A method for hierarchical modeling of the command of flexible manufacturing systems

The present paper focuses on the modeling of the command and proposes a hierarchical and modular approach which is oriented on the physical structure of FMS. The requirements issuing from monitoring of FMS are discussed and integrated in the proposed model. Its modularity makes the approach open for extensions concerning as well the production resources as the products. As modeling tool, we have chosen object Petri nets. The first part of the paper describes desirable features of an FMS command such as safety, robustness, and adaptability. As it is shown, these features result from the flexibility of the installation. The modeling method presented in the second part of the paper begins with a structural analysis of FMS and defines a natural command hierarchy, where the coordination of the production process, the synchronization of production resources on products, and the internal coordination are treated separately. The method is rigorous and leads to a structured and modular Petri net model which can be used for FMS simulation or translated into the final command code