| 1. |
- Rashidinejad, Aida, et al.
(författare)
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Non-blocking Supervisory Control of Timed Automata using Forcible Events
- 2020
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 53:4, s. 356-362
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Konferensbidrag (refereegranskat)abstract
- Real-valued clocks make the state space of timed automata (TA) infinite. Conventional supervisory control synthesis techniques are only applicable to finite automata (FA). Therefore, to synthesize a supervisor for TA using conventional techniques, an abstraction of TA to FA is required. For many applications, the abstraction of real-time values results in an explosion in the finite state space. This paper presents a supervisory control synthesis technique applied directly to TA without any abstraction. The plant is given as a TA with a set of uncontrollable events and a set of forcible events that may preempt the passage of time. To obtain a non-blocking controlled system, a synthesis algorithm is proposed that delivers a supervisor (also as a TA) avoiding the blocking states. The algorithm works by (iteratively) strengthening the guards of edges labeled by controllable events and invariants of locations where time progress can be preempted by forcible events.
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| 2. |
- Rashidinejad, Aida, et al.
(författare)
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Supervisory control of discrete-event systems in an asynchronous setting
- 2019
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Ingår i: IEEE International Conference on Automation Science and Engineering. - 2161-8070 .- 2161-8089. ; 2019-August, s. 494-501
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Konferensbidrag (refereegranskat)abstract
- In conventional supervisory control theory, a plant and supervisor are supposed to work synchronously such that enabling an event by the supervisor, execution of it in the plant, and observation of the executed event by the supervisor all occur at once. Therefore, these occurrences are all captured by means of a single event. However, when a supervisor synthesized from conventional supervisory control theory is implemented in real life, it will face problems since exact synchronization can hardly happen in practice due to delayed communications. In this paper, we propose a synthesis technique to achieve a supervisor that does not face the problems caused by inexact synchronization. For this purpose, we first introduce an asynchronous setting in which enablement, execution, and observation of an event do not occur simultaneously but with some delay. We present a model representing the behavior of the plant in the asynchronous setting which we call the asynchronous plant. For the asynchronous plant, we present an algorithm synthesizing an asynchronous supervisor which satisfies (asynchronous) controllability and nonblockingness.
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| 3. |
- Rashidinejad, Aida, et al.
(författare)
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Supervisory Control of Timed Discrete-Event Systems Subject to Communication Delays and Non-FIFO Observations
- 2018
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 51:7, s. 456-463
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Tidskriftsartikel (refereegranskat)abstract
- Conventional supervisory control synthesis techniques are not adequate anymore when a network between the plant and the supervisor introduces communication delays. This paper presents a method to synthesize a networked supervisor handling delays in both observation and control channels. To deal with the problem of delayed observations, we propose an automaton modeling the behaviour of the plant observed by a supervisor through a network, called observed plant. In this automaton, events observed by a supervisor are delayed from those occurring in the plant. Moreover, since observation channels are considered not to have the first in first out (FIFO) characteristic, events may not be necessarily observed in the same order as they occurred within the plant. A safe, observable, controllable and nonblocking supervisor is synthesized for the observed plant by means of an adapted synthesis algorithm for timed discrete-event systems (TDES). By enabling the achieved supervisor to predict the effects of control delays, it will be further transformed to a networked supervisor. The networked supervisor makes decisions ahead of time to ensure that the commands will be applied on the right (plant) state.
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| 4. |
- Rashidinejad, Aida, et al.
(författare)
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Supervisory Control Synthesis of Timed Automata Using Forcible Events
- 2024
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Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 69:2, s. 1074-1080
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an algorithm for synthesizing a supervisor for timed automata (TA) using the conventional supervisory control theory. The algorithm is directly applicable to TA without explicit transformation into finite automata, and iteratively strengthens the guards of edges labeled by controllable events and invariants of locations where the progression of time can be preempted by forcible events. The synthesized supervisor, also a TA, is controllable, maximally permissive, and guarantees a non-blocking and safe supervised plant. The use of real-valued clocks in TA makes it a practical modeling framework, however, the infinite state space brings challenges. The proposed algorithm addresses these by providing a synthesis method that avoids the state-space explosion of finite automata and the loss of information that can result from abstraction of real-time values.
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