Schnieder, E.; Manz, H.; Müller, J. R.; Lu, D.:
Integrity Verification for the Structure of a Satellite based Train Localisation Unit by Means of Petri net.
ENC 2011 - European Navigation Conference 2011, Dezember 2011.
The Satellite based Train Localisation Unit (Salut) is an emerging and promising application for future railway signalling systems. To provide a presupposition for an implementation into a safety relevant train control system, the verification of the functional integrity in Salut is an important aspect for system safety concerns. Therefore the existing railway standards have to be obeyed by the satellite based train localisation unit applied in railways. The localisation unit facilitated by the Institute for Traffic Safety and Automation Engineering (iVA) of TU Braunschweig consists of a Global Navigation Satellite System (GNSS) receiver and an eddy current sensor, the two sensors are fused with a certifiable safety digital map. With those three independent components of Salut, the output quality can be improved significantly. To prevent failures, all sensor data have to be integrated safely. Therefore the structure of the localisation unit has to be analysed. To ensure the safe and certifiable structure of data fusion, the authors developed a Petri net based modelling approach. With this approach the behaviour of Salut can be analysed. Thus the integration possibilities are listed and a Petri net is derived, therefore the probabilities of all system states both safe and unsafe can be simulated. The structural analysis of the Petri net model makes it possible to verify the integrity of the system structure behaviour. Furthermore improvements can be achieved; better system integrity can be implemented. The example shown in the paper illustrates that integrity aspects of the system structure can be analysed, system structural faults can be eliminated by the intuitive technique.