A Measuring and Analysis Method of Coupled Range of Motion of the Human Hands

This paper proposed a method of modeling the range of motion (ROM) of the human hand, which has multiple joints that move in coordination. Traditionally, ROM of the hand was defined by independently bounding each joint angle from observation of extreme posutres. For example, the joint angle when fully extended (maximum) and that when fully flexed (minimum) were observed. However, it is difficult to express actual human\´s complex ROM with such simple boundaries. Therefore, we modeled ROM of the hand by defining outer boudary of collected various posture data. Each relationship between two of the joint angles was presented as a united area in which all the projected measured postures on the plane were minimally bounded using the a-convex hull algorithm. Such area was called "a coupled ROM" in this paper. Measurement and modeling experiments on four subjects were conducted to demonstrate basic characteristics of the proposed ROM model. The occupied volume of the proposed ROM was compared with that of the simple upper-lower ROM. The coordinatinated relationships were ranked and categorized for comparison among subjects.