Research On Dependability Of Train Integrated Positioning System

Train Real-time positioning is one of the important part of Train Control System, the integrated positioning system using GNSS and IMU is the trend of current researches. It is important to do research on the reliability, availability, maintainability and safety of the system to improve the system dependability in several ways. And it has a great significance on practice.The paper proposed a vital problem before the research on the dependability of the system. That is the system working state and the output result state of the system to find the error source of each positioning result. This has become the main part discussed in this paper.Based on the principle for designing an integrated positioning system, a 2 multiplies 2 out of 2 system with diagnostic module is proposed, and the output states are listed, several GNSS enhancement and monitoring methods are analyzed.According to the standards in railway safety application, the Markov Chain model is used to analyze the hardware structure of the sub-system in the train integrated positioning system, and gives the safety integrity level result of the whole system. And after this, the GNSS and IMU measurement errors are tested, a weighted parity vector method for calculating the protection limit is proposed, this method delivers different weights when system is in different states and calculates the error in real time.A set of data is also collected in the Qing-Tibet railway, the data is used for the algorithm to test, compare and analyze. The test result shows that the algorithm is valid, and an evaluation is made from the error estimation prospective. Finally, several suggestions are given.