1,511 research outputs found
Controller synthesis with very simplified linear constraints in PN model
This paper addresses the problem of forbidden states for safe Petri net
modeling discrete event systems. We present an efficient method to construct a
controller. A set of linear constraints allow forbidding the reachability of
specific states. The number of these so-called forbidden states and
consequently the number of constraints are large and lead to a large number of
control places. A systematic method for constructing very simplified controller
is offered. By using a method based on Petri nets partial invariants, maximal
permissive controllers are determined.Comment: Dependable Control of discrete Systems, Bari : Italie (2009
Feedback control logic synthesis for non safe Petri nets
This paper addresses the problem of forbidden states of non safe Petri Net
(PN) modelling discrete events systems. To prevent the forbidden states, it is
possible to use conditions or predicates associated with transitions.
Generally, there are many forbidden states, thus many complex conditions are
associated with the transitions. A new idea for computing predicates in non
safe Petri nets will be presented. Using this method, we can construct a
maximally permissive controller if it exists
Petri Games: Synthesis of Distributed Systems with Causal Memory
We present a new multiplayer game model for the interaction and the flow of
information in a distributed system. The players are tokens on a Petri net. As
long as the players move in independent parts of the net, they do not know of
each other; when they synchronize at a joint transition, each player gets
informed of the causal history of the other player. We show that for Petri
games with a single environment player and an arbitrary bounded number of
system players, deciding the existence of a safety strategy for the system
players is EXPTIME-complete.Comment: In Proceedings GandALF 2014, arXiv:1408.556
Practical Distributed Control Synthesis
Classic distributed control problems have an interesting dichotomy: they are
either trivial or undecidable. If we allow the controllers to fully
synchronize, then synthesis is trivial. In this case, controllers can
effectively act as a single controller with complete information, resulting in
a trivial control problem. But when we eliminate communication and restrict the
supervisors to locally available information, the problem becomes undecidable.
In this paper we argue in favor of a middle way. Communication is, in most
applications, expensive, and should hence be minimized. We therefore study a
solution that tries to communicate only scarcely and, while allowing
communication in order to make joint decision, favors local decisions over
joint decisions that require communication.Comment: In Proceedings INFINITY 2011, arXiv:1111.267
Similarity-Based Supervisory Control of Discrete Event Systems
Due to the appearance of uncontrollable events in discrete event systems, one
may wish to replace the behavior leading to the uncontrollability of
pre-specified language by some quite similar one. To capture this similarity,
we introduce metric to traditional supervisory control theory and generalize
the concept of original controllability to \ld-controllability, where \ld
indicates the similarity degree of two languages. A necessary and sufficient
condition for a language to be \ld-controllable is provided. We then examine
some properties of \ld-controllable languages and present an approach to
optimizing a realization.Comment: 22 pages, 5 figure
A Fuzzy Petri Nets Model for Computing With Words
Motivated by Zadeh's paradigm of computing with words rather than numbers,
several formal models of computing with words have recently been proposed.
These models are based on automata and thus are not well-suited for concurrent
computing. In this paper, we incorporate the well-known model of concurrent
computing, Petri nets, together with fuzzy set theory and thereby establish a
concurrency model of computing with words--fuzzy Petri nets for computing with
words (FPNCWs). The new feature of such fuzzy Petri nets is that the labels of
transitions are some special words modeled by fuzzy sets. By employing the
methodology of fuzzy reasoning, we give a faithful extension of an FPNCW which
makes it possible for computing with more words. The language expressiveness of
the two formal models of computing with words, fuzzy automata for computing
with words and FPNCWs, is compared as well. A few small examples are provided
to illustrate the theoretical development.Comment: double columns 14 pages, 8 figure
Petri net controllers for Generalized Mutual Exclusion Constraints with floor operators
In this paper a special type of nonlinear marking specifications called stair generalized mutual exclusion constraints (stair-GMECs) is defined. A stair-GMEC can be represented by an inequality whose left-hand is a linear combination of floor functions. Stair-GMECs have higher modeling power than classical GMECs and can model legal marking sets that cannot be defined by OR–AND GMECs. We propose two algorithms to enforce a stair-GMEC as a closed-loop net, in which the control structure is composed by a residue counter, remainder counters, and duplicate transitions. We also show that the proposed control structure is maximally permissive since it prevents all and only the illegal trajectories of a plant net. This approach can be applied to both bounded and unbounded nets. Several examples are proposed to illustrate the approach
Optimal Supervisory Control Synthesis
The place invariant method is well known as an elegant way to construct a
Petri net controller. It is possible to use the constraint for preventing
forbidden states. But in general case, the number forbidden states can be very
large giving a great number of control places. In this paper is presented a
systematic method to reduce the size and the number of constraints. This method
is applicable for safe and conservative Petri nets giving a maximally
permissive controller.Comment: Journ\'ee sur l'Instrumentation Industrielle J2I, ORAN : Alg\'erie
(2009
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