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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.

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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.

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.