Andrew H. Tilstra

A high-definition design structure matrix (HDDSM) for the quantitative assessment of product architecture

As the field of engineering design matures, new techniques and methods are continuously being developed to conceptualise and analyse product architecture. These techniques and methods require product representations with higher sophistication, granularity, and fidelity. To address these needs, the high-definition design structure matrix (HDDSM) is presented as a new and evolved product representation model that captures a spectrum of interactions between components of a product, such that characteristics of product architecture can be assessed and compared. The HDDSM includes an interaction basis to capture a variety of standardised types of interactions and a hierarchical modelling method to facilitate modular, more efficient compilation of a design structure matrix with a high level of detail. To illustrate the types of quantitative analyses supported by the HDDSM, it is used as a foundation for quantifying the degree of nesting and identifying the presence of frameworks in product architectures – two characteristics that are related to product customisation.

EMPIRICALLY-DERIVED PRINCIPLES FOR DESIGNING PRODUCTS WITH FLEXIBILITY FOR FUTURE EVOLUTION

Product designers seek to create products that are not only robust for the current marketplace but also can be redesigned quickly and inexpensively for future changes that may be unanticipated. The capability of a design to be quickly and economically redesigned into a subsequent product offering is defined as its flexibility for future evolution. Tools are needed for innovating and evaluating products that are flexible for future evolution. In this paper, a comprehensive set of design guidelines is created for product flexibility by merging the results of two research studies—a directed patent study of notably flexible products and an empirical product study of consumer products analyzed with a product flexibility metric. Via comparison of the results of these two studies, the product flexibility guidelines derived from each study are merged, cross-validated, and revised for clarity. They are organized in categories that describe how and under what circumstances they increase flexibility for future evolution. Examples are included to illustrate each guideline. The guidelines are also applied to an example application—the design of a new guitar string changer.Copyright

ANALYSIS OF PRODUCT FLEXIBILITY FOR FUTURE EVOLUTION BASED ON DESIGN GUIDELINES AND A HIGH-DEFINITION DESIGN STRUCTURE MATRIX

The design of a product determines the flexibility of that product for future evolutions, which may arise from a variety of change modes such as new market needs or technological change. The energy, material, and information exchanged between components of a product along with the spatial relationships and movement between those components all influence the ability of that product’s design to be evolved to meet the new requirements of a future generation. Previous work has produced a set of guidelines for product flexibility for future evolution that have been shown to improve the ability of a design to be adapted when new needs arise. Although these guidelines are conceptually easy to understand, it is difficult to assess the extent to which a product follows the guidelines. This paper presents a systematic method to analyze the flexibility for future evolution of products based on selected guidelines. The High-Definition Design Structure Matrix is presented as a product representation model which captures sufficient interaction information to highlight potential design improvements based on the aforementioned guidelines. An interaction basis is used to facilitate the consistency and comparison of HD-DSM models created by different examiners and/or for different systems. The selected guidelines are interpreted in terms of the HD-DSM by creating analysis processes that relate to the characteristics described by the guideline. Two similar power screwdrivers are compared for flexibility for future evolution based on a quantitative analysis of their respective HD-DSMs.

Development of a changeable airfoil optimization model for use in the multidisciplinary design of Unmanned Aerial Vehicles

Complex systems need to perform in a variety of functional states and under varying operating conditions. Therefore, it is important to manage the different values of design variables associated with the operating states for each subsystem. The research presented in this paper uses multidisciplinary optimization (MDO) and changeable systems methods together in the design of a reconfigurable Unmanned Aerial Vehicle (UAV). MDO is a useful approach for designing a system that is composed of distinct disciplinary subsystems by managing the design variable coupling between the subsystem and system level optimization problems. Changeable design research addresses how changes in the physical configuration of products and systems can better meet distinct needs of different operating states. As a step towards the development of a realistic reconfigurable UAV optimization problem, this paper focuses on the performance advantage of using a changeable airfoil subsystem. Design principles from transformational design methods are used to develop concepts that determine how the design variables are allowed to change in the mathematical optimization problem. The performance of two changeable airfoil concepts is compared to a fixed airfoil design over two different missions that are defined by a sequence of mission segments. Determining the configurations of the static and changeable airfoils is accomplished using a genetic algorithm. Results from this study show that aircraft with changeable airfoils attain increased performance, and that the manner by which the system transforms is significant. For this reason, the changeable airfoil optimization developed in this paper is ready to be integrated into a complete MDO problem for the design of a reconfigurable UAV.

INDUSTRIAL CASE STUDIES IN PRODUCT FLEXIBILITY FOR FUTURE EVOLUTION: AN APPLICATION AND EVALUATION OF DESIGN GUIDELINES

A product’s flexibility for future evolution is its ability to be quickly and economically adapted to meet changing requirements. In previous work, a set of guidelines has been developed for designing flexible products. In this paper, two similar industrial case studies are presented to investigate the effectiveness of these guidelines for designing small-lot products with flexibility for future evolution. The systems are real products that have been designed and built by the authors, providing unrestricted insight into the design process and outcome of each project. The first product, a large testing system for high pressure seals, was designed without the aid of flexibility for future evolution guidelines. The second product, an automated welding test station, was designed with flexibility for future evolution as a specific deliverable of the final product. The flexibility of each system was measured by considering its adaptability to prototypical change modes. Of the two systems, the welding system was found to be more flexible than the seal testing system. The welding system also served as an example of integrating product flexibility guidelines throughout the development process.

THE REPEATABILITY OF HIGH DEFINITION DESIGN STRUCTURE MATRIX (HDDSM) MODELS FOR REPRESENTING PRODUCT ARCHITECTURE

Product architecture has implications for product success that go beyond meeting basic customer needs or performance requirements. The mapping of functions to components and the interactions between them impacts the potential for using all or part of the product to build a family of products, the ease with which the product can be redesigned to meet previously unanticipated customer needs, and the way in which engineering design changes propagate during the design process. For practical applications of design theory, it would be beneficial to have a comprehensive and robust model that captures product architecture and can be used for multiple purposes. Some fields of design research have used variations of a Design Structure Matrix (DSM) to record the interactions between elements of a system. The High Definition Design Structure Matrix (HDDSM) has been proposed as a model that limits the subjectivity required from designers by capturing the existence of very specific types of interactions between product components. This work evaluates the repeatability of HDDSM models created by different examiners for a set of electromechanical products. The inter-rater agreement between HDDSM models created by pairs of examiners is determined by calculating the kappa agreement index for each type of component interaction. The results of this initial study demonstrate very encouraging levels of repeatabili ty across examiners for different types of products. Based on these results, recommendations are provided for creating objective models of product architecture and using such models for a number of exploratory research tasks, such as automated analysis of design guidelines.