Assessing the Use of Function Models and Interaction Models Through Concept Sketching

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 the level of functional detail that should be included in a model or the appropriate level of abstraction to model artifacts. Further, there is limited experimental evidence that designers use function models when generating concepts, and controlled experiments in the literature have focused on ideation rather than function models. Therefore, this research focuses on how artifacts should be modeled to guide concept generation in conceptual design. In this research, three artifact representations are studied: function models, interaction models, and pruned function models. A user study was conducted in which participants were asked to design a new device based on a problem statement, a set of requirements, and a treatment. Participants were randomly assigned a treatment of a function model, interaction model, pruned model, or no model. A conformance metric was developed to measure the extent to which participants used a model when generating concept sketches. The results show that the functional conformance of participants using a pruned model is approximately 40% higher than that of participants using a function model. These results demonstrate that the use of a specific level of functional detail improves the use of functions within the model for concept generation.