Comparing Functional Analysis Methods for Product Dissection Tasks

Abstract

The purpose of this study is to begin to explore which function identification methods work best for specific tasks. We use a three-level within-subject study (n = 78) to compare three strategies for identifying functions: energy-flow, top-down, and enumeration. These are tested in a product dissection task with student engineers who have minimal prior experience. Participants were asked to dissect a hair dryer, power drill, and toy dart gun and generate function trees to describe how these work. The function trees were evaluated with several metrics including the total number of functions generated, the number of syntactical errors, and the number of unique (relevant and nonredundant) functions. We found no statistical, practical, or qualitative difference between the trees produced by each method. This suggests that the cognitive load for this task for novices is high enough to obscure any real differences between methods. We also found some generalized findings through surveys that the most difficult aspects of using functional decomposition include identifying functions, choosing function verbs, and drawing the diagram. Together, this may also mean that for novice engineers, the method does not matter as much as core concepts such as identifying functions and structuring function diagrams. This also indicates that any function identification method may be used as a baseline for comparison between novices in future studies.

Tangible augmented reality intervention for a product dissection task

“…The most common function identification methods found throughout the literature include the energy-flow, top-down, enumeration and bottom-up methods [5] [6], according to the function diagrams that are used to describe the methods.…”

“…Functions are mapped at points of change in these flows. The flow method appears the most in engineering design textbooks [5]. [4], each function element is represented as a box with the function written inside.…”

“…But while functional decomposition has been lauded as an important tool for engineering in industry, it is a subject often difficult for engineers, especially novice engineers, to fully understand and apply successfully [5]. Prior work has identified a deficiency in working knowledge of function, especially when engineers are asked to decompose a product into its subfunctions [5] [6].…”

“…Booth et al [5] tested engineering students on product dissection tasks to evaluate which function identification method is most suited for that particular design task. The study used a within-subjects design to compare the three methods.…”

“…While no statistical or qualitative differences were found between the diagrams generated during the AR-supported and non-AR supported tasks, from study of the vii users' function diagram and pre-and post-study test scores, several observations were made and trends were noted about users' understanding of function and their difficulty in applying different aspects of functional decomposition. identified a deficiency in working knowledge of these methods [5] [6] and wide-ranging definitions of function in general [6]. This is most likely due to notions that decomposition is too simple, too complex or not useful [7] and multiple meanings attached to the term function which hamper its use for communication of functional descriptions [8].…”