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/

To subscribe/unsubscribe to this newsletter, send e-mail to: destcsubm@cas.mcmaster.ca

To submit news items and articles to this newsletter, go here.

It is the responsibility of the contributor to ensure that they have the necessary permissions/clearance required for the transmittal of their news item.

Contents:

1. Editorial

2. Announcements
 2.1 DESUMA: new software tool for DES
 2.2 DES Technical Committee Meeting at CDC'05
 2.3 DESTC Website Revamped
 2.4 Online Newsletter Article Submission
 2.5 Online Submission of DES Researchers Information

3. Conferences
 3.1 The IASTED International Conference on INTELLIGENT SYSTEMS AND CONTROL (ISC
     2005), Cambridge, USA, October 31 - November 2, 2005
 3.2 The 25th IASTED International Conference on MODELLING, IDENTIFICATION, AND
     CONTROL (MIC 2006), Lanzarote, Canary Islands, Spain, February 6 -
     8, 2006
 3.3  The Eighth IASTED International Conference on CONTROL AND APPLICATIONS  (CA
     2006),  Montreal , Canada, May 24 - 26, 2006
 3.4 2006 American Control Conference (ACC), Minneapolis, Minnesota, USA, June
     14 - 16, 2006
 3.5 The 6th World Congress on Intelligent Control and Automation, Dalian,
     China, June 21 - 23, 2006
 3.6 8th International Workshop on Discrete Event Systems - WODES'06, Ann
     Arbor, Michigan, USA, July 10 - 12, 2006
 3.7 Control 2006, Glasgow, Scotland, United Kingdom, August 30 - September 1,
     2006
 3.8 45th IEEE Conference on Decision and Control, San Diego, California USA,
     December 13 - 15, 2006

4. Journals
 4.1 Selections from IEEE Transactions on Automatic Control, Volume 50, Issue
     6, May 2005
 4.2 Selections from IEEE Transactions on Automatic Control, Volume: 50,
     Issue: 7, July 2005
 4.3 Selections from IEEE Transactions on Automatic Control, Volume: 50,
     Issue: 8, August 2005
 4.4 Selections from Automatica, Volume 41, Issue , August 2005
 4.5 Discrete Event Dynamic Systems, Theory and Applications, Volume 15,
     Number 3, September 2005
 4.6 Selections from Control Engineering Practice, Volume 13, Issue 10,
     October 2005

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

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

Personal note from the editor:

I hope everyone enjoyed their summer holidays. This newsletter will be fairly
 packed as I have been holding off sending one out until the DESTC website was
 revamped.

Contributed by: Stephane Lafortune <stephane@eecs.umich.edu>

DESUMA: NEW SOFTWARE TOOL FOR DES

Laurie Ricker and I are happy to announce the release of the new
toolbox called DESUMA, which is now publicly available at the web
site www.umich.edu/umdes (click on Toolboxes). Executables are
available for Linux, Mac, and Windows. You will need to download the
DESUMA software and the new release of the UMDES-LIB executables
(dated July 31, 2005).

DESUMA is an integration of the UMDES library with the graphical
environment for visualizing discrete event systems, called GIDDES
(written in Java), developed at Mount Allison University by Laurie
Ricker.  DESUMA allows the user to perform a variety of manipulations
of discrete event systems modeled by FSM's related to model-building,
fault diagnosis, verification, control under full and partial
observation, and decentralized control. 

Give it a try and send us your comments!

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

DES TECHNICAL COMMITTEE MEETING AT CDC'05

There will be a meeting of the IEEE Control Systems Technical
Committee Group on Discrete Event Systems at the 2005 Conference on
Decision and Control (http://www.esi2.us.es/~cdcecc05/) in Seville, 
Spain on Monday, Dec. 12, 2005, from 7:00-8:00pm. The location is
the Triana room.

If you are interested in helping out with the committee's activities
and will be at the CDC'05, please send me an e-mail
(destc@cas.mcmaster.ca) to let me know to expect you. How much you
choose to participate is always up to you. Whether you simply give us
the benefit of your experience and wisdom during discussions, or take
a more active role in organizing activities, you will be equally
welcome. 

If you are interested in participating but will not be at the CDC'05,
please send me an e-mail to let me know. I can tell you afterwards what
took place.

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

DESTC WEBSITE REVAMPED

The DESTC website has undergone a much needed set of
improvements. Rather than one page, it now sports a menu bar at top
and bottom. We have added a conferences page showing DES related
conferences.  Under the links page, there is now a page for DES
related software (four listed), as well as DES related journals (if we
have missed any, please let us know).

On the newsletters page, new  issues will also have a webpage with
links to the individual articles (the version sent out will still be
in text). There is also online submissions for both newsletter
articles as well as for DES researcher entries (more details on this
in their own announcements).

Many thanks to Yu Wang who not only reworked much of the web pages, but
also wrote the submission web pages, as well as a database backend to
generate various web pages, as well as the newsletters.

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

ONLINE NEWSLETTER ARTICLE SUBMISSION

At the top of the newsletter page of the DESTC website
(http://www.cas.mcmaster.ca/destc/des_nltr.php), there is now a link
that lets you submit online your newsletter item or article.  You will
be presented with a set of forms that allow you to enter an
announcement, book, conference or journal item.  You can then preview
how your item will look, before submitting it.  After submission, the
item goes into a database that is then used to automatically generate
both the text version that is sent to the mailing list, as well as a
new html version with internal links to the articles that will go on
the webpage.

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

ONLINE SUBMISSION OF DES RESEARCHERS INFORMATION

The DES Researchers web page (http://www.cas.mcmaster.ca/destc/des_rsch.php)
 is slowly growing, currently at 17 researchers.  The web page is now
indexed by last name. You can jump to the first entry (if it
exists) with a last name of the given letter.

The webpage now also has a link to an online entry form for adding an entry
for yourself to the list. The form allows you to enter the needed
information, preview it, and then submit it.  I encourage everyone to
add an entry for yourself to the list. I have already found it very
useful for finding information for a conference article, or for
contacting a given researcher.  However, the list's usefulness is
limited if we don't take the time to populate it.

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

THE IASTED INTERNATIONAL CONFERENCE ON INTELLIGENT SYSTEMS AND CONTROL (ISC
2005)
Cambridge, USA
October 31 - November 2, 2005

SPONSORS
The International Association of Science and Technology for
Development

Technical Committee on Control
Technical Committee on Intelligent Systems and Control

ISC 2005 will act as an international forum for researchers and
practitioners interested in the advances in and applications of
intelligent systems and control. It is an opportunity to present and
observe the latest research, results, and ideas in these areas. ISC
2005 will aim to strengthen relationships between industry, research
laboratories and universities. All papers submitted to this
conference will be peer evaluated by at least two reviewers.
Acceptance will be based primarily on originality and contribution.

ISC 2005 will be held in Cambridge, Massachusetts at the Hotel@MIT.
Founded in 1630 as the first seat of government for the Massachusetts
Bay Colony, Cambridge has developed into an international community
merging history, education, arts, and culture within its lively
neighborhoods. Cambridge is located just across the Charles River
from Boston and is home to two of the country's most prestigious
educational institutions: MIT (the Massachusetts Institute of
Technology) and Harvard University. Other attractions include Harvard
Square, Beacon Hill, and the Faneuil Hall Marketplace.
ISC 2005 will be held in conjunction with the IASTED International
Conferences on:
Robotics and Applications (RA 2005)
Communications, Internet and Information Technology (CIIT 2005)

IMPORTANT DEADLINES
Submissions due: August 15, 2005
Notification of acceptance: September 1, 2005
Camera-ready manuscripts due: September 8, 2005
Registration Deadline: September 15, 2005

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

THE 25TH IASTED INTERNATIONAL CONFERENCE ON MODELLING, IDENTIFICATION, AND
CONTROL (MIC 2006)
Lanzarote, Canary Islands, Spain
February 6 - 8, 2006

SPONSORS
The International Association of Science and Technology for
Development (IASTED)

Technical Committee on Modelling and Simulation
Technical Committee on Control

World Modelling and Simulation Forum (WMSF)

PURPOSE
This conference provides an opportunity for prominent international
specialists, researchers, and engineers to present and observe the
latest research, results, and ideas in the areas of modelling,
identification, and control. MIC 2006 aims to strengthen relations
between industry, research laboratories and universities. All papers
submitted to this conference will be peer evaluated by two reviewers.
Acceptance will be based primarily on originality and contribution.

MIC 2006 will be held in conjunction with the IASTED International
Conferences on:

Advanced Technology in the Environmental Field (ATEF 2006)

LOCATION
Lanzarote is the easternmost of the Canary Islands, just 125km from
the Moroccan coast. Declared one of six universal models of
sustainable development by the World Tourism Organization, this
island paradise has warm weather the entire year, allowing sun
worshippers to enjoy its clear waters and white-sand beaches. Known
by inhabitants as Conejera, Lanzarote is also known as the island of
100 volcanoes. The National Park of Timanfaya is a volcanic field
where visitors can appreciate the natural forces that formed the
island, as well as a great variety of biological and geological
phenomena. Native son and world famous artist Cesar Manrique's
sensitive response to Lanzarote's unique geography and people is
shown by his numerous breathtaking works of landscape architecture.
His foundation houses paintings by Manrique, as well as works by
Picasso, Miro, Chillida, and other famous artists.


INTERNATIONAL PROGRAM COMMITTEE
Click here for a list of the program committee for MIC 2006.


SUBMISSION OF PAPERS
Initial Paper
Submit your paper via our website at:
http://www.iasted.org/conferences/2006/Spain/submit-500.htm. All
submissions should be in Adobe Acrobat (.pdf), Postscript (.ps), or
MS Word (.doc) format. The IASTED Secretariat must receive your paper
by October 1, 2005. Receipt of paper submission will be confirmed by
email. 

IMPORTANT DEADLINES
Submissions due: October 1, 2005
Notification of acceptance: November 1, 2005
Camera-ready manuscripts due: December 1, 2005
Registration Deadline: December 8, 2005

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

THE EIGHTH IASTED INTERNATIONAL CONFERENCE ON CONTROL AND APPLICATIONS (CA
2006)
Montreal , Canada
May 24 - 26, 2006

SPONSORS
The International Association of Science and Technology for
Development (IASTED)

PURPOSE
The IASTED International Conference on Control and Applications (CA
2006) will act as a major forum for international researchers and
practitioners interested in all areas of control and applications. It
will be an opportunity to present and observe the latest research,
results, and ideas in these areas. All papers submitted to this
conference will be peer evaluated by at least two reviewers.
Acceptance will be based primarily on originality and contribution.

CA 2006 will be held in conjunction with the IASTED International
Conference on: Modelling and Simulation (MS 2006)

LOCATION
Visiting the island city of Montreal is truly an experience. During
its 360-year history, Montreal has been a French settlement, a
British stronghold, and today is the world's second-largest
French-speaking city. European flair has blended with North American
savoir-faire and old world charm has mixed with modern style.

Initial Papers
Submit your paper via our website at:
http://www.iasted.org/conferences/2006/greece/submit-529.htm. All
submissions should be in Adobe Acrobat (.pdf), Postscript (.ps), or
MS Word (.doc) format. The IASTED Secretariat must receive your paper
by January 15, 2006. Receipt of paper submission will be confirmed by
email.

IMPORTANT DEADLINES
Submissions due: January 15, 2006
Notification of acceptance: February 15, 2006
Camera-ready manuscripts due: March 15, 2006
Registration Deadline: April 1, 2006

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

2006 AMERICAN CONTROL CONFERENCE (ACC)
Minneapolis, Minnesota, USA
June 14 - 16, 2006

The 2006 American Control Conference (ACC) will be held Wednesday through 
Friday, June 14-16, 2006 at the Hilton Minneapolis in Minneapolis, Minnesota 
USA. The ACC is held in cooperation IFAC and provides an opportunity for 
cooperation among people working in the fields of control, automation, and 
related areas from AIAA, AIChE, AIST, ASCE, ASME, IEEE, ISA, and SCS. The 
technical program will cover topics from control theory, industrial 
applications, and control education and will be presented in technical, 
special, interactive, and tutorial sessions and pre-conference workshops. 
For more information on special and interactive sessions, contact Michael 
Piovoso, Vice Chair for Special Sessions, at mjp5@gv.psu.edu. For the most 
current information, visit the conference website 
http://www.a2c2.org/conferences/acc2006/.

PAPER SUBMISSION
All papers submitted to the ACC for review must be prepared in the standard 
2-column Proceedings format. See the Authors Kit at the conference web site 
for Word and LaTex style files. For the purposes of review, regular and 
invited papers are limited to 8 pages and short papers to 3 pages. Papers 
exceeding these limits will NOT be reviewed. All papers will be submitted 
through the IEEE Control Systems Society submission website 
(http://www.paperplaza.net).

KEY DATES		
Deadline for all submissions and proposals: September 15, 2005
Notification of Acceptance/Rejection: January 31, 2006
Final manuscript submission deadline: March 15, 2006

GENERAL CHAIR
Eduardo Misawa, Oklahoma State University, misawa@ceat.okstate.edu

PROGRAM CHAIR
Karlene A. Hoo, Texas Tech University, Karlene.Hoo@ttu.edu

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

THE 6TH WORLD CONGRESS ON INTELLIGENT CONTROL AND AUTOMATION
Dalian, China
June 21 - 23, 2006

The 6th World Congress on Intelligent Control and Automation (WCICA06) is 
now a bi-annual event and a major international control conference held in 
China. The WCICA06 will be held in the popular summer resort city Dalian in 
northeastern China in June 21-23 2006. The WCICA06 is sponsored by IEEE 
Robotics and Automation Society, IEEE Control System Society(Beijing 
Chapter), National Natural Science Foundation of China and Chinese 
Association of Automation. The congress aims to provide a broad international 
forum for world researchers, engineers and professionals working in the areas 
of Intelligent Control and Automation to discuss and exchange their findings, 
ideas, and views. The congress will focus on both theory and applications. 

Important Dates
Paper submission deadline, Nov. 1, 2005
Notification of paper acceptance, Feb. 1, 2006
Final version of paper submission deadline, March 1, 2006

For further information, please visit the web site http://wcica06.dlut.edu.cn
or contact wcica06@dlut.edu.cn, panxj@dlut.edu.cn

Web site: click here

Contributed by: Stephane Lafortune <stephane@eecs.umich.edu>

8TH INTERNATIONAL WORKSHOP ON DISCRETE EVENT SYSTEMS - WODES'06
Ann Arbor, Michigan, USA
July 10 - 12, 2006

The 8th edition of WODES will be held in the USA in 2006, in Ann
Arbor on the campus of the University of Michigan, July 10-12. It
will provide researchers from different fields (control theoreticians
and control engineers, software engineers and computer scientists,
operations research specialists) with an opportunity to exchange
information and new ideas, and to discuss new developments in the
field of DES theory and application. 

Important  Dates:
     January 16, 2006: Deadline for submission of papers and special
sessions
     April 15, 2006: Notification of acceptance
     May 15, 2006: Deadline for submission of final versions

Please consult the conference web site for further details.

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

CONTROL 2006
Glasgow, Scotland, United Kingdom
August 30 - September 1, 2006

This is the sixth biennial UKACC Control Conference, which traditionally 
brings together the practitioners and the scientists working in the general 
area of control engineering. The Conference covers Methods, Technology, 
Applications and Education in Control Engineering.

The Conference will include Plenary sessions, Invited sessions, Regular 
sessions, Poster sessions, Workshops and Industrial sessions. Submissions 
will be invited for any of these sessions.

Important Deadlines:
Submission of Draft Paper: 10th Feb. 2006
Notification: 10th April 2006
Final Submission: 2nd June 2006

For further information, visit the web-site http://www.control2006.org

Organised by the University of Strathclyde and the University of Glasgow. 
The Conference will be hosted by the University of Glasgow and the University 
of Strathclyde.

Address: Control 2006, Industrial Control Centre
University of Strathclyde, 
50 George Street, Glasgow G1 1QE, UK
Email: info@control2006.org 
Tel: (+44)(0)141 548 2880 Fax: (+44)(0)141 548 4203

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

45TH IEEE CONFERENCE ON DECISION AND CONTROL
San Diego, California USA
December 13 - 15, 2006

Invitation to the 45th IEEE Conference on Decision and Control

The 45th IEEE Conference on Decision and Control will be held Tuesday
through Thursday, December 13-15, 2006 at the Manchester Grand Hyatt
Hotel in San Diego, California USA. The conference will be preceded
by technical workshops on December 11-12, 2005.
The CDC annually brings together an international community of
researchers and practitioners in the field of automatic control to
discuss the latest advancements of the discipline, shape its future
directions, and promote its diffusion among the scientific community
at large.

The 45th CDC will feature the presentation of contributed and invited
papers, as well as tutorial sessions and workshops. In addition to
the standard oral presentations, the conference will also feature
interactive presentations in order to encourage an interaction
exchange with the audience. Topics for the interactive sessions will
be selected specifically to benefit from the time for interaction and
discussion that are not available in a typical lecture session, and
the authors will be encouraged to make creative use of poster boards
as well as hands-on computer simulations and demonstrations.

The CDC is hosted by the IEEE Control Systems Society (CSS), and is
organized in cooperation with the Society for Industrial and Applied
Mathematics (SIAM), the Institute for Operations Research and the
Management Sciences (INFORMS), the Japanese Society for Instrument
and Control Engineers (SICE), and the European Union Control
Association (EUCA).

San Diego is California's second largest city, blessed by an ideal
climate, miles of pristine beaches, and unique world-class
attractions, including Balboa Park, the San Diego Zoo, and Sea World.

Pradeep Misra: General Chair
Rick Middleton: Program Chair

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

SELECTIONS FROM IEEE TRANSACTIONS ON AUTOMATIC CONTROL
VOLUME 50, ISSUE 6
MAY, 2005

1) A basic formula for online policy gradient algorithms

Xi-Ren Cao  
Hong Kong Univ. of Sci. & Technol., Kowloon, China;

Abstract

This note presents a (new) basic formula for sample-path-based
estimates for performance gradients for Markov systems (called policy
gradients in reinforcement learning literature). With this basic
formula, many policy-gradient algorithms, including those that have
previously appeared in the literature, can be easily developed. The
formula follows naturally from a sensitivity equation in perturbation
analysis. New research direction is discussed.

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

SELECTIONS FROM IEEE TRANSACTIONS ON AUTOMATIC CONTROL
VOLUME: 50, ISSUE: 7
JULY, 2005

1) Fault Diagnosis in Discrete-Event Systems: Incorporating Timing
Information

 Zad, S.H.    Kwong, R.H.   Wonham, W.M. 

Abstract

A framework is introduced for fault diagnosis in timed discrete-event
systems. In this approach, the required estimates for system
condition are updated only when the output changes or when deadlines
associated with output changes expire. Thus updates at every clock
tick are not required. This in many cases results in reduction in
online computing requirements and in the size of the diagnosis
system, at the expense of more offline design calculations. The issue
of failure diagnosability is also discussed.

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

SELECTIONS FROM IEEE TRANSACTIONS ON AUTOMATIC CONTROL
VOLUME: 50, ISSUE: 8
AUGUST, 2005

1) Decentralized Supervisory Control With Conditional Decisions:
Supervisor Realization

 Yoo, T.-S.    Lafortune, S.   

Abstract

The strategy of decentralized supervisory control of discrete-event
systems using so-called "conditional decisions" initiated in
prior work is further investigated in this note. Specifically, a
constructive methodology for realizing supervisors that employ
conditional decisions is developed. This methodology is based on the
construction of (deterministic) observers of nondeterministic
automata that are built so as to track violations of C&P and D&A
coobservability.

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

SELECTIONS FROM AUTOMATICA
VOLUME 41, ISSUE
AUGUST, 2005

1) Maximally permissive mutually and globally nonblocking supervision
with application to switching controlstar, open

Ratnesh Kumara,  Shigemasa Takaib,  Martin Fabian, and Toshimitsu
Ushiod

Abstract

A supervisor is said to be mutually nonblocking with respect to a
pair of specifications if upon completing a task in any of the
specifications, it can continue on to complete the task in the other
specification, i.e., the two specifications do not block each other.
The notion of mutually nonblocking supervisor was introduced in
Fabian and Kumar [2000. Automatica, 36(12), 1863-1869]. In this
paper, we present an algorithm of polynomial complexity for computing
a maximally permissive mutually and globally nonblocking supervisor.
In case such a supervisor does not exist, we present a technique for
relaxing the specifications for which a supervisor exists. The
algorithms are based on a notion of attractability, and as a special
case offer a new way of computing the maximally permissive
nonblocking supervisors. The results are then applied to design of
maximally permissive switching supervisors so as to allow for
switching between the specifications at any time while the system is
executing. 

2) Safe diagnosability for fault-tolerant supervision of
discrete-event systems

Andrea Paolia, and Stephane Lafortune

Abstract

The problem of achieving fault-tolerant supervision of discrete-event
systems is considered from the viewpoint of safe and timely diagnosis
of unobservable faults. To this end, the new property of safe
diagnosability is introduced and studied. Standard definitions of
diagnosability of discrete-event systems deal with the problem of
detecting the occurrence of unobservable fault events using
model-based inferencing from observed sequences of events. In safe
diagnosability, it is required in addition that fault detection occur
prior to the execution of a given set of forbidden strings in the
failed mode of operation of the system. For instance, this constraint
could be required to prevent local faults from developing into
failures that could cause safety hazards. If the system is safe
diagnosable, reconfiguration actions could be forced upon the
detection of faults prior to the execution of unsafe behaviour, thus
achieving the objective of fault-tolerant supervision. Necessary and
sufficient conditions for safe diagnosability are derived. In
addition, the problem of explicitly considering safe diagnosability
in controller design, termed "active safe diagnosis
problem", is formulated and solved. A brief discussion of safe
diagnosability for timed models of discrete-event systems is also
provided. 

3) Robust optimal control of regular languages

Constantino M. Lagoa, Jinbo Fu, and Asok Ray

Abstract

This paper presents an algorithm for robust optimal control of
regular languages under specified uncertainty bounds on the event
cost parameters of the language measure that has been recently
reported in literature. The performance index for the proposed robust
optimal policy is obtained by combining the measure of the supervised
plant language with uncertainty. The performance of a controller is
represented by the language measure of the supervised plant and is
minimized over the given range of event cost uncertainties. Synthesis
of the robust optimal supervisory control policy requires at most n
iterations, where n is the number of states of the deterministic
finite-state automaton (DFSA) model, generated from the regular
language of the unsupervised plant behavior. The computational
complexity of the control synthesis method is polynomial in n. 

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

DISCRETE EVENT DYNAMIC SYSTEMS, THEORY AND APPLICATIONS
VOLUME 15, NUMBER 3
SEPTEMBER, 2005

1) Ghost Simulation Model for the Optimization of an Urban Subway
System

Felisa J. Vazquez-Abad, and Lourdes Zubieta

Abstract  

The first part of the paper presents a model of a complex
subway network that includes an operational cost and social costs
measured in terms of passenger waiting times. We reformulate the
model with a simple discrete event simulation model that considerably
reduces the complexity of the simulation. The simplified model uses
conditional expectations to filter out rapid dynamics, and it can be
interpreted in terms of a subway network with "fluid" passenger
levels. Because this network only sees train movements and no
individual passengers are described, we call it the "ghost" model.
In the second part of the paper, we explore the benefits of using
stochastic approximations to adjust the service level (headway) of
different subway lines as the network is operating, thus learning
passenger traffic patterns and adaptively seeking the best service
values. Our formulation of the ghost model is amenable for
decentralized estimation of gradients of the cost function with
respect to the control parameters (the line headways) and we use
ersatz estimation methods to formulate a control scheme that uses
minimal measurements and virtually no overhead.

2) Modular Fault Diagnosis Based on Discrete Event Systems

E. Garcia,  A. Correcher, F. Morant, E. Quiles, and R. Blasco

Abstract  

An awareness of failure type and location is an
indispensable requirement for the establishment of adequate recovery
strategies and the maintenance of Factory Automation and Process
Control systems.
The failure diagnosis methodology presented in this paper is based on
Discrete Event Systems models and in the diagnoser concept, which
enable the off-line and on-line analysis of systems failures. We
present an approach for models and associated diagnosers based on a
modular decomposition of the global system, with the aim of avoiding
problems of exponential explosion in the number of states and
computational complexity of the diagnosis process.

3) Control of Discrete-Event Systems with Partial Observations Using
Coalgebra and Coinduction

Jan Komenda, and Jan H. van Schuppen

Abstract  Control of discrete-event systems with partial observations
is treated by concepts and results of coalgebra and coinduction.
Coalgebra is part of abstract algebra and enables a generalization of
the computer science concept of bisimulation. It can be applied to
automata theory and then provides a powerful algebraic tool to treat
problems of supervisory control. A framework for control of
discrete-event systems with partial observations is formulated in
terms of coalgebra. The contributions to control theory are besides
the framework, algorithms for supremal normal and supremal normal and
controllable sublanguages of the plant.

Web site: click here

Contributed by: Ryan Leduc <leduc@mcmaster.ca>

SELECTIONS FROM CONTROL ENGINEERING PRACTICE
VOLUME 13, ISSUE 10
OCTOBER, 2005

1) An approach to control automated warehouse systems

Francesco Amato, Francesco Basile, Ciro Carbone, and Pasquale
Chiacchio

Abstract

The goal of this paper is the development of control algorithms for
the management of an automated warehouse system. As usual, the
implementation of a control algorithm requires three preliminary
steps: development of a reliable model; design of control procedures
according to some optimality criteria; validation of these control
procedures. As for modelling, a new level in the control
architecture, namely an optimizer system, is introduced which
performs real-time optimization thus simplifying the low-level
control and improving the overall performance. In this context, the
role of a detailed model of the whole warehouse is discussed and such
a model is built up by using the colored timed Petri nets framework.
As for control, we propose two control algorithms, derived under the
simplifying continuity assumption of the rack locations, to optimize
the operations of the cranes (moving within the aisles of the
warehouse) and the operations of the shuttle (moving on a straight
line placed between the aisles and the picking/refilling area),
respectively. To evaluate the performance of the proposed control
algorithms we define three different cost indices. As for the
validation, extensive simulations are performed on the model in order
to prove the effectiveness of the proposed control algorithms. A
further validation of the algorithms has been performed on a test bed
in order to take into account communication delays and computation
times. Finally, the proposed architecture and control algorithms have
been applied to a real plant. 

2) On the execution of sequential function charts

Anders Hellgren, Martin Fabian and Bengt Lennartson

Abstract

The transition between the supervisory control theory (SCT) and its
implementation in programmable logic controllers (PLCs) is not
straightforward. This is mainly due to the fact that the SCT is
stated in an event-based asynchronous setting whilst PLCs are
signal-based, synchronous and sequential. Based on Petri nets, the
PLC programming language sequential function chart (SFC) seems to be
the ideal choice for this transition. However, the transition
requires detailed knowledge of how the PLC and SFCs work. Different
execution models for SFCs are presented and compared with the
international standard IEC 61131-3. Often, the application of the SCT
to a control problem results in a set of modules between which mutual
exclusion and synchronisation are important aspects. The results
indicate, however, that for modular SFC programs it seems generally
impossible to simultaneously achieve both mutual exclusion between
modules as well as synchronisation of modules without using
workarounds that may be either manual or suffer from state space
explosion. Nevertheless, one of the presented execution models, the
immediate transit/immediate action model, together with a handshaking
procedure is shown to give a simple solution to both mutual exclusion
and synchronisation. 

3) Optimal scheduling method for a bell-type batch annealing shop and
its application

Quan-li Liu, Wei Wang, Hong-ren Zhan, and Rui-guo Liu

Abstract

The production scheduling for a bell-type batch annealing process in
heat treatment of steel coils is a typical multi-machine multi-stage
re-entrant problem with complex constraint of resources including
energy source. It is very difficult to build its mathematical model
due to the large number of constraints in the process. This paper
proposes an optimal scheduling method for the bell-type batch
annealing process that combines an improved genetic algorithm with
discrete event simulation techniques. The optimal scheduling method
developed in this paper has been applied to the annealing shop in
Shanghai Baosteel Yichang Sheet Co. Ltd, China, for nearly 2 years.
The industrial application result shows that the proposed optimal
scheduling method improves production efficiency and gains economic
benefits. 

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