Research On System Safety Modeling And Analysis Based On Four-variable Model

In recent years, with the rapid incerase of the complexity of the embedded system and the rapid enlargement scale of the system software, to ensure the safety and reliability of embedded systems and software is a major challenge in the field of safety critical systems engineering(such as nuclear power plants, aerospace, transportation, etc.). Thus, the safety analysis and verification of the system is very important in the field of safety critical systems engineering. At the same time, system safety analysis and verification method based on model has become a mainstream method in the field of embedded safety critical systems engineering. In the process of safety analysis and verification based on the model of the system, how to carry on the requirement analysis of the system and design the model according to the requirement result is an important problem in the analysis and research of the embedded safety critical systems.The main work of this paper is to study the safety analysis of the model based on the system requirements and design level respectively, propose a system safety modeling and analysis method base on the four-variable model, based on the requirement analysis of the system by using the four-variable model, the AltaRica model is carried out by using the AltaRica modeling language, and study the problem of how to transform from the four-variable requirement model to the AltaRica design model. The details are listed as follows:(1) According to the problem of system safety modeling in thesystem requirementanalysis level and system design level, it mainly studies the four-variable model and AltaRica modeling language. In thesystem requirement analysis level, we analyze the structure of the four variables and the four types of relations in the four-variable model, and combined with the SCR requirement analysis method tostudy the formal semantics of the four-variable model method. In the system design level, we analyze the AltaRica modeling language, including the basic syntax structure of AltaRica, semantic features and formal semantics defined by the guarded transition system.(2) Aming at the transition between system requirement and design models, this paper studies the semantic mapping rules between the four-variable model and the AltaRica model. Based on the formal semantics of the two to construct the semantic mapping, including the mapping between the four kinds of variables withthe flow variables and state variables of AltaRica, and the mapping between the four kinds of relations with the assertion structure of AltaRica. Based on the mapping rules, we can carry out the transition from the four-variable requirement model to AltaRica design model.(3) Design a safety analysis framework from the system requirement analysis to the model design. First, the requirement analysis of the system is carried out by using the four-variable model. Next,based on the semantic mapping rules between the four-variable model and the AltaRica model, using the AltaRica modeling language to design the system model, and construct the system safety attributes based on AltaRica rules. Finally, the safety analysis and verification of the model are carried out.(4) Givean example ofsafety analysis of the aircraft wheel brake system based on the above method, including the construct of the four-variable model, design AltaRica model according to therules of semantic mapping between the four-variable model and the AltaRica model, build the fault tree based on the AltaRica model, analyze the system safety, varify the safety attributes and so on.