Operational Space Formulation and Inverse Kinematics for an Arm Exoskeleton with Scapula Rotation

The operational space of an 8-axis arm exoskeleton is partitioned into "tasks" based on the human arm motion, and a task priority approach is implemented to perform the inverse kinematics. The tasks are prioritized in the event that singularities or other constraints such as joint limits render the full desired operational space infeasible. The task reconstruction method is used to circumvent singularities in a deterministic manner so that the arm is never physically in a singular configuration. This is especially advantageous when the arm is fully extended because it allows the hand to move smoothly along the workspace boundary. The task priority inverse kinematics approach is also more computationally efficient than full Jacobian inverse methods and naturally manages the motion of the arm in a more anthropomorphic-friendly manner. The new methodology is demonstrated with four operational tasks on the MGA Exoskeleton.