Recovery analysis of supervisory control of discrete event systems

The Ramadge-Wonham (RW) framework for designing a supervisory controller for a given plant and user specification, has been widely addressed by many researchers. The framework accepts a generator (or plant model), G, and a specification (or imposed constraint on the plant), H, and generates the supervisory controller, S. It assumes that plant is known and deterministic. However, in many practical cases the designer is not completely aware of the real generator G_R. In this paper the above assumption is removed. It is assumed that G is not fully known. Using the available G and the user specification H, the RW procedure is applied to a supervisor S. Then the family of (real) generators, {G_R}, which can be supervised under S while satisfying the specification H is introduced and different cases are discussed. We establish the mathematical framework for one of the cases where some events originally controllable become uncontrollable or vice versa. It is argued that the complement of {G_R} which violates the specification H can be partially synthesized by available recovery and diagnosis techniques in RW literature if the violation is already known. Otherwise the violated specification must be handled in run time.