Improving the PAC shop-floor control architecture to better support implementation

Abstract

Development of shop-floor control (SFC) systems is a very complex task. Not only are such systems inherently complex, but their development also requires skills from several different fields. The lack of a common overview of SFC systems often results in hard-coded SFC systems that have little of the flexibility one might expect from a CIM system. To help developers of automated manufacturing systems to better structure their design, and thus improve the implementation of the SFC system, an SFC architecture could be used. It enables developers to structure their problems and to discuss them using a common language. In this paper, parts of the COSIMA (COntrol Systems for Integrated MAnufacturing) SFC architecture are analysed and improvements to better support implementations are suggested. This paper shows that although the COSIMA production activity control (PAC) provides a sound basis for an SFC cell-level architecture it has its shortcomings. Its weaknesses are mainly twofold: its granularity at the work-station level is too coarse and its information-flow handling is too centralised. By splitting the mover and producer into several such entities, each corresponding to a work-station in the cell, and moving parts of the information-handling from the monitor to these new entities, both problems can be solved.