Abstract
The purpose of this study is to construct a model for the operations with forearm torsion, such as screw driving and knob turning. In the first report rotational ranges of the object rotated by the arm were measured for each working position during operations with the forearm torsion. As a result, it was demonstrated that the rotational ranges of the object varied depending on the working posture. Then degree of coincidence was defined among direction vectors for each segment in the link model consisting of upper limb and the rotated object, and the method to estimate the rotational ranges of the object from the degree of coincidence was proposed.
