3,708 research outputs found
Supervisory Control Synthesis of Discrete-Event Systems using Coordination Scheme
Supervisory control of discrete-event systems with a global safety
specification and with only local supervisors is a difficult problem. For
global specifications the equivalent conditions for local control synthesis to
equal global control synthesis may not be met. This paper formulates and solves
a control synthesis problem for a generator with a global specification and
with a combination of a coordinator and local controllers. Conditional
controllability is proven to be an equivalent condition for the existence of
such a coordinated controller. A procedure to compute the least restrictive
solution is also provided in this paper and conditions are stated under which
the result of our procedure coincides with the supremal controllable
sublanguage.Comment: 29 pages, 11 figure
Observability and Decentralized Control of Fuzzy Discrete Event Systems
Fuzzy discrete event systems as a generalization of (crisp) discrete event
systems have been introduced in order that it is possible to effectively
represent uncertainty, imprecision, and vagueness arising from the dynamic of
systems. A fuzzy discrete event system has been modelled by a fuzzy automaton;
its behavior is described in terms of the fuzzy language generated by the
automaton. In this paper, we are concerned with the supervisory control problem
for fuzzy discrete event systems with partial observation. Observability,
normality, and co-observability of crisp languages are extended to fuzzy
languages. It is shown that the observability, together with controllability,
of the desired fuzzy language is a necessary and sufficient condition for the
existence of a partially observable fuzzy supervisor. When a decentralized
solution is desired, it is proved that there exist local fuzzy supervisors if
and only if the fuzzy language to be synthesized is controllable and
co-observable. Moreover, the infimal controllable and observable fuzzy
superlanguage, and the supremal controllable and normal fuzzy sublanguage are
also discussed. Simple examples are provided to illustrate the theoretical
development.Comment: 14 pages, 1 figure. to be published in the IEEE Transactions on Fuzzy
System
On Conditional Decomposability
The requirement of a language to be conditionally decomposable is imposed on
a specification language in the coordination supervisory control framework of
discrete-event systems. In this paper, we present a polynomial-time algorithm
for the verification whether a language is conditionally decomposable with
respect to given alphabets. Moreover, we also present a polynomial-time
algorithm to extend the common alphabet so that the language becomes
conditionally decomposable. A relationship of conditional decomposability to
nonblockingness of modular discrete-event systems is also discussed in this
paper in the general settings. It is shown that conditional decomposability is
a weaker condition than nonblockingness.Comment: A few minor correction
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