Research Papers

On the Design of a Mechanically Programmable Underactuated Anthropomorphic Prosthetic Gripper

[+] Author and Article Information
Clément Gosselin

e-mail: gosselin@gmc.ulaval.ca
Laboratoire de robotique,
Département de Génie Mécanique,
Université Laval,
Québec, QC G1V 0A6, Canada

François Routhier

Département de Réadaptation,
Université Laval,
Québec, QC G1V0A6, Canada

Contributed by the Design Innovation and Devices of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received October 16, 2012; final manuscript received August 9, 2013; published online October 4, 2013. Assoc. Editor: Alexander Slocum.

J. Mech. Des 135(12), 121008 (Oct 04, 2013) (9 pages) Paper No: MD-12-1520; doi: 10.1115/1.4025493 History: Received October 16, 2012; Revised August 09, 2013

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.

Copyright © 2013 by ASME
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Fig. 1

CAD model of the proposed underactuated finger, showing its coverings and its compliant base

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Fig. 2

Insertion of a finger into the palm to obtain compliance at its base

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Fig. 3

CAD model of the thumb in its two limit configurations

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Fig. 4

Schematic illustration of the proposed mechanism

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Fig. 5

Schematic illustration of one floating part during actuation, showing the two phenomena of underactuation

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Fig. 6

Principle of the mechanical selector

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Fig. 7

Schematic representation of a typical mechanical selector, showing its blocking pattern of outputs in its three possible configurations, together with the corresponding actions of the gripper. In the top configuration of the selector, the last two fingers are locked (pinch grasp with three fingers, shown on the upper right photograph), in the middle configuration of the selector, all fingers close (shown on the lower left photograph) and in the bottom configuration of the selector, the index finger does not close (shown on the lower right photograph, for pointing or pushing buttons).

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Fig. 8

Photograph of the back of the prototype, showing the manual switch

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Fig. 9

Photograph of the gripper, showing the insertion of the mechanical selector in a slot in the palm

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Fig. 10

Photograph of the underactuated gripper without its cover pointing the index finger with the use of a mechanical selector

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Fig. 11

Schematic drawing of the lever

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Fig. 12

Effect of angle φ on output forces during actuation with φ1 = φ2 = φ, ψ0 = π/6, a1 = a2 = a3 = 1 and K = 1

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Fig. 13

Photograph of the prosthetic anthropomorphic gripper, including all the features presented in this paper

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Fig. 14

Participant completing the button board ADL task of the SHAP with the gripper

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Fig. 15

Pictures of the prosthetic hand performing different tasks of the SHAP




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