Date of Award

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Mechanical Engineering

Advisor

Mocko, Gregory M

Committee Member

Summers , Joshua D

Committee Member

Fadel , Georges M

Committee Member

Greenstein , Joel S

Abstract

Functional representations are often used in the conceptual stages of design because they encourage the designer to focus on the intended use and purpose of a system rather than the physical solution. Function models have been proposed by many researchers as a tool to expand the solution search space and guide concept generation, and many design tools have been created to support function-based design. These tools require designers to create function models of new or existing artifacts, but there is limited published research describing what types of functions should be included in a model or the appropriate level of abstraction to model artifacts. Further, there is little experimental evidence that function models are useful for concept generation. Therefore, this research focuses on how artifacts should be modeled to support ideation in conceptual design.
In this research, three functional representations are studied: function models, interaction models, and pruned function models. First, a user study is conducted to test the level of understanding of functional representations by designers. Second, a computational similarity metric is used to identify the appropriate level of abstraction for creating models. Third, a user study is conducted to determine the effects and usefulness of functional representations in concept generation. The three studies show that pruned function models are easier to understand, improve the use of the model by designers, improve the quality of concepts generated, and are more useful for computing functional similarity. Function models contain additional, solution-specific descriptions of functionality that are not useful in conceptual design for ideation, similarity, or interpretation. The interaction model, which is developed in this research, provides a preliminary representation capable of capturing user actions and interactions in addition to artifact functionality, and shows potential for describing non-functional requirements in a manner that is useful to designers. These outcomes serve as a foundation for guidelines for creating conceptual-level models that support ideation in conceptual design.

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