The applications for IEC 61499 that is standard architecture for developing the applications of distributed control and measurement in factory automation, have the connected structure of the graphical elements called BFB(basic function block), SIFB(service interface function block) and CFB(composite function block). The research on the composite function block has been regarded as important issues in implementing hierarchy, multi-functionality and simplicity of software. Nowadays many researchers have been investigated IEC61499 in the fields of the software modeling composed of basic function block and service interface function block, the transformation from IEC61131 to IEC61499 and syntactic extension of ECC of basic function block. However, work related to the mathematical modeling for IEC61499 composite function block using in designing software with hierarchical structure is still lacking. This paper presents the mathematical model for the structure and execution analysis of IEC 61499 composite function blocks by using notation of the set theory. Also a subaplication configuration algorithm is suggested for the subapplication corresponding to the composite function block. Then its effectiveness through the computation experiment of several distributed control applications is shown. The proposed model can be used effectively as a basis for analyzing a runtime environment of a software tool for designing and developing the applications.
IEC 61499 is international standard which emerged at 2005 year and acknowledged officially and begins to apply for designing and building distributed control system [1~3]. For designing distributed control systems, this standard can be used to unify design and implementation of overall control system from field level to management. It also shows intuitively the configuration and behavior of hardware and software using function blocks. There are described rules that are necessary for designing and implementing the distributed control system, including architectures and function blocks, software tools.
Nowadays the IEC 61499 standard has been founded widely application in many areas of factory automation. In N. Kashyap et al. [4], presents the analysis and simulation results of the performance of fault location and isolation (FLI) using the IEC 61499, distribution automation standard in an automated power distribution feeder. In G. Zhabelova et al. [5], proposes the hybrid agent architecture specific to the power system automation domain using the industrial standards IEC 61850 and IEC 61499. In P. Lindgren et al. [6], proposes the method to provide safe end-to-end response times for distributed IEC 61499 applications communicating over switched Ethernet networks. In L. I. Pinto et al. [7], presents the results implementing the traffic light systems and PID controllers using IEC 61499 in ICARU-FB environment. In F. Andren et al. [8], a standard-based control approach for distributed energy resources is introduced and implemented. In Tao Penga et al [9], the function block technique, i.e. IEC 61499, is used for the development of energy demand models as it brings advantages such as modularity, encapsulation, extensibility and reusability.
The IEC 61499 standard defines execution processing of the each function block and simple scheduling function on network of the function blocks that compose of basic and service interface function blocks. Hence, the different implementations of the standard have made different assumptions how to execute the applications. As a result, the same application might behave differently when executed on different platforms [10]. In S. Panjaitan et al. [11], proposes the method for modeling of IEC 61499 functionality design using UML diagram. In M. Fletcher et al. [12], describes how function blocks can be used to build the holonic manufacturing systems. In Kim et al. [13], proposes the structural model of IEC 61499 application with composite functional blocks.
In [14,15], is presented new design framework with hierarchical and concurrent novel extension of ECC (Execution Control Chart) for basic function blocks. In W. Dai et al. [16], proposes a new methodology of migration from IEC 61131-3 to IEC 61499 function blocks. In V. Dubinin et al. [17], a formal definition of an IEC 61499 application using the set theory notation is presented along with a semantic function block model that is based on a state-transition approach. This model is done by choosing the next transition from the enabled function block transitions according to the execution semantics modeled. Only sequential hypothesis execution semantic is mentioned in particular. In G. C ̌engić et al. [18], presents formal definitions of the application model using definitions of the types and instances of function blocks, application state space, external input and output sets. Only semantics of basic and service interface function blocks are of importance. In G. C ̌engić et al. [19], presents formal definitions on the three different execution models, based on formal model described in [18], buffered sequential execution model (BSEM), non-preempted multithreaded resource (NPTMR), cyclic buffered sequential model (CBEM), and shows its comparison results. In J. Carlson et al. [20], presents simple model of the applications with different function blocks, and analyzes its runtime behavior. Other attempts at formal modeling and verification of control related languages have been published [21], [22]. In D. L. Her et al. [21], sequential function charts (part of IEC 61131) are modeled and verified using time automata while in J.-R. Beauvais et al. [22] State charts are formally modeled using the SIGNAL language.
The previous researches of the application model are described mainly on the formal model for IEC 61499 applications that compose of basic and service interface function blocks, and are not discussed profoundly for the formal definitions and execution analysis on composite function blocks that can represent simply and hierarchically the application with complex structure and behavior.
This paper presents the formal definitions on the composite functional blocks of the IEC 61499 standard. The mathematical definitions have been used as a basis for implementation of a software tool for a runtime environment and formal verification. This paper is organized as follows. Section II describes the structure of the function blo
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