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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)
This paper presents an approach for functionally dealing with multiple tasks in the supervisory control of discrete-event systems (DES). The colored marking generator (CMG), a special type of Moore automaton, is introduced as a model that distinguishes classes of tasks in DES. The main results of supervisory control theory are extended to this model,(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)