A kinematic arm model based on the transverse elbow axis

To determine the exact direction and location of the human joint in motion is crucial in developing an accurate human model. All the previous studies investigated, in vitro, the passive movement of the joint from cadavers and the suggested location of the joint axis was difficult to make practical applications due to the lack of the direction of joint axis. So, each joint axis has been assumed to lie horizontally or vertically to the adjacent links in many biomechanical models. In this study, the direction and location of the transverse elbow axis was obtained with respect to the global coordinate system whose origin is on the lateral epicondyle of the humerus. From the experiments conducted for five subjects, the direction and location of the transverse elbow axis was determined for each subject by the helical axis method. A statistical validation was also performed to confirm the result. The result was applied to develop an elbow model, which is apart of the kinematic arm model. The elbow model was developed to validate the significance of the result and the kinematic arm model was able to describe the geometry of any complex linkage system. As a result, the errors incurred from the proposed model were significantly reduced when compared to the ones from existing models.