Crops: Implementation of a knowledge-based system to plan and monitor the production of a flexible line

Abstract

CROPS (Coherent Rules for On-line Production Scheduling) is a general system aimed to plan and to control a flexible manufacturing system. The CROPS system receives production orders on a time-scale of one or two weeks from a medium-range planning (MRP) system. The planning and scheduling of those orders are made using a hierarchical temporal network that allows the easy use of rules which represent expert knowledge and common-sense reasoning. Furthermore, the hierarchical temporal network is flexible enough to take into account unavoidable perturbations occurring during plan execution without the need to replan all operations every time a perturbation occurs. Once the operations are planned, the control system transforms them into orders that are sent to the workshop (or to a simulator). With the help of rules, the control system monitors and diagnoses the execution of the orders using a model that maintains a continuous image of the workshop.