Integrated GNSS with different accuracy of track database for safety-critical railway control systems

摘要

The primary object of this research is to test and to assess a tightly coupled GNSS and railway track data system for railway applications. One of the key features of this system is its ability to take into account uncertainties in both GPS observables and the spatial railway network data. Since trains travel on pre-defined fixed routes, 3-D positioning becomes a 1-D positioning problem that fixes the position of the train along the track. The spatial railway network database is then used to estimate the other two coordinates. In this way, the accuracy of the railway network database is crucial for the integrated positioning system. Unfortunately, the necessary accuracy of the railway network database is not known. Additionally, the integrity and availability performance of GNSS-based train location system are also essential for the safety-critical railway control systems. The required navigation performances (RNP) for the safety-critical railway applications in terms of accuracy, integrity and availability are investigated. We test different accuracies of the track database for the integrated system. Based on the result, when the GPS is integrated with the track database, the accuracy, integrity and availability are improved. The higher the accuracy of the track database, the better the positioning accuracy is guaranteed. For the integrity and availability performance, the result shows that the medium accuracy of the track database is more cost-effective for the integrated system.