On observability with delay: antitheses and syntheses

Bose, S.; Patra, Amit; Mukhopadhyay, Sudipta

doi:10.1109/9.286256

Cited by 5 publications

(5 citation statements)

References 3 publications

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“…Note that Definition 5 is the same as the definition of the "trajectory of state estimates" in [10]. The authors of [10] argue that the definition of always observability in [11] has shortcomings and use the "trajectory of state estimates" to define the notion of always observability. In [10], the construction of the trajectory of estimates is not considered.…”

Section: Opacity In Desmentioning

confidence: 97%

“…The authors of [10] argue that the definition of always observability in [11] has shortcomings and use the "trajectory of state estimates" to define the notion of always observability. In [10], the construction of the trajectory of estimates is not considered. In this paper, we construct an observer with K-delay (or K-delayed observer) which is capable of capturing the Kdelayed estimates.…”

Section: Opacity In Desmentioning

confidence: 99%

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Notions of security and opacity in discrete event systems

Saboori

Hadjicostis

2007

2007 46th IEEE Conference on Decision and Control

208

164

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In this paper, we follow a state-based approach to extend the notion of opacity in computer security to discrete event systems. A system is (S, P )-opaque if the evolution of its true state through a set of secret states S remains opaque to an observer who is observing activity in the system through the projection map P . In other words, based on observations through the mapping P , the observer is never certain that the current state of the system is within the set of secret states S. We also introduce the stronger notion of (S, P, K)-opacity which requires opacity to remain true for K observations following the departure of the system's state from the set S. We show that the state-based definition of opacity enables the use of observer constructions for verification purposes. In particular, the verification of (S, P, K)-opacity is accomplished via an observer with K-delay which is constructed to capture state estimates with K-delay. These are the estimates of the state of the system K observations ago and are consistent with all observations (including the last K observations). We also analyze the properties and complexity of the observer with Kdelay.

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Section: Opacity In Desmentioning

confidence: 97%

Section: Opacity In Desmentioning

confidence: 99%

Notions of security and opacity in discrete event systems

Saboori

Hadjicostis

2007

2007 46th IEEE Conference on Decision and Control

208

164

View full text Add to dashboard Cite

show abstract

“…Another characterization of observability has been given in terms of the state. A plant is said to be (state) observable if by observing a sufficiently long string in P(L (~)), after a finite number of events, the state of the system can be determined exactly (13zveren & Willsky 1990;Bose et al 1994). Concepts of stability and stabilization have also been introduced in terms of state space (Brave & Heymann 1990;Ozveren et al 1991 ;13zveren & Willsky 1991).…”

Section: Control Pgtternmentioning

confidence: 99%

Logical models of discrete event systems: A comparative exposition

Patra¹,

Mukhopadhyay²,

Bose

1996

Sadhana

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The increasing complexity of man-made systems calls for new tools and techniques to model them efficiently and at the desired level of abstraction. Well-established modelling paradigms, such as finite state machines, petri nets, communicating sequential processes etc., which are borrowed from the fields of computer science and operations research, often lack certain essential features for capturing discrete event dynamics. New tools such as state charts, timed transition models, finitely recursive processes etc., are evolving to take into account some of these requirements. In this paper we first characterize such systems as well as typical problems related to them. We then discuss and critically evaluate several modelling frameworks through examples. At the end we provide a comparison among the frameworks and directions for future research.

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“…The task of state-estimation for DESs has received considerable attention (see for example [1], [2], [3], [4]). The state estimation problem has also been studied in the setting of Petri nets, where the goal is to find the set of markings consistent with the observation sequence (see for example [5], [6], [7], [8], [9]).…”

Section: Introductionmentioning

confidence: 99%

Distributed state estimation in discrete event systems

Kumar

2009

2009 American Control Conference

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Knowledge of the current system state is crucial to many discrete event systems (DESs) applications such as control, diagnosis and prognosis. Due to limited sensing capabilities, the current state information is generally not available and needs to be estimated. In this paper, we propose a novel distributed state estimation algorithm for discrete event plants. According to the proposed algorithm, local sites maintain and update local state estimates based on their local observations of the plant behavior and the observations of the plant behavior sent from the other sites over communication channels with delays. For efficiency of storage, redundant history information about the possible plant evolution is truncated each time a local state estimate is updated. At each local site, the truncation is performed independently requiring no synchronization among the sites. The state estimate maintained at each of the local sites is shown to remain finite regardless of whether the system can execute an unbounded sequence of unobservable events. It is also shown that the proposed algorithm is sound and complete, i.e., each local estimate always contains the true current states (soundness), and it only contains the reachable states of the traces which give rise to a same history of observations (as received from the plant and the other local sites) as does the one executed by the plant (completeness). Also the proposed algorithm can support an architecture in which there is no communication from a certain site to certain other sites. An illustrative example is provided to demonstrate the proposed distributed state estimation algorithm.

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On observability with delay: antitheses and syntheses

Cited by 5 publications

References 3 publications

Notions of security and opacity in discrete event systems

Notions of security and opacity in discrete event systems

Logical models of discrete event systems: A comparative exposition

Distributed state estimation in discrete event systems

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