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Research Papers: Design of Mechanisms and Robotic Systems

A Family of Dual-Segment Compliant Joints Suitable for Use as Surrogate Folds

[+] Author and Article Information
Isaac L. Delimont

Department of Mechanical Engineering,
Brigham Young University,
Provo, UT 84604

Spencer P. Magleby

Professor Department of Mechanical Engineering,
Brigham Young University,
Provo, UT 84604
e-mail: magleby@byu.edu

Larry L. Howell

Professor
Department of Mechanical Engineering,
Brigham Young University,
Provo, UT 84604

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received September 25, 2014; final manuscript received June 12, 2015; published online July 22, 2015. Assoc. Editor: Oscar Altuzarra.

J. Mech. Des 137(9), 092302 (Jul 22, 2015) Paper No: MD-14-1639; doi: 10.1115/1.4030875 History: Received September 25, 2014

Origami-inspired design is an emerging field capable of producing compact and efficient designs. The object of a surrogate fold is to provide a foldlike motion in a nonpaper material without undergoing yielding. Compliant mechanisms provide a means to achieve these objectives as large deflections are achieved. The purpose of this paper is to present a continuum of compliant joints capable of achieving motions not currently available with existing compliant joints. A series of compliant joints are presented in which the joint can be designed to allow or resist a variety of secondary motions. Closed-form solutions are presented for these compliant joints.

Copyright © 2015 by ASME
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Figures

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Fig. 1

The parameter φ affects the response of the surrogate fold to tension and compression

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Fig. 2

The pseudo-rigid-body equivalent of a surrogate fold

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Fig. 3

Six possible motions of surrogate folds to be compared for each joint. (a) Folding, (b) torsion, (c) lateral bending, (d) shear, (e) compression, and (f) tension.

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Fig. 4

Guide for the selection of surrogate folds with dual-segment joints included

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Fig. 5

Comparison of Eq. (3) and FEA results for varying values of φ from 0 deg to 90 deg. The compliant members of the joint have a length of L = 5 cm, w = 0.4 cm, and t = 0.4 cm; E = 1.4 GPa; and ν = 0.34. The selected values represent a physical prototype constructed by the author.

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Fig. 6

The % error of Eq. (3) versus β for a variety of cross sections and lengths

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Fig. 7

There exists some value of β such that the stiffness to actuate the dual-segment joint is independent of φ

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Fig. 8

Deflection stiffness to actuate the dual-segment joint versus the angle φ as given by Eq. (3)

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Fig. 9

When φ=0, the dual-segment joint is called the bending-orthogonal joint, also called the simple reduced area joint

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Fig. 10

The addition of a center buckling member to the mixed tension resistant, labeled LB, decreases the force required to actuate the joint in compression

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Fig. 11

The actuation force versus deflection for the mixed tension resistant joint in tension and compression. φ=25 deg, Lt = 38.07 mm, w = 3.18 mm, t = 3.43 mm, and E = 1.37 GPa. The rapid change of slope seen in compression represents the initiation of buckling.

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Fig. 12

An illustration of the boundary conditions used to derive Eq. (7). Note that buckling only occurs when values of δ are negative. Equation (7) is not valid when δ is negative.

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Fig. 13

The torsion-parallel joint is a specialized case of the dual-segment joint when φ is equal to 90 deg

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Fig. 14

The mixed compression resistant joint gives a stiffer resistance to compression than tension

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Fig. 15

The mixed compression resistant joint rotating out of plane when placed in tension

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Fig. 16

The actuation force versus deflection for the mixed compression resistant joint in tension and compression. φ=110 deg, Lt = 59 mm, w = 3.18 mm, t = 1.27 mm, and E = 1.37 GPa. The rapid change of slope seen in tension occurs as the flexures rotate out of plane as illustrated in Fig. 15.

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Fig. 17

The inverted bending-orthogonal joint occurs when φ=180 deg. The inversion causes the compliant members to be in tension when the joint is in compression. This avoids the possibility of buckling in this loading condition.

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Fig. 21

By combining the mixed tension and compression resistant joints a small amount of lateral bending can be achieved while maintaining high resistance to other motions

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Fig. 20

Torsion-parallel joint patterned along the line of the fold for further increased resistance to tension and compression

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Fig. 19

A comparison of the torsion-parallel joint with buckling member and the outside LET joint when placed in tension. Both joints have L = 5 cm, w = 0.4 cm, t = 0.4 cm, and E = 1.4 GPa.

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Fig. 18

The torsion-parallel joint with a buckling member added to give increased resistance to tension and compression as compared to the outside LET

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