Prototype development of a prosthetic derivative of the minimal anthropomorphic artificial hand

Abstract

In this work, the issue of simplicity and low weight of a prosthetic hand versus its dexterity is addressed through a “minimal anthropomorphic” approach, which focusses on trying to replicate solely those features of the natural hand that contribute most to its dexterity, while sacrificing features that contribute less. In this regard, the design of a larger, heavier hand that was previously developed using this approach, but that was intended for teleoperation applications rather than as a prosthesis, is modified to satisfy the mechanical requirements for a prosthetic hand. The design, development, and evaluation of the first exploratory prototype prosthesis, designated UM-PRO-I, is described in detail. The new hand incorporates two fingers and a thumb, with eight joints and five independent degrees of freedom actuated using embedded linear DC motors. The main innovative features are the implementation of a substantial, coupled abduction / adduction motion of the index and middle fingers, and the use of an optimally inclined 90o hinge joint at the base of the thumb. The hand weighs less than 300 g, and has the capability to execute a wide variety of human-like grasps. The dexterity of the prototype is explored also through the conduction of a standard clinical dexterity test, carried out with the support of an input / output data glove developed specifically for the kinematic configuration of the prototype hand.