Research On Safety Analysis Method For Complex System Based On STPA

Several improvements were proposed in this paper for System-Theoretic Process Analysis(STPA).A more comprehensive hierarchical functional control structure was put forward;process model was extended with information flow,control law and energy supply;the categories of the unsafe control actions were refined and expanded with the combination,sequence,characteristics,interaction types for the problem of two control behaviors;the idea and method of controlling behavior feature extraction was proposed;control information dictionary and other forms of storage were established;MATLAB was used to realize the recognition of safe control behavior and the cause of that;artificial analysis was taken based on the results of computer identification,at the same time,the programs of computer identification and the process model can be improved.Finally,case analysis of the simplified function model of the aircraft braking system in the landing process was carried out to validate the feasibility of the overall STPA improved method.Meanwhile,it has been proved that the feature extraction is a kind of creative work in the improvement to the method of STPA,because a variety of functions can be realized through different custom functions based on the extracted feature,which can largely reduce the workload of manual analysis and the artificial factors of interference.