IEEE CONTROL SYSTEMS SOCIETY TECHNICAL COMMITTEE
ON DISCRETE EVENT SYSTEMS

    Ryan J. Leduc
    Chair, IEEE CSS Technical Committee on DES
    Dept. of Computing and Software
    McMaster University
    1280 Main Street West
    Hamilton, Ontario
    Canada L8S 4K1

    Phone: (905) 525-9140 Ext. 27962
    Fax: (905) 524-0340
    e-mail: leduc@mcmaster.ca
    WWW: http://www.cas.mcmaster.ca/~leduc/

DESTC Web Page: http://www.cas.mcmaster.ca/destc/

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Contents:

1. Editorial


2. Journals
 2.1 Selections from IEEE Transactions on Automatic Control, Volume: 53,
     Issue: 10, November 2008
 2.2 Selections from IEEE Transactions on Systems, Man and Cybernetics, Part
     A, Volume: 38,Issue: 6, November 2008

Welcome to the newsletter of the IEEE Control Systems Technical Committee on Discrete Event Systems!

See http://www.cas.mcmaster.ca/destc/ for information on the DESTC.

Personal note from the editor:

Welcome to the November 2008 edition of the newsletter,

Ryan 

Contributed by: Ryan Leduc <leduc aT mcmaster dOT ca>

SELECTIONS FROM IEEE TRANSACTIONS ON AUTOMATIC CONTROL
VOLUME: 53, ISSUE: 10
NOVEMBER, 2008

1) Nonblocking Hierarchical Control of Decentralized Discrete Event
Systems

Schmidt, K.; Moor, T.; Perk, S.

Abstract:

This contribution investigates the hierarchical control of
decentralized discrete event systems (DES) that are synchronized by
shared events. A hierarchical control architecture providing
hierarchical consistency is introduced. Moreover, it allows for
composition of decentralized subsystems on the high-level of the
hierarchy and hence reduces the computational complexity of supervisory
control synthesis for language inclusion specifications. In this
context, a crucial issue is the nonblocking operation of the overall
system. Our main theorem identifies sufficient conditions for this
desirable property.

2) Decentralized Control of Discrete Event Systems Using Prioritized
Composition With Exclusion

Qiu, W.; Kumar, R.; Chandra, V.

Abstract: 

A necessary and sufficient condition for decentralized control of
discrete event systems via prioritized composition with exclusion (PCX)
is provided. PCX was extended from prioritized synchronous composition
(PSC) in order to model various Boolean modes of decision fusion by
allowing the exclusivity of participation in system interactions  . A
notion of PCX-coobservability is introduced that captures the nature of
PCX-based decision fusion, and a testing algorithm with polynomial
complexity in the states of plant and specification is presented. The
result is extended for mutiple supervisors with multiple exclusivity
sets based on an extended PCX definition.

web site: click here

Contributed by: Ryan Leduc <leduc aT mcmaster dOT ca>

SELECTIONS FROM IEEE TRANSACTIONS ON SYSTEMS, MAN AND CYBERNETICS, PART
A
VOLUME: 38,ISSUE: 6
NOVEMBER, 2008

1) Firing Sequences Estimation in Vector Space Over  $Z_{3}$ for
Ordinary Petri Nets

Lefebvre, D.

Abstract:

Event sequences estimation is an important issue for fault diagnosis of
Discrete event systems, so far as fault events cannot directly be
measured. This paper is about event sequences estimation with Petri net
models. Events are assumed to be represented with transitions, and
firing sequences are estimated from measurements of the marking
variation. Estimation with and without measurement errors are discussed
in  $n$-dimensional vector space over alphabet $Z_{3} = {-1, 0, 1}$.
Sufficient conditions and estimation algorithms are provided.
Performance is evaluated, and the efficiency of the approach is
illustrated on two examples from manufacturing engineering.

2) Selective Siphon Control for Deadlock Prevention in Petri Nets

Piroddi, L.; Cordone, R.; Fumagalli, I.

Abstract:

Deadlock prevention is a crucial step in the modeling of flexible
manufacturing systems. In the Petri net framework, deadlock prevention
policies based on siphon control are often employed, since it is easy
to specify generalized mutual exclusion constraints that avoid the
emptying of siphons. However, such policies may require an excessive
computational load and result in impractical oversized control subnets.
This is often a consequence of the redundancy in the control conditions
derived from siphons. In this paper, a novel method is proposed that
provides small size controllers, based on a set covering approach that
conveniently relates siphons and markings. Some examples are provided
to demonstrate the feasibility of the approach and to compare it with
other methods proposed in the literature.

web site: click here