1. Department of Machinery and Control Systems; Shibaura Institute of Technology; 307 Fukasaku, Minuma Saitama 337-8570 Japan
2. Department of Mechanical Engineering and Science; Kyoto University; Yoshida-honmachi, Sakyo, Kyoto 606-8501 Japan
3. Department of Mechanical Science and Engineering; Nagoya University; Furo, Chikusa, Nagoya 464-8603 Japan