Research And Implementation Of GPS Aided Train Integrity Monitoring Algorithm

In low cost train control system, the train positioning can not rely on the track circuit. Train integrity monitoring as a part of the system plays an important role of ensuring the train safety. GPS (Global Positioning System)is widely used for its good performance, high precision and low cost in the field of transportation, mapping, military and so on. Applying GPS to Train Integrity Monitoring is a new direction of research.Conventionally at least 4 visible satellites are required and certain combination of visible satellites is chosen to obtain GPS fix. In the process of train integrity monitoring, the availability and accuracy of GPS-based systems can be degraded due to blocking of the satellite signals at the end of the train which lead to incomplete condition(less than four satellites are visible) and the GPS solution is invalid using conventional methods. A method of train integrity monitoring aided by GPS position with three satellites in incomplete condition is proposed in the thesis. The key technology is the positioning algorithm only using three satellites in incomplete condition. Based on the theory of coordinate transformation in topocentric terrestrial coordinate system, the coordinates of the end of train and observed satellites can be projected onto plane of coordinate with the origin at the head of train. The theory achieves a new mode of positioning with three satellites on plane which is different from the conventional mode of positioning with four satellites in space. When more than 3 satellites are visible, positioning data of different combination of satellites are processed by the method of residual error, the result which is the coordinate of the end is applied to calculate related position between head and end in order to monitor train integrity. Writer design and implement simulation software for the algorithm of train integrity monitoring.Detailed mathematical positioning algorithms are deduced in this thesis. In the end, an experiment has been carried out to verify the algorithms. The accuracy of the positioning algorithms can meet the requirement of train integrity monitoring.