1. Laboratory for Clinical Evaluation with Robotics, Assistive Robot Center, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan
2. Department of Rehabilitation Medicine, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan
3. Assistive Robot Center, National Center for Geriatrics and Gerontology, Obu 474-8511, Japan