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This paper considers a failure diagnosis problem for discrete event systems subject to permanent sensor failures. A notion of diagnosability subject to permanent sensor failures is introduced with respect to a certain nondeterministic observation mask. For its verification, an aggregated Mealy automaton with a deterministic and state-dependent observation mask is defined. It is shown that the diagnosability of the aggregated Mealy automaton is equivalent to the diagnosability of the original system subject to permanent sensor failures. Then, a method for verifying the diagnosability of the aggregated Mealy automaton is presented. Moreover, the delay bound within which the occurrence of any failure string can be detected subject to permanent sensor failures is computed.

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No abstract

In this paper, we consider a failure diagnosis problem for discrete event systems subject to permanent sensor failures. A notion of diagnosability subject to permanent sensor failures is introduced with respect to a certain nondeterministic observation mask. For its verification, we define an aggregated Mealy automaton with a deterministic and state-dependent observation mask. We show that diagnosability of the aggregated Mealy automaton is equivalent to diagnosability of the original system subject to permanent sensor failures. Then, we present a method for verifying diagnosability of the aggregated Mealy automaton. Moreover, we synthesize a diagnoser for the original system as an online diagnoser.