Browsing by Author "Moor, Thomas"

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Citation Count: Moor, T.; Schmidt, K.; Wittmann, T., "Abstraction-Based Control for Not Necessarily Closed Behaviours", Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 44, No. 1-1, pp. 6988-6993, (2011).
Abstraction-Based Control for Not Necessarily Closed Behaviours
(IFAC Secretariat, 2011) Moor, Thomas; Schmidt, Klaus Werner; Wittmann, Thomas
This paper addresses abstraction-based supervisory control for plant and specification behaviours that are not necessarily ω-closed, i.e. plant behaviours that exhibit eventuality properties and specifications that impose eventuality properties on the closed loop. Technically, the core idea is to combine results from previous work on abstraction-based supervision of input-output behaviours with results on supervisory control of ω-languages. As our main result, we identify a controllability condition for the plant, that ensures a nonblocking closed-loop behaviour with a controller that has been obtained for a plant abstraction.
Citation Count: Moor, T.; Schmidt, K.; Perk, S.,"Applied Supervisory Control for A Flexible Manufacturing System",Ifac Proceedings Volumes (Ifac-Papersonline), Vol. 10, No. 1, (2010).
Applied Supervisory Control for A Flexible Manufacturing System
(2010) Moor, Thomas; Schmidt, Klaus Werner; Perk, Sebastian
This paper presents a case study in the design and implementation of a discrete event system (DES) of real-world complexity. Our DES plant is a flexible manufacturing system (FMS) laboratory model that consists of 29 interacting components and is controlled via 107 digital signals. Regarding controller design, we apply a hierarchical and decentralised synthesis method from earlier work in order to achieve nonblocking and safe closed-loop behaviour. Regarding implementation, we discuss how digital signals translate to discrete events from a practical point of view, including timing issues. The paper demonstrates how both, design and implementation, are supported by the open-source software tool libFAUDES.
Citation Count: Moor, Thomas; Schmidt, Klaus Werner (2015). "Fault-tolerant control of discrete-event systems with lower-bound specifications", IFAC-PapersOnLine, Vol. 28, No. 7, pp. 161-166.
Fault-tolerant control of discrete-event systems with lower-bound specifications
(2015) Moor, Thomas; Schmidt, Klaus Werner
Fault-tolerant control addresses the control of dynamical systems such that they remain functional after the occurrence of a fault. To allow the controller to compensate for a fault, the system must exhibit certain redundancies. Alternatively, one may relax performance requirements for the closedloop behaviour after the occurrence of a fault. To achieve fault tolerance for a hierarchical control architecture, a combination of both options appears to be advisable: on each individual level of the hierarchy, the controller may compensate the fault as far as possible, and then pass on responsibility to the next upper level. This approach, when further elaborated for discrete-event systems represented by formal languages, turns out to impose a hard lower-bound inclusion specification on the closed-loop behaviour. The present paper discusses the corresponding synthesis problem and presents a solution. © 2015, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.
Citation Count: Boutalis, Yiannis; Moor, Thomas; Schmidt, Klaus (2012). "Fuzzy Hybrid Systems modeling with application in decision making and control", IS'2012 - 2012 6th IEEE International Conference Intelligent Systems, Proceedings, pp. 290-296.
Fuzzy Hybrid Systems modeling with application in decision making and control
(2012) Boutalis, Yiannis; Moor, Thomas; Schmidt, Klaus
Hybrid Systems are systems containing both discrete event and continuous variable components. Many recent contributions address crisp situations, where ambiguity or subjectivity in the measured data is absent. In this paper, we propose Fuzzy Hybrid Systems to account for inaccurate measurements and uncertain dynamics. We present a strategy to determine the most appropriate control actions in a sampled data setting. The proposed approach is based on three basic steps that are performed in each sampling period. First, the current discrete fuzzy state of the system is determined by a sensor evaluation. Next, the future discrete fuzzy state is predicted for the possible control actions and the best action, in respect to desired continuous states, is selected. Finally, the decision is cross-evaluated by a limited horizon prediction of the continuous system variables. The proposed method is explained and demonstrated for a variation of the a well-known two-tank scenario.
Citation Count: Moor, Thomas; Schmidt, Klaus Werner, "The controllability prefix for supervisory control under partial observation with an application to fault-tolerant control", Ifac Papersonline, Vol.50, No.1, pp. 13642-13647, (2017).
The controllability prefix for supervisory control under partial observation with an application to fault-tolerant control
(Elsevier Science BV, 2017) Moor, Thomas; Schmidt, Klaus Werner
The controllability prefix is known as a useful concept for the discussion and solution of synthesis problems in supervisory control of cp-languages, i.e., formal languages of infinite-length words. There, the controllability prefix is defined as the set of all finite-length prefixes that can be controlled to satisfy prescribed liveness and safety properties. In this paper, we discuss a variation of the controllability prefix to address supervisory control under partial observation for regular *-languages, i.e., formal languages of finite-length words. We derive algebraic properties that are useful for a quantitative analysis on how an upper-bound language-inclusion specification affects achievable lower-bound specifications. Our study is motivated by the synthesis of fault-tolerant supervisory controllers, where the possible occurrence of a fault may restrict the achievable pre-fault behaviour so severe, that a relaxation of the upper-bound specification becomes a practical option. As our study shows, such a relaxation can be systematically constructed in terms of the controllability prefix. (