A model based on a Petri net (PN) is proposed for controlling flexible manufacturing systems (FMSs). The model can describe not only normal sequential processes but also interruptive exceptional handling processes by means of simple structures. A layered structure and two types of token are introduced into a PN to describe exception handling and error recovery. An application in which this model was used to program a programmable logic controller (PLC) is described. The description of cell control can be simplified by the model.>

The experimental Advanced Integrated Designer's Activity Support (A-IDAS) system is intended to be a base for a total engineering system rather than a pure graphic system. The system provides a database in which graphic data, geometric data and engineering data are stored in a relational data model. It also provides a graphic management facility which can manipulate not only pictures drawn with lines, but those drawn as areas. Areas are represented by crosshatched lines or colors. In more complicated ways, they can be represented as texture or scenery. The system controls two kinds of graphic display devices: a vector display and a raster display. These devices are supported through a device independent user interface when pictures are drawn with lines. With this experimental system, it has been found out that one can develop an engineering system having fairly general purpose capabilities.