1. Laboratory of Clinical Evaluation with Robotics, Assistive Robot Center, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511, Japan
2. Laboratory of Practical Technology in Community, Assistive Robot Center, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511, Japan
3. Department of Rehabilitation Medicine, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511, Japan
4. Mechanical System Safety Research Group, National Institute of Occupational Safety and Health, Japan Japan Organization of Occupational Health and Safety, 1-4-6 Umezono, Kiyose, Tokyo 204-0024, Japan
5. Department of Mechanical Systems Engineering, Graduate School of Systems Design, Tokyo Metropolitan University, 6-6 Asahigaoka, Hino, Tokyo 191-0065, Japan
6. Department of Robotics, Tohoku University, 6-6-1 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579, Japan
7. Assistive Robot Center, National Center for Geriatrics and Gerontology, 7-430 Morioka-cho, Obu, Aichi 474-8511, Japan