Research On BDS/SIMS-based Integrated Train Positioning Method

Train Positioning System plays an important part in Train Control System, and obtaining the position of the train is the prerequisite for Train Control System to make control decision. BeiDou navigation satellite system (BDS) is a global navigation satellite system that is researched and developed by our country, it’s a practical need to informationize and intelligentize Train Control System by integrating train positioning based on BDS. The operation environment of the train is very complicated, since there are tunnels and canyons that can block the sight line of the satellites, making the autonomous positioning only by BDS unable to meet the application requirements of continuity and reliability. Taking advantage of multi-sensor information, can help the Train Positioning System to provide a more precise and reliable positioning result.Firstly, the present status at home and abroad of train autonomous positioning based on GNSS is introduced. By summarizing the existing train positioning methods, a train autonomous positioning method based on the integration of BDS and SINS is proposed. Since the information for train positioning is from different onboard sensors, a time synchronization and compensation method between BDS and GNSS is proposed in this thesis in order to integrate them.BDS can provide position and velocity information, however, the accuracy of position solutions under BDS-challenged environment occasionally degrades due to the poor line of sight of the satellites. In order to solve the problem, a selective integration system of BDS, SINS and ODO using Weighted DOP is adopted. The WDOP concept is derivation as the performance index and the calculation was derived. A selective integration system architecture is designed and to verify the performance of the proposed WDOP method, and a comparative analysis is conducted with the conventional DOP and position error using collected data. It turns out that, WDOP method shows close agreement with the position error trends. The experimental results also show that, the selective integration system indicates a significant action in enhancing the positioning accuracy and obtaining reliable positioning information.When the integrated train positioning systems enters in a tunnel or canyon, degraded positioning solutions are yielded in the absence of satellite. In order to get the position of the train during BDS outages, the thesis proposed a BDS/SINS/ODO integrated system after analyzing the error model of different position subsystem and combining their advantage.Finally, a testbench of the BDS/SINS integrated system is built to evaluate the performance of the proposed positioning method. An experimental test in Qinghai-Tibet railway is also implemented. The experimental result indicates that the proposed train positioning method can provide precise and reliable solution, which meet the requirements of the Train Control System.