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

Automatic generation of safe handlers for multi-task systems

International audienceWe are interested in the programming of real-time embedded control systems, such as in robotic, automotive or avionic systems. They are designed with multiple tasks, each with multiple modes. It is complex to design task handlers that control the switching of activities in order to insure safety properties of the global system. We propose a model of tasks in terms of transition systems, designed especially with the purpose of applying existing discrete controller synthesis techniques. This provides us with a systematic methodology, for the automatic generation of safe task handlers, with the support of synchronous languages and associated tools

Robust State-Based Supervisory Control of Hierarchical Discrete-Event Systems

Model uncertainty due to unknown dynamics or changes (such as faults) must be addressed in supervisory control design. Robust supervisory control, one of the approaches to handle model uncertainty, provides a solution (i.e., supervisor) that simultaneously satisfies the design objectives of all possible known plant models. Complexity has always been a challenging issue in the supervisory control of discrete-event systems, and different methods have been proposed to mitigate it. The proposed methods aim to handle complexity either through a structured solution (e.g. decentralized supervision) or by taking advantage of computationally efficient structured models for plants (e.g., hierarchical models). One of the proposed hierarchical plant model formalisms is State-Tree-Structure (STS), which has been successfully used in supervisor design for systems containing up to 10^20 states. In this thesis, a robust supervisory control framework is developed for systems modeled by STS. First, a robust nonblocking supervisory control problem is formulated in which the plant model belongs to a finite set of automata models and design specifications are expressed in terms of state sets. A state-based approach to supervisor design is more convenient for implementation using symbolic calculation tools such as Binary Decision Diagrams (BDDs). In order to ensure that the set of solutions for robust control problem can be obtained from State Feedback Control (SFBC) laws and hence suitable for symbolic calculations, it is assumed, without loss of generality, that the plant models satisfy a mutual refinement assumption. In this thesis, a set of necessary and sufficient conditions is derived for the solvability of the robust control problem, and a procedure for finding the maximally permissive solution is obtained. Next, the robust state-based supervisory framework is extended to systems modeled by STS. A sufficient condition is provided under which the mutual refinement property can be verified without converting the hierarchical model of STS to a flat automaton model. As an illustrative example, the developed approach was successfully used to design a robust supervisor for a Flexible Manufacturing System (FMS) with a state set of order 10^8

Verificação de conflito na supervisão de sistemas concorrentes usando abstrações

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.A explosão do espaço de estados associada ao teste para detecção do conflito é um dos principais problemas que impedem a aplicação da Teoria de Controle Supervisório de Sistemas a Eventos Discretos a sistemas industriais reais. O conflito é uma propriedade global dos sistemas concorrentes sendo que, para sua detecção, deve-se verificar não-bloqueio da composição dos subsistemas que estão sendo verificados. Esta tese trata do problema de detecção de conflito de forma eficiente. Neste trabalho, propõe-se um novo teste de não-conflito baseado em abstrações dos supervisores, obtidas pela operação de projeção natural. Apresentam-se dois conjuntos de condições sobre as abstrações para os quais o teste de não-conflito pode ser aplicado, com resultado equivalente àquele do teste sobre os supervisores originais. No primeiro conjunto de condições os eventos compartilhados são mantidos nas abstrações e a projeção deve possuir a propriedade do observador. O segundo conjunto de condições sobre as abstrações leva em conta propriedades estruturais dos supervisores originais para derivar o conjunto de eventos a serem mantidos nas abstrações, além da propriedade do observador sobre a projeção obtida. As duas abordagens podem ser utilizadas em conjunto para obter abstrações possivelmente melhores, de forma a obter maior redução do espaço de estados na verificação de não-conflito. Apresenta-se ainda um algoritmo para verificação da propriedade do observador. Esta propriedade é utilizada exaustivamente nos resultados apresentados e sua verificação torna-se de grande interesse para a aplicação dos resultados obtidos

Supervisory Control of Product and Hierarchical Discrete Event Systems, in "European

In 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 o