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Research Papers

Design of a Shape Memory Alloy Actuated Compliant Smart Structure: Elastica Approach

[+] Author and Article Information
M. Sreekumar

Department of Mechanical Engineering, Precision Engineering and Instrumentation Laboratory, Indian Institute of Technology Madras, Chennai-600 036, Indiamsk@iiitdm.ac.in msk_iitm2004@yahoo.co.in

T. Nagarajan

Department of Mechanical Engineering, Precision Engineering and Instrumentation Laboratory, Indian Institute of Technology Madras, Chennai-600 036, Indiatnaga@iitm.ac.in

M. Singaperumal

Department of Mechanical Engineering, Precision Engineering and Instrumentation Laboratory, Indian Institute of Technology Madras, Chennai-600 036, Indiamsingam@iitm.ac.in

J. Mech. Des 131(6), 061008 (May 21, 2009) (11 pages) doi:10.1115/1.3125202 History: Received September 24, 2007; Revised March 26, 2009; Published May 21, 2009

Large displacement static analysis of a fully compliant spatial mechanism is presented here. This mechanism is made up of a superelastic nitinol pipe as its compliant structural member and actuated by three shape memory alloy (SMA) wires. The coupled effect of the force developed by the SMA actuation and the force required for elastica deflection is simplified by incorporating the geometric parameters of the mechanism using a deflection plane approach. An iterative algorithm with elliptical integration has been developed, which is suitable for a wider range of actual and arbitrary inputs. The solutions are obtained for the effect of one-wire and two-wire actuation methods. Results obtained from the deflection plane approach and simulation have been compared and found that the relative error is less than 1% within the safe operating range of 5% strain value recommended for SMA actuators. Based on the analytical and simulation inputs, the mechanism is miniaturized further with the aim of increasing its workspace and is fabricated for further experimental investigations.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 2

Geometric parameters of the compliant mechanism and components of SMA actuation force

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Figure 3

Components of total actuation force developed by the effect of two-wire SMA actuation

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Figure 6

Rate of convergence for one-wire actuation: (a) for actuation force and (b) for parametric angle β.

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Figure 7

Rate of convergence for two-wire actuation: (a) for actuation force and (b) for parametric angle β

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Figure 8

Out of convergence in two-wire actuation for β>30 deg

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Figure 9

Maximum displacement in two-wire actuation for ε=8%

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Figure 10

Trajectory of the center of the moving platform: (a) one-wire actuation and (b) two-wire actuation

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Figure 11

Tilt angle versus force generated in one SMA wire (from elliptical integration)

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Figure 5

Solution algorithm for the coupled effect of elastica deflection and SMA actuation.

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Figure 4

Deflection plane XX bounded by geometric constraints: (a) one-wire actuation and (b) two-wire actuation

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Figure 1

Compliant mechanisms under development with dimensions in millimeters: (a) manipulator fabricated from Be–Cu for initial investigation, (b) photograph of the manipulator, and (c) compliant smart structure made from NiTi SMA

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Figure 12

Strain versus force generated in one SMA wire

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Figure 13

Workspace of the mechanism (plan view): (a) with three wires and (b) with six wires

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Figure 14

The mechanism modified: (a) 3D view and (b) sectioned view for one wire with dimensions in millimeters

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