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Research Papers

A Low Profile Electromagnetic Actuator Design and Model for an Origami Parallel Platform

[+] Author and Article Information
Marco Salerno

EPFL,
EPFL STI IGM RRL,
Station 9,
Lausanne CH-1015, Switzerland
e-mail: marco.salerno@epfl.ch

Amir Firouzeh

EPFL,
EPFL STI IGM RRL,
Station 9,
Lausanne CH-1015, Switzerland
e-mail: amir.firouzeh@epfl.ch

Jamie Paik

EPFL,
EPFL STI IGM RRL,
Station 9,
Lausanne CH-1015, Switzerland
e-mail: jamie.paik@epfl.ch

1Corresponding author.

Manuscript received July 26, 2016; final manuscript received March 27, 2017; published online May 2, 2017. Assoc. Editor: Jian S. Dai.

J. Mechanisms Robotics 9(4), 041005 (May 02, 2017) (11 pages) Paper No: JMR-16-1214; doi: 10.1115/1.4036425 History: Received July 26, 2016; Revised March 27, 2017

Thin foldable origami mechanisms allow reconfiguration of complex structures with large volumetric change, versatility, and at low cost; however, there is rarely a systematic way to make them autonomously actuated due to the lack of low profile actuators. Actuation should satisfy the design requirements of wide actuation range, high actuation speed, and backdrivability. This paper presents a novel approach toward fast and controllable folding mechanisms by embedding an electromagnetic actuation system into a nominally flat platform. The design, fabrication, and modeling of the electromagnetic actuation system are reported, and a 1.7 mm-thick single-degree-of-freedom (DoF) foldable parallel structure reaching an elevation of 13 mm is used as a proof of concept for the proposed methodology. We also report on the extensive test results that validate the mechanical model in terms of the loaded and unloaded speed, the blocked force, and the range of actuation.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Parallel mechanism designed as a proof of concept of the foldable actuation mechanism: the unfolded 2D configuration top and side views (left), and 3D folded configuration upon actuation, top and side views (right). The arrows mark the direction of motion of the platform components after coil powering.

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Fig. 2

Miniaturized electromagnetic actuator: working principle and main components. The arrows mark the magnetization direction of magnet and coils.

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Fig. 3

Schematic of the layers composing the platform (left), assembled system in the unfolded 2D state (center), and folded 3D system configuration (right)

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Fig. 4

Double slider mechanism. The proposed platform is axially symmetric and composed of three double sliders arranged at 120 deg from one another and sharing the prismatic joint.

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Fig. 5

Working principle of the miniaturized electromagnetic actuator: (a) schematic of the assembled actuator and (b) exploded view of the layers composing the actuator

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Fig. 6

Magnet–coils interactions. The reference system used to define the position of the magnet with respect to the coils (a). Resultant force acting on the magnet with increasing X positions (b). Resulting FEM forces in X and Z directions by changing magnet X position ((c)–(d)). Resulting FEM forces in X direction by changing magnet X position and magnet elevation along Z (e). Resulting FEM forces in Z direction by changing magnet X position and magnet elevation along Z (f).

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Fig. 7

Schematics of the articulated parallel platform in pop-up (left) and planar (right) configurations with design parameters used. The values of the parameters used are reported in Table 2.

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Fig. 8

Mask and coil prototypes. Comparison of masks ((a) and (b)); corresponding resulting coils ((c)–(d)). In the manufactured coil, the underetching effect is visible; conductor tracks are much thinner than the corresponding mask tracks.

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Fig. 9

Platform prototype. The alignment holes used during the fabrication process are visible in both pictures. The assembled system is in the 2D state (left) and in the pop-up state (right).

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Fig. 10

Platform prototype sizes. The weights of the components and subcomponents highlighted in the figure are reported in Table 3.

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Fig. 11

Free-body diagrams of the three links composing the double slider mechanism

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Fig. 12

Description of experimental setups and tests performed. The setup for the verification of the coils' time constant is composed of a Hall effect sensor and the coil system (a). The setup for verification of the single rail dynamics is composed of a high-speed camera and a tracking marker (b).

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Fig. 13

Magnetic field development with time: for actuation voltages of 20 and 30 V, verifying negligible electromagnetic transient response

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Fig. 14

Normalized magnetic flux density decrease due to thermal increase: simulation (a), experimental (b), and B field expected decrease per second for different input voltages (c)

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Fig. 15

The slider's position on the rail. The Fx for different positions along the rail is reported (a). For different voltages, the magnet position in time is reported (b). Calculated parameters used in the comparison with the model (c).

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Fig. 16

Magnet motion calculated parameters comparison: maximum speed (a), maximum position (b), final position (c), and motion time (d). Simulations (circles), and experiments (dots). The error bars are calculated from the standard deviation of three repetitions.

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Fig. 17

Description of experimental setups and tests performed. The setup for the verification of the platform dynamics includes a marker on each leg (a). The setup for the payload tests includes a mass placed on top of the platform (b).

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Fig. 18

The pop-up platform's tracking performance. At the different voltages we report the top platform position (a), speed (b), and acceleration (c).

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Fig. 19

Pop-up platform with a mass on top. For different weights, we report the top platform position (a), speed (b), and acceleration (c). We report the minimum elevation and powering voltage to initiate motion in the legend.

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Fig. 20

Pop-up platform calculated motion parameters comparison: maximum speed (a), maximum position (b), final position (c), and motion time (d). Comparison of the experimental (dots) and simulated (circles) results is reported. The trends are very similar, and the simulation captures well the platform motion.

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Fig. 21

Legged system steady forces tests. Experimental setup (a) includes a force sensor and a microstage placed on top of the platform. The comparison between experimental (dots) and theoretical results is reported (b).

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Fig. 22

Pop-up platform with mass on top, simulation results. For different weights and input voltages, the top platform achievable position ranges (a) and speeds (b) are reported.

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Fig. 23

Envisioned platform where a delta robot is interfaced with the proposed actuation system: folded portable configuration (left) and 3D pop-up configuration (right)

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