Joint Coupling for Human Shoulder Complex

Abstract

In this paper, we present an inverse kinamtics method to determining human shoulder joint motion coupling relationship based on experimental data in the literature. The joint coupling relationship is available in the literature, but it is an Euler---angle-based relationship. This work focuses on transferring Euler-angle-based coupling equations into a relationship based on the Denavit-Hartenberg (DH) method. We use analytical inverse kinematics to achieve the transferring. Euler angles are obtained for static positions with intervals of 15 degrees, and the elevation angle of the arm varied between 0 and 120 degrees. For a specific posture, we can choose points on clavicle, scapula, and humerus and represent the end-effector positions based on Euler angles or DH method. For both systems, the end-effectors have the same Cartesian positions. Solving these equations related to end-effector positions yields DH joint angles for that posture. The new joint motion coupling relationship is obtained by polynomial and cosine fitting of the DH joint angles for all different postures.