On the Design of a Mechanically Programmable Underactuated Anthropomorphic Prosthetic Gripper

Abstract

This paper introduces a novel underactuated anthropomorphic gripper for prosthetic applications. In order to extend the grasping capabilities of underactuated prosthetic grippers and improve the force transmission ratio, a mechanical lever is mounted inside the palm that allows a proper distribution of the forces and provides mechanical advantage. A static model is developed and the possibilities offered by the lever transmission are investigated. Also, a compact mechanism is introduced to synchronize the motion of the four fingers. Additionally, a mechanical selector is designed that functions as a means of mechanically programming the motion of the fingers by selectively blocking their closing motion. Finally, a prototype, including all the above features, is described and experimental validation is briefly reported.

Underactuated tendon-driven robotic/prosthetic hands: design issues

“…In [1], several pulley and floating-body arrangements are studied for their force transmission qualities. A combination of some of these arrangements has been used in [2] with good results. One limitation noted by the authors was the lack of grasping force for a given actuation force.…”

“…1. The remainder of the mechanism is similar to the one presented in [2]. The motion of the fingers and the thumb are coupled to the actuation motion through a transmission lever L. The motion of the thumb is coupled to the motion of the other fingers while preserving the shape adaptation capability because they work in opposition (the adaptation is naturally performed by the relative motion between the object and the hand during the closing phase).…”

“…In some designs (see for instance [2]), the tendon actuating the closing motion of the thumb passes through the base pivot of the thumb, which guarantees that the closing action of the tendon does not affect the configuration of the thumb. However, in the design presented in this paper, the tendon does not pass through the base axis, which means that if the thumb is not stabilized, the closing action of the tendon will tend to move the thumb to the configuration associated with spherical grasps (thumb opposing the fingers).…”

A model for the grasping analysis of an underactuated finger driven by unextensible tendon

“…These devices are based on mechanical systems using a number of motors [7][8][9][10] or on selfadapting devices using a single motor [11][12][13] .…”

Simulation results of the grasping analysis of an underactuated finger

“…[1][2][3][4][5][6][7][8][9][10][11][12][13]); this both for human prostheses and for industrial or agricultural purposes. Among these studies the authors conceived developed and patented a new mechanical hand (Federica mechanical hand) based on a self-adaptive patented scheme (patent n. 0001415546 and n. 102015000059873, the latter pending) based on a selfadaptive scheme and under-actuated fingers operated by un-extendible tendons.…”