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.