An orthotic hand-assistive exoskeleton for actuated pinch and grasp

Abstract

Over 450,000 Americans suffer from debilitative disorders resulting in the loss of proper hand function. A lightweight, non-cumbrous, orthotic hand exoskeleton was designed to restore normal pinching and grasping finger motions. Three functional digit mechanisms were designed: a thumb, index, and grouped third digit, comprised of the middle, ring, and small fingers. Each phalange was enclosed by a series of cylindrical aluminum bands connected at the centers of rotation of each joint. Bowden cables were mounted beneath each digit to provide active flexion, mimicking the tendons in the hand. A spring extension mechanism maintained constant tension in the Bowden cables, and during relaxation, returned the actuated digits to a fully extended resting position. Individually controlled actuators mounted on a forearm assembly produced 15 N of tensile force in each cable. The orthotic hand exoskeleton will be integrated with a digital control system currently under development in this laboratory. The complete system was designed to restore hand functionality through the amplification of precision pinch and/or power grasp.