Design Innovation

Spherical Bistable Micromechanism

[+] Author and Article Information
Craig P. Lusk1

Department of Mechanical Engineering, University of South Florida, 4202 East Fowler Avenue, ENB 118, Tampa, FL 33620-5350clusk2@eng.usf.edu

Larry L. Howell

Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602lhowell@et.byu.edu

In geography, circles of longitude and the equator are great circles. Circles of latitude other than the equator are not great circles.


Corresponding author.

J. Mech. Des 130(4), 045001 (Mar 18, 2008) (6 pages) doi:10.1115/1.2885079 History: Received October 03, 2006; Revised June 19, 2007; Published March 18, 2008

A new micromechanism, the spherical bistable micromechanism (SBM), is described. The SBM has several advantageous features, which include two stable positions that require power only in transitioning from one position to the other; robustness against small disturbances; and a compact footprint and an output link with a stable out-of-plane orientation. The SBM may be useful in applications such as 2D optical mirror arrays or in erecting out-of-plane structures.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

An annotated SEM of a SBM in its fabricated position, which is its first stable position. The mechanism is made by the combination of a Young mechanism (7,17) and a spherical slider crank (15).

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Figure 2

Schematic of a SBM in its fabricated position. The Young mechanism portion of the device is shaded gray, and the spherical slider-crank portion is white.

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Figure 8

Two kinematically identical spherical links: (a) a spherical arc with angle θ and (b) a quasirectangle with joints at an angle θ apart

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Figure 9

The rotation of the links in the SBM as a function of the input rotation ∣Δθ2∣

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Figure 10

The predicted potential (strain) energy stored in the compliant segments of the SBM as a function of the input rotation ∣Δθ2∣

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Figure 3

SEM of a SBM in its second stable position

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Figure 4

SEM close-up view of the spherical slider-crank portion of a SBM in its second stable position

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Figure 11

The predicted input torque required to hold the SBM in equilibrium at a given value of the input rotation ∣Δθ2∣

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Figure 12

The predicted strain in the compliant segments in the SBM as a function of the input rotation ∣Δθ2∣

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Figure 13

A top view of the second stable equilibrium position, where ∣Δθ2∣ is measured as 79deg and s7 is measured as 72deg.

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Figure 5

Illustration of (a) a Young mechanism, (b) its PRBM, and (c) parameters for its position analysis (adapted from Ref. 7)

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Figure 6

Spherical triangle with sides subtending angles of k, m, and n, and dihedral angles θ, σ, and ξ

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Figure 7

Combined sketch of the spherical slider crank and the PRBM of the Young mechanism, i.e., a combined kinematic model of the SBM




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