Design and control of a three finger hand exoskeleton for translation of a slender object

Abstract

A three finger hand exoskeleton is designed and controlled for translation of a slender object held at the finger tips. The design incorporates actuation of the three flexion/extension joints of the index and middle fingers. For the thumb exoskeleton, a design is proposed with two degrees of freedom. First, trajectory data of all the phalanges for translation of a slender object are obtained through video capture and post-processing involving coordinate transformations and mean representations to minimize the experimentation errors. Due to non-circular loci of these trajectories, planar four-bar linkages are synthesized using three accuracy point method, and optimized using genetic algorithm. The four-bar linkages for each finger exoskeleton are concatenated serially in a plane. The exoskeleton is mounted on the dorsal side of the hand using Velcro bands at each phalanx, along with a fixture attached to forearm. Eight micro-servo motors are employed for actuation, and open loop control for trajectory following is implemented.

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