Generalised Verification of the Observer Property in Discrete Event Systems

Bravo, Hugo; Cunha, Antonio Eduardo Carrilho da; Pena, Patrícia N.; Malik, Robi; Cury, J.E.R.

doi:10.3182/20121003-3-mx-4033.00054

Cited by 8 publications

(16 citation statements)

References 27 publications

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“…Proposition 2: Consider the setting of Problem 3 and the languages defined in (3). Let sup C k denote the language sup C(P k (sup rC 1+k )∩P k (sup rC 2+k ), L(G k ), Σ k,u ).…”

Section: B Relaxed Coordination Control Frameworkmentioning

confidence: 99%

“…Theorem 7 (Optimality conditions): Consider the setting of Problem 3 and the languages defined in (3). If the projection P i+k is an L(G 1 G 2 )-observer and OCC (LCC) for L(G 1 G 2 ), i = 1, 2, then the parallel composition of the supervisors contains the optimal solution, i.e., sup C(K, L(G 1 G 2 ), Σ u ) ⊆ sup rC 1+k sup rC 2+k .…”

Section: B Relaxed Coordination Control Frameworkmentioning

confidence: 99%

“…Let L = L(G 1 G 2 ) be a plant, and let K ⊆ L denote a specification as in Problem 1. Consider the computation of supervisors sup rC 1+k and sup rC 2+k as defined in (3). For simplicity, we assume that the languages under consideration are prefix-closed.…”

Section: Comparison With the Relaxed Frameworkmentioning

confidence: 99%

“…Recall the languages sup rC 1+k and sup rC 2+k defined above in (3). By definition, we immediately have that sup rC 1+k sup rC 2+k ⊆ P 1+k (K) P 2+k (K) = K i.e., it is potentially a solution of Problem 1.…”

Section: Application Of the Relaxed Frameworkmentioning

confidence: 99%

“…5. The optimal supervisors S1 and S2 for the problem obtained by considering infimal superlanguages Theorem 8: Consider the setting of Problem 1 and the languages defined in (2), (3). If the supervisors sup rC 1+k and sup rC 2+k are synchronously nonconflicting (e.g., prefix-closed), then their parallel composition is controllable.…”

Section: Application Of the Relaxed Frameworkmentioning

confidence: 99%

See 4 more Smart Citations

On a distributed computation of supervisors in modular supervisory control

Komenda

Masopust

Schuppen

2015

2015 International Conference on Complex Systems Engineering (ICCSE)

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In this paper, we discuss a supervisory control problem of modular discrete-event systems that allows for a distributed computation of supervisors. We provide a characterization and an algorithm to compute the supervisors. If the specification does not satisfy the properties, we make use of a relaxation of coordination control to compute a sublanguage of the specification for which the supervisors can be computed in a distributed way. I. INTRODUCTION AND MOTIVATIONWe investigate distributed supervisory control of concurrent discrete-event systems. Supervisory control theory of discrete-event systems modeled as finite automata was introduced by Ramadge and Wonham [24] and studied by many others. It aims to guarantee that the control specifications consisting of safety and of nonblockingness are satisfied in the controlled (closed-loop) system. Safety means that the language of the closed-loop system is included in a prescribed specification, and nonblockingness means that all controlled behaviors can always be completed to a marked controlled behavior. Supervisory control is realized by a supervisor that runs in parallel with the system and imposes the specification by disabling, at each state, some of the controllable events in a feedback manner. Since only controllable specifications can be achieved, one of the key issues is the computation of the supremal controllable sublanguage of the specification, from which the supervisor can be constructed.Supervisory control theory is well developed for monolithic systems, i.e., systems where the plant is modeled as a single generator. However, most of the current complex engineering systems can be abstracted as a composition of many components. Systems that model technological systems typically consist of small generators that communicate with each other in a synchronous [5] or asynchronous [7] way. Such systems are often called modular (or concurrent or distributed) discrete-event systems. It is known that to compute the overall monolithic plant for such a system can be unrealistic because the number of states of a modular system grows exponentially with respect to the number of components. This limits the applicability of the monolithic supervisory control synthesis to relatively small systems. On the other hand, the purely decentralized control consisting of an independent construction of a supervisor for each subsystem is only applicable for a local (decomposable) specification.Specifically, let G 1 and G 2 be two systems over the respective alphabets Σ 1 and Σ 2 modeled as finite generators forming the overall plant G 1 G 2 , the computation of which we want to avoid, and let K ⊆ L m (G 1 G 2 ) denote a specification. There exists a monolithic supervisor for the monolithic plant G 1 G 2 if and only if the specification is controllable with respect to the plant. However, to avoid the computation of the monolithic plant G 1 G 2 , the naive approach to compute supervisors for each subsystem separately does not work in general. To demonstrate this, assume tha...

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“…Proposition 2: Consider the setting of Problem 3 and the languages defined in (3). Let sup C k denote the language sup C(P k (sup rC 1+k )∩P k (sup rC 2+k ), L(G k ), Σ k,u ).…”

Section: B Relaxed Coordination Control Frameworkmentioning

confidence: 99%

Section: B Relaxed Coordination Control Frameworkmentioning

confidence: 99%

Section: Comparison With the Relaxed Frameworkmentioning

confidence: 99%

Section: Application Of the Relaxed Frameworkmentioning

confidence: 99%

Section: Application Of the Relaxed Frameworkmentioning

confidence: 99%

See 3 more Smart Citations

On a distributed computation of supervisors in modular supervisory control

Komenda

Masopust

Schuppen

2015

2015 International Conference on Complex Systems Engineering (ICCSE)

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Coordination control of discrete-event systems revisited

Komenda

Masopust

Schuppen³

2014

Discrete Event Dyn Syst

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Abstract. In this paper, we revise and further investigate the coordination control approach proposed for supervisory control of distributed discrete-event systems with synchronous communication based on the Ramadge-Wonham automata framework. The notions of conditional decomposability, conditional controllability, and conditional closedness ensuring the existence of a solution are carefully revised and simplified. The paper is generalized to non-prefix-closed languages, that is, supremal conditionally controllable sublanguages of not necessary prefixclosed languages are discussed. Non-prefix-closed languages introduce the blocking issue into coordination control, hence a procedure to compute a coordinator for nonblockingness is included. The optimization problem concerning the size of a coordinator is under investigation. We prove that to find the minimal extension of the coordinator event set for which a given specification language is conditionally decomposable is NP-hard. In other words, unless P=NP, it is not possible to find a polynomial algorithm to compute the minimal coordinator with respect to the number of events.

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Distributed supervisory control of discrete-event systems with communication delay

Zhang

Cai

Gan

et al. 2015

Discrete Event Dyn Syst

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This paper identifies a property of delay-robustness in distributed supervisory control of discrete-event systems (DES) with communication delays. In previous work a distributed supervisory control problem has been investigated on the assumption that inter-agent communications take place with negligible delay. From an applications viewpoint it is desirable to relax this constraint and identify communicating distributed controllers which are delay-robust, namely logically equivalent to their delay-free counterparts.For this we introduce inter-agent channels modeled as 2-state automata, compute the overall system behavior, and present an effective computational test for delay-robustness. From the test it typically results that the given delay-free distributed control is delay-robust with respect to certain communicated events, but not for all, thus distinguishing events which are not delay-critical from those that are. The approach is illustrated by a workcell model with three communicating agents.

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Generalised Verification of the Observer Property in Discrete Event Systems

Cited by 8 publications

References 27 publications

On a distributed computation of supervisors in modular supervisory control

On a distributed computation of supervisors in modular supervisory control

Coordination control of discrete-event systems revisited

Distributed supervisory control of discrete-event systems with communication delay

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