Monitoring and control of centralized and decentralized partially-observed discrete-event systems

Centralized and decentralized monitoring and control of discrete-event systems under partial observation are considered.; For the centralized control problem, algorithms computing supremal sublanguages developed in the context of supervisory control theory are revisited and a new algorithm providing an uniform tool for computing supremal sublanguages is developed. The problem of verifying the property of diagnosability is considered in the context of centralized monitoring. A new polynomial time algorithm for deciding diagnosability is presented. We also consider the problem of finding an observable event set with minimum cardinality with respect to three properties: diagnosability, normality, and observability. We prove that these search problems are computationally hard by showing that the corresponding decision problems are NP-complete.; We consider a generalized form of the conventional decentralized control architecture for discrete-event systems where the control actions of a set of supervisors can be “fused” using both union and intersection of enabled events. Namely, the supervisors agree a priori, on choosing “fusion by union” for certain controllable events and “fusion by intersection” for certain other controllable events. We show that under this architecture, a larger class of languages can be achieved than before since a relaxed version of the notion of co-observability appears in the necessary and sufficient conditions for the existence of supervisors. The computational complexity of verifying these new conditions is studied. A method of partitioning the controllable events between “fusion by union” and “fusion by intersection” is presented. The algebraic properties of co-observability in the context of this architecture are presented. We show that appropriate combinations of fusion rules with corresponding decoupled local decision rules guarantee the safety of the closed-loop behavior with respect to a given specification that is not co-observable. We characterize an “optimal” combination of fusion rules among those combinations guaranteeing the safety of the closed-loop behavior. In addition, a simple supervisor synthesis technique generating the infimal prefix-closed controllable and co-observable superlanguage is presented.; Finally, we consider a decentralized control architecture for discrete-event systems where local supervisors are allowed to change dynamically the manner in which their local decisions are combined globally. This is done by employing dynamic default decisions regarding the enablement of controllable events. In the general architecture, this default was fixed a priori and remained constant throughout the operation of the system. We show that under dynamic decision fusion rules that result from dynamic default decisions, a larger class of languages can be achieved as compared with architectures with static fusion rules. A dynamic version of the notion of co-observability appears in the necessary and sufficient conditions for the existence of supervisors in the new architecture. Dynamic co-observability relaxes (static) co-observability. The existence of a set of local dynamic default decision rules that ensures dynamic co-observability can be decided in polynomial time. A constructive methodology for updating dynamically default decisions for the enablement of controllable events is developed.