A Method to Specify Part of a System to Change in Improvement Design

Improvement design, which is characterized by minimum necessary changes to a past product, is employed to reuse verified and experienced parts to create a new product faster, reliable, and economically sound. However, as products become so complex that changes to some parts propagates concomitant changes to other parts, which makes it difficult to enjoy the advantages of improvement design. Therefore, design changes have to be contemplated at the early phase of design. This paper proposes an improvement design planning method based on House of quality. Parts of a product to be changed and directions on which they are changed are explored in terms of opportunity to improve product and risk of worsening other parts. By exploring the possible design in the trade-off between the opportunity and the risk, design change plan that comprises proper parts of a product to be changed can be decided. A case study on a solar boat design demonstrates the applicability and validity of the proposed method.