The Research Of System Safety Modeling And Cross Verification

People are living in a world made up of systems and risks. Along with constant development of science and technology, especially gallop of computer and electronic techniques, modern systems, including aerospace, nuclear power stations and high-speed railways, have become enhanced in performance, increasingly complex in structures and higher in costs. Once accidents occur, serious casualties, property damage and environmental damage might be caused. Therefore, it is all the more necessary to analyze system safety.Through safety analysis, hazards can be recognized, eliminated, controlled or recorded.With hazards restricted to the acceptable range, serious losses caused by potential accidents can be avoided. Functional Hazard Analysis(FHA) and Preliminary Hazard Analysis(PHA)are top choices for the early-period safety analysis. However, both call for a collection,processing and feedback of a large quantity of data, materials and information. Without computer-aided tools, a huge amount of labor input is required and some work might be done repeatedly. Worse still, due to lack of personnel experiences, negligence of artificial analysis and limit of human bran's processing of mass data, omission or errors might be caused.To solve the problem of easy to ignore hazard and its control in traditional PHA and FHA, and the problem of easy to make mistake and lack of effectiveness, this paper research a method of cross verification with a designed and developed visual tool of automatic modeling and analysis to system safety. And using this tool applies to the system with typical security requirement.This paper first introduces development status and trend of system safety both at home and abroad. Second, concepts related to system safety are illustrated. Third, FHA, PHA and cross-verification are expounded. From the perspective of functions and hazards, safety of the whole system is analyzed so as to avoid or reduce hazards, improve functions, fully control hazards and increase system safety and reliability. Fourth, according to the above research content, a tool for system safety analysis and cross- verification is realized. The tool can support visualized and graphic functional structure modeling; FHA and summary;PHA modeling, analysis and summary; independent verification; cross-verification; hazard database, and other functions. At last, the tool is used for safety analysis and verification of the aircraft landing gear system.Results suggest that automatic modeling, analysis and cross-verification from theperspective of FHA that based on functional analysis and PHA that based on hazard analysis can help solve omission incurred by the traditional one-way analysis and achieve the goal of chasing leaks and making up gaps. Besides, the tool designed in this paper boasts a favorable human-computer interaction interface and convenient graphic modeling. It can improve system safety modeling and analysis capability as well as working efficiency, and realize reuse of models and analytical results.