Benjamin W. Caldwell

Evaluation of the functional basis using an information theoretic approach

Abstract A metric for computing the information content of function models in mechanical engineering design is proposed. Function models are graph-based representations used to describe the functionality of engineered artifacts, where the nodes are function verbs and the edges are the objects of action. The functional basis, a controlled vocabulary of these verbs and nouns organized in a three level hierarchy, is intended to support consistent representation of function models. The Design Repository is a Web-based archive of function models of consumer products described with the functional basis. This paper presents the theoretical underpinnings of a metric for the information content of function models, the assumptions required to support it, the definitions of key terms associated with it, and its practical interpretation. Finally, the metric is used to study the usefulness of the functional basis through a series of experiments on function models within the Design Repository. The results of the experiment indicate that the secondary level of the functional basis is the most beneficial to designers, both in terms of information content and information density.

An empirical study of the expressiveness of the functional basis

Abstract Function models are frequently used in engineering design to describe the technical functions that a product performs. This paper investigates the use of the functional basis, a function vocabulary developed to aid in communication and archiving of product function information, in describing consumer products that have been decomposed, analyzed, modeled functionally, and stored in a Web-based design repository. The frequency of use of function terms and phrases in 11 graphical and 110 list-based representations in the repository is examined and used to analyze the organization and expressiveness of the functional basis and function models. Within the context of reverse engineering, we determined that the modeling resolution provided by the hierarchical levels, especially the tertiary level, is inadequate for function modeling; the tertiary terms are inappropriate for capturing sufficient details desired by modelers for archiving and reuse, and there is a need for a more expressive flow terms and flow qualifiers in the vocabulary. A critical comparison is also presented of two representations in the design repository: function structures and function lists. The conclusions are used to identify new research opportunities, including the extension of the vocabulary to incorporate flow qualifiers in addition to more expressive terms.

Empirical Examination of the Functional Basis and Design Repository

This paper investigates the use of functional basis within the design repository through the observation of eleven functional models. It also examines the amount of information contained in the functional model of a hair dryer at various hierarchical levels. Two experiments show that the secondary level of the functional basis hierarchy is used most often because the secondary level provides significantly more information than the primary level, and the tertiary level does not provide enough additional information to be useful.

A User Study to Evaluate the Function Model and Function Interaction Model for Concept Generation

Function modeling is often performed during the conceptual design phase to identify what the product must do in a solution independent form. However, function-based design approaches do not adequately enable designers to capture and analyze the non-functional requirements, interactions between the product of interest and other products and interactions between the product of interest and human users. This paper presents the results of a user study to evaluate how two models: (1) traditional function models (FM) and (2) the function interaction model (FIM), relate to functional and non-functional engineering requirements, and how they affect the creation of design solutions. Forty students were divided into two groups and asked to generate solutions for a design problem using either the function model (FM) or the function interaction model (FIM). The concepts were then evaluated in terms of quantity and quality by an external panel. Results from this study indicate that the quantity of solutions generated by the function model (FM) group is greater than the function interaction model (FIM) group. However, the quality of design concepts from the function interaction model (FIM) group is greater than the function model (FM) group. Further, nonfunctional requirements that are important to the design solutions cannot be captured in function model and thus are not reflected in the associated solution concepts.Copyright

Towards Rules for Functional Composition

Functional decomposition is used in conceptual design to divide an overall problem with an unknown solution into smaller problems with known solutions. The procedure for functional decomposition, however, has not been formalized. In a larger effort to understand and develop rules for functional decomposition, this paper develops rules for composition of reverse-engineered functional models. First, the functional basis hierarchy is used in an attempt to compose the functional model of a hair dryer, which does not produce the desired results. Second, a set of rules for composition is presented and applied to the hair dryer functional model. This composed functional model is more similar to the desired decomposition result than the functional model developed by changing hierarchical levels. Ten additional functional models are also composed and the results shown. The findings demonstrate that composition rules can be developed empirically through analysis of functional models.Copyright

Product Data Management in Undergraduate Education

Product Data Management (PDM) systems provide a means for sharing and controlling documents in collaborative product development. PDM are used in industrial applications for long-term archival of product information, to enhance collaboration and communication throughout the design process, support distributed design teams through advanced document sharing, track changes in product information, and control design documents ranging from requirements information to CAD. However, undergraduate mechanical engineering students typically graduate with limited or no exposure to PDM systems. This paper investigates the benefits and challenges associated with modern PDM systems. Moreover, the need for PDM systems in undergraduate education are discussed and means for integrating this technology is presented. A survey of engineering institutions in the U.S. is completed to understand the current usage in academic settings. Specifically, this paper describes appropriate course and project support of PDM systems.Copyright

Automotive lightweight engineering: a method for identifying lazy parts

This paper presents a method for evaluating the lightweightedness of a vehicle, specifically addressing those components whose primary purpose is to aid in manufacturing and assembly rather than to provide end-user function. Seven laziness indicators are described. These indicators are used to evaluate individual vehicle components to aid in identifying mass reduction potential and focus the attention of designers on components or assemblies with high potential for mass reduction. This method is applied to a complete automotive vehicle, demonstrating a mass savings potential of the overall vehicle of approximately 5% of the total mass of the vehicle.

Limitations to Function Structures: A Case Study in Morphing Airfoil Design

This paper presents an application of function structures in the design of single component morphing airfoils. A series of function structures are developed in an attempt to create an accurate model of a passively morphing airfoil. This paper describes each approach taken, while noting their modeling aspects that were successful or unsuccessful to identify representation features of existing function structure syntax and rules that relate to the usability of the models. System boundaries and definitions, function and flow definitions, carrier flows, and system state definitions are investigated. It was found that function structures in their current state, are incapable of accurately modeling the functionality of the shape changing aspect of a passively morphing airfoil. These limitations are identified and recommendations necessary to model artifacts similar to the morphing airfoil are presented. Finally, previous research efforts in the design of morphing airfoil technology are presented as solutions to certain key functions identified, thereby demonstrating the possible benefits of implementing function structures to this field.© 2010 ASME

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.Copyright

Investigating Spontaneous Flexibility in Concept Generation

Guilford’s Alternate Uses Test (ALTU) measures a person’s spontaneous flexibility, a propensity for generating many varied responses to a situation, by requiring them to list six possible uses for a given object. Shah’s metrics of ideation effectiveness measure the innovative qualities of engineering concepts with similar scales. The study presented in this paper explores the relationship between spontaneous flexibility and engineering concept generation through a research study. Fifty-two participants generated ideas for three items on a spontaneous flexibility test (SFT) and three problems on an engineering ideation test (EIT). The participants’ responses were analyzed for fluency and flexibility. Correlations between the SFT and EIT were identified in order to better understand the role of spontaneity and divergent thinking in an engineering environment. It was found that both fluency and flexibility of responses were strongly correlated between the two test types. It is hypothesized that the EIT complements the SFT in measuring spontaneous flexibility in engineering design.Copyright