A Cosmetic Prosthetic Hand with Tendon Driven Under-Actuated Mechanism and Compliant Joints: Ongoing Research and Preliminary Results

Abstract

This paper presents recent results aimed at developing a functional prosthetic hand characterized by an EMG-control and by a simple and low cost fabrication technology. In order to overcome some limitations of current prosthetic hands mainly related to the poor functionality and controllability, the prosthetic hand has been designed following a biomechatronic approach based on biologically-inspired design solutions. The core of the project described in this paper is the fabrication of a compliant under-actuated prosthetic hand: the structure of the hand (both palm and fingers) is moulded as a soft polymeric single part with compliant joints and embedded tendon driven underactuated mechanism for providing adaptive grasp. In order to make user trials, the hand is equipped with simple but functional EMG-based control of the single motor incorporated in the hand, and is integrated with a prosthesis socket. The paper presents the biomechatronics design, the fabrication process, the integration of the prosthetic device and first experimental results.

Notice of Retraction: Geometric optimization of pinching and grasping underactuated finger

“…Underactuated hand which consists of underactuated fingers with higher number of degree of freedom (DOF) compared to its number of actuators [4] is an alternative to these artificial hands. This mechanism replaces the commonly large size and unnatural designs while preserving the hand or fingers functionality by replacing the traditional actuators such as electro-magnetic motors with small passive elements such as springs and mechanical stops [5].…”

Grasping force control of a tendon-driven prosthetic finger based on force estimation using motor current signals

“…Under-actuated coupling prosthetic hands have significantly reduced the number of prosthetic hand drivers, lowering the control difficulty of prosthetic hands and also ensuring a certain adaptive grasping ability of their fingers [3]. Under-actuated coupling prosthetic hands have a relatively simple structure-the tendon-driven structure, which adopts a kind of driving mode that uses the tendon to transmit power and motion [4].…”

A simple design rule for 1st order form-closure of underactuated hands

“…After an infinitesimal rotation, the object is stopped from rotating in case (b), whereas it is free to escape in case (c). This phenomenon can be modeled considering the local curvatures of the contact surfaces as explained in Carrozza et al (2005). Grasp (a) is 1st order formclosed, because a 1st order modeling of the grasp is sufficient to demonstrate form-closure, whereas grasp (b) is 2nd order form-closed, because 2nd order modeling is required for demonstrating form-closure.…”