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.

Estimation and Verification of Partially Observed Discrete‐Event Systems

“…Another related topic in the static observation setting is the robust state estimation problem when the observation is unreliable. This problem has been investigated in the context of detectability analysis [113], diagnosability anlaysis [15,16,97,100] and supervisory control [1,52,65,79,105,114] for partially-observed DES.…”

Diagnosability of intermittent sensor faults in discrete event systems

“…Differently from the works in [8], [9], [10], [11], in this paper, we are not proposing a system that can cope with sensor faults but a system that actually detects sensor malfunction. In order to do so, we modify a previously introduced model of loss of observations [10] to consider only sensor malfunction, and convert the problem of detecting intermittent sensor faults into a problem of diagnosing intermittent faults similar to that proposed in [12].…”

“…Sensor faults have already been addressed in the context of supervisory control [8], [9], and as part of the design requirements of fault diagnosing systems [10], [11] -in the latters, the resulting diagnosing systems are said to be robust against intermittent and permanent loss of observations, respectively. Differently from the works in [8], [9], [10], [11], in this paper, we are not proposing a system that can cope with sensor faults but a system that actually detects sensor malfunction.…”

Diagnosability of discrete event systems subject to permanent sensor failures

“…In Rohloff (2005), Sánchez and Montoya (2006), Rohloff (2012), a situation where a certain observable event becomes unobservable due to a permanent sensor failure was dealt with. In Ushio and Takai (2009), Xu and Kumar (2009), supervisory * Corresponding author.…”