Abstract
Robust design enables the products to ensure robust performance in diverse conditions due to increased individuation of user needs and the globalization of markets, and many robust design methods have been proposed. Conventional methods are applicable to design problem in which robustness is ensured by using unique control factor. However, these methods are not applicable to design problem in which robustness is guaranteed only by using a control factor that has an adjustable range or a multilevel. In the present study, a robust design method was proposed to derive the optimum adjustable range and optimum multilevel that enable users to adjust or choose to meet their needs. In the proposed method, first, the relation between the objective characteristic and the adjustable control factor is modeled using the robustness index or the weighted robustness index. The robustness index is to evaluate the feasibility of the objective characteristic value within the tolerance for all the values of the adjustable control factor. On the other hand, the weighted robustness index is added a weighted function to the robustness index, in order to estimate the importance of the objective characteristic value within the tolerance. Second, considering the characteristic of design problems, the optimum adjustable range or the optimum multilevel is derived by using three calculation methods based on two indices. We also applied the proposed method to two examples where the cushion angle of a public vehicle seat and the height of a public water fountain are determined.
