Priority State Machine (PriSMa): A practical tool for DES control system developers

In this paper a formalism which allows to describe the logics characterizing industrial discrete processes in a simple and intuitive way is described together with the tool developed for its actual implementation. The formalism, named PriSMa (Priority State Machine), is derived from the state diagrams concepts from which in particular inherits its graphical representation adding to these two main features: the priority in the events evaluation and the communication synchronisms. These features aim to help control system developers when dealing with constraints on real systems as well as to simplify their work allowing for an intuitive partitioning of whole system project into smaller ones. A tool, the PriSMaVIEW, has been developed which allow editing the PriSMas, simulating their evolution and finally implementing them in a real system. A special effort has been made in order to develop a methodology which could allow for a direct implementation of the described system without requiring further operational step or compilation for the actual execution. Examples taken from real system applications further illustrate the functionalities of the proposed tool.