Design And Implementation Of Safety Communication Protocol In Double 2-Vote-2 Safety Computer System Internal

With the development of China’s railway density, overloading, high-speed, railway signal system developed from double machine hot standby to three choose two formats, to double 2-vote-2 formats. Because double 2-vote-2 formats has some advantages,such as high safety and good reliability and low cost, it is widely used in the existing railway signaling equipment, especially in high-speed computer interlocking equipment.Based on the data medium of security information transmission in existing two stations, this paper introduces a new double 2-vote-2 safety computer system, and focuses on analyzing the issues about safety communications in this system’s inter-system and between-systems. First of all, according the basic work principles of double 2-vote-2 safety computer system, this paper introduces the building blocks and the achieved main functions. Second, this paper uses the method named seven steps of risk analysis to analysis the process of inter-system’s and between-systems’data communication. The risk analysis process starts from the main functions of this system, and uses the method of FMECA, event tree and fault tree to identify the hazard, to analysis consequences and reasons of the data communicating risk. On this basis, in order to prevent serious consequences caused by data transmission error, it is need to take measures, which protects the threats appeared in the process of inter-system’s and between-systems’data communication, such as repetition, delete, disorder, destruction and delay. The protected measures use the forward sequence number, the backward sequence number, the type code, the cycle number, the timeout mechanism, CRC check and other safety technology to design some safety communication protocol. Finally, in order to validate the validity and practicability of the safety communication protocol, simulating the process of inter-system’s and between-systems’ data communication, adding repetition, delete, disorder, destruction, delay and other threats to the sender, the receiver will check the received data whether meet features, which including the complete and order, real-time and truth.