Simplified modeling of manufacturing systems: an introduction to sensor activation graphs

This paper presents a graphical modeling formalism, sensor activation graphs, which simplifies the design of discrete event models for a class of physical systems common within manufacturing industry. Sensor activation graphs captures, in an intuitive way, the relations between binary sensors, the physical entities that activate them, and the actuators of the system. Models expressed as sensor activation graphs are in most cases significantly simpler than corresponding automata or Petri net models. The presented formalism support two levels of detail, one that gives the general view on the order of sensor activation, and one with full control semantics that incorporates guard conditions on transitions. In addition, an algorithm for converting sensor activation graphs into a number of small deterministic finite state automata is presented.