Analysis of arm trajectories of everyday tasks for the development of an upper-limb orthosis

Spatiotemporal arm and body movements of able-bodied subjects performing nine everyday tasks were recorded for the purpose of guiding the development of an upper-limb orthosis. To provide a user the opportunity to carry out these tasks with natural movements, the orthosis should allow replication of the measured trajectories. We outline the orthosis architecture, which supports the user's upper arm and forearm, and analyze the movement data to obtain orthosis design specifications. Trajectories were obtained using six-degree-of-freedom magnetic position sensors affixed to the wrist, elbow shoulder, trunk and head. Elbow trajectory data were decomposed into ranges along the principal Cartesian axes to provide a generally useful envelope measure. The smallest Cartesian parallelepiped that contained the elbow trajectories for most tasks was approximately 30 cm front/back, 15 cm side/side, and 17 cm up/down. A rough lower bound estimate obtained by asking subjects to repeat the tasks while minimizing elbow movement substantially reduced movement in the up/down and side/side dimensions. Elbow angles were generally in the range 50/spl deg/-150/spl deg/, and the angle of the forearm with respect to vertical was 10/spl deg/-110/spl deg/.