Research On Safety Communication Network Of Railway Section Distributed Track-side Signal Control System

With the development of communication technology and computer network, railway communication network is also closely following the pace of development, using many new technologies. Among them, safety communication network of the railway section distributed track-side signal control system is a typical application of new technologies in railway communication system. The system can achieve real-time monitor and distributed control for the signal devices(signal and track-circuit) in the railway section. At the same time, it can grasp the status of signal devices and can ensure train safety and efficient operation. Because the railway signaling system is a safety-critical system, the safety and reliability of the communication network plays an important role in the railway communication safety.The structure of railway section distributed track-side signal control system is similar to the all-electronic computer interlocking system. The system consists of monitoring layer, logic control layer, track-side execution units, field devices layer and track-side safety communication network. Monitoring layer achieves human-computer interaction. Logic control layer achieves a variety of control logic operation. Track-side execution units achieve control and state acquisition of field signal devices. Track-side safety communication network can achieve reliability, real-time and safety of transmit information between field devices and monitoring layer. Therefore, the safety communication network is the most critical part in the railway section distributed track-side signal control system. This thesis is based on the new communication technologies and the structure of railway section distributed track-side signal control system, combined with network communication technology, distributed control technology and optical-fiber communication technology, proposes a novel reliable track-side safety communication network. In other words, the network is used optical-fiber in place of the signal cable as the communication medium and the thesis establishes a reliable optical-fiber communication network.Firstly, this thesis introduces the application status of track-side execution units and railway communication network, analyzes the functional requirements and main transport information of railway section distributed track-side signal control system, designs the overall structure of the system and track-side safety communication network topology. Then, this thesis designs the hardware and software of communication interface converter module in the track-side communication unit. The module includes Ethernet-optical-fiber communication converter module and optical-fiber-CAN communication converter module. Among them, the former is based on FPGA and the latter is based on AT90CAN128 and FPGA. According to information transmission requirements of reliability, real-time, safety and some advantages of optical-fiber communication technology, the communication network between the track-side execution units and the control host was designed the optical-fiber communication network structure with self-healing and double-loop redundancy. In addition, on the basis of the overall structure of safety communication protocol and HDLC communication protocol, the safety communication protocol was designed and its safety was analyzed. Finally, this thesis tests safety communication network according to the PING program and debugs the track-side communication unit. The test results show that track-side safety communication network has higher reliability and safety compared with the traditional communication network. And the electronic control units which are placed the track-side next to the field signal devices constitute the track-side execution units and can realize distributed control. The track-side execution units not only reduce the amount of signal cable, but also conducive to distributed remote control the field devices and can better reflect the running state of the field devices.