Research On Subway Train Approach Warning System

With the rapid development of urban railway systems, railway transportation safety has drawn extensive attention across the society. For the purpose of operation safety, railway train automatic control system serves as the major anti-collision measure in present world. Current on-board control equipment for railway trains is only capable of obtaining the current railway track information through the ground devices. If ground devices failure, resulting in fatal train-to-train collision accidents. With the purpose of avoiding such train collisions, the approach warning system is introduced in this thesis, which enables the direct communication between moving trains.The thesis introduced a general design scheme for train approach warning system, of which the functions are achieved through precise positioning technology and wireless radio communication. The composition of this system includes four subsystems which are the positioning, the wireless communication, the information processing and the power subsystems. The thesis presented the system algorithm of train positioning, stated the solution of common question of channel interference during information interchange, defined the wireless communication protocols and detailed the design for the hardware and software of the system.Information processing subsystem is the core of the system hardware and software design. It has implemented the acquisition of positioning subsystem acceleration signal, the reception of the transponder reader signal, receiving and sending messages of wireless communications subsystem, and system storage function, displaying and warning functions. System software includes positioning, wireless communication, storage, display and warning functions and security procedures for continuous reliable operation. Positioning and storage subroutines are difficulties in system software design. In the thesis, we described positioning program and microcontroller-based SD card FAT file system migration in detail.Finally, in order to verify the reliability of the system, the system has experimented four kinds of experiments, including test accelerometer positioning experiments in the car and subway, transponder correcting positioning experiment in the car on the road, wireless communications experiment on the ground and underground, simulated tracking experiment in the environment of highway. The results showed that the positioning accuracy of the system was less than20m. The wireless communication was reliable within one kilometer range on the ground, and also within700m range under no right-angle turn on the underground. The tracking simulation experiments on the road verified the feasibility of the system. Alarm function can be realized to achieve the desired requirements.