Assessment of redundant systems with imperfect coverage by means of binary decision diagrams

In this article, we study the assessment of the reliability of redundant systems with imperfect fault coverage. We term fault coverage the ability of a system to isolate and correctly accommodate failures of redundant elements. For highly reliable systems, such as avionic and space systems, fault coverage is in general imperfect and has a significant impact on system reliability. We review here the different models of imperfect fault coverage. We propose efficient algorithms to assess them separately (as k-out-of-n selectors). We show how to implement these algorithms into a Binary Decision Diagrams engine. Finally, we report experimental results on real life test cases that show on the one hand the importance imperfect coverage and on the other hand the efficiency of the proposed approach.