GEMMA, the complementary tool of the GRAFCET

The basic features of GEMMA, a design guide for start and stop modes, are described. It is noted that the completed GEMMA takes the form of a macro-GRAFCET and can be programmed as such on some programmable controllers. It is an active tool, as it prompts design-oriented questions very early in the project. It is applicable as an analytical checklist, a standardized communication/specification tool for training or contractual agreements, and a programming approach if the appropriate material is available. Its macro-representation allows the designer to zoom to detailed hardware and software specifications progressively and to consider possible human interventions from general functional requirements. This feature minimizes the number of iterations in the design phase, helps to decouple functional principles from mechanical fine-tuning, and fosters safe operation by providing a logical framework to make the most of the conclusions of various safety analysis techniques or plain common sense. It is concluded that GEMMA is well suited to a wide variety of cases in the field of programmable automation