A Failure Propagation Model Based Framework For System Safety Analysis

Safety is an ever-lasting topic for safety system in which any anomaly will result in serious damage to both life and property, as well as destruction of environment. It is therefore indispensable for the design and development of the system of this type to identify, control and trace the hazard events of the system, by means of scientific and systemic safety analysis. However, computer system, since the beginning of the 21st century, tends to coordinate computation, communication and automotive technology to construct a controllable and reliable system with a network of physical equipments. Consequently, the complexity, dynamics and hybridity of the system is increasing dramatically, such that it surpasses human beings'apprehension of the behavior and the principles for the design of the controlling computer systems, and brings about a challenge for safety analysis of the system.The thesis, on the basis of the specification of the sequence rule of the deviant behavior of the system, defines the Failure Temporal Logic (FTL) for linear time, with respect to the characterization of Safety Critical Cyber Physical System (CPS). It provides the descriptive language and qualitative solution method for Temporal-FPTN model, and a more accurate and effective analysis of the motivation for the harm of the system and the generalization of the evolution of the system. Furthermore, the present study explores the dynamic feature of the behavior and the structure of CPS, and establishes a Hierarchical Component Based Dynamic Analysis Framework (hence, HiCBD), based on Temporal-FPTN model, thus decompounding the function and structure complexity of the system, accommodating the lifecycle of the system.The innovation of the thesis is as follows:(1) The study proposes a FTL system depending on linear time which is applied to the characterization of sequential relation of deviant events, and establishes a framework for the transformation of FTL into LTL, on the basis of which a reduction rule for the formula of FTL is demonstrated.(2) The study, through the addition of the FTL system into Failure Propagation Transformation Notation (hence, FPTN), offers a description of Temporal-FPTN in advanced text, effectively avoids the constraints on the automatic analysis of the Failure Propagation Model with the vague graphics description.(3) The study, based on ZBDDs, presents a resolution method for Minimum Cut Set seQuence (MCSQ). The application of ZBDD compress the storage space for the computation of cut-set, and simultaneously increases the convergence rate of the iterative search for MCSQ.(4) The study also forms a framework of Hierarchical Component Based Dynamic Analysis (hence, HiCBD) on the basis of Temporal-FPTN, transforming the Temporal-FPTN model into a hierarchical model.The thesis ends with an accomplishment of the safety analysis of a kind of typical safety-critical CPS-CBTC system by means of HiCBD. And the MCSQ of each system level hazards has been calculated. The achievements of this study prove to be a reinforcement of the design of CBTC in China.