1. Department of Finemechanics, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579, Japan (Corresponding author), e-mail: tohmyoh@ism.mech.tohoku.ac.jp
2. Toyota Motor East Japan, Inc., 1 Nishinemoriyama, Kanegasaki, Iwate 029-4503, Japan