Fault-tolerant control for safety of discrete event systems

This paper considers fault-tolerant control that ensures the safety of a discrete event system. We consider multiple faulty modes. Each faulty mode is modeled by an automaton. These automata, together with the automaton modeling the normal mode, describe a discrete event system with faults. Each faulty mode has some illegal states that must be avoided by control so that the fault can be tolerated. We assume that fault-tolerant control will take action (disablements) only when the occurrence of a fault is certain. We consider both full event observation and partial event observation. We derive necessary and sufficient conditions for the existence of fault-tolerant control. We also provide formula and algorithm to calculate control actions if the necessary and sufficient conditions are satisfied. Both offline control synthesis (for full event observation) and online control synthesis (for partial event observation) are investigated.