Fuzzy-based methodology for multi-objective scheduling in a robot-centered flexible manufacturing cell

Scheduling problems in Flexible Manufacturing Cells present varying degrees of difficulty. The objective of the present work is to develop a fuzzy logic based methodology for generating the sequence of flow of parts through the cell by selecting appropriate movements of the robot within the manufacturing cell. The goal is to meet certain production objectives, given a multi-product batch. The production objectives taken into account are maximization of the throughput and machine utilization, as well as, minimization of penalty for tardy jobs and robot travel time.; The fuzzy-based approach uses membership functions to find the contribution of each part type to the objectives according to the specifications of the batch. The evaluation of these contributions generates the sequence of the parts within the cell. Two fuzzy based strategies have been developed: fuzzy job and fuzzy-machine. These strategies are compared to well known dispatching rules. The effects of using priorities such as loading versus unloading, and sequencing parts in a sequential/non-sequential mode are investigated as well. Custom designed software is created to control the robot moves within the cell. The software has the ability of processing information in simulation (off-line) and in real time (on-line), and is successfully implemented and tested in the experimental cell. In general, the proposed fuzzy-based methodologies especially fuzzy-job show a superior performance compared to traditional dispatching rules. The model can be further expanded or modified to include different or more objectives.