Limited lookahead supervisory control of probabilistic discrete-event systems

Winacott, Creag; Rudie, Karen

doi:10.1109/allerton.2009.5394925

Cited by 6 publications

(5 citation statements)

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“…For example, they can be a function of time, of past performance and/or of current system composition. For example, in [15], the authors propose a framework where the supervisor may choose to switch between a number of control policies during runtime.…”

Section: A Control Specificationsmentioning

confidence: 99%

Dynamic discrete-event systems with instances for the modelling of emergency response protocols

Grigorov

Rudie

2011

Proceedings of the 2011 American Control Conference

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A type of model, dynamic discrete-event systems with instances, is proposed for use with time-varying systems where a number of system components may share common behavior. The motivation for this model comes from the area of emergency response protocols where systems may change unexpectedly, however, there are predefined types of actors. The model is based on previous work on dynamic discreteevent systems and on template design. Synchronization patterns are introduced which allow the generic definition of component interactions regardless of a particular system composition. The synchronous product operation is updated in order to employ these patterns. Advantages of the proposed model include compactness of representation, preservation of the identity (history) of individual components and, with the use of online control, amenability to dynamic changes of control specifications.

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Section: A Control Specificationsmentioning

confidence: 99%

Dynamic discrete-event systems with instances for the modelling of emergency response protocols

Grigorov

Rudie

2011

Proceedings of the 2011 American Control Conference

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“…They concluded that RUBLL's performance was consistent with the optimal solution but was more readily applied to scenarios where exhaustive approaches are infeasible. 44 44 Winacott and Rudie, 2009 For hybrid systems, such as a switching circuit, Dupuis and Fan compared an LLP supervisor's performance with that of an evolved finite state controller. They concluded that the LLP supervisor was better adapted to systems with slow dynamics and a vector field that flows towards the target, although their study only considered a 1-step lookahead policy for the LLP supervisor.…”

Section: Different Underlying Plantsmentioning

confidence: 99%

Limited Lookahead Policies for the Control of Discrete-Event Systems: A Tutorial

Moulton,

Marasco,

Rudie

2020

Preprint

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Some problems in discrete-event systems (DES) model large, timevarying state spaces with complex legal languages. To address these problems, Chung et al. introduced limited lookahead policies (LLP) to provide online supervisory control for discrete-event systems. This seminal paper, along with an addendum of technical results, provided the field with a series of very important and powerful results, but in a notationally-and conceptually-dense manner. In this tutorial, we present Chung et al.'s problem formulation for online control and unravel the formal definitions and proofs from their original work with the aim of making the ideas behind limited lookahead accessible to all DES researchers. Finally, we introduce the Air Traffic Control problem as an example of an online control problem and demonstrate the synthesis of LLP supervisors.

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“…Limited lookahead control [20], [66] offers a novel solution to the problem of an unmanageable state space. Rather than calculate a complete supervisor offline, which may not be feasible, an N -step "lookahead" tree of possible system behaviour is analyzed to determine control policy.…”

Section: Literature Reviewmentioning

confidence: 99%

“…A compartmental model undergoes simulation in [11] to compare the cost of approaches to reduce mortality (e.g., universal vaccination and emergency surveillance and response). Pandemic influenza is also a concern; spreadsheet-based software known as FluSurge has been used in [20], [66] Parameterized DES --Mitigates state-space explosion from a supervisory perspective [10] Timed DES Assigns timing intervals to events -No approach to probability; subject to state-space explosion [13], [33] Probabilistic / Stochastic DES -…”

Section: Modelling Health-care Response To a Disastermentioning

confidence: 99%

“…Precomputing all possible system behaviour into a single graph for analysis may not be computationally feasible, let alone desirable.Restricted directed acyclic graphs are introduced in this chapter to reduce the effects of state-space explosion. These structures are inspired by limited lookahead trees[20],[66] in the field of discrete-event systems. One of these trees contains a portion of the system behaviour calculated from the current state.…”

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Augmenting Petri Nets to Model Health-Care Protocols

Whittaker

Rudie

McLellan

et al. 2010

IFAC Proceedings Volumes

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An outbreak of an infectious illness can have a devastating impact on a population. Once confirmed, local health care organizations will attempt to reduce the spread of the disease by adopting a set of pre-defined guidelines. Modelling such a system presents a number of unique challenges: timing and probability constraints must be captured, scaling must be seamless and methods for analysis must be robust and efficient. To satisfy these requirements, an augmented form of Petri net known as a choice-point net is introduced in this thesis. In this data structure, timing is associated with event-based transitions that may fire multiple times to simulate the same event occurring several times in parallel. Events may result in several possible outcomes, or choices, each of which is given a probability of occurrence. A choice-point net may be scaled without requiring structural changes to the model and may be analyzed by unravelling it into a finite-state automaton representing (perhaps portions of) its behaviour. By translating questions about the protocol into the mathematical language of the net, recursive algorithms may then be employed to provide health-care professionals with answers to their questions. To demonstrate the expressiveness of choice-point nets, an actual, in-use protocol to control respiratory infection outbreaks in long-term care homes is modelled. Three similar abridged scenarios set in a small long-term care home are also modelled, analyzed and compared.

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Limited lookahead supervisory control of probabilistic discrete-event systems

Cited by 6 publications

References 10 publications

Dynamic discrete-event systems with instances for the modelling of emergency response protocols

Dynamic discrete-event systems with instances for the modelling of emergency response protocols

Limited Lookahead Policies for the Control of Discrete-Event Systems: A Tutorial

Augmenting Petri Nets to Model Health-Care Protocols

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