The Role of the Thumb: Study of Finger Motion in Grasping and Reachability Space in Human and Robotic Hands
通过统计分析人类抓取动作数据，发现拇指位移对抓取形状起主导作用，并比较人类与机器人拇指的可达空间，指出机器人拇指偏向精确抓取，为优化机器人手部设计提供参考。
It is well acknowledged that the opposing thumb granted humans advanced manipulation capabilities. However, such a feature is not statistically quantified, and its representation is not formally addressed in robotics yet. This paper studies whether the displacement of the opposing thumb in humans is a determining factor for shaping the grip. Using statistical analysis of the variability of motion capture data from the GRASP database, we found that the displacement of the thumb plays a leading role on the shaping of the grip, independently from the specific object being grasped. Furthermore, we map and compare the reachability spaces of the human thumb and two state-of-the-art robotic thumbs: (1) the shadow and (2) the iCub hands. We conclude that the kinematics of robotic thumbs does not evenly span the reachability space of the human thumb, favoring precision grasping motions. Hence, our findings contribute to the discussion of the optimal modeling of robotic hands.