30 years of the Ramadge-Wonham Theory of Supervisory Control: A Retrospective and Future Perspectives
Full-Day Workshop at the 56th IEEE Conference on Decision and Control (CDC), on Monday December 11, 2017
This workshop took place on December 11, 2017, and was a great success. This wiki is being maintained as a public archive of this event.
- Stéphane Lafortune (University of Michigan, USA)
- Karen Rudie (Queen's University, Canada)
- Stavros Tripakis (Aalto University, Finland)
List of Speakers (and their slides)
- Stéphane Lafortune, on behalf of the organizers -- Slides: Media:Lafortune-Rudie-Tripakis.pdf
- Peter Ramadge (Princeton University, USA) -- Slides: Not available
- Calin Belta (Boston University, USA) -- Slides: Media:Belta.pdf
- Kai Cai (Osaka City University, Japan) -- Slides: Media:Cai.pdf
- José Cury (Federal University of Santa Catarina, Brazil) -- Slides: Media:Cury.pdf
- Martin Fabian (Chalmers University, Sweden) -- Slides: Media:Fabian.pdf
- Alessandro Giua (University of Cagliari, Italy) -- Slides: Media:Giua.pdf
- Hervé Marchand (INRIA, France) -- Slides: Media:Marchand.pdf
- Richard Murray (Caltech, USA) -- Slides: Media:Murray.pdf
- Necmiye Ozay (University of Michigan, USA) -- Slides: Media:Ozay.pdf
- George Pappas (University of Pennsylvania, USA) -- Slides: Media:Pappas.pdf
- Sanjit Seshia (University of California at Berkeley, USA) -- Slides: Media:Seshia.pdf
- W. Murray Wonham (University of Toronto, Canada) -- Slides (presented by Kai Cai): Media:Wonham.pdf
Workshop Location: University of Melbourne Law School, Level 6, Room 608, Law Building, 185 Pelham St, Carlton VIC 3053
- 8:30-8:45am: Participants arrive
- 8:45-9:00am: Opening remarks (organizers)
- 9:00-9:30am: Peter Ramadge: "The Early Days of the RW Discrete Event System Model"
- 9:30-10:00am: Martin Fabian: "Computing RW supervisors: 20 odd years of battling complexity"
- 10:00-10:30am: Alessandro Giua: "Control of discrete event systems using Petri net structural approaches"
- 10:30-10:50am: Morning coffee break
- 10:50-11:20am: Richard Murray: "Rapprochement Between Formal Methods and Control Theory"
- 11:20-11:50am: Kai Cai: "Creating smart agents: a distributed control theory for DES"
- 11:50-12:00pm: Murray Wonham: "SCDES Retro-Pro-Spective: Parting (if not Parthian) Shots" [presented by Kai Cai]
- 12:00-1:30pm: Lunch (not provided - list of nearby restaurants will be provided)
- 1:30-2:00pm: José Cury: "An RW inspired research trajectory: Modeling and (Modular and Hierarchical) Control aspects"
- 2:00-2:30pm: Sanjit Seshia: "Control Improvisation"
- 2:30-3:00: Afternoon coffee break
- 3:00-3:30pm: Calin Belta: "Resilient Formal Synthesis"
- 3:30-4:00pm: Hervé Marchand: "Opacity and Supervisory Control"
- 4:00-4:30pm: George Pappas: "A theory of approximation for discrete event and continuous time systems"
- 4:30-5:00pm: Necmiye Ozay: "Scalability in formal methods"
- 5:00-5:30pm: Open discussion (all speakers and participants)
Introduction and Motivation
2017 marked the 30-year anniversary of the publication of the two seminal papers of Ramadge and Wonham on supervisory control of discrete event systems, in the January and May issues of the SIAM Journal on Control and Optimization (SICOPT) in 1987:
- [RW1] P.J. Ramadge and W.M. Wonham, "Supervisory Control of a Class of Discrete Event Processes", SIAM J. Control Optim., 25(1), 206-230.
- [RW2] W.M. Wonham and P.J. Ramadge, "On the Supremal Controllable Sublanguage of a Given Language", SIAM J. Control Optim., 25(3), 637-659.
These two papers launched the area of supervisory control of discrete event systems within the control engineering community. Their general framework based on regular languages and their finite automata representations provided powerful foundations for the development of this supervisory control theory by a worldwide community of researchers in control engineering, including continued contributions by Ramadge and Wonham with their students and collaborators. Nowadays, supervisory control à la Ramadge-Wonham is a broad theory that covers partially-observed systems, a variety of control architectures that exploit horizontal and vertical modularity, and extensions to timed systems. Indeed, [RW1] has over 3,300 citations according to Google Scholar, with yearly citations in the range of 121-171 since 2003. Supervisory control à la Ramadge-Wonham remains an active area of research, and several real-world applications have recently been demonstrated in domains ranging from electric vehicles in theme parks to patient support systems in MRI scanners, among others.
More recently, the area of formal methods in control has gained prominence in the control community, primarily in the context of cyber-physical systems that are abstracted as discrete transition systems subject to specifications expressed in temporal logic. The terminology "formal methods" comes from the computer science literature and it encompasses a set of mathematically-formal techniques that have been developed for the verification of hardware and software systems, and more recently for the synthesis of systems or programs that interact with their environment, or reactive systems. Reactive synthesis, as this latter problem is called, is fundamentally a problem of feedback control.
The Ramadge-Wonham theory of supervisory control is itself a formal method in control, for the case of specifications that can be expressed as regular languages, the same modeling paradigm as the uncontrolled system. In that sense, it is complementary to works on reactive synthesis that handle certain classes of specifications expressed using various fragments of temporal logics.
The goal of the workshop was to offer a retrospective of the Ramadge-Wonham theory of supervisory control and to present some of its recent developments and applications. In addition, the workshop connected the Ramadge-Wonham theory with the emerging area of formal methods in control and more generally with the work in reactive synthesis in computer science. To this end, the list of speakers comprised researchers associated primarily with the area of supervisory control of discrete event systems and researchers associated primarily with the area of formal methods in control.
This workshop was very timely given the emergence of autonomous systems, especially in the context of cyber-physical systems, where stringent requirements of correctness and safety are placed on the higher-level supervisory control layer. At the same time, it gave our community an opportunity to reflect on seminal papers published 30 years ago that defined a new sub-discipline in control science and engineering.
The speakers gave talks that were accessible to a wide audience. The objective was to combine the retrospective theme with the future perspectives theme, in presentations that have tutorial value. Given the emergence of cyber-physical systems as an important area of research and given that there are typically multiple CDC sessions on discrete event systems, formal methods in control, and hybrid systems, a large number of CDC attendees, in particular students, were interested in this workshop.
Credits for photos: Yiding Ji, anonymous
IEEE Control Systems Article
Link to IEEE Control Systems conference report on this workshop.
We thank all the workshop participants for making this a memorable event!