Formal Modeling of Grafcets With Time Petri Nets

Abstract

Grafcet standard (IEC60848) is a formalism used in the world of manufacturing control, at the behavioral specification stage of a system. For specifying safe-critical systems, mathematical models associated with model-checking tools are necessary for the validation of the correctness. However, grafcets (meaning grafcet diagrams) are only semiformal models since certain aspects may be a source of different interpretations. The usual practice is to go through an intermediate formalism. In this brief, time Petri nets (TPNs) are chosen because they combine simplicity with wide-spreading and they also allow quantitative time analyses useful for the verification of real-time specifications. The main goal is to propose a principle of transforming a grafcet into TPN and to define the rules of this translation. The obstacle to overcome is to conciliate synchronous semantics of grafcet with asynchronous semantics of TPN.