| 1. |
- Falkman, Petter, 1972, et al.
(author)
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Generation of STEP AP214 models from discrete event systems for process planning and control
- 2008
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In: IEEE Transactions on Automation Science and Engineering. - 1545-5955 .- 1558-3783. ; 5:1, s. 113-126
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Journal article (peer-reviewed)abstract
- The aim of this paper is to show how the international standard STEP-AP214 can be used for communication and storing of process specifications. Even though there are several software tools available for the generation of both product and resource information systems, there is still a lack of tools related to the STEP standard for producing process information, e.g., sequence of operations and system capabilities for resource allocation. Therefore, such a tool is suggested, which makes use of a high-level language for discrete-event systems based on process algebra and Petri nets. This language, called process algebra Petri net), has been developed in accordance with the process relations defined in STEP-AP214. More specifically, it is shown how process specifications created with the PPN tool can be mapped to the STEP AP-214 format. Note to Practioners-Rapidly changing market needs is making demands on flexibility and ability to shorten lead times. Standards for exchanging information, as well as formal methods for automatic development of programmable controller code have been important research topics for many years. There are a lot of software tools available for the generation of both product- and resource information, but there is still a lack of tools for producing process information. Moreover, the connection between information exchange standards and such tools is absent, which makes the development of programmable controller code an isolated activity. This activity is often time consuming and performed in an ad hoc manner resulting in unnecessary production delay. The aim of this paper is to show how the international standard STEP-AP214 (a standard for exchange of product-, process-, and resource related information) can be used for communicating and storing process specifications. In order to achieve this, a tool which makes use of a formal high-level language is suggested. This tool can be used for automatic control generation and has been developed in accordance with the process relations defined in STEP-AP214. A further aim is to shown how the mentioned tool can be used to specify complex systems in a compact, yet highly readable manner, which is a crucial incentive for industry to use formal methods. The presented method will guarantee-that expected information is delivered quickly and without errors caused by the human factor, something that is very important in our ambition to achieve shortened lead times. The quick information exchange also makes it possible to perform simulation, supervisor synthesis, and verification early in the development phase. This is a first attempt at using a formal language for creating a tool that can automatically generate specifications in accordance with the international STEP-standard.
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| 2. |
- Shoaei, Mohammad Reza, 1983, et al.
(author)
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Abstractions for nonblocking supervisory control of Extended Finite Automata
- 2012
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In: IEEE International Conference on Automation Science and Engineering. - : IEEE. - 2161-8070 .- 2161-8089. - 9781467304290 - 9781467304283 ; , s. 6-
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Conference paper (peer-reviewed)abstract
- An abstraction method for Extended Finite Automata (EFAs), i.e., finite automata extended with variables, using transition projection is presented in this work. A manufacturing system modeled by EFAs is abstracted into subsystems that embody internal interacting dependencies. Synthesis and verification of subsystems are achieved through their model abstractions rather than their global model. Sufficient conditions are presented to guarantee that supervisors result in maximally permissive and nonblocking control. An examples demonstrate the computational effectiveness and practical usage of the approach.
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| 3. |
- Shoaei, Mohammad Reza, 1983, et al.
(author)
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On the Computation of Natural Observers for Extended Finite Automata
- 2014
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In: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 2405-8963 .- 1474-6670. - 9783902823625 ; 19, s. 2448-2455
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Conference paper (peer-reviewed)abstract
- Compared to finite automata, Extended Finite Automata (EFAs) allows us to efficiently represent discrete-event systems that involve non-trivial data manipulation. However, the complexity of designing supervisors for such systems is still a challenge. In our previous works, we have studied model abstraction for EFAs using natural projections with observer property on events as well as data. In this paper, we provide sufficient conditions for verifying the observer properties and further enhance the EFAs when the property does not hold. To this end, we introduce symbolic simplification techniques for data and generalize existing algorithms in the literature for the events to compute natural observers for EFAs. The importance of this combined abstraction and symbolic simplification method is demonstrated by synthesis of a nonblocking controller for an industrial manufacturing system.
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| 4. |
- Shoaei, Mohammad Reza, 1983, et al.
(author)
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Supervisory Control of Extended Finite Automata Using Transition Projection
- 2012
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In: Proceedings of the IEEE Conference on Decision and Control. - : IEEE. - 2576-2370 .- 0743-1546. ; :Article number 6427390, s. 7259-7266, s. 7259-7266
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Conference paper (peer-reviewed)abstract
- A limitation of the Ramadge and Wonham (RW) framework for the supervisory control theory is the explicit state representation using finite automata, often resulting in complex and unintelligible models. Extended finite automata (EFAs), i.e., deterministic finite automata extended with variables, provide compact state representation and then make the control logic transparent through logic expressions of the variables. A challenge with this new control framework is to exploit the rich control structure established in RW's framework. This paper studies the decentralized control structure with EFAs. To reduce the computational complexity, the controller is synthesized based on model abstraction of subsystems, which means that the global model of the entire system is unnecessary. Sufficient conditions are presented to guarantee that the decentralized supervisors result in maximally permissive and nonblocking control to the entire system.
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| 5. |
- Theorin, Alfred, et al.
(author)
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An Event-Driven Manufacturing Information System Architecture
- 2015
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In: 15th IFAC Symposium onInformation Control Problems inManufacturing - INCOM 2015. - : Elsevier BV. ; 48:3, s. 547-554
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Conference paper (peer-reviewed)abstract
- Future manufacturing systems need to be more flexible, to embrace tougher and constantly changing market demands. They also need to make better use of plant data, ideally utilizing all data from the entire plant. Low-level data should be refined to real-time information for decision making, to facilitate competitiveness through informed and timely decisions. The Line Information System Architecture, LISA, is designed to enable flexible factory integration and data utilization. In LISA, international standards and established off-the-shelf technologies have been combined with the main objective to be industrially applicable. LISA is an event-driven architecture with a prototype-oriented information model and formalized transformation services. It features loose coupling, flexibility, and ease of retrofitting legacy devices. The architecture has been evaluated on both real industrial data and industrial demonstrators and is also being installed at a large automotive company.
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| 6. |
- Theorin, Alfred, et al.
(author)
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An event-driven manufacturing information system architecture for Industry 4.0
- 2017
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In: International Journal of Production Research. - : Taylor & Francis. - 0020-7543 .- 1366-588X. ; 55:5, s. 1297-1311
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Research review (peer-reviewed)abstract
- Future manufacturing systems need to be more flexible, to embrace tougher and constantly changing market demands. They need to make better use of plant data, ideally utilising all data from the entire plant. Low-level data should be refined to real-time information for decision-making, to facilitate competitiveness through informed and timely decisions. The Line Information System Architecture (LISA), is presented in this paper. It is an event-driven architecture featuring loose coupling, a prototype-oriented information model and formalised transformation services. LISA is designed to enable flexible factory integration and data utilisation. The focus of LISA is on integration of devices and services on all levels, simplifying hardware changes and integration of new smart services as well as supporting continuous improvements on information visualisation and control. The architecture has been evaluated on both real industrial data and industrial demonstrators and it is also being installed at a large automotive company. This article is an extended and revised version of the paper presented at the 2015 IFAC Symposium on Information Control in Manufacturing (INCOM 2015). The paper has been restructured in regards to the order and title of the chapters, and additional information about the integration between devices and services aspects have been added. The introduction and the general structure of the paper now better highlight the contributions of the paper and the uniqueness of the framework.
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