Automatic modelling of one-of-a-kind production systems by temporised object-oriented Petri nets with changeable structure (TOPNs-CS)

摘要

Temporised object-oriented Petri nets with changeable structure (TOPNs-CS), which is an extension of OPNs-CS, is capable of modelling one-of-a-kind production (OKP) systems subject to changes. This paper proposes an automatic approach to overcoming the difficulty in building complex TOPNs-CS models for an OKP system. TOPNs of production resources are simplified by the characteristic modelling elements. Message passing relations are classified into four protocols, each of which is characterised by its characteristic modelling elements. A formal description is given for product production structure (PPS) and production service structure (PSS) in an OKP environment to supply systematic and easily usable data necessary for building the model. Algorithms are specified to transfer the data in terms of a formal description in an OKP environment into the characteristic modelling elements, and to identify the protocols of the message passing relations. With this approach, a TOPNs-CS model can be updated automatically to reflect changes in PPS and PSS as a result of the changes in a product and its processing processes.