Safety and Fault-Tolerance in Computer-Controlled Railway Signalling Systems
This paper presents safety and fault-tolerance technology of railway signalling controls. First,the type of faults to be handled and the required level of safety and reliability are given. Next,two types of microcomputer architectures with hardware redundancy are shown. Safety methods for a video display unit and data transmission are also given. Fault-tolerant system structures with triple-modular-redundancy, duplex and single,which have been applied to signalling systems in JR are also described. Further, software approach to fail-safety and fault-tolerance is discussed. Field data on 4 kinds of microcomputer-controlled signalling systems are shown. Since 1985 about 650 sets of fail-safe microcomputers have been operating in JR. An endangering failure has never occurred and the safe-side failure rate up to now including an initial error period has been in the order of 10−5 to 10−6/h.
KeywordsSignalling System Redundant Structure Double Error Transient Error Operator Console
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