1. Digital Human Research Center, National Institute of Advanced Industrial Science and Technology (AIST)2-41-6, Aomi, Koto-ku, Tokyo 136-0064, Japan
2. The Robotics Institute, Carnegie Melon University5000 Forbes Avenue, Pittsburgh, PA 15213, USA
3. Graduate School of Information Science and Technology, The University of Tokyo7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8856, Japan