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Applied Bionics and Biomechanics
Volume 5 (2008), Issue 4, Pages 213-223

Analysis of Physical Human–Robot Interaction for Motor Learning with Physical Help

Shuhei Ikemoto,1,2 Takashi Minato,2 and Hiroshi Ishiguro1,2

1Adaptive Machine System, Osaka University, Osaka, Japan
2Japan Science and Technology Agency, ERATO, Asada Synergistic Intelligence Project, Saitama, Japan

Received 10 February 2009

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In this paper, we investigate physical human–robot interaction (PHRI) as an important extension of traditional HRI research. The aim of this research is to develop a motor learning system that uses physical help from a human helper. We first propose a new control system that takes advantage of inherent joint flexibility. This control system is applied on a new humanoid robot called CB2. In order to clarify the difference between successful and unsuccessful interaction, we conduct an experiment where a human subject has to help the CB2 robot in its rising-up motion. We then develop a new measure that demonstrates the difference between smooth and non-smooth physical interactions. An analysis of the experiment’s data, based on the introduced measure, shows significant differences between experts and beginners in human–robot interaction.