Hierarchical Control Structure in Flexible Manufacturing Systems

Summary

The authors have been actively involved in the selection and application of AMT techniques within Edbro Plc, and the current paper describes the need for hierarchical control and communication structures in FMS, both from a logical and physical standpoint. A critical appraisal is given of evolving modular approaches and these are compared with the more theoretical CIM hierarchies. Next a generic control hierarchy for FMS is described and its ability to meet the needs of systems from CNC to full FMS, and even integrated factories is discussed with specific reference to two working systems. The problems encountered with these systems in terms of control and expandability are highlighted together with a description of how one system uses an integrated DNC link from the CAD/CAM system to the shopfloor. The relevance and need for standards such as MAP, Ethernet and RS232 are also examined.