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Research Papers

Fabrication of Composite and Sheet Metal Laminated Bistable Jumping Mechanism

[+] Author and Article Information
Sun-Pill Jung

Biorobotics Laboratory,
School of Mechanical and Aerospace Engineering/
SNU-IAMD,
Seoul National University,
1 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Korea
e-mail: sunpill20@snu.ac.kr

Gwang-Pil Jung

Biorobotics Laboratory,
School of Mechanical and Aerospace Engineering/
SNU-IAMD,
Seoul National University,
1 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Korea
e-mail: ceaser97@snu.ac.kr

Je-Sung Koh

Biorobotics Laboratory,
School of Mechanical and Aerospace Engineering/
SNU-IAMD,
Seoul National University,
1 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Korea
e-mail: kjs15@snu.ac.kr

Dae-Young Lee

Biorobotics Laboratory,
School of Mechanical and Aerospace Engineering/
SNU-IAMD,
Seoul National University,
1 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Korea
e-mail: winter2nf@gmail.com

Kyu-Jin Cho

Associate Professor
Biorobotics Laboratory,
School of Mechanical and Aerospace Engineering/
SNU-IAMD,
Seoul National University,
1 Gwanak-ro, Gwanak-gu,
Seoul 151-742, Korea
e-mail: kjcho@snu.ac.kr

1Corresponding author.

Manuscript received August 19, 2014; final manuscript received December 23, 2014; published online February 27, 2015. Assoc. Editor: Aaron M. Dollar.

J. Mechanisms Robotics 7(2), 021010 (May 01, 2015) (10 pages) Paper No: JMR-14-1225; doi: 10.1115/1.4029489 History: Received August 19, 2014; Revised December 23, 2014; Online February 27, 2015

A layer-based manufacturing method using composite microstructures is widely used for mesoscale robot fabrication. This fabrication method has enabled the development of a lightweight and robust jumping robot, but there are limitations in relation to the embedding of elastic components. In this paper, a fabrication method for embedding an elastic component at an angled position is developed, extending the capability of the composite microstructures. This method is then used to build an axial spring attached to the bistable mechanism of a jumping robot. Sheet metal is used as an elastic component, which is stamped after the layering and curing process, thereby changing the neutral position of the spring. Two linear springs are designed to be in parallel with a joint to impose bistability; thereby delivering two stable states. This bistable mechanism is triggered with a shape memory alloy (SMA) coil spring actuator. A small-scale jumping mechanism is then fabricated using this mechanism; it jumps when the snap-through of the bistable mechanism occurs. A model of the stamped sheet metal spring is built based on a pseudo rigid body model (PRBM) to estimate the spring performance, and a predictive sheet metal bending model is also built to design the die for stamping. The experimental results show that the stamped sheet metal spring stores 12.63 mJ of elastic energy, and that the mechanism can jump to a height of 175 mm with an initial takeoff velocity of 1.93 m/s.

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References

Figures

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Fig. 1

(a) Simple bistable structure. (b) Conceptual graph of elastic energy in relation to the shape of the bistable structure.

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Fig. 2

Conceptual design of the bistable jumping mechanism and schematic drawing of bistable structure actuation

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Fig. 3

(a) SCM process with sheet metal, (b) rotational spring with stamped sheet metal, and (c) axial spring with stamped sheet metal

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Fig. 4

Implementation of the conceptual bistable jumping mechanism using stamped sheet metal

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Fig. 5

Parameters of the sheet metal spring

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Fig. 6

(a) Model of stamped sheet metal. (b) Simplified model including rigid links and torsional springs.

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Fig. 7

PRBM of the end moment loading

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Fig. 8

Pseudo rigid model of the force loading on the curved beam by the moment

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Fig. 9

Simplified model of the half side of an axial spring in the bistable jumping mechanism

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Fig. 10

Graphical representation of the combination of R and T in elastic region (w = 5 mm, Dneutral = 25.6 mm, Dmax = 30.8 mm, L = 22 mm, Lc = 9.5 mm)

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Fig. 11

The force–deflection relationship of the stamped sheet metal spring model (w = 5 mm, Dneutral = 25.6 mm, Dmax = 30.8 mm, L = 22 mm, Lc = 9.5 mm); (a) when R varies with constant T ( = 0.08 mm) and (b) when T varies with constant R ( = 1 mm)

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Fig. 12

Fabrication process of bistable jumping mechanism with the spring integrative SCM process using stamping the sheet metal

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Fig. 13

Wiping die bending method

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Fig. 14

Schematic diagram of springback phenomonen

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Fig. 15

Experimental results of the springback factor versus Ri/T

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Fig. 16

Graphical representation of the available combination of R and T and the position of the specimen (w = 5 mm, Dneutral = 25.6 mm, Dmax = 30.8 mm, L = 22 mm, Lc = 9.5 mm)

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Fig. 17

Comparison between simplified force–deflection model and experimental results

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Fig. 18

Fabrication results of the bistable jumping mechanism

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Fig. 19

Sequential high-speed images of bistable jumping mechanism at takeoff

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Fig. 20

Jumping trajectory of bistable jumping mechanism

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