A New Train Integrity Resolution Method Based on Online Carrier Phase Relative Positioning

Train integrity resolution is an important part of a train operation control system. In current train operation control systems, train integrity resolution is achieved by using information on the track circuit or the wind pressure. However, both approaches have limitations; the utilization of the track circuits requires high construction and maintenance costs, and the wind pressure approach has to overcome the problem of low update rate and false alarm caused by the incident pipe leakage. In this paper a new train integrity resolution method based on double-differenced carrier phase relative positioning is proposed. To improve the system performance, an online integer ambiguity fixing method is applied to overcome the frequent integer ambiguity re-fixing problem caused by the high train speed and the complex operational environment. Moreover, the elevation angle constraint optimal distribution based reference satellite selection method is applied to guarantee optimal satellite geometry distribution during train operation. To evaluate the performance of the proposed train integrity resolution method, a real train test was carried out on the Beijing-Shenyang high speed railway. The experimental results show that the proposed train integrity resolution method can provide train integrity solutions with an accuracy of better than 0.5 m, with STD and RMS of 0.15 m and 0.17 m respectively. Compared with the conventional GNSS single point positioning based train integrity method, the proposed method can achieve a much better performance, with an improvement, in this test, of 77%.