Neutralizing semantic ambiguities of function block architecture by modeling with ASM

Abstract

The Function Blocks Architecture of the IEC 61499 standard is an executable component model for distributed embedded control systems combining block-diagrams and state machines. The standard aims at the portability of control applications that is however hampered by ambiguities in its execution semantics descriptions. In recent years several execution models have been implemented in different software tools that generate mutually incompatible code. This paper proposes a general approach to neutralizing these semantic ambiguities by formal description of the IEC 61499 in abstract state machines (ASM). The model embodies all known execution semantics of function blocks. The ASM model is further translated to the input format of the SMV model-checker which is used to verify formally properties of applications. In this way the proposed verification framework enables the portability checking of component-based control applications across different implementation platforms compliant with the IEC 61499 standard. The paper first discusses different existing execution semantics of function blocks and the portability issues across different IEC 61499 tools. Then a modular formal model of function blocks’ operational semantics in ASM is introduced and exemplified in the paper by the cyclic execution semantics case for a composite function block. Subsequently, the SMV model is generated and model-checking is illustrated for a simple test case.