Integrating control devices following different network architectures

Abstract

The paper deals with some of the problems which can appear when automation technologies are applied in the manufacturing sector. In particular, communication via a network of control equipment such as PLC's, CNC's or robot controllers is established. A novel solution is described which allows the cell controller (represented by a PC under the Unix OS) to communicate with all of them, assuming that they follow the IEEE 802.3 standard at the lower level of its communication architecture. The solution presented, is based on using finite automata theory for formalising the particular protocol used by each device as well as information exchange during each operation, e.g., changing a set point on a PLC or sending a file to the CNC. Once this information is formalised as a finite state automaton, and making use of the software developed, the user is easily driven through the necessary steps in order to generate the complete application. Thus, the so called cell controller can not only be used for monitoring the processes controlled by the devices involved in the plant, but it can also be used as a central supervisor of single loop controllers sending for instance stop orders, new set points, etc.