EO), in a context of High Speed Lines (HSL). The expected improvement of the Enhanced ETCS Odometry is the overall improvement of Train Location accuracy (reduction in safety distances and tolerances). Operational benefits may also be derived from the increase of the location confidence. The focus of the project will be in the following features: - Validation of the system in a real environment, bringing the prototype closer to a product. - Going further in the safety demonstration compatible with a future certification process, following rail practices.
The main objectives of this project are: - Definition of user and system requirements. From the work done in GRAIL requirements for the system components shall be reviewed, adapted and completed. - Development of a GNSS-based EO system prototype. - Validation of the prototype by means of an extensive test campaign. The focus of the test campaign is put on the demonstration that the required functionality and performances are met. - Demonstration that the safety requirements for the application can be met by the system, by means of simulation, testing, modelling, etc. - Roadmap towards certification.
Work performed & results
The project is aimed at testing, validating and approaching the certification of a GNSS subsystem that acts as an additional sensor to the ETCS Odometry to solve existing odometry problems in current high speed lines where ERTMS is already operational. The project will make significant progress in: - Defining the adequate solutions in order to achieve the required performance and safety levels - Carrying out an extensive test campaign. The validation process to be undertaken in GRAIL-2 would not be limited to the comparison between the test results and the system requirements (design validation). A complete validation process in compliance with CENELEC EN50126 norm and in close relationship with the safety activities in the project would be applied. This would be carried out in a real environment. - Carrying out a safety demonstration activity, commensurable with CENELEC process for a safety case and in parallel an independent ISA activity. From a technological point of view, the main innovations of GRAIL-2 project include: - Development of the GRAIL-2 User Terminal and its interface to the onboard ETCS equipment via PROFIBUS (development of functional, physical requirements?). - Development of the ETCS OBU adapted to the new functions.