Two-layer on-line scheduling of flexible manufacturing systems

The paper deals with the scheduling problem in production units which consist of several subsystems, e.g. workshops or flexible manufacturing cells. A two-layer architecture is proposed were on the local level intelligent control units perform an optimization, and the upper-level scheduler coordinates the subsystems. The coordination problem is solved based on the mathematical description of the overall system in terms of the so-called minimax algebra. The proposed decomposition-and-coordination-strategy will be successful if local schedules can be found such that the local deadlines are met. We therefore discuss algorithms for the local scheduling problems which have the property to avoid excessive delays.