Study On Train Positioning Methods Based On BeiDou Satellite System

ABSTRACT:Train Control System need reliable and high-precision real time of train location to achieve high efficiency and safety in the train operation. The construction of the BeiDou system will have an important impact on methods of train positioning in China, however, BeiDou satellite train positioning should mainly focus on how to improve the precision and reliability of the positioning results. Based on the BeiDou positioning principle, the dissertation proposed algorithms of BeiDou train positioning. The main contributions and innovation are as follows:(1) Considering the features of the BeiDou triple frequency carrier, combinations of the BeiDou triple frequency satellite carrier phase are explored and the ionosphere residual combined methods are proposed to reduce the impacts of ionosphere residuals. BeiDou triple frequency Ionosphere-Free Geometry-Free combination, and carrier phase hardware delay model is established, the method of rapid estimation for the deviation of the BeiDou receiver carrier phase hardware delay are proposed to effectively eliminate the carrier phase combinations deviation.(2) As the BeiDou satellite carrier phase is affected by observation error, receiver clock jumps and nonlinear error, three methods of cycle slip detection are proposed. The method of BeiDou triple frequency phase combinations less pseudorange cycle slip detection reduced the influence of pseudorange measurement error and enhanced the resolution cycle slip detection. The method of multiple observation equations fusion applied in cycle slip detection, fused with the detection results of multiple combined observation equations by adaptive kalman filter, along with the single frequency supplying high precision and multi-frequency combination distinguishing clock jumps, improved the precision of the cycle slip detection. The method of adaptive particle filter applied in cycle slip detection by real time updating filter model coefficients, enhanced accuracy of the nonlinear carrier phase observation equation cycle slip detection, coupled with characteristics of simpler initialization and faster convergence.(3) BeiDou high-precision point positioning algorithm is put forward to meet the demand for train positioning precision. On account of the high precision of carrier BeiDou satellite phase and no ambiguity of pseudorange, the pseudo-range measurement noise is reduced and the ionosphere delay is eliminated by dual frequency carrier phase smoothing pseudo-range algorithm. The BeiDou satellite Difference Code Bias(DCB) model is estimated and all kinds of errors are removed, which ultimately improve the precision of BeiDou point positioning.(4) BeiDou/GPS dual-mode point positioning algorithm is proposed to insure the high reliability of train positioning technology. BeiDou/GPS dual-mode positioning increases satellite data redundancy, improves the spatial geometry of visible satellites. The integrity monitoring algorithm can remove the failed satellites effectively and finally enhances the reliability of the positioning results.The theory and algorithms put forward in the dissertation are proved by the calculation of the raw data obtained from BeiDou and GPS satellites, can effectively improve the accuracy and reliability of BeiDou train positioning.