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. Announcements
 2.1 Idaho National Laboratory Employment Opportunity
 2.2 IET CTA News - Increase Frequency of Publication

3. Conferences
 3.1 9th International Workshop on Discrete Event Systems (WODES'08),
     Gothenburg, Sweden, May 28 - 30, 2008
 3.2 8th International Conference on Application of Concurrency to System
     Design, Xidian University, Xi'an, China, June 23 - 27, 2008

4. Journals
 4.1 Selections from International Journal of Control, Volume 80 Issue
     10, October 2007
 4.2 Discrete Event Dynamic Systems, Volume 17 Number 3, September 2007
 4.3 Selections from Control Engineering Practice, Volume 15, Issue 11,
     November 2007
 4.4 Selections from IEEE Transactions on Automatic Control, Volume: 52,
     Issue: 9, September 2007

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 September DESTC newsletter,

Ryan

Contributed by: Thomas Steele <thomas.steele@inl.gov>

IDAHO NATIONAL LABORATORY EMPLOYMENT OPPORTUNITY

Electrical/Nuclear Engineer

Idaho National Laboratory (INL) is seeking qualified candidates to 
fill a staff research, development, and demonstration (RD&D) 
position.  The successful candidate will participate in the 
development and demonstration of technical solutions to a variety of 
moderately large and/or complex problems related to systems 
technologies, including modeling and simulation, through the general 
use and application of design/development practices, theories, and 
techniques.  Typical RD&D areas of interest may include, but not 
necessarily be limited to, instrumentation and control, sensor 
networks/systems, decision support systems, process control, 
artificial intelligence, dynamic threat surveillance and detection, 
system integration issues, and on-line condition monitoring and 
anomaly detection and interpretation, with pattern recognition, 
diagnostic, and prognostic capabilities.  Additional R&D activities 
may involve the development of dynamic process and operations models, 
data acquisition and supervisory systems, and embedded sensory 
networks and interfaces.  Main application areas are national 
security, nuclear processes, and energy systems.

Potential candidates must hold a PhD in Electrical Engineering, 
Nuclear Engineering, or related fields.  Strong expertise or/and 
experience in systems technologies and in dynamic modeling, 
simulation, and analysis is desirable.  The position requires a 
highly motivated individual with the ability to work effectively in a 
team and under minimal supervision.  The candidate will participate 
and provide leadership in the development and demonstration of 
advanced engineering systems and solutions using current and emerging 
systems technologies.  

We are approximately 150 miles from Sun Valley, Idaho, and 100 miles 
from Jackson Hole, Wyoming, and Yellowstone National Park, three of 
the world's most sought after resort vacation destinations.  INL 
offers a competitive salary and exceptional benefits package, 
including Health/Dental/Life, retirement, vacation, tuition 
reimbursement, relocation assistance, and much more.

Please apply on line at http://www.inl.gov/careers for job reference 
#002757.  For questions, send e-mail message to Thomas Steele at 
Thomas.Steele@inl.gov.

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

IET CTA NEWS - INCREASE FREQUENCY OF PUBLICATION

IET Control Theory & Applications is delighted to announce that from
January 2008, the publication frequency 
of the journal will increase from 6 to
12 issues per year.

The decision to publish IET CTA on a monthly basis has been made
possible by a year-on-year increase in the number 
of submissions received over the past 3
years, as well as our ability to provide authors with very fast times
to decision. Indeed, authors of submitted manuscripts can now fully expect
to receive a first decision within 12 weeks of submitting a paper. It is
now important that we continue our commitment to our authors by making
their research available in print and online as quickly as possible.

IET CTA is enjoying this success largely as a result of the continued
efforts of our referees who diligently supply authors with high quality,
detailed review reports. On behalf of the journal's Editor-in-Chief, Prof. Brett
Ninness, I would like to thank everyone involved (not least our
dedicated editorial board) in helping to make IET CTA a journal that really is
going from strength to strength.

For more information on IET Control Theory & Applications please visit
the journal webpage at: http://www.ieedl.org/IET-CTA

or you can contact me directly at: lbaldwin@theiet.org

Lee Baldwin
Managing Editor - IET Control Theory & Applications

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

9TH INTERNATIONAL WORKSHOP ON DISCRETE EVENT SYSTEMS (WODES'08)
Gothenburg, Sweden
May 28 - 30, 2008

Call for Papers

The 9th edition of WODES will be held in Gothenburg, Sweden, on the
campus of Chalmers University of Technology, May 28-30, 2008.

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. 

Authors are invited to submit papers and proposals for special sessions
by January 18, 2008.

Topics

The workshop will cover all topics in discrete event theory and
applications, including (but not limited to) the following:

    * Formalisms and modeling methodologies: Petri nets, state
      automata, statecharts, process algebras, max/plus-algebra...
    * Control of discrete-event systems with emphasis on supervisory
      control and on real time control
    * Performance evaluation, diagnosis, optimization, implementation
      and scheduling
    * Discrete approaches of hybrid, reactive and embedded systems
    * Applications including manufacturing systems, transportation
      systems, process control, distributed systems, software engineering,
      office automation, protocols...
    * Emerging applications in telecommunication systems and related
      fields: performance evaluation, on-line control...
    * Software tools enabling efficient handling of industrial-sized
      systems.

Papers

All papers submitted for review and publication after acceptance must
be delivered electronically in PDF format and formatted in the standard
2-column IEEE format. Accepted papers will be limited to six (6) pages
in the proceedings unless an overlength fee is paid.

The accepted papers will be published electronically by IEEE Explorer,
and therefore the copyright will be held by IEEE.

Important Dates

    * January 18, 2008: Submission of full papers and special sessions.
    * March 21, 2008: Notification of acceptance.
    * April 18, 2008: Submission of final camera ready papers and
      registration.
    * May 28-30, 2008: Workshop!

web site: click here

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

8TH INTERNATIONAL CONFERENCE ON APPLICATION OF CONCURRENCY TO SYSTEM
DESIGN
Xidian University, Xi'an, China
June 23 - 27, 2008

*** CALL FOR PAPERS ***

*** Deadline for paper submission: 4 January 2008 ***

Dates and Venue

    23-27 June 2008, Xidian University, Xi'an, China

ACSD 2008 will be co-located with

   29th International Conference on Application and
   Theory of Petri Nets and Other Models of Concurrency

   http://www.informatik.uni-hamburg.de/TGI/PetriNets/meetings/pn2008/

and the two conferences will share invited speakers as well as the
satellite workshops and tutorials

Joint web page of the co-located conferences

   http://ictt.xidian.edu.cn/atpn-acsd2008/Pages/main.jsp

Conference Focus

The International Conference on Application of Concurrency to System
Design (ACSD) serves as a forum for disseminating theoretical results
with application potential and advanced methods and tools for the
design of complex concurrent systems. While there are already quite
 a few success stories in the field, there is still
 a strong need to bring theory and practice closer together. 
The conference aims at cross-fertilising both
theoretical and applied research on topics including, but not limited
to, the following:

   * Design methods, tools and techniques based on models of
     computation and concurrency (data-flow models, communicating
     automata, Petri nets, process algebras, state charts, MSCs, etc.),
     (performance) analysis, verification, testing and synthesis.

* Hardware / software co-design, platform-based design, component-based
     design, refinement techniques, hardware / software abstractions,
     co-simulation and verification

   * Synchronous and asynchronous design, asynchronous circuits,
     globally asynchronous locally synchronous systems, interface
design,
     multi-clock systems, functional and timing verification.

   * Concurrency issues in systems-on-a chip, massively parallel
     architectures, networks-on-a-chip, task 
     and communication scheduling, resource,
     memory and power management, fault-tolerance
     and quality of service issues.

   * (Industrial) case studies of general interest, gaming
     applications, consumer electronics and 
     multimedia, automotive systems,
     (bio-)medical applications, Internet and grid computing, etc.

   * Concurrency issues in ad-hoc, mobile and wireless networking,
     sensor networks, communication 
     protocols, cross-layer optimization,
     resource and power management, fault-tolerance,
     concurrency-related security issues.

   * Business process modelling, simulation and verification,
     (distributed) workflow execution, business
      process (de-)composition, interorganisational and
     heterogeneous workflow systems, computer-supported collaborative
     work systems, web services

   * Synthesis and control of concurrent systems, (compositional)
     modelling and design, (modular) synthesis
     and analysis, distributed simulation
     and implementation, (distributed) controller synthesis, adaptive
     systems, supervisory control

ACSD Keynote Speaker

   Mike Kishinevsky (Intel, Hillsboro, Oregon, USA)

General Chair

   Zhenhua Duan (Xidian University, China)

Program Committee Co-Chairs

   Jonathan Billington (University of South Australia, Australia)
   Maciej Koutny (University of Newcastle upon Tyne, UK)

Steering Committee

   Alex Yakovlev (University of Newcastle upon Tyne, UK), Chair
   Benoît Caillaud (IRISA, France)
   Jordi Cortadella (Universitat Politecnica de Catalunya, Spain)
   Jörg Desel (Katholische Universität Eichstätt-Ingolstadt, Germany)
   Alex Kondratyev (Cadence, USA)
   Luciano Lavagno (Politecnico di Torino, Italy)
   Antti Valmari (Tampere University of Technology, Finland)

Regular Papers

   Submitted papers should be in IEEE Computer Society Press 2-column
   format
   (ftp://pubftp.computer.org/Press/Outgoing/proceedings/instruct.pdf).
   ***
   Both long papers (7 to 10 pages) and short papers (5 to 6 pages) can
   be submitted. Authors submitting long papers should indicate in
their submission
   whether they would be prepared to reduce the length of their
submissions to 6
   pages on the recommendation of the programme committee.
   ***
   The cover page should include the corresponding
   author, physical and e-mail addresses, phone and FAX numbers, and an
   abstract of at most 60 words. The deadline for submission of regular
   papers is *4 January 2008*. Paper submission will be handled
   electronically.

   Submitted papers should describe original work that has not been
   previously published and is not under 
   review for publication elsewhere. More
   information will be provided through the conference web-pages.

Tool Papers and Demonstrations

   Submissions for tool demonstrations should be no more than 5 pages
   in IEEE CS Press format and should be submitted by *4 January 2008*.
Tool
   papers will be reviewed by the programme 
   committee. Acceptance of a tool paper implies
   that a tool demonstration should be given at the conference. For
   facility arrangements and questions, 
   please contact Xiaobing Wang
   (xbwang@mail.xidian.edu.cn).

Proceedings

   Proceedings containing accepted regular papers, invited papers and
   tool papers are planned to be published 
   by IEEE Computer Society Press.

Best Paper Award

   A best paper award will be given to the author(s) of the best
   regular paper presented at ACSD 2008.

Special Issue Fundamenta Informaticae

   Best papers of ACSD will be considered for publication in extended
   and revised form in a special issue of the journal Fundamenta
   Informaticae.

Organising Committee

   Zhenhua Duan (general chair)
   Xinbuo Gao (co-chair)
   Shouzhi Wang (co-chair)
   Bin Yu (publicity chair)
   Xiaobing Wang (tool exhibition chair)

Sponsorship and Cooperation

   National Natural Foundation of China
   Shaanxi Province Computer Federation
   Institute of Computing Theory and Technology, Xidian University
   International Cooperation and Exchange Office, Xidian University


Important Dates

   - Deadline for paper submission: 4 January 2008
   - Notification of acceptance: 1 March 2008
   - Deadline for final version: 11 April 2008
   - Tutorials & Workshops: 23-24 June 2008
   - Conference: 25-27 June 2008

web site: click here

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

SELECTIONS FROM INTERNATIONAL JOURNAL OF CONTROL
VOLUME 80 ISSUE 10
OCTOBER, 2007

1) Evaluation of language measure parameters for discrete event
manufacturing systems with multiproduct machines

A. Khatab; M. Nourelfath

Abstract: 

The concept of language measure provides a mathematical framework for
quantitative analysis and synthesis of discrete event supervisory
control systems. The language measure is assigned two parameters,
namely the state transition cost matrix and the state cost vector. In a
recent paper (Khatab and Nourelfath 2006), an analytical approach has
been formulated to evaluate the language measure parameters for
discrete event manufacturing systems composed of several monoproduct
machines, i.e., each machine is able to perform only one kind of
product. This paper generalizes these results to the multiproduct case,
i.e., to the case where each machine in the manufacturing system is
able to perform different kinds of products. The proposed approach is
based on the theory of Markov stochastic processes and Kronecker
algebra. The main advantage of the proposed approach is that the
mathematical expressions of the system language measure parameters are
derived from data of individual elementary machines without generating
the whole, possibly huge, system state space.

web site: click here

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

DISCRETE EVENT DYNAMIC SYSTEMS
VOLUME 17 NUMBER 3
SEPTEMBER, 2007

1) Trellis Processes : A Compact Representation for Runs of Concurrent
Systems

Eric Fabre

Abstract:

The unfolding of a concurrent system represents in a compact manner all
possible runs of this system. Unfoldings are used in many applications,
ranging from model-checking (offline) to failure diagnosis (on-line).
Their factorization properties form the basis of modular/distributed
algorithms to achieve these tasks. The trellis structure proposed here
is an alternate and more compact representation for the trajectory set
of a concurrent system. In this structure, time is unfolded, but not
the conflict relations. Trellis nets are the generalization to
concurrent systems of the usual notion of trellis for an automaton. As
for unfoldings, factorization properties are evidenced on trellises,
which makes these more compact structures a possible candidate for
distributed model checking or diagnosis algorithms. As an example, we
show how trellises can be used for diagnosis purposes in a distributed
observation setting.

2)Efficient PAC Learning for Episodic Tasks with Acyclic State Spaces

Spyros Reveliotis, Theologos Bountourelis

Abstract:

This paper considers the problem of computing an optimal policy for a
Markov decision process, under lack of complete a priori knowledge of
(1) the branching probability distributions determining the evolution
of the process state upon the execution of the different actions, and
(2) the probability distributions characterizing the immediate rewards
returned by the environment as a result of the execution of these
actions at different states of the process. In addition, it is assumed
that the underlying process evolves in a repetitive, episodic manner,
with each episode starting from a well-defined initial state and
evolving over an acyclic state space. A novel efficient algorithm for
this problem is proposed, and its convergence properties and
computational complexity are rigorously characterized in the formal
framework of computational learning theory. Furthermore, in the process
of deriving the aforementioned results, the presented work generalizes
Bechhofer’s “indifference-zone” approach for the ranking & selection
problem, that arises in statistical inference theory, so that it
applies to populations with bounded general distributions.

3) Stable Model Predictive Control for Constrained Max-Plus-Linear
Systems

Ion Necoara, Bart De Schutter, Ton J. J. Boom, Hans Hellendoorn

Abstract:

Discrete-event systems with synchronization but no concurrency can be
described by models that are “linear” in the max-plus algebra, and they
are called max-plus-linear (MPL) systems. Examples of MPL systems often
arise in the context of manufacturing systems, telecommunication
networks, railway networks, parallel computing, etc. In this paper we
provide a solution to a finite-horizon model predictive control (MPC)
problem for MPL systems where it is required that the closed-loop input
and state sequence satisfy a given set of linear inequality
constraints. Although the controlled system is nonlinear, by employing
results from max-plus theory, we give sufficient conditions such that
the optimization problem that is performed at each step is a linear
program and such that the MPC controller guarantees a priori stability
and satisfaction of the constraints. We also show how one can use the
results in this paper to compute a time-optimal controller for linearly
constrained MPL systems.

4) Partial Order Techniques for Distributed Discrete Event Systems: Why
You Cannot Avoid Using Them

Eric Fabre, Albert Benveniste

Abstract:

Monitoring or diagnosis of large scale distributed Discrete Event
Systems with asynchronous communication is a demanding task. Ensuring
that the methods developed for Discrete Event Systems properly scale up
to such systems is a challenge. In this paper we explain why the use of
partial orders cannot be avoided in order to achieve this objective. To
support this claim, we try to push classical techniques (parallel
composition of automata and languages) to their limits and we
eventually discover that partial order models arise at some point. We
focus on on-line techniques, where a key difficulty is the choice of
proper data structures to represent the set of all runs of a
distributed system, in a modular way. We discuss the use of previously
known structures such as execution trees and unfoldings. We propose a
novel and more compact data structure called “trellis.” Then, we show
how all the above data structures can be used in performing distributed
monitoring and diagnosis. The techniques reported here were used in an
industrial context for fault management and alarm correlation in
telecommunications networks. This paper is an extended and improved
version of the plenary address that was given by the second author at
WODES’ 2006.

5) Insensitive Traffic Models for Communication Networks

T. Bonald

Abstract: 

We present a survey of traffic models for communication networks whose
key performance indicators like blocking probability and mean delay are
independent of all traffic characteristics beyond the traffic
intensity. This insensitivity property, which follows from that of the
underlying queuing networks, is key to the derivation of simple and
robust engineering rules like the Erlang formula in telephone networks.

web site: click here

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

SELECTIONS FROM CONTROL ENGINEERING PRACTICE
VOLUME 15, ISSUE 11
NOVEMBER, 2007

1) Industrial applications of agent technologies

Vladimir Marik and Jiri Lazansky

Abstract:

This paper is aimed at summarizing the current state-of-the-art in the
development of agent-based solutions in three areas connected with
industrial production, namely in holonic control, production management
and virtual enterprises. This paper shows how the results in these
three sub-areas are converging and discusses how the agent-oriented
technologies could provide a good background for developing a unifying
approach. Two industrial applications of agent-based systems are
described in some detail. The paper also presents both the positive and
negative aspects of applying agent-based technologies in industry. 

2) Improving automation software dependability: A role for formal
methods?

Timothy L. Johnson

The growth of manufacturing control software from simple NC and
PLC-based systems to concurrent networked systems incorporating PCs,
PLCs, CNCs, and enterprise databases has created new challenges to the
design, implementation, and maintenance of safe and dependable
manufacturing systems. Key milestones in this evolution, and the
prospects for the use of formal verification methods in achieving
enhanced dependability of future manufacturing software, are examined
in this paper and presentation.

3) Automatic model generation and PLC-code implementation for
interlocking policies in industrial robot cells

H. Flordal, M. Fabian, K. Akesson and D. Spensieri

In industrial production lines, for example in the automotive industry,
cells with multiple industrial robots are common. In such cells, each
robot has to avoid running into static obstacles and when the robots
work together in a shared space they must also avoid colliding with
each other. Typically, the latter is enforced by manually implementing
interlocks in programmable logic controllers (PLCs). This is a tedious,
error-prone task that is a bottleneck in the development of production
lines. The PLC-code being man-made also greatly complicates the
maintenance and reconfiguration of such production lines. However, in
industry today, a lot of development of robot cells is made offline in
3D simulation environments which enables the use of computers also for
deciding and implementing the necessary coordination. This paper
presents a method that makes use of information in a robot simulation
environment in order to automatically extract finite state models.
These models can be used to generate supervisors for ensuring that the
deadlock situations that may arise as a consequence of the introduced
interlocks are avoided. It is also possible to optimize the work cycle
time for the cell. Finally, PLC-code to supervise the production cell
can be automatically generated from the deadlock-free and possibly
optimized system model. This approach results in a high flexibility in
that the coordination function can be quickly reimplemented whenever
necessary. A prototype implementation has been developed making use of
a commercial 3D robot simulation tool, and a software tool for
supervisor synthesis and code generation. The approach is general and
should be possible to implement in most offline robot simulation tools.

4) Controller dependability analysis by probabilistic model checking

Marta Kwiatkowska, Gethin Norman and David Parker

This paper demonstrates how probabilistic model checking, a formal
verification method for the analysis of systems which exhibit
stochastic behaviour, can be applied to the study of dependability
properties of software-based control systems. By using existing
formalisms and tool support from this area, it is possible to construct
large and complex Markov models from an intuitive high-level
description and to take advantage of the efficient implementation
techniques which have been developed for these tools. This paper
provides an overview of probabilistic model checking and of the tool
PRISM which supports these techniques. It illustrates the applicability
of the approach through the use of a case study and demonstrates that a
wide range of useful dependability properties can be analysed in this
way.

web site: click here

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

SELECTIONS FROM IEEE TRANSACTIONS ON AUTOMATIC CONTROL
VOLUME: 52, ISSUE: 9
SEPTEMBER, 2007

1) On the Reachability Problem for Uncertain Hybrid Systems

Gao, Y.; Lygeros, J.; Quincampoix, M.

Abstract: 

In this paper, we revisit the problem of designing controllers to meet
safety specifications for hybrid systems, whose evolution is affected
by both control and disturbance inputs. The problem is formulated as a
dynamic game and an appropriate notion of hybrid strategy for the
control inputs is developed. The design of hybrid strategies to meet
safety specifications is based on an iteration of alternating discrete
and continuous safety calculations. We show that, under certain
assumptions, the iteration converges to a fixed point, which turns out
to be the maximal set of states for which the safety specifications can
be met. The continuous part of the calculation relies on the
computation of the set of winning states for one player in a two
player, two target, pursuit evasion differential game. We develop a
characterization of these winning states (as well as the winning states
for the other player for completeness) using methods from nonsmooth
analysis and viability theory.

2) On the Hybrid Optimal Control Problem: Theory and Algorithms

 Shaikh, M. S.; Caines, P. E.

Abstract: 

A class of hybrid optimal control problems (HOCP) for systems with
controlled and autonomous location transitions is formulated and a set
of necessary conditions for hybrid system trajectory optimality is
presented which together constitute generalizations of the standard
Maximum Principle; these are given for the cases of open bounded
control value sets and compact control value sets. The derivations in
the paper employ: (i) classical variational and needle variation
techniques; and (ii) a local controllability condition which is used to
establish the adjoint and Hamiltonian jump conditions in the autonomous
switching case. Employing the hybrid minimum principle (HMP) necessary
conditions, a class of general HMP based algorithms for hybrid systems
optimization are presented and analyzed for the autonomous switchings
case and the controlled switchings case. Using results from the theory
of penalty function methods and Ekeland's variational principle the
convergence of these algorithms is established under reasonable
assumptions. The efficacy of the proposed algorithms is illustrated via
computational examples.

3) Energy- and Entropy-Based Stabilization for Lossless Dynamical
Systems via Hybrid Controllers

 Haddad, W. M.; Chellaboina, V.; Hui, Q.; Nersesov, S. G.

Abstract: 

A novel class of dynamic, energy-based hybrid controllers is proposed
as a means for achieving enhanced energy dissipation in lossless
dynamical systems. These dynamic controllers combine a logical
switching architecture with continuous dynamics to guarantee that the
system plant energy is strictly decreasing across switchings. The
general framework leads to closed-loop systems described by impulsive
differential equations. In addition, we construct hybrid dynamic
controllers that guarantee that the closed-loop system is consistent
with basic thermodynamic principles. In particular, the existence of an
entropy function for the closed-loop system is established that
satisfies a hybrid Clausius-type inequality. Special cases of
energy-based and entropy-based hybrid controllers involving
state-dependent switching are described.

4) Bisimilarity Control of Partially Observed Deterministic Systems

 Zhou, C.; Kumar, R.

Abstract: 

Control for safety and nonblockingness using a deterministic supervisor
requires the specification language be controllable and observable
(under the setting that marking is also decided by a supervisor). We
argue that there exist cases where the above properties do not hold,
yet a safe and nonblocking control can be synthesized by allowing the
supervisor to be nondeterministic. Use of a nondeterministic supervisor
yields a controlled system that is nondeterministic for which a
language equivalence only preserve the safety but not the nonblocking
property, and so instead we require the stronger equivalence of
bisimilarity (which preserves "sequential" behavior such as safety as
well as "branching" behavior such as nonblockingness). This motivates
us to consider control of deterministic systems for achieving
bisimulation equivalence to possibly nondeterministic specifications.
We introduce the notions of state-achievability (SA) and
state-achievability-bisimilar (SAB) as part of the existence condition,
and develop effective algorithms for verify the existence conditions as
well as for synthesizing a supervisor when the existence condition
holds. We show that the complexity of verifying the existence of a
controller is polynomial, whereas that of computing a controller (when
one exists) is singly exponential. The proposed approach can be applied
to enforce any property that depends on branching and sequential behavior.

5)  Event-Triggered Real-Time Scheduling of Stabilizing Control Tasks

Tabuada, P.  

Abstract: 

In this note, we revisit the problem of scheduling stabilizing control
tasks on embedded processors. We start from the paradigm that a
real-time scheduler could be regarded as a feedback controller that
decides which task is executed at any given instant. This controller
has for objective guaranteeing that (control unrelated) software tasks
meet their deadlines and that stabilizing control tasks asymptotically
stabilize the plant. We investigate a simple event-triggered scheduler
based on this feedback paradigm and show how it leads to guaranteed
performance thus relaxing the more traditional periodic execution
requirements.

6) Marking Estimation of Petri Nets With Silent Transitions

 Giua, A.; Seatzu, C.; Corona, C.

Abstract: 

In this paper, we deal with the problem of estimating the marking of a
labeled Petri net system based on the observation of transitions
labels. In particular, we assume that a certain number of transitions
are labeled with the empty string $varepsilon$ , while unique labels
taken from a given alphabet are assigned to each of the other
transitions. Transitions labeled with the empty string are called
silent because their firing cannot be observed. Under some technical
assumptions on the structure of the unobservable subnet, we formally
prove that the set of markings consistent with the observed word can be
represented by a linear system with a fixed structure that does not
depend on the length of the observed word.

web site: click here