| 1. |
- Goorden, Martijn, et al.
(författare)
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Compositional coordinator synthesis of extended finite automata
- 2021
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Ingår i: Discrete Event Dynamic Systems: Theory and Applications. - : Springer Science and Business Media LLC. - 0924-6703 .- 1573-7594. ; 31:3, s. 317-348
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Tidskriftsartikel (refereegranskat)abstract
- To avoid the state-space explosion problem, a set of supervisors may be synthesized using divide and conquer strategies, like modular or multilevel synthesis. Unfortunately, these supervisors may be conflicting, meaning that even though they are individually non-blocking, they are together blocking. Abstraction-based compositional nonblocking verification of extended finite automata provides means to verify whether a set of models is nonblocking. In case of a blocking system, a coordinator can be synthesized to resolve the blocking. This paper presents a framework for compositional coordinator synthesis for discrete-event systems modeled as extended finite automata. The framework allows for synthesis of a coordinator on the abstracted system in case compositional verification identifies the system to be blocking. As the abstracted system may use notions not present in the original model, like renamed events, the synthesized coordinator is refined such that it will be nonblocking, controllable, and maximally permissive for the original system. For each abstraction, it is shown how this refinement can be performed. It turns out that for the presented set of abstractions the coordinator refinement is straightforward.
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| 2. |
- Goorden, Martijn, et al.
(författare)
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Model properties for efficient synthesis of nonblocking modular supervisors
- 2021
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Ingår i: Control Engineering Practice. - : Elsevier BV. - 0967-0661. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- Supervisory control theory provides means to synthesize supervisors for systems with discrete-event behavior from models of the uncontrolled plant and of the control requirements. The applicability of supervisory control theory often fails due to a lack of scalability of the algorithms. This paper proposes a format for the requirements and a method to ensure that the crucial properties of controllability and nonblockingness directly hold, thus avoiding the most computationally expensive parts of synthesis. The method consists of creating a control problem dependency graph and verifying whether it is acyclic. Vertices of the graph are modular plant components, and edges are derived from the requirements. In case of a cyclic graph, potential blocking issues can be localized, so that the original control problem can be reduced to only synthesizing supervisors for smaller partial control problems. The strength of the method is illustrated on two case studies: a production line and a roadway tunnel.
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| 3. |
- Goorden, Martijn, et al.
(författare)
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No synthesis needed, we are alright already
- 2019
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2019-August, s. 195-202
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Konferensbidrag (refereegranskat)abstract
- Supervisory control theory provides means to synthesize supervisors for cyber-physical systems based on models of the uncontrolled plant and models of the control requirements. In general, it has been shown that supervisory control synthesis is NP-hard, which is not beneficial for the applicability to industrial-sized systems. However, supervisory control synthesis seems to be easy for several industrial-sized systems compared to the theoretical worst-case complexity. In this paper, we propose properties to identify easy supervisory control problems. When a system satisfies these properties, we show that the plant models and the requirement models together are a controllable, nonblocking, and maximally permissive supervisor, i.e., no synthesis is needed to calculate a supervisor. Furthermore, these properties allow for local verification of each plant and requirement model separately.
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