3 results for Akesson, Knut

  • Supremica – An integrated environment for verification, synthesis and simulation of discrete event systems

    Akesson, Knut; Fabian, Martin; Flordal, Hugo; Malik, Robi (2006)

    Conference item
    University of Waikato

    An integrated environment, Supremica, for verification, synthesis and simulation of discrete event systems is presented. The basic model in Supremica is finite automata where the transitions have an associated event together with a guard condition and an action function that updates automata variables. Supremica uses two main approaches to handle large state-spaces. The first approach exploits modularity in order to divide the original problem into many smaller problems that together solve the original problem. The second approach uses an efficient data structure, a binary decision diagram, to symbolically represent the reachable states. Models in Supremica may be simulated in the environment. It is also possible to generate code that implements the behavior of the model using both the IEC 61131 and the IEC 61499 standard.

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  • Compositional synthesis of maximally permissive supervisors using supervision equivalence

    Flordal, Hugo; Malik, Robi; Fabian, Martin; Akesson, Knut (2007)

    Journal article
    University of Waikato

    This paper presents a general framework for efficient synthesis of supervisors for discrete event systems. The approach is based on compositional minimisation, using concepts of process equivalence. In this context, a large number of ways are suggested how a finite-state automaton can be simplified such that the results of supervisor synthesis are preserved. The proposed approach yields a compact representation of a least restrictive supervisor that ensures controllability and nonblocking. The method is demonstrated on a simple manufacturing example to significantly reduce the number of states constructed for supervisor synthesis.

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  • Nonblocking and safe control of discrete-event systems modeled as extended finite automata

    Ouedraogo, L.; Kumar, R.; Malik, Robi; Akesson, Knut (2011)

    Journal article
    University of Waikato

    Extended Finite Automata (EFA), i.e., finite automata extended with variables, are a suitable modeling framework for discrete event systems owing to their compactness, resulting from the use of variables. In this paper, we propose a symbolic algorithm that efficiently synthesizes a supervisor for a plant modeled by an EFA and a specification defined by another EFA. The principle of the algorithm is to iteratively strengthen the guards of the plant EFA so that forbidden or blocking states become unreachable in the controlled plant. As a consequence of the algorithm, the controlled behavior is modeled by an EFA having the same structure as the plant EFA, having stronger guards and is shown to be maximally permissive. We illustrate our algorithm via a simple manufacturing example.

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