A Basic Study on Modeling of Forearm Torsional Operations for Digital Human

The purpose of this study is to propose a method to evaluate operations involving forearm torsion, such as screw driving and knob turning, for digital human models. The rotational ranges of an object gripped with a hand and the working postures of the upper limb were measured at various positions of the object. The results demonstrated that the rotational ranges of the object varied depending on the working posture. The degree of coincidence was defined among direction vectors for each segment in the link model consisting of the upper limb and the rotated object. A method was proposed to estimate the rotational ranges of the object from the degree of coincidence. Based on this method, software has been developed in order to evaluate operations involving forearm torsion.