Study On Train Navigation And Positioning Based On GPS/BeiDou

Global Navigation Satellite System (GNSS) can provide real-time, accurate information about position for the users, and the industry of satellite navigation and positioning as represented by GPS has been widely used in train positioning.BeiDou Navigation Satellite System is a satellite positioning system which is independently developed by China.The construction and development of BeiDou system will have an important impact on methods of train positioning in China. In order to meet the urgent needs of real-time and precise train positioning for the train control system, enhancing the positioning accuracy and reliability of train positioning based on Beidou satellite system has practical significance. According to the theory of train positioning based on GNSS, this article make an intensive study of the train positioning technology based on GPS and Beidou system.The main work is summarized as follows:(1)Expore the mathematical model of GPS intermediate-frequency signals and simulate the generation of digital intermediate-frequency signal by MATLAB; Implement the acquisition of GPS intermediate frequency signal by the method of parallel acquisition; According to the principle and implementation method of carrier tracking loop and code tracking loop, study on the third-order phase lock loop in dynamic environment, simulate and implement the GPS frequency hopping and ramp tracking.(2)Considering the features of the BeiDou triple frequency carrier, combinations of the BeiDou triple frequency are explored.Choose the optimal combination of observations and use Beidou satellite triple frequency data to implement cycle slip detection and correction by the method of BeiDou triple frequency phase conbinations less pseudorange cycle slip detection.In oder to reduce the measurement noise fastly,add a weight factor into the BeiDou carrier phase smoothing pseudorange algorithm,and calculate the optimal weight factors of different smoothing epoch.(3)Analysis the method of unifying the coordination and time system in GPS/Beidou dual-mode positioning. According to priciple and mathematical model of the GPS/Beidou dual-mode positioning system, explore the GPS/Beidou dual-mode point positioning algorithm, increase the positioning satellite signals, enhance the positioning reliability and precision, and reduce the reliance on a single system. Use the weighted GPS/Beidou dual-mode positioning to reduce the impaction of satellite signal with poor quality on the positioning result, enhance the precision of train positioning based on GPS/Beidou dual-mode positioning.