Assessment of the accuracy of a human arm model with seven degrees of freedom

We are proposing a human arm model that consists of three rigid segments wi th seven degrees of freedom. The shoulder joint was modeled as a ball-and-s ocket joint and the elbow and wrist joints were modelled as skew-oblique jo ints. Optimal parameters for this model were calculated on the base of in v ivo recordings with a spatial tracking system. The criterion of optimality was defined as the minimum or. the mean-square deviation between the experi mentally obtained sensor positions and orientations and their positions and orientations calculated by solving the direct kinematics problem. The mini mal value of the direct kinematics error was found to be 0.5-0.6 cm for sen sor positions and 5-7 degrees for sensor orientations. We are proposing tha t these Values serve as the assessment for the accuracy of the arm model. ( C) 2001 Elsevier Science Ltd. All rights reserved.