Design of a Compliant, Multi-Phalanx Underactuated Prosthetic Finger

Abstract

Highly advanced robotic hand prostheses are praised for their impressive grasping and pinching capabilities. Nevertheless, a high demand remains for grasping mechanisms that are cheaper to produce, easier to assemble and lower in overall maintenance. In this paper, the idea of creating a 3D printable underactuated grasper was realized to fulfill these desires. Through a literature survey on existing grasper mechanisms, a basic structure was defined of a three phalanx finger with anthropomorphic dimensions. By using a Pseudo Rigid Body model, a generation optimization analysis was conducted that resulted in a partially compliant conceptual design. This underactuated, anthropomorphic compliant finger was able to reach a fingertip trajectory of 180 degrees. A prototype based on this final design was manufactured out of flexible, high strength nylon, and experimentally evaluated to compare with the simulation model. It was found that the finger met all the set design criteria. Furthermore, despite consisting out of multiple components, no additional assembly steps are required once the design is completed in the 3D printer. In addition, a basic 3D printable compliant hand was created to further show the feasibility of the design as a compact yet versatile low-cost, underactuated hand prosthetic.