Holonic manufacturing scheduling: architecture, cooperation mechanism, and implementation

Ž . A Holonic Manufacturing System HMS is a manufacturing system where key elements, such as machines, cells, factories, parts, products, operators, teams, etc., are modeled as ‘holons’ having autonomous and cooperatiÕe properties. The decentralized information structure, the distributed decision-making authority, the integration of physical and informational aspects, and the cooperative relationship among holons, make the HMS a new paradigm, with great potential for meeting today’s agile manufacturing challenges. Critical issues to be investigated include how to define holons for a given problem context, what should be the appropriate system architecture, and how to design effective cooperation mechanisms for good system performance. In this paper, holonic scheduling is developed for a factory consisting of multiple cells. Relevant holons are identified, and their relationships are delineated through a novel modeling of the interactions among parts, machines, and cells. The cooperation mechanisms among holons are established based on the pricing concept of market economy following ‘Lagrangian relaxation’ of mathematical optimization, and cooperation across cells is performed without accessing individual cells’ local information nor intruding on their decision authority. The system also possesses structural recursivity and extendibility. Numerical testing shows that the method can generate near-optimal schedules with quantifiable quality in a timely fashion, and has comparable computational requirements and performance as compared to the centralized method following single-level Lagrangian relaxation. The method thus provides a theoretical foundation for guiding the cooperation among holons, leading to globally near-optimal performance. q 1998 Elsevier Science B.V. All