A Map-aided GNSS Positioning Method of EoT (End-of-Train) Units for Train Integrity Monitoring

In recent years, the satellite-based positioning of railway trains is a very attractive technique in many safety-critical railway applications, i. e. rail signaling systems. In order to detect the presence of a train inside a block, the Train Integrity Monitoring (TIM) is required by the control center where a safe distance between it and the target preceding train is effectively updated. The cost-efficiency and autonomy capabilities of the traditional TIM solutions cannot meet the requirements in future railway systems (i. e. Next Generation Train Control systems). Therefore, the GNSS (Global Navigation Satellite System) based train integrity monitoring architecture and corresponding algorithms are attracting more attention. In this paper, a GNSS-based train integrity monitoring solution is investigated, where the GNSS is exploited to locate the rear and the front end of the train through HoT (Head-of-Train) and EoT (End-of-Train) units, and train integrity status is determined using the localization results. Due to the challenged operation conditions of EoT units, the accurate and reliable positioning of EoT units under a constrained observation environment is concentrated. The track map database and the low-cost inertial sensors are coupled in the EoT units. We investigate the improvement of the GNSS constellation and the enhanced Autonomous Receiver Integrity Monitoring (RAIM) using the virtual satellite observations. To further improve the performance of EoT positioning, inertial measurements and the track map data are coupled with a nonlinear filter. The advantage of the proposed solution is to make use of the prior knowledge of the track coordinate from the track map for improving the positioning performance of EoT units under challenged operation conditions, with which the availability and correctness of TIM could be ensured. The proposed solution is tested with field data from the Qinghai-Tibet Railway in China. The results illustrate the capability of the proposed solution and verify the positive effects from the track map database, which can provide great supports to the development and implementation of the next-generation train control systems using GNSS.