Schedule Execution for a Holonic Shop Floor Control System

The control structure of a traditional shop floor control system (SFCS) is built according to a strict multi-level hierarchy. Such a SFCS is very rigid and does not support evolution nor adaptation to the factory needs. Holonic manufacturing is a new approach to deal with these problems. A holonic manufacturing system is a highly decentralised system consisting of co-operative, intelligent, autonomous modules, called 'holons', that together yield an agile and self-organising manufacturing system and support global optimisation. This paper presents a holonic architecture for a SFCS. The architecture supports the use of several control strategies, like hierarchical control, heterarchical control and other holonic control strategies. These intermediate strategies are based on a tight cooperation between scheduler and SFC holon. It is shown that a Gantt chart does not contain sufficient information to execute a schedule while being subject to disturbances. Using partial derivatives of the objective functions to the disturbances, the SFC holon can autonomously react to disturbances while considering global performance.