Fault Diagnosis in Finite-State Automata and Timed Discrete-Event Systems

In this paper, we propose a framework for fault diagnosis in discreteevent systems. In this approach, the system and the diagnoser (the fault detection system) do not have to be initialized at the same time. Furthermore, no information about the state or even the condition (failure status) of the system before the initiation of diagnosis is required. First, a state-based approach for on-line passive fault diagnosis in finitestate automata is presented. The design of the fault detection system, in the worst case, has exponential time complexity. A model reduction scheme with polynomial time complexity is introduced to reduce the computational complexity of the design. Next we consider the use of timing information to improve the accuracy of diagnosis. Instead of directly extending our framework to timed discrete-event systems, we take an alternative apporach which leads to significant reduction in on-line computing power requirements and, in many cases, in the size of the diagnoser at t..