1. Graduate School of Robotics and Design, Osaka Institute of Technology, Osaka 530-8568, Japan
2. Faculty of Robotics and Design, Osaka Institute of Technology, Osaka 530-8568, Japan
3. Faculty of Information Sciences and Technology, Osaka Institute of Technology, Hirakata 573-0196, Japan
4. Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan