An Efficient Modular Method for the Control of Concurrent Discrete Event Systems: A Language-Based Approach

International audienceIn this paper, we are interested in the control of a particular class of Concurrent Discrete Event Systems defined by a collection of components that interact with each other. We investigate the computation of the supremal controllable language contained in the language of the specification. We do not adopt the decentralized approach. Instead, we have chosen to use a modular centralized approach and to perform the control on some approximations of the plant derived from the behavior of each component. The behavior of these approximations is restricted so that they respect a new language property for discrete event systems called partial controllability condition that depends on the specification. It is shown that, under some assumptions, the intersection of these ``controlled approximations'' corresponds to the supremal controllable language contained in the specification with respect to the plant. This computation is performed without having to build the whole plant, hence avoiding the state space explosion induced by the concurrent nature of the plant. It is finally shown that the class of specifications on which our method can be applied strictly subsumes the class of separable specifications

Supervisory Control of Product and Hierarchical Discrete Event Systems

International audienceIn this paper, the supervisory control of a class of Discrete Event Systems is investigated. Discrete event systems are modeled either by a collection of Finite State Machines that behave asynchronously or by a Hierarchical Finite State Machine. The basic problem of interest is to ensure the invariance of a set of particular configurations in the system. When the system is modeled as asynchronous FSMs, we provide algorithms that, based on a particular decomposition of the set of forbidden configurations, solve the control problem locally (i.e. on each component without computing the whole system) and produce a global supervisor ensuring the desired property. We then provide sufficient conditions under which the obtained controlled system is non-blocking. This kind of objectives may be useful to perform dynamic interactions between different parts of a system. Finally, we apply these results to the case of Hierarchical Finite State Machine

Une approche modulaire pour le contrôle de systèmes à événements discrets concurrents

National audienceDans cet article, nous nous intéressons au contrôle de systèmes à événements discrets concurrents définis par une collection de sous-systèmes interagissant les uns avec les autres. Étant donné un objectif de contrôle, le but consiste à calculer un superviseur maximal assurant cet objectif, sans construire explicitement le système à contrôler. Des approximations du système G sont dérivés à partir des sous-systèmes qui le composent, et une propriété appelée contrôlabilité partielle, devant être vérifiée par l'objectif sur ces approximations, est introduite. Assurer la contrôlabilité partielle de l'objectif sur chacune des approximations permet, sous certaines hypothèses, d'en déduire un superviseur maximal assurant l'objectif de contrôle sur G. Les calculs effectués ont une faible complexité et ne nécessitent pas de construire explicitement le système G, évitant ainsi l'explosion combinatoire inhérente aux systèmes concurrent

Supervisory Control of Asynchronous and Hierarchical Finite State Machines

International audienceIn this paper, modular supervisory control of a class of Discrete Event Systems is investigated. Discrete event systems are modeled by a Hierarchical Finite State Machine. The basic problem of interest is to solve the State Avoidance Control Problem. We provide algorithms that, based on a particular decomposition of the set of forbidden configurations, locally solve the control problem (i.e. on each component without computing the whole system) and produce a global supervisor ensuring the desired property. This kind of objectives may be useful to perform dynamic interactions between different parts of a syste

Safety Control of Hierarchical Synchronous Discrete Event Systems: A State-Based Approach

International audienceIn this paper, we discuss the control of a particular class of Hierarchical Discrete Event Systems and the state avoidance control problem is considered. A methodology is provided that locally computes on each component of the system the set of bad states (these are the states that may lead to the forbidden states via an uncontrollable trajectory). This is performed without computing the whole system. At this point, the supervisor is evaluated on the fly w.r.t. the bad states and thus requires an on-line evaluation in order to determine the set of events that has to be disabled by control. It is performed in such a way that the global partial transition function does not need to be built

Supervisory Control Problems of Hierarchical Finite State Machines

International audienceThe situation under consideration is that of a given Discrete Event System (DES), whose behavior has to be modified by means of a feedback control (named Supervisor) in order to achieve a given set of requirements that the initial DES did not satisfy. To do so, the DES is modeled as a Hierarchical Finite State Machine (HFSM). Further, instead of translating the HFSM to ordinary state machines and using classical synthesis tools on the resulting FSM, we here present algorithms that solve the Supervisory Control Problem (for a particular case of forbidden state avoidance problem) as well as the Optimal Control Problem without expanding the HFS

Supervisory Control and Deadlock Avoidance Control Problem for Concurrent Discrete Event Systems

International audienceIn this paper, we tackle the Supervisory Control Problem control for Concurrent Discrete Event Systems. These are systems that are defined by a collection of components that interact with each other. In this study, we first outline the method allowing to solve the state avoidance control problem on concurrent system, without having to compute the whole system. We then present results offering an efficient method to detect deadlock states in the controlled system due either to the composition or to the control that is performed on the syste

Contrôle de systèmes à événements discrets hiérarchiques

National audienceDans ce papier, nous nous intéressons au contrôle de systèmes à événements discrets modélisés par des machines à états finis hiérarchiques. Le problème du contrôle que nous nous posons est d'assurer l'interdiction d'un ensemble particulier de configurations dans le système. Nous présentons des algorithmes qui, basés sur une décomposition particulière de cet ensemble, résolvent localement les problèmes de contrôle (i.e. sur chaque composant du système sans avoir à calculer explicitement le système) et produisent un contrôleur global assurant la propriété attendue. Ce type d'objectifs peut être utilisé pour décrire/assurer des interactions entre différents sous-systèmes

Organisational communication management during the Volkswagen diesel emissions scandal: A hermeneutic study in attribution, crisis management, and information orientation

The discovery in September 2015 of diesel emissions software cheat technology in Volkswagen (VW) cars initiated a process of organisational crisis management and damage limitation by VW, reflected in the contemporaneous intensive production of public information statements, including press releases, statements to shareholders and investors, and transcripts of oral evidence. Through taking stock of a selection of these public information statements, this article examines the organisational communication management strategies employed to respond to the crisis situation, making an integrated use of attribution, crisis management, and information orientation theories as an interpretive lens. An interpretivist, hermeneutic approach was used to carry out qualitative content analysis on selected statements issued by VW. The analysis reveals that there is a connection between statements relating to attribution and statements relating to information orientation, at the time of the crisis and in preparing future action. Priorities for action form part of the overall crisis management and image restoration approach. Proposed changes in information orientation constitute a key dimension of the company's public response to mitigate the offensiveness of the crisis. The analysis performed demonstrates the applicability of the proposed integration of attribution, crisis management, image restoration, and information orientation theories to better understand and explain how large corporations respond publicly to organisational crisis episodes, more specifically the ways in which attributions, crisis management, and image restoration strategies are related to aspects of information orientation as both components and consequences of the crisis

Modular supervisory control with general indecomposable specification languages

International audienceModular supervisory control of discrete-event systems (DES), where the global DES is composed of local components that run concurrently, is considered. For supervisory control of large-scale modular DES the possibility of performing control-related computations locally (in components) is of utmost importance to computational complexity. Recently we have treated the case, where the specification language is decomposable into local specification languages and is included in the (global) plant language. In this paper the case of general specification languages that are neither necessarily decomposable nor contained in the global plant language is studied. Sufficient conditions are found under which any manipulation with the global plant is avoided for the computation of supremal controllable sublanguages of (global) indecomposable specification languages