1 Department of Mechanical Engineering, Center of Human and Robotics Symbiosis Research, Toyohashi University of Technology, Hibarigaoka 1-1, Tempaku-cho, Toyohashi 441-8580, Japan 2Graduate School of Medicine, Rehabilitation, Physicotherapeutics, Nagoya University, Taikou Minami 1-1-2, Higashi-ku, Nagoya 461-8673, Japan 3 Leiter Institut für Systemdynamik, Universität Stuttgart, Pfaffenwaldring 9, 70569 Stuttgart, Germany 4Division of Mechanical Engineering, Graduate School of Engineering, Mie University, Kurimamachiya 1577, Tsu 514-8507, Japan 5Department of Mechanical Engineering, Faculty of Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu 514-8507, Japan 6Center for Human-Robot Symbiosis Research, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi 441-8580, Japan