Integration of satellite positioning and a track database for safety-critical railway control systems.
Doctoral thesis, UCL (University College London).
Although Global Navigation Satellite Systems (GNSS) have been widely used in aviation, vehicle and marine navigation, and have also found non-safety railway applications (e.g. for locating trains in order to provide passengers with arrival and departure information), they still cannot be used in a standalone mode for safety critical railway applications such as automatic train control, automatic door opening or train integrity monitoring. This is because GNSS suffers from the line-of-sight problem, namely, GNSS might be unavailable when trains run through the areas with low satellite visibility (e.g. in urban canyons, deep cutting sides and tunnels). A potential solution is to integrate satellite navigation measurements with other sensors such as a track database, INS or an augmentation system. This thesis is concerned with the evaluation of the potential role of a track database for this purpose. A rigorous mathematical model for the integration of GNSS with the track database is developed. The key feature of this model is its ability to model errors in both GNSS measurements and the track database to achieve realistic performance statistics for the combined system. Knowledge of the position of the railway lines turns positioning, in principle, into a one dimensional problem. This thesis uses both simulated London area information and real railway satellite availability information from the Birmingham area to assess the improvements in Required Navigation Performance (RNP) parameters that might be obtained if railway authorities invest in a track database. The stimulation shows that the integration system improves the accuracy and increases the redundancy so that the system only needs as few as two satellites to calculate the position and accuracy, three satellites to computes the Receiver Autonomous Integrity Monitoring (RAIM) and four satellites to do the Fault Detection and Exclusion (FDE). The cost-efficient accuracy of track database and suitable RNPs are also discussed for safety-critical railway requirements.
|Title:||Integration of satellite positioning and a track database for safety-critical railway control systems|
|Additional information:||Pending digitisation|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Civil, Environmental and Geomatic Engineering|
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