Title: Risk informed approach for complex safety-critical digital application development
Abstract:Safety-critical applications should be designed with a multiple-redundancy, highly reliable components, strengthened monitoring mechanisms, and well-verified software. These features are focusing on m...Safety-critical applications should be designed with a multiple-redundancy, highly reliable components, strengthened monitoring mechanisms, and well-verified software. These features are focusing on maintaining the capability to perform the given safety function when a demand arrives. Probabilistic safety assessment (PSA) is expected to provide useful tools for balancing the safety, performance and cost aspects since it provides information on a system under design. Thanks to its design flexibility, a digital system is one of the most suitable candidates for risk-informed design (RID) of which the main goal is a reduction of system unavailability in a balanced manner. On the other hand, this greater flexibility implies a higher ambiguity in design. In order to provide information for decision making, PSA will play a very important role. However, a repeated PSA analysis for every design change is impractical. This study aims to suggest a more convenient frame for the RID procedure for digital systems even though it is not sophisticated enough at present. The safety-critical functions of the digital I and C system could be defined as: Generating an automatic actuation signal and providing information to a human operator. A high redundancy would clearly reduce the risk from the single failure of components,more » but raise the importance of a common cause failure (CCF) and a dependency analysis. It is also notable that the operator performance largely depends on the information supplied by information processing system. The proposed procedure could be summarized by the following steps: - Derive the dominant risk contributors and their correlation with system unavailability - Determine the design factors whose characteristics is related to the dominant contributors - Develop an unavailability equation whose variables are design factors The PSA events are hard to understand for design staffs, so these events should be interpreted to the design factors which are more familiar to designers. Some of these relationships will be linear but others might be nonlinear. Therefore, the third step should be highlighted in the proposed procedure. In order to perform this step, a careful investigation of the target system and the PSA methodologies is required. (authors)« lessRead More
Publication Year: 2006
Publication Date: 2006-07-01
Language: en
Type: article
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