Robust Design for robustness of design variables

There are a lot of studies on Robust Design which treat robucstness only for objective function and/or for considering not to break constraints. But most likely, we would like to have solution which are unchanged even with small perturbation in design conditions such as design parameters. The word “Unchange” means results of the robust design which should be expressed as design variables keep unchanged with these perturbations. In this study, we treat these problems and shows basic difficulties and the method of robust design by thinking of the processes of optimization.