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Browsing by Author "Schmidt, Klaus"

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    Computation of Reduced Diagnosers for the Fault Diagnosis of Discrete Event Systems
    (2014) Kart, Bora Eser; Schmidt, Klaus
    Many complex systems in different areas such as manufacturing, telecommunications or transportation can be modeled as discrete event systems (DES). In this paper, we consider the fault diagnosis for DES which is concerned with detecting fault occurrences in a DES within a bounded number of event occurrences by a diagnoser automaton. Hereby, such diagnoser is able to observe a subset of the system events and the maximum required number of event occurrences until a fault detection is denoted as the worst case detection delay (WCDD). The main contribution of the paper is an approach for reducing the number of required observations for fault diagnosis without increasing the WCDD. As a result, it is possible to determine a diagnoser with a small size which is essential in practical applications. We first develop an algorithm for computing the WCDD and then adapt an approach for the reduction of the observable event set in order to obtain a reduced diagnoser. The application of our method to a communication system example demonstrates its practicability.
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    Citation - WoS: 5
    Citation - Scopus: 9
    Hierarchical Control With Partial Observations: Sufficient Conditions
    (Ieee, 2011) Boutin, Olivier; Komenda, Jan; Masopust, Tomas; Schmidt, Klaus; van Schuppen, Jan H.
    In this paper, hierarchical control of both monolithic and modular discrete-event systems under partial observations is studied. Two new conditions, called observation consistency and local observation consistency, are proposed. These conditions are sufficient for the preservation of observability between the original and the abstracted plant. Moreover, it is shown that both conditions are compositional, that is, they are preserved by the synchronous product. This property makes it possible to use hierarchical and decentralized supervisory control for discrete-event systems with partial observations.
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    Citation - WoS: 52
    Citation - Scopus: 72
    Maximally permissive hierarchical control of decentralized discrete event systems
    (Ieee-inst Electrical Electronics Engineers inc, 2011) Schmidt, Klaus; Breindl, Christian
    The subject of this paper is the synthesis of natural projections that serve as nonblocking and maximally permissive abstractions for the hierarchical and decentralized control of large-scale discrete event systems. To this end, existing concepts for nonblocking abstractions such as natural observers and marked string accepting (msa)-observers are extended by local control consistency (LCC) as a novel sufficient condition for maximal permissiveness. Furthermore, it is shown that, similar to the natural observer condition and the msa-observer condition, also LCC can be formulated in terms of a quasi-congruence. Based on existing algorithms in the literature, this allows to algorithmically compute natural projections that are either natural observers or msa-observers and that additionally fulfill LCC. The obtained results are illustrated by the synthesis of nonblocking and maximally permissive supervisors for a manufacturing system.
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    Citation - WoS: 0
    Citation - Scopus: 24
    Optimal Message Scheduling for the Static Segment of Flexray
    (Ieee, 2010) Schmidt, Klaus; Schmidt, Ece G.
    In this paper, we study the scheduling of periodic messages in the static segment of the FlexRay protocol. Our approach is based on two performance metrics. Similar to previous work, we seek to allocate a minimum number of frame IDs (FIDs) in the static segment. In addition, different from existing work, we want to minimize the message jitter, i.e., the deviation of the message transmission from the required periodicity. To this end, we first derive analytical expressions that quantify the FID allocation and the jitter, and then formulate a linear integer programming problem whose solution is the desired message schedule. An example illustrates our schedule optimization.
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    Citation - WoS: 0
    Citation - Scopus: 14
    Schedulability Analysis and Message Schedule Computation for the Dynamic Segment of Flexray
    (Ieee, 2010) Schmidt, Klaus; Schmidt, Ece G.
    In this paper, we perform the schedulability analysis and schedule computation for sporadic real-time messages in the dynamic segment of the FlexRay protocol. We first formulate a linear integer programming problem that allows to determine if a given message schedule is feasible, i.e., the worst-case delay of each message is smaller than its deadline. Then, we develop a heuristic algorithm that enables the efficient computation of feasible schedules. Our results are illustrated by an experimental setup with three FlexRay nodes.