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Research Papers

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

[+] Author and Article Information
Giovanni Berselli

Diem, Department of Mechanical Engineering, University of Bologna, Bologna 40136, Italygiovanni.berselli@unibo.it

Rocco Vertechy

Diem, Department of Mechanical Engineering, University of Bologna, Bologna 40136, Italyrocco.vertechy@unibo.it

Gabriele Vassura

Diem, Department of Mechanical Engineering, University of Bologna, Bologna 40136, Italygabriele.vassura@unibo.it

Vincenzo Parenti Castelli

Diem, Department of Mechanical Engineering, University of Bologna, Bologna 40136, Italyvincenzo.parenti@unibo.it

J. Mechanisms Robotics 1(3), 031007 (Jul 14, 2009) (7 pages) doi:10.1115/1.3147182 History: Received May 09, 2008; Revised January 15, 2009; Published July 14, 2009

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator, which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Concept behind the proposed solution and actuator 3D model: deactivated state (a), activated state (b), assembly exploded view (c), and compliant frame schematic (d)

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Figure 2

Forces acting in the system in the ON state mode (a) and in the OFF state mode (b)

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Figure 3

FL relationship showing the effect of the film/frame coupling

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Figure 4

Actuator force versus stroke relationship: real behavior (a) and ideal behavior (b)

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Figure 5

FL relationship showing the “negative stiffness” effect

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Figure 13

DE film FL relationship and overall actuator FL relationship: K3=0.20 N m/rad, ϑ30=−29 deg, r2=21.5 mm, r3=26.8 mm, and l1=16 mm

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Figure 6

Actuator configuration under no load and no voltage

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Figure 7

Production steps for the manufacture of the actuator

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Figure 8

DE film force under different actuation voltages, elastomer layer material=Wacker Elastosil RT 625, electrode material=carbon black, l0f=14.9 mm, w=45.0 mm, and t=104.0 μm

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Figure 9

Compliant frame half model schematic

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Figure 10

Frame FL relationship: K3=0.20 N m/rad and ϑ30=−29°

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Figure 11

Analytical FL relationship showing film force Ff and frame force absolute value |Fs|

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Figure 12

Final design of the actuator frame

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