Trajectory formation based on a human arm model with redundancy

Human arm trajectory formations have been widely investigated to understand how we control the trajectories in the central nervous system. The trajectory formations proposed in most of studies are for now limited to a plane motion, and the arm model used for analyses are mostly restricted within three degrees of freedom. On the contrary, the structure of the human arm has redundancy for locating a hand to any position in a three dimensional space. This study presents the trajectory formation applicable to a redundant arm model which is capable of moving in a three dimensional space. The criterion is defined by the angular jerk for all joint angles, and a constraint is provided for the motion of the elbow joint in order to exhibit the hand velocity profile of the human arm trajectory. This trajectory formation is applied to a redundant arm model of which structure is similar to a human arm. The trajectories produced under the proposed trajectory formation are evaluated by the trajectories observed in a three dimensional space as well as in a sagittal plane. Consequently, the relevance of the trajectory formation for demonstrating human arm trajectories has been discussed.