Control Architecture for Discrete-Event Dynamic Systems:
From Monolithic to Heterarchical and to Distributed
Slides of workshop (a single pdf file, updated 2013.01.10)
Cluster Tool example demonstrated in software libFAUDES (software download page, files required to run the example)
1. Background
A discrete-event system is a dynamic system, which is equipped with a discrete 'state space' and a event-driven 'state transition structure'. States have duration in time, while events happening instantaneously and asynchronously.
From a system-theoretic point of view, a control architecture is an organization of system-wide information feedback for conversion to actionable decision-making. Familiar architectures are monolithic (or centralized), heterarchical (some combination of hierarchical and decentralized), and distributed (purely flat, or leaderless).
In his celebrated 1962 essay on the “architecture of complexity” Herbert Simon argued that many complex physical, biological, and social systems are organized in sophisticated architectures. Likewise, the control of complex engineering systems calls for well-designed architectures. Starting from the seminal work “theory of multi-level hierarchical systems” by Mesarovic, Macko and Takahara, the systems control community has made much progress in understanding and designing sophisticated architectures, which is key to bridging systems control theory to large-scale engineering practice.
This workshop is an attempt to present such progress in the control of discrete-event systems modeled by automata. The recent years have witnessed a number of breakthroughs in systematically synthesizing heterarchical and distributed control architectures, the results being scattered in the literature. This workshop is timely to bring these results together, and present them in a unified, accessible manner.
2. Content
The workshop will present the "state of the art" of control architectures for large, complex discrete-event systems (DES) modeled by automata. Stimulated by the twin goals of reducing computational effort of control synthesis and improving comprehensibility of control logic, the DES literature has witnessed a surge of heterarchical and distributed architectures designed for large interconnected systems. This workshop attempts to bring together recent developments of key approaches for systematically synthesizing these architectures, and present the results in a unified, tutorial manner.
We will start with a detailed survey of existing control synthesis methods for large complex DES. Then we focus on describing decomposition-aggregation based structural approach to constructing heterarchical and distributed control architectures, the key being creating model abstractions effective in hiding part of underlying system dynamics irrelevant to control. We will present in a coherent style recently developed key notions and properties of such abstractions, as well as efficient algorithms and software tools for their computation. Based on these results, we further introduce a top-down localization approach that decomposes a synthesized heterarchical architecture into a purely distributed architecture where component agents are self-driven and cooperative. Finally, we will address a range of large-scale applications which points to practical implementation of heterarchical and distributed architectures, and discuss future core problems of control architecture.
The intended audiences of the workshop are graduate students and researchers specialized in discrete-event systems and systems theory in general who are interested in learning recent developments of control architectures. The workshop will also be useful for practitioners who are interested in applying systems control theory to large complex engineering systems. The workshop will feature tutorial-style lectures, providing the audience accessible introduction to the most recent key theory of control architectures.
3. Schedule of Nov. 14, 2012, Friday (tentative)
Morning
8:30 - 9:00 Opening, and introduction of supervisory control theory of discrete-event systems.
Speaker: Kai Cai
9:00 - 9:30 Literature review on decentralized/hierarchical control, and overview of workshop content
Speaker: Klaus Werner Schmidt
9:30 - 10:30 Control architecture I
Speaker: Lei Feng
10:30 - 10:45 break
10:45 - 11:45 Control architecture II
Speaker: Klaus Werner Schmidt
Afternoon
13:30 - 14:30 Control architecture III
Speaker: Rong Su
14:30 - 15:30 Control architecture IV
Speaker: Kai Cai
15:30 - 15:45 break
15:45 - 16:30 Software libFAUDES
Speaker: Klaus Werner Schmidt
16:30 - 17:00 Summary and discussions
4. Outline
W. M. Wonham, Supervisory Control of Discrete-Event Systems, Systems Control Group, Dept. of Electrical and Computer Engineering, University of Toronto, updated July 1, 2012. Available online at www.control.utoronto.ca/DES
P. J. Ramadge and W. M. Wonham, Supervisory control of a class of discrete event processes, SIAM J. of Control and Optimization, vol. 25, no. 1, pp. 206–230, 1987.
L. Feng and W. Wonham, Supervisory control architecture for discrete-event systems, IEEE Trans. Autom. Control, vol. 53, no. 6, pp. 1449-1461, 2008.
L. Feng and W. Wonham, On the computation of natural observers in discrete-event systems, Discrete Event Dyn. Syst.: Theo. Appl., vol. 20, no. 1, pp. 63-102, 2010.
[Software] TCT for discrete-event systems. Available online at www.control.utoronto.ca/DES
K. Schmidt, T. Moor, and S. Perk, Nonblocking hierarchical control of decentralized discrete event systems, IEEE Trans. Autom. Control, vol. 53, no. 10, pp. 2252-2265, 2008.
K. Schmidt, Ch. Breindl, Maximally permissive hierarchical control of decentralized discrete event systems, IEEE Trans. Autom. Control, vol. 56, no. 5, pp. 723-737, 2011.
[Software] libFAUDES. (2006–2012) libFAUDES software library for discrete event systems. Available online at: www.rt.eei.uni-erlangen.de/FGdes/faudes
R. Su, J. H. van Schuppen, J. E. Rooda, Model abstraction of nondeterministic finite-state automata in supervisor synthesis. IEEE Trans. Autom. Control, vol. 55, no. 11, pp. 2527-2541, 2010.
Rong Su, Jan H. van Schuppen and Jacobus E. Rooda. Maximum permissive coordinated distributed supervisory control of nondeterministic discrete-event systems, Automatica, in press 2012.
[Software] SuSyNA (Supervisor Synthesis for Nondeterministic Automaton). Available online at http://devel.se.wtb.tue.nl/trac/automata
K. Cai and W.M. Wonham, Supervisor localization: a top-down approach to distributed control of discrete-event systems, IEEE Trans. Autom. Control, vol. 55, no. 3, pp. 605-618, 2010.
[Software] TCT for discrete-event systems. Available online at www.control.utoronto.ca/DES
5. Instructors Biographies
Kai Cai received the B. Eng. degree in Electrical Engineering from Zhejiang University (China) in 2006, the M.A.Sc. degree in Electrical and Computer Engineering from the University of Toronto (Canada) in 2008, and the Ph.D. degree in Systems Science from Tokyo Institute of Technology (Japan) in 2011. He is currently a Postdoctoral Fellow in Systems Control, with the Department of Electrical and Computer Engineering of the University of Toronto. His research interests are distributed control of multi-agent systems, distributed control of discrete-event systems, and theory of control architecture.
Rong Su received the M.A.Sc. and Ph.D. degrees both in electrical engineering from the University of Toronto, Toronto, Canada, in 2000 and 2004 respectively. He is currently affiliated with the School of Electrical and Electronic Engineering at Nanyang Technological University in Singapore. His research interests include discrete-event modeling, supervisory control and fault diagnosis of discrete-event dynamic systems. Dr. Su is an IEEE Member and has been a member of IFAC technical committee on discrete event and hybrid systems (TC 1.3) since 2005.
Klaus Werner Schmidt received the Diploma and Ph.D. degrees from the University of Erlangen-Nuremberg, Germany, in 2002 and 2005, respectively, both in Electrical, Electronic, and Communication Engineering. He is currently an Associate Professor at the Department of Mechatronics Engineering, Cankaya University, Ankara. His research interests include controller synthesis and failure diagnosis for large-scale discrete event systems, industrial automation systems, vehicular communication networks and industrial project control. Dr. Schmidt has been a member of IFAC technical committee on discrete event and hybrid systems (TC 1.3) since 2008.
Lei Feng received the B. Eng. And M. A.Sc. Degrees in Mechatronics from Xi’an Jiaotong University (China) in 1998 and 2001, respectively. In 2007, he received the Ph.D. degree in Electrical and Computer Engineering from the University of Toronto (Canada). He is currently an assistant professor at the Mechatronics Division, Department of Machine Design, KTH Royal Institute of Technology in Stockholm, Sweden. Meanwhile he is co-appointed by Volvo Group Trucks Technology as a research engineer for automotive embedded systems. His research interests include the application of DES control theory on evolvable production systems, model-based development of automotive embedded systems, model-based analysis and testing of safety-critical systems.