A behavior model for IEC 61499 function blocks
Abstract
This paper deals with designing industrial applications to control critical processes. This kind of applications has to respect some real time constraints. A component-based approach called function blocks (IEC 61499 standard) is classically used to specify such software and its execution support. A function block is an event trigger component. To validate temporal properties, we propose a state machine model compliant with this standard. Nevertheless, a function block cannot handle simultaneous input event occurrences. During the execution, some event occurrences may be lost leading to non predictable behavior. For critical systems, events loosing is not suitable. We propose to design offline scheduling of FBs execution in order to avoid simultaneous event occurrences. The scheduling construction relies on sufficient schedulability conditions that we propose. Finally, we verify the scheduling correctness using the state machine model.