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Reference TypeConference Proceedings
Author(s)Mistry, M.;Mohajerian, P.;Schaal, S.
TitleArm movement experiments with joint space force fields using an exoskeleton robot
Journal/Conference/Book TitleIEEE Ninth International Conference on Rehabilitation Robotics
Keywordscomputational motor control trajectory planning inverse kinematics force control human motor control torque perturbations
AbstractA new experimental platform permits us to study a novel variety of issues of human motor control, particularly full 3-D movements involving the major seven degrees-of-freedom (DOF) of the human arm. We incorporate a seven DOF robot exoskeleton, and can minimize weight and inertia through gravity, Coriolis, and inertia compensation, such that subjects' arm movements are largely unaffected by the manipulandum. Torque perturbations can be individually applied to any or all seven joints of the human arm, thus creating novel dynamic environments, or force fields, for subjects to respond and adapt to. Our first study investigates a joint space force field where the shoulder velocity drives a disturbing force in the elbow joint. Results demonstrate that subjects learn to compensate for the force field within about 100 trials, and from the strong presence of aftereffects when removing the field in some randomized catch trials, that an inverse dynamics, or internal model, of the force field is formed by the nervous system. Interestingly, while post-learning hand trajectories return to baseline, joint space trajectories remained changed in response to the field, indicating that besides learning a model of the force field, the nervous system also chose to exploit the space to minimize the effects of the force field on the realization of the endpoint trajectory plan. Further applications for our apparatus include studies in motor system redundancy resolution and inverse kinematics, as well as rehabilitation.
Place PublishedChicago, Illinois, June 28-July 1
Short TitleArm movement experiments with joint space force fields using an exoskeleton robot
Research Notes¥ By using an exoskeleton robot manipulandum, the authors perturbed the elbow joint of subjects with a force field during point-to-point reaching movements with the unconstrained arm. Subjects learned to compensate for this force field and return after tr

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