Identifying functional modules using generalized directed graphs: Definition and application
We extend traditional directed graphs to generalized directed graphs, making them capable of representing function structures as graphs. In a generalized directed graph, vectors are used to denote the edges, which are pairs of sub-function vertices connected by a relationship, and elements of the vectors indicate different types of flow (i.e., material, energy, or signal) on which sub-functions operate. Based on these definitions, we formalize the three heuristics proposed by Stone et al. into rules to identify functional modules in function structures: (I) sequential flow rule, (2) parallel flow rule and (3) flow transformation rule. The arithmetic for identifying functional modules based on these formalized rules is developed, and a computer-aided software tool is created to facilitate this process. Finally, the proposed approach is applied to a function structure for a power screwdriver, and the results compare favorably to those obtained using the three heuristics. (C) 2009 Elsevier B.V. All rights reserved.
generalized directed graph design methodology product development conceptual design product modeling