On Optimization Methods in the House of Quality: Facilitating the Early Stages of Product Design

During a conceptual design effort we find we are making the most far-reaching decisions on product and process form and robustness, while under great pressure to quickly definitize the product. Success is a function of how well we optimize to market needs and producibility, among other constraints. In this paper we focus on implementation of optimization early in the design process, within the structured environment of the House of Quality. Using a normalized weighting format for parameter correlations and relationships, several formulations are presented and discussed, each with its own appropriate use. Using mathematical programming techniques, opportunities exist to greatly reduce the rank of the matrix, facilitating early design iteration and optimization. We present several new roles for the correlation matrix, or roof of the house of quality, which to date has been underutilized in product optimization. Formulations are proposed to employ design information contained in the roof to facilitate concurrent design optimization and management of complexity at the early stages of design.

Theoretical Underpinnings of Functional Modeling: Preliminary Experimental Studies

A model of how a product should function to satisfy customers is an essential element in clarifying, identifying, and establishing product architectures. Such functional models greatly enhance the generation of creative form solutions to a chosen architecture. A wider breadth of solutions is generally possible, implementing new and stable technologies. In turn, using the recent concepts of design repositories, the possibilities exist to archive, retrieve, compute, reconfigure, and reason with the product forms. To realize these benefits to the fullest extent possible, functional modeling needs further theoretical development. A formalism of function classes, vocabulary, topologies, and methodology is a first step towards this goal. Recent research efforts have focused on each of these elements, where great strides toward repeatable formalisms have been made. Yet, across the engineering design field, very little active experimentation has been pursued to test the veracity of these elements, individually and as a whole. We address this issue here through a preliminary set of experiments conducted at three separate universities. Design teams and individuals are asked to create functional models, in the context of product development, with and without the formalisms. The outcomes of the modeling effort are analyzed to determine the repeatability of the process. Early results are quite encouraging. Very repeatable results are obtained for three product evolutions, including a toaster, a power screwdriver, and a toy dart gun. In addition, weaknesses in current formalisms are uncovered, pointing to new directions for advancing the field and for carrying out more advanced experimentation.

Application of Design Axioms to Marine Design Problems

The Design Axioms proposed by N. P. Suh consist of Independence Axiom and Information Axiom. The Independence Axiom assists a designer in generating good design alternatives by considering the relations between the functions and the physical product using a hierarchical mapping procedure. The Information Axiom, which is related to the probability of achieving the given functional requirements, can be used as a criterion for the selection of the best solution among the proposed alternatives in the conceptual or preliminary design stage. In the early stages of marine design, especially ship design, there exists a lot of uncertainty because of the size and complexity of a marine vehicle. The uncertainty often leads to a probabilistic approach rather than a deterministic approach. The ship designs are mostly routine design to change an existing design case a little. In this paper, the availability of the Design Axioms in this marine design field will be investigated through three examples. In the conceptual design of a thruster, the Independence Axiom will be proven to be useful in examining the independence of functional requirements at each level of the decomposition process. In main engine selection example, the Information Axiom will be used for selecting the best solution among the given alternatives by estimating their respective information contents under the uncertain and ambiguous condition. In the structural design, some difficulties arise in maintaining the independence of functional requirements in general because the number of design parameters is greater than that of functional requirements. Therefore, there is much trouble in generalizing the application of the Design Axioms for the structural design, especially for the preliminary design where the principal design parameters of a design object have to be determined after its shape fixed. This paper will try a generalized approach to the similarity-based design where it is important to select which parameters should be changed and in what order they should be changed. How to make use of the Design Axioms will be showed in a barge design example. However, a lot of research is needed for the generalized application of the Design Axioms for the structural design.

Enabling the Use of Shape Grammars: Shape Grammar Interpretation Through General Shape Recognition

Shape grammars have recently shown promise in engineering applications. The need to efficiently implement such grammars, rather than hard code them, in a way that supports creativity through shape emergence has still remained an ongoing research challenge. This paper introduces a shape grammar interpreter that supports parametric shape recognition, and thereby shape emergence. The approach divides shapes into hierarchies of subshapes based on specified geometric relationships within the shape. A default hierarchy based on geometric relations often found in engineering and architectural designs is presented as an efficient example of one appropriate hierarchy. A classic shape grammar demonstrates the interpreter’s shape recognition and generation abilities.

Function Integration Explained by Allocation and Activation of Wirk Elements

In mechanical engineering design, the conceptual design phase involves the determination of the structural means for realizing the functions of a product. Function integration is a means for achieving an efficient design, where the same means contributes to the realization of multiple functions. This paper contributes to a phenomenological understanding of function integration and aims at refining design theories treating this subject. The work rests upon and contributes to German design theory and the design theories of the WDK School. For explaining function integration, the concept of wirk element is introduced. A wirk element is defined as a functionally active form element that is part of an organ and contributes to the realization of a function. Furthermore, based upon the allocation and activation of wirk elements, a definition of function integration is given, and six kinds of integration are classified. Finally, opportunistic design is explained by the wirk element concept and the implication of function integration on product modeling in configuration systems is treated. Throughout the paper, several examples are given to illustrate the explanatory power of the proposed modeling concept.

On Evaluation Method During Conceptual Design

This study proposes an evaluation method that integrates the existing ordinal, cardinal and matrix methods for decision making. Normalized values are recommended for the pairwise comparisons of evaluation items to determine the weighting factors. These values also assist in determining the weighting eigenvectors for alternatives of the potential products. Web diagrams are generated for all alternatives and their areas are compared to identify the most preferred one. The proposed method can reduce drawbacks of the Pahl and Beitz method and the Saaty method when the two most preferred alternatives have the same summed weighted values in the Pahl and Beitz method or the same composite weighting factors in the Saaty method.

Validating Design Methods and Research: The Validation Square

Validation of engineering research is typically anchored in the scientific inquiry tradition that is based primarily on logical induction and / or deduction. Since much engineering research is based on mathematical modeling, this kind of validation has worked — and still works — very well. There are, however, other areas of engineering research that rely on subjective statements as well as mathematical modeling, which makes this type of validation problematic. One such area is that of design methods within the field of engineering design. In this paper, we explore the question of how one validates design research in general, and design methods in particular. Being anchored in the scientific inquiry tradition, research validation is strongly tied to a fundamental problem addressed in epistemology, namely, what is scientific knowledge and how is new knowledge confirmed? Thus, we first look to epistemology for answers to why an approach solely based on ‘formal, rigorous and quantifiable’ validation constitutes a problem, and for an augmented approach to research validation. We then propose the ‘Validation Square’ which we validate by testing its internal consistency based on logic in addition to testing its external relevance based on its usefulness with respect to a purpose. We recognize that no one has the complete answer to the question we pose. To help us converge on an answer to these questions we “think aloud” and invite you to join us in doing the same. It is our hope that in so doing we, the members of this design research community, will all be the richer for it.

Quantifying Design Freedom in Decision-Based Conceptual Design

Formal methods for conceptual design must embrace the uncertainty that pervades the earliest parts of the design process. Operating over this uncertainty, decision-based design measures the value of restricting the design space as well as the impact of refining design evaluation or analysis models. Missing from this framework is the cost in terms of design freedom of restricting the design space. We propose a measure of design freedom based on probabilistic entropy and demonstrate its application to two example conceptual design problems.

Learning From Experience of Peers: An Empirical Study of Knowledge Sharing in a Product Design Community

In this paper, we describe usage patterns of a design information database observed from four years of data, and discuss issues of learning through social and technology mediated interactions in a product design community. From the period of 1994 to 1999, an increasing amount of the design information in a project-based course at Stanford University has been captured in electronic format. This design information consists of design notes, drawings, reports, slide presentations, emails, vendor references, and even, in some cases, summaries of phone conversations, meeting minutes, and the like. The large corpus of captured information was made available to the project teams during each academic year on the assumption that one would be able to achieve better performance by building on and learning from experiences of peers. Because the data was all made available over a webserver, we were able to collect information on access to it We have thus had a chance to learn from studying the usage of a large body of captured design information. Preliminary analysis on the first two years of data was reported in DETC conference in 1998 (Liang, Cannon et al. 1998). Results from our current analysis show some interesting patterns of file utilization. Those patterns includes a surprising high ratio of access to process-related files, as opposed to product-related files; a temporal access pattern that closely matches project deliverables and milestones; and, an increased correlation between database usage and team-based performance over time. The results from quantitative data analysis are augmented with qualitative user interviews. When interviewed, all engineers agreed that there could be a lot of benefits from learning from peer experiences. Nevertheless, physical and psychological barriers often prevent one from doing so. Physical barriers include distance, time, and organizational distance. Some psychological barriers include the perceived value of the archived information, and perceived effort of finding useful information. These pragmatic organizational learning issues arise from the fact that the teams were working on diverse projects and are all pressured by time and resources. We hypothesize that these real-world constraints of time and resources prohibited many learning opportunities to occur which would otherwise have been very productive and effective. This tension between learning and working is the backdrop of this learning experiment. We suggest that the patterns reported in this paper will be typical of a small product design consulting firm that has many fast-paced projects running in parallel.

Quantitative Measures for Design by Analogy

In this paper a quantitative measure for design-by-analogy is developed. This measure is based on the functional similarity of products. By using this product similarity measure, designers are able to formalize and quantify design-by-analogy techniques during concept and layout design. The similarity measure and its application is clarified and validated through a case study. The case study is the original design of a pickup winder.