Design of a Single-Input, Five-Output Differential Actuation Unit for Underactuated Hands

Abstract

Robotic hands, prosthetics, and hand exoskeletons struggle with replicating the natural dexterity of human hands: the mechanical intelligence of our muscles can be hardly replicated with rigid actuators, while soft mechanisms compromise precision. Underactuated hand mechanisms represent a trade-off between these extremes. However, single-motor solutions, while robust and compact, generally actuate a maximum of four fingers or present critical differences in force transmission between the fingers. Here, we propose a design for a single-input, five-output differential gearbox that delivers balanced transmission thanks to a unique asymmetrical layout. This feature enables adaptive grasp control through mechanical intelligence only, providing the user with a reliable, safe, and lightweight solution for tendon-driven hand mechanisms. A preliminary 3D-printed prototype is presented to demonstrate the concept.