Anthropomorphically Inspired Design of a Tendon-Driven Robotic Prosthesis for Hand Impairments

Abstract

This thesis presents the design of a robotic prosthesis, which mimics the morphology of a human hand. The primary goal of this work is to develop a systematic methodology that allows a custom-build of the prosthesis to match the specific requirements of a person with hand impairments. Two principal research questions are addressed toward this goal: 1) How do we cater to the large variation in the distribution of overall hand-sizes in the human population? 2) How closely do we mimic the complex morphological aspects of a biological hand in order to maximize the anthropomorphism (human-like appearance) of the robotic hand, while still maintaining a customizable and manageable design? This design approach attempts to replicate the crucial morphological aspects in the artificial hand (the kinematic structure of the hand skeleton, the shape and aspect ratios of various bone-segments, and ranges of motion). The hand design is partitioned into two parts: 1) A stiff skeleton structure, comprising parametrically synthesized segments that are simplified counterparts of nineteen bone-segments—five metacarpals, five proximal phalanges, four middle phalanges, and five distal phalanges—of the natural hand-skeleton and simplified mechanical substitutes of the remaining eight carpal bones. 2) A soft skin-like structure that encompasses the artificial skeleton to match the cosmetics and compliant features of the natural hand. A parameterized CAD model representation of each synthesized segment is developed by using the feature of design-tables in SolidWorks, which allows easy customization with respect to each person. Average hand measurements available in the literature are used to guide the dimensioning of parameters of each synthesized segment. Tendon-driven actuation of the fingers allows the servo actuators to be mounted remotely, thereby enabling a sleek finger design. A prototype of the robotic hand is constructed by 3D-printing all the parts using an Object 30 Prime 3D printer. Results reported from physical validation experiments of the robotic hand demonstrate the feasibility of the proposed design approach