Design Of A Safety-Critical Computer System For Urban Rail Transit Signaling System

The pressure of urban railway system is on the rise because of the more and more urban population. As to improve the train speed and line operational efficiency, Communication-Based Train Control system(CBTC) has been the main development tendency of urban rail transit. The performance of the safety-critical computer as the core of CBTC system is directly related to the performance of the whole system. CBTC is a safety-critical system. Once suffering failure, not only economic loss will be resulted, but also the personal safety may be endangered. Therefore, the safety-critical computer must be safe and reliable. On the other hand, the computer must be more powerful because of the increasing traffic pressure. This paper proposes a new architecture of double two out of two safety-critical computer with high performance, in order to meet the demands of signal system of urban rail.Firstly, this paper introduces the standards at home and abroad which are related to safety-critical computer in the field of urban rail transit, and gets the safety and reliability requirements of safety-critical computer.Secondly, the paper introduces the common design method of safety-critical computer, such as evading technology, fault-tolerant technology, fail-safe technology and so on. Then the performance of the three structures of safety-critical computer,which are "hot standby","two out of three" and "double two out of two ", is compared. And double two out of two structure has been taken as the basis of the overall structure of the safety-critical computer system.Thirdly, the system architecture is designed based on the double two out of two structure. The bus of the system is determined and the advantages of the system are showed. Then, the system is designed with modular division. A detailed description of the implementation of the modules is given in this paper.Finally, the reliability analysis software of Isograph is used to analysis the safety and reliability of the new safety-critical computer, and the result shows that the new computer meets the demands of the signal system of urban rail. Then the system function is tested. The performance is also tested in the simulation environment. The result shows that the new safety-critical computer delivers superior performance.A new implementation of safety-critical computer with high performance is given in this paper, and it should be useful to the researchers and engineers.