Research And Development Of Time Synchronization Subsystem For Urban Rail Transit

The clock system is an important part of urban rail transit system, with the deepeningapplication of network in urban rail transit system and the increasing traffic density.It putsforward new requirements on clock system for urban rail transit, while the traditional timesynchronization methods have a lot of problems. At present network time protocol (NTP) hasdeveloped into the mainstream technology of internet time synchronization. Through theanalysis of network structure and the characteristics of operation and scheduling commandtask of urban rail transit system, adopting the method combined GPS and the NTP to achieveclock synchronization.The thesis designs a NTP time server and time synchronizationsoftware for client.The clock system using the NTP work principles, communication mode,data format, and related algorithms, etc. It enhances the precision of time synchronization, theclock system can meet the requirements of time synchronization for each subsystems in urbanrail transit system.Through the analysis and comparison of the methods to implement the NTP server, theARM9microprocessor and related hardware modules are adopted to develop the NTP timeserver. Designing and implementation of hardware and software are based on the requirementand analysis of the system. The main work of the hardware part includes designing hardwareprinciple diagram for server, selection of hardware devices, and designing circuits of eachmodules in detail. The software designing and implementation are based on the hardwaredesigning, the software part is composed by operating system for embedded server anddedicated time synchronization software, this designing transplants the embedded Linuxoperating system in embedded development board, and states the migration process in detail.The server software is developed by the cross compiler development environment using Clanguage, and describes the process of establishment of a cross compiling environment andsoftware implementation in detail.Finally,VC++6.0tool is used to develop a time synchronization software for Windowsclients, the main work to develop the client software includes data encapsulation according tothe definition of NTP data format, network socket is used to implement accepting and sendingof NTP packages, the correlation algorithms are used to synchronize the client time, andrealization process and key technology are given in detail. Finally, the developed embeddedLinux NTP time server and client software are tested in LAN and WAN, and the test datas areanalyzed.