A Quantitative Similarity Metric for Design-by-Analogy

During the design and development of new products, design engineers use many tech- niques to generate and define new and ''good'' concepts. Inherent in this search for solutions is the conscious and unconscious reliance on prior experience and knowledge, or design-by-analogy. In this paper, a quantitative metric for design-by-analogy is devel- oped. This metric is based on the functional similarity of products. By using this product- similarity metric, designers are able to formalize and quantify design-by-analogy tech- niques during concept and layout design. The methods, as developed in this paper, allow a designer with limited experience to develop sophisticated solutions that enhance the overall design of a new product. Also, a designer's current design-by-analogy vocabulary can be extended beyond his or her immediate experience, providing access and contribu- tions to new domains by discovering different products with common functions. The simi- larity metric and its application are clarified and validated through a case study. The case study is the original design of a pickup winder. @DOI: 10.1115/1.1475317# During the design and development of new products, design engineers use many techniques to generate and define new and ''good'' concepts. Inherent in this search for solutions is the con- scious and unconscious reliance on prior experience and knowl- edge. Numerous attempts have been made to organize, qualify, and make accessible the critical design experience and knowledge needed to solve particular problems. Some of these techniques take the form of knowledge-based design, expert design systems, and design rules or design guidelines. In this paper, quantitative metrics are developed that allow designers to identify products that are similar in a manner critical to the success of a design. This focused identification allows these similar products to be reviewed within the context of the design problem at hand for configuration, concept, and embodiment information. These metrics allow for- malized design-by-analogy efforts by identifying products that have design-critical similarity. The paper is organized in the following way. First, the notion of similarity as used here is clarified. Toward the goal of finding the important product similarities, groundwork is developed to make comparisons between products. In the remainder of this paper, these notions of product similarity in the search for analogies are explored. Also, a procedure for applying these techniques to a design problem is presented. Lastly, an example application of the design-by-analogy techniques is applied to an original design case study. The paper concludes with a brief discussion of the contri- butions of the work presented here. 2 Relevant Analogies The notions of similarity and analogies based on similarity are broad. From Moody charts to the Periodic Table, organizing schemes based on similarities and differences are critical tools in engineering and science. In fluid mechanics, the comparison of different objects based on similarities in the Reynolds number, the Biot number, or other meaningful metrics for comparison, is not only common place but critical to the fundamental understanding of the relevant physics that affect the systems. Before developing a design tool based on analogy, the basis for making the compari- son is necessary. For example, based on a color comparison, a car and a watch may be similar. In fact, they also may share the similarity of manufacturing country of origin. Reviewing a watch as an exercise to find alternative ways to mix fuel and air in the car is likely a fruitless exercise. Before searching for design in- formation in existing and similar designs, the notion of similarity needs to be understood in the context of design.