Object-oriented model of an open communication architecture for flexible manufacturing control

Abstract

From the functional point of view, it is considered that the model of a manufacturing system consists of four layers: Machine, Data Acquisition and Control, Communication, and Aggregate Application. In modeling these layers, two important initial premises have been considered which will further allow for a modular, expandable structuring of any particular user-defined application. First, the top-down decomposition strategy is used: the global FMCell architecture and aggregate application are first defined as abstract, high-level objects and then decomposed into child objects during the design steps. The multiple abstraction levels for modeling the cell resources and the Computer Manufacturing Control (CMC) components are used: modeling at part level. modeling at component level and modeling at application level. In order to derive the generic Object-Oriented model of the FMCell communication system, there have been defined an ensemble of CLASS Trees or hierarchies and a Virtual Node Tree. The ensemble of CLASS Trees defines structures and models of the manufacturing environment objects according to relationships identical to the INCLUDE hierarchy. The Virtual Node Tree (VNT) concept is used to model the modular, open-architecture of the communication layer for inter-device connection in the manufacturing environment. The class objects are: “Node” and “Level”.The present paper exemplifies these OO modeling concepts by structuring the communication system of a three-station FMCell which contains two different CNC machine tools tended by one Industrial Robot, one storage and assembly workstation tended by a second Industrial Robot, which is also feeding the final assemblies for integrated quality control to a vision-based CAQC workstation.