Probabilistic Fault Detection in Finite-State Machines Based on State Occupancy Measurements1

This paper discusses a probabilistic methodology for detecting permanent or transient functional changes in the statetransition mechanism of a deterministic finite-state machine (FSM). The associated detector observes the frequencies with which states are occupied and detects faults by analyzing the deviation between the expected frequencies and the actual measurements. In addition to state occupancy measurements, the detector requires a statistical characterization of the input, but does not need to know the order with which states appear or the input sequence that is applied to the FSM. The discussion in the paper focuses on the case of a single fault and on the performance of the fault detector in terms of the probabilities of detection and false alarm, the number of states, and the length of the observation window.