Title

Holonic manufacturing scheduling: Architecture, cooperation mechanism, and implementation

Date of Completion

January 1997

Keywords

Engineering, Electronics and Electrical|Engineering, Industrial|Engineering, System Science

Degree

Ph.D.

Abstract

A Holonic Manufacturing System (HMS) is a manufacturing system where key elements, such as machines, cells, factories, parts, products, persons, teams, etc., have autonomous and cooperative properties. These elements are called "holons." In an HMS, each holon's activities are determined through cooperation with other holons, as opposed to being determined by a centralized mechanism. An HMS could therefore enjoy high agility, which is critical for today's manufacturing systems. How to define holons for a given problem context, what should be the appropriate holonic architecture, how to design effective cooperation mechanism among holons for overall system performance, however, are critical issues to be investigated before HMS can be realized in practice.^ Scheduling is a key factor for manufacturing productivity. In this dissertation, holonic scheduling is developed for a factory consisting of multiple cells. The co-operation mechanisms among holons are established based on the "Lagrangian relaxation technique" of mathematical optimization. The method thus provides a theoretical foundation for guiding the cooperation among holons, leading to globally near-optimal performance. Through a novel modeling of the interactions among cells and a decomposition-coordination solution method, cooperation across cells is performed without accessing the private information and intruding the decision authority of individual cells. The embedded route selection mechanism also balances the load among candidate cells. Schedules generated have comparable computational requirements and solution quality as compared to those generated through a centralized method, and speedup can be obtained by better initialization and distributed processing. In addition, the clear delineation of information, responsibilities, and interfaces of individual holons and the object-oriented implementation make the system extendible to more complicated manufacturing settings.^ As one of the test case, the scheduling system is extended for the manufacturing of Toshiba's gas insulated switchgears. The manufacturing is characterized by significant machine setup times, strict local buffer capacities, the option of choosing a few alternative processing routes, and long horizon as compared to the time resolution required. The modeling of these features and the mathematical resolution of the resulting scheduling problem are presented. The effective handling of group-dependent setups is of particular significance, and should shed light on many similar problems. The treating of finite capacity buffers as machines, the embedded routing selection mechanism, and the time-step reduction technique also contribute to the state-of-the-art and practice of scheduling methodology. ^