Research On Train Safety Location Method In CBTC System

For the rail transportation system, the main goals are safety and efficiency. In Communication Based Train Control (CBTC) system, the safe and accurate location of the train is the precondition to ensure the train run safely and efficiently.The train location subsystem is very important in train operation control system. The basic function of the train location subsystem is to precisely determine the position of the train, including the safety related train space, speed and acceleration any time, any where.Firstly, this paper searches for the methods of calculating safety location of the train according to the CBTC system characterized with the train's self-localization and train-wayside bidirectional, great capability wireless communication. Secondly, the train's position error is analyzed. Lastly, the rationality of this method is proved by using empirical test.On the whole, this paper proposes the definition and methods of calculating train's safety location. In addition, by analyzing the characteristics of the train's running, position error and the delay of train-wayside communication, the components of safety profile is designed, which refers to the distance added to the non-safety location in order to ensure the safety of the train. Further, the paper focuses on analyzing the main component of the safety profile- position error. It is pointed out that the slip and slide of train are the key factors leading to position errors in the train location system on the basis of speed sensor and odometer. Moreover, this paper summarizes the reasons of slip and slide as well as the controlling strategies and at the same time discusses the detection methods and the error compensation. Then by setting up mathematical model which researches the relationship between the train's position error and the detection threshold of slip and slide, the optimal detection threshold is founded in which the position error is minimized.Finally, this paper improves and simplifies the safety profile according to both the theoretical analysis and the real needs of CBTC project. Furthermore, the calculation methods of safety location are put up by computer programming and the rationality of this calculation method is proved through empirical test in which the data verifies the balance between the train safety and the system efficiency.