Safe Supervisory Control Under Observability Failure

Abstract

This paper discusses about supervisory control under possible loss of observability. The final goal of this work is to design a safe (avoiding disaster states) supervisory control loop structure taking into consideration the uncertainty that stems from the fact that some event(s) may turn into unobservable at some point along the normal system operation. This kind of failure may correspond to the breakdown of some plant sensor. The supervisor finally obtained is in general: a) more permissive than the supervisor obtained assuming those events as unobservable from the beginning, since at some points it shall be better informed, and b) more restrictive than the supervisor obtained assuming that those events shall never fail, since it will have to prevent the system from following some undesirable trajectories that the system could take in presence of an observability failure. This paper presents results to obtain a safe controller that avoids disaster states in presence of the described uncertainty, and also ensures that the system behaviour will not run out from its specifications in absence of failure.