Functional Representations in Conceptual Design: A First Study in Experimental Design and Evaluation


Functional modeling is an abstraction technique intended to help engineering designers perform conceptual design. Functions are constructs that describe a transformation between an input flow and an output flow. A primary characteristic of functions is their independence from the physical aspects of a device or artifact. In this sense, functions are form independent and deliberately lack reference to geometry that would otherwise describe how a design solution is physically instantiated. This form independence is generally thought to facilitate designer thinking and reasoning about designs in a manner that benefits designer performance. The purpose of this work is to develop an experimental method with metrics to examine the effects of functional modeling on designer performance in a controlled setting and to test the hypothesis that functional modeling has a positive impact on designer performance. Our approach is to test the effectiveness of concept generation by measuring a carefully selected set of parameters. The values of these parameters are determined from the results of a controlled conceptual design exercise. This approach effectively circumvents the need to perform protocol analyses of the engineers. Instead, the results of an experimental design task such as a set of concept sketches and descriptions are used as a data source. Recent work in the design research community has provided examples of how to relate empirical results of this form to underlying performance parameters of interest. Outcomes of this research are an improved experimental technique, a refined set of metrics, and an improved understanding of the manner and degree to which functional modeling supports conceptual design practice and design education. This study shows that functional modeling, for the experimental parameters and design problem selected, is indistinguishable from the experimental control and does not inhibit the idea generation process. While this result is incomplete to address the hypothesis, important contributions of the study include a development and investigation of general experimental metrics, a greater understanding of how to design and structure concept generation experiments, and the need to empower participants with either inventive functions or with a full-fledged functional methodology.


Mechanical and Aerospace Engineering


University of Texas at Austin

Keywords and Phrases

Concept Generation; Conceptual Design; Design Method Effectiveness; Empirical Design Study; Functional Modeling

Document Type

Article - Conference proceedings

Document Version


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© 2005 American Society for Engineering Education (ASEE), All rights reserved.

Publication Date

01 Jan 2005