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This paper is an overview of the current research on hierarchical control of discrete-event systems. Four major approaches are identified and described: bottom-up design, top-down design, state aggregation, and interface-based design. The research examined is grouped into these sections, in an attempt to unify the terminology and concepts where possible(More)
| The concept of observer was introduced in previous work by the authors on a hierarchical control theory of discrete-event systems (DES). It was shown that the observer property ensures that in a two-level hierarchy the low-level implementation of a nonblocking high-level supervisor is also nonblocking. In this paper we investigate the following problem:(More)
Natural projections with the observer property have proved effective in reducing the computational complexity of nonblocking supervisory control design, and the state sizes of the resulting controllers. In this paper we present an algorithm to verify this property, or if necessary to achieve it. A natural projection is a special type of general causal(More)
A state-based approach for on-line passive fault diagnosis in systems modelled as finite-state automata is presented. In this framework, the system and the diag-noser (the fault detection system) do not have to be initialized at the same time. Fhrthermore, no information about the state or even the condition (failure status) of the system before the(More)
In this paper we present a hierarchical method that decomposes a discrete-event system (DES) into a high level subsystem which communicates with ¢ ¡ ¤ £ parallel low level subsystems through separate interfaces, which restrict the interaction of the subsystems. We first review the setting for the serial case (¦ ¥ § £) [1], and then generalize it for¨¡ © £.(More)
The time complexity of supervisory control design for a general class of problems is studied. It is shown to be very unlikely that a polynomial-time algorithm can be found when either (1) the plant is composed of m components running concurrently or (2) the set of legal behaviors is given by the intersection of n legal specifications. That is to say, in(More)