Tolerating intermittent faults in input/state asynchronous sequential machines with a bounded delay

We address fault diagnosis and tolerance in dynamics of asynchronous sequential machines based on corrective control theory. The controlled asynchronous machine has input/state type where the present state is given as the output value. We consider a kind of intermittent faults that cause unauthorized state transitions to the machine, and that persist for finite time after the initial occurrence. Not only does the machine's stable reachability decrease as a result of the fault occurrence, but also immediate state recovery is made impossible. We examine the existence condition and design algorithm for a corrective controller that tolerates the adverse effect of intermittent faults with degraded performance, that is, the closed-loop system regains the normal behavior within a bounded delay. Through an illustrative example, we demonstrate the proposed fault tolerant control methodology.