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52
Games for synthesis of controllers with partial observation
 THEORETICAL COMPUTER SCIENCE
"... The synthesis of controllers for discrete event systems, as introduced by Ramadge and Wonham, amounts to computing winning strategies in parity games. We show that in this framework it is possible to extend the specifications of the supervised systems as well as the constraints on the controllers ..."
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Cited by 117 (15 self)
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The synthesis of controllers for discrete event systems, as introduced by Ramadge and Wonham, amounts to computing winning strategies in parity games. We show that in this framework it is possible to extend the specifications of the supervised systems as well as the constraints on the controllers by expressing them in the modal µcalculus. In order to express unobservability constraints, we propose an extension of the modal µcalculus in which one can specify whether an edge of a graph is a loop. This extended µcalculus still has the interesting properties of the classical one. In particular it is equivalent to automata with loop testing. The problems such as emptiness testing and elimination of alternation are solvable for such automata. The method proposed in this paper to solve a control problem consists in transforming this problem into a problem of satisfiability of a µcalculus formula so that the set of models of this formula is exactly the set of controllers that solve the problem. This transformation relies on a simple construction of the quotient of automata with loop testing by a deterministic transition system. This is enough to deal with centralized control problems. The solution of decentralized control problems uses a more involved construction of the quotient of two automata. This work extends the framework of Ramadge and Wonham in two directions. We consider infinite behaviours and arbitrary regular specifications, while the standard framework deals only with specifications on the set of finite paths of processes. We also allow dynamic changes of the set of observable and controllable events.
Diagnosis of Asynchronous Discrete Event Systems, a Net Unfolding Approach
 IEEE TRANS. ON AUTOMATIC CONTROL
, 2001
"... In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order ..."
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Cited by 92 (29 self)
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In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time, in which local events are ordered if they are either generated on the same site, or related via some causality relation. Our basic mathematical tool is that of net unfoldings originating from the Petri net research area. This study was motivated by the problem of event correlation in telecommunications network management.
Linear time logic control of discretetime linear systems
 IEEE Transactions on Automatic Control
, 2006
"... Abstract. The control of complex systems poses new challenges that fall beyond the traditional methods of control theory. One of these challenges is given by the need to control, coordinate and synchronize the operation of several interacting submodules within a system. The desired objectives are no ..."
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Cited by 61 (4 self)
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Abstract. The control of complex systems poses new challenges that fall beyond the traditional methods of control theory. One of these challenges is given by the need to control, coordinate and synchronize the operation of several interacting submodules within a system. The desired objectives are no longer captured by usual control specifications such as stabilization or output regulation. Instead, we consider specifications given by Linear Temporal Logic (LTL) formulas. We show that existence of controllers for discretetime controllable linear systems and LTL specifications can be decided and that such controllers can be effectively computed. The closedloop system is of hybrid nature, combining the original continuous dynamics with the automatically synthesized switching logic required to enforce the specification. 1.
A General Architecture for Decentralized Supervisory Control of DiscreteEvent Systems
 ACCEPTED FOR PUBLICATION IN DISCRETE EVENT DYNAMIC SYSTEMS: THEORY AND APPLICATIONS
, 2002
"... We consider a generalized form of the conventional decentralized control architecture for discreteevent systems where the control actions of a set of supervisors can be "fused" using both union and intersection of enabled events. Namely, the supervisors agree a priori on choosing "fu ..."
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Cited by 60 (5 self)
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We consider a generalized form of the conventional decentralized control architecture for discreteevent systems where the control actions of a set of supervisors can be "fused" using both union and intersection of enabled events. Namely, the supervisors agree a priori on choosing "fusion by union" for certain controllable events and "fusion by intersection" for certain other controllable events. We show that under this architecture, a larger class of languages can be achieved than before since a relaxed version of the notion of coobservability appears in the necessary and sufficient conditions for the existence of supervisors. The computational complexity ofverifying these new conditions is studied. A method of partitioning the controllable events between "fusion by union" and "fusion by intersection" is presented. The algebraic properties of coobservability in the context of this architecture are presented. We show that appropriate combinations of fusion rules with corresponding decoupled local decision rules guarantee the safety of the closedloop behavior with respect to a given specification that is not coobservable. We characterize an "optimal" combination of fusion rules among those combinations guaranteeing the safety of the closedloop behavior. In addition, a simple supervisor synthesis technique generating the in mal prefixclosed controllable and coobservable superlanguage is presented.
For the grid and through the grid: The role of power line communications in the smart grid,” to appear
 in Proceedings of the IEEE, 2011. [Online]. Available: http://arxiv.org/abs/1010.1973
"... is to address this important question. To do so we provide an overview of what PLC can deliver today by surveying its history and describing the most recent technological advances in the area. We then address Smart Grid applications as instances of sensor networking and network control problems and ..."
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Cited by 36 (1 self)
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is to address this important question. To do so we provide an overview of what PLC can deliver today by surveying its history and describing the most recent technological advances in the area. We then address Smart Grid applications as instances of sensor networking and network control problems and discuss the main conclusion one can draw from the literature on these subjects. The application scenario of PLC within the Smart Grid is then analyzed in detail. Since a necessary ingredient of network planning is modeling, we also discuss two aspects of engineering modeling that relate to our question. The first aspect is modeling the PLC channel through fading models. The second aspect we review is the Smart Grid control and traffic modeling problem which allows us to achieve a better understanding of the communications requirements. Finally, this paper reports recent studies on the electrical and topological properties of a sample power distribution network. Power grid topological studies are very important for PLC networking as the power grid is not only the information source but also the information delivery system a unique feature when PLC is used for the Smart Grid. Index Terms—Smart grid, power grid, power line communications, power line channel, cyberphysical systems. I.
I.: Distributed games
, 2003
"... Abstract. We propose a notion of distributed games as a framework to formalize and solve distributed synthesis problems. In general the problem of solving distributed games is undecidable. We give two theorems allowing to simplify, and possibly to solve, some distributed games. We show how several ..."
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Cited by 29 (2 self)
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Abstract. We propose a notion of distributed games as a framework to formalize and solve distributed synthesis problems. In general the problem of solving distributed games is undecidable. We give two theorems allowing to simplify, and possibly to solve, some distributed games. We show how several approaches to distributed synthesis found in the literature can be formalized and solved in the proposed setting. 1
Decentralized control of discrete event systems using prioritized composition with exclusion,”
 IEEE Trans. Autom. Control,
, 2008
"... AbstractWe study the decentralized control of discrete event systems with multiple local specifications. Only a subset of events occur at a local site, and a local specification as well as control/observation capabilities of a local supervisor are defined with respect to such local events. The goa ..."
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Cited by 22 (1 self)
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AbstractWe study the decentralized control of discrete event systems with multiple local specifications. Only a subset of events occur at a local site, and a local specification as well as control/observation capabilities of a local supervisor are defined with respect to such local events. The goal of control is to ensure that the executed behavior at each local site is as desired, i.e., there are multiple specifications, one for each site. We show that the control problem for multiple local specifications is different from that of a single global specification, and present a necessary and sufficient condition for the existence of decentralized supervisors for enforcing the given multiple local specifications. The synthesis of decentralized control for enforcing multiple local specifications is also presented. We also specialize our results to the case of concurrent plants (one which is composed of several local subplants), which offers certain computational savings. The results are illustrated through a simple manufacturing system example. Note to PractitionersFor physically distributed systems, only a certain local set of events is available for control and observation to a controller located at that site. The paper studies the design of a group of local controllers, one for each local site, so the behavior at each site is as desired. Existence conditions for a monolithic plant as well as for a plant composed of multiple subplants are obtained. The results can be used to enforce multiple local specifications using the decentralized control strategy presented in the paper. Index TermsDiscrete event systems, supervisory control, multiple local specifications.
Diagnosis of asynchronous discreteevent systems: A net unfolding approach
 IEEE Transactions on Automatic Control
, 2003
"... Abstract—In this paper, we consider the diagnosis of asynchronous discrete event systems. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time. Our basic mathemat ..."
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Cited by 19 (2 self)
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Abstract—In this paper, we consider the diagnosis of asynchronous discrete event systems. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time. Our basic mathematical tool is that of net unfoldings originating from the Petri net research area. This study was motivated by the problem of event correlation in telecommunications network management. Index Terms—Alarm correlation, asynchronous diagnosis, diagnosis, discrete event systems, Petri nets, unfoldings. I.
Quantitative model checking revisited: neither decidable nor approximable
 In FORMATS’07, LNCS 4763
, 2007
"... Abstract. Quantitative model checking computes the probability values of a given property quantifying over all possible schedulers. It turns out that maximum and minimum probabilities calculated in such a way are overestimations on models of distributed systems in which components are loosely coup ..."
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Cited by 17 (10 self)
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Abstract. Quantitative model checking computes the probability values of a given property quantifying over all possible schedulers. It turns out that maximum and minimum probabilities calculated in such a way are overestimations on models of distributed systems in which components are loosely coupled and share little information with each other (and hence arbitrary schedulers may result too powerful). Therefore, we focus on the quantitative model checking problem restricted to distributed schedulers that are obtained only as a combination of local schedulers (i.e. the schedulers of each component) and show that this problem is undecidable. In fact, we show that there is no algorithm that can compute an approximation to the maximum probability of reaching a state within a given bound when restricted to distributed schedulers. 1
Partial Order Techniques for Distributed Discrete Event Systems: why you can’t avoid using them
, 2007
"... 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 canno ..."
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Cited by 15 (1 self)
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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 online 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.