Requirements and obstacles for the transformation of GRAFCET specifications into IEC 61131–3 PLC programs

GRAFCET is a powerful means for the specification of controllers in discrete event systems. As GRAFCET is a specification language and not a programming language, GRAFCET specifications have to be transformed into executable control programs, e.g. in a programming language according IEC 61131-3. Such a transformation requires consideration of particular characteristics of GRAFCET, such as transient evolutions. In previous research concerning this transformation, only subclasses of GRAFCET have been taken into account, and e.g. time dependencies have been neglected so far. The current research of the authors intends to contribute to a wider acceptance of GRAFCET as a control specification standard by developing algorithms for an unambiguous transformation of GRAFCET constructs into controller programs in accordance with the IEC61131-3 standard.