Development of the upper body of an underwater humanoid robot for research of unsteady fluid forces acting on a swimmer

The primary objective of this study was to develop a robot for research of human swimming. In order to address this objective, we developed the upper body of an underwater humanoid robot and realized the human swimming stroke. The developed humanoid robot had the same body proportions and appearance at half the size of a real human. The upper limbs were actuated by 12 motors, and one motor was installed for the waist. The motor case and gear housing were newly designed for waterproofing and space saving. Each arm had six degrees of freedom; four were for the shoulder and two were for the elbow. On the shoulder, we installed additional joints imitating human's scapular retraction to avoid singularities during the swimming stroke. We demonstrated the importance of an additional joint by realizing the crawl stroke arm motion, which is the most complicated of the four strokes.