On Definition of a Formal Model for IEC 61499 Function Blocks
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Research Article On Definition of a Formal Model for IEC 61499 Function Blocks Victor Dubinin1 and Valeriy Vyatkin2 1 Department 2 Department
of Computer Engineering, University of Penza, Krasnaya Street 40, Penza 440026, Russia of Electrical and Computer Engineering, Faculty of Engineering, University of Auckland, Auckland 1142, New Zealand
Correspondence should be addressed to Valeriy Vyatkin, [email protected] Received 29 January 2007; Revised 19 June 2007; Accepted 8 October 2007 Recommended by Luca Ferrarini Formal model of IEC 61499 syntax and its unambiguous execution semantics are important for adoption of this international standard in industry. This paper proposes some elements of such a model. Elements of IEC 61499 architecture are defined in a formal way following set theory notation. Based on this description, formal semantics of IEC 61499 can be defined. An example is shown in this paper for execution of basic function blocks. The paper also provides a solution for flattening hierarchical function block networks. Copyright © 2008 V. Dubinin and V. Vyatkin. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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INTRODUCTION
The IEC 61499 standard provides an architectural model for distributed process measuring and control systems, primarily, in factory automation. The IEC 61499 model is based on the concept of function block (FB), that is, a capsule of intellectual property (IP) captured by means of state machines and algorithms. Activated by an input event, the encapsulated process evolves through several states and emits events, then passed to other blocks according to the event connections. An application is defined in IEC 61499 as a network of function blocks connected via event and data connection arcs. The model of IEC 61499 better suits the needs of distributed automation systems than other more universal models, for example, unified modelling language (UML). In particular, it combines the dataflow model, the component model, and the deployment model. However, unlike UML, the IEC 61499 was meant to provide a complete and unambiguous semantics for any distributed application. In reality, however, many semantic loopholes of IEC 61499 have been revealed and reported, for example, in [1–3]. Due to these loopholes, the actual semantics of a function block application is not obvious and requires investigation through its representation in terms of more traditional semantic description mechanisms. The semantics will unam-
biguously define the sequence of function block activation for any input from the environment. So far, there have been different semantic ideas tried in research implementations. The NPMTR model (nonpreemptive multithreaded resource) is implemented in FBDK/FBRT [4]. Sequential semantics was discussed in [1, 5, 6], and implemented in run-time platforms μCrons and FUBER, respectively. The model used in the Archime
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