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Research Papers

A Computational Design Method for a Shape Memory Alloy Wire Actuated Compliant Finger

[+] Author and Article Information
Chao-Chieh Lan1

Department of Mechanical Engineering, National Cheng Kung University, No. 1 University Road, Tainan 701, Taiwancclan@mail.ncku.edu.tw

You-Nien Yang

Department of Mechanical Engineering, National Cheng Kung University, No. 1 University Road, Tainan 701, Taiwanmiddle1023@gmail.com

1

Corresponding author.

J. Mech. Des 131(2), 021009 (Jan 21, 2009) (9 pages) doi:10.1115/1.3042152 History: Received March 17, 2008; Revised October 24, 2008; Published January 21, 2009

This paper presents a computational method to design a compliant finger for robotic manipulations. As traditional mechanical fingers require bulky electromagnetic motors and numerous relative moving parts to achieve dexterous motion, we propose a class of fingers; the manipulation of which relies on finger deflections. These compliant fingers are actuated by shape memory alloy (SMA) wires that exhibit high work-density, frictionless, and quiet operations. The combination of compliant members with embedded SMA wires makes the finger more compact and lightweight. Various SMA wire layouts are investigated to reduce their response time while maintaining sufficient output force. The mathematical models of finger deflection caused by SMA contraction are then derived along with experimental validations. As finger shapes are essential to the range of deflected motion and output force, we find its optimal initial shapes through the use of a shape parametrization technique. We further illustrate our method by designing a humanoid finger that is capable of three-dimensional manipulation. Since compliant fingers can be fabricated monolithically, we expect the proposed design method to be utilized for applications of various scales.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 8

Schematic of a hooked type finger

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Figure 9

Experiment validations (V-shaped)

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Figure 10

Schematic of design domain

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Figure 11

Optimal shape with experimental validation (M-shaped)

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Figure 12

Experiment setup (M-shaped)

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Figure 18

Various actuated finger configurations

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Figure 19

Displacements of the fingertip

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Figure 20

Cutaway view of adduction motion design

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Figure 21

Snapshot of a three-dimensional finger

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Figure 22

Workspace of a humanoid finger

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Figure 1

Contraction force and relaxation time of SMA wires (23)

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Figure 2

Experiment setup

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Figure 3

Types of SMA wire layouts

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Figure 4

Contraction ratio versus load (wire diameter=0.2 mm)

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Figure 5

Deformation model of a compliant finger

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Figure 6

(a) Schematic of a fixed type finger and (b) free body diagram of a SMA wire

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Figure 7

(a) Schematic of a hooked type finger and (b) free body diagram of the hook

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Figure 17

M-shaped SMA wire layout

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Figure 13

Displacement of tip with respect to various loads

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Figure 14

Schematic of design domain

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Figure 15

Optimal shape of a hooked type finger (V-shaped)

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Figure 16

Schematic of a humanoid finger

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