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ISO 26262 describes a safety engineering approach in which the safety of a system is considered from the early stages of design through a process of elicitation and allocation of system safety requirements. These are expressed as automotive safety integrity levels (ASILs) at system level and are then progressively allocated to subsystems and components of the system architecture. In recent work, we have demonstrated that this process can be automated using a novel combination of model-based safety analysis and optimization metaheuristics. The approach has been implemented in the HiP-HOPS tool, and it leads to optimal economic decisions on component ASILs. In this paper, first, we discuss this earlier work and demonstrate automatic ASIL decomposition on an automotive example. Secondly, we describe an experiment where we applied two different modes of ASIL decomposition.

Failure Modes and Effects Analysis (FMEA) is a well established safety analysis technique used for the assessment of safety critical engineering systems in the automotive industry. Although FMEA has been shown to be useful, the analysis is typically restricted to the effects of single component failures; even partial analysis of combinations or sequences of multiple failures is in practice considered too complex, laborious and costly to perform. In this paper, we describe a new technique in which FMEAs are semi-automatically built from the topology of a system and component-level specifications of failure data. The proposed technique allows an extended form of “combinatorial & sequential FMEA” in which assessment of the effects of combinations and sequences of failures becomes feasible and cost effective.

Recent work in the area of safety analysis has shown that system Fault Trees and Failure Modes and Effects Analyses (FMEAs) can be automatically derived from a topological model of the system that has been annotated with local, component-level, specifications of failure. In this paper, the concept of a component failure specification is extended to enable description and reuse of generalized patterns of failure behaviour that are commonly exhibited by components. A language for the description of such patterns is specified, useful patterns are presented and the use of such patterns is demonstrated on an example of a Time-Triggered system. The paper tentatively concludes that careful reuse of failure patterns in conjunction with automated fault tree and FMEA synthesis algorithms can help to rationalize, and simplify, complex safety assessments.