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Research Papers

# A Multistable Linear Actuation Mechanism Based on Artificial Muscles

[+] Author and Article Information
Rahim Mutlu

School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522, Australiarm991@uow.edu.au

Gürsel Alıcı1

School of Mechanical, Materials and Mechatronic Engineering and ARC Centre of Excellence for Electromaterials Science, University of Wollongong, New South Wales 2522, Australiagursel@uow.edu.au

1

Corresponding author.

J. Mech. Des 132(11), 111001 (Oct 20, 2010) (8 pages) doi:10.1115/1.4002661 History: Received November 13, 2009; Revised September 15, 2010; Published October 20, 2010

## Abstract

In this paper, we report on a multistable linear actuation mechanism articulated with electroactive polymer actuators, widely known as artificial muscles. These actuators, which can operate both in wet and dry media under as small as 1.0 V potential difference, are fundamentally cantilever beams made of two electroactive polymer layers (polypyrrole) and a passive polyvinylidene fluoride substrate in between the electroactive layers. The mechanism considered is kinematically analogous to a four-bar mechanism with revolute-prismatic-revolute-prismatic pairs, converting the bending displacement of a polymer actuator into a rectilinear movement of an output point. The topology of the mechanism resembles that of bistable mechanisms operating under the buckling effect. However, the mechanism proposed in this paper can have many stable positions depending on the input voltage. After demonstrating the feasibility of the actuation concept using kinematic and finite element analyses of the mechanism, experiments were conducted on a real mechanism articulated with a multiple number (2, 4, or 8) of electroactive polymer actuators, which had dimensions of $12×2×0.17 mm3$. The numerical and experimental results demonstrate that the angular displacement of the artificial muscles is accurately transformed into a rectilinear motion by the proposed mechanism. The higher the input voltage, the larger the rectilinear displacement. This study suggests that this multistable linear actuation mechanism can be used as a programmable switch and/or a pump in microelectromechanical systems (MEMS) by adjusting the input voltage and scaling down the mechanism further.

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## Figures

Figure 1

Five layers and bending mechanism of the trilayer polypyrrole polymer actuator

Figure 2

Proposed linear multistable mechanism and its kinematically equivalent counterpart

Figure 3

The kinematic analysis mechanism with four polymer actuators (on the left) and a zoomed view of the mechanism (on the right)

Figure 4

Steps of the mechanism (from top; 0–5 s with 1 s intervals and under 1.0 V)

Figure 5

(a) Bending angle of the polymer actuator, (b) change in the length of the polymer actuator, and (c) rectilinear displacement of the middle cylinder versus time

Figure 6

PVC middle cylinder’s displacement of the finite element model with four polymer actuators. The last data point corresponds to the distributed load of 39 N/m2 V

Figure 7

Simulated and experimental force outputs of the mechanism with four polymer actuators measured from the front face of the PVC middle cylinder

Figure 8

Simulated and experimental force outputs of the mechanism with eight polymer actuators measured from the front face of the PVC middle cylinder

Figure 9

Simulated and experimental rectilinear displacements of the mechanism with eight polymer actuators

Figure 10

3D design of the multistable linear actuation mechanism (on the left) and manufactured multistable linear actuation mechanism (on the right)

Figure 11

Typical displacement and force outputs of the multistable linear actuation mechanism under a 1 V input voltage (2 V peak to peak). The input voltage, the current passed, and the displacement of the PVC middle cylinder and the blocking force are shown in plots (a)–(d), respectively.

Figure 12

Schematic representation of the experimental system

Figure 13

Displacement results of the experiment measured from the PVC middle cylinder in a range of frequency (0.1–1.0 Hz) under 1.0 V input voltage

Figure 18

Experimental displacement results with eight polymer actuators measured from the PVC middle cylinder under a fixed 1.0 V input voltage with a variable frequency range (0.1–1.0 Hz)

Figure 14

Force output results of the experiment measured from the PVC middle cylinder under 1.0 V input voltage and a range of frequency (0.1–1.0 Hz)

Figure 15

Force output results of the experiment measured from the PVC middle cylinder under 1.0 Hz frequency and a range of input voltage (0.1–1.0 V)

Figure 16

Displacement measurement (on the left) and force output measurement (on the right) of the multistable linear actuation mechanism with eight polymer actuators

Figure 17

Experimental displacement results with eight polymer actuators measured from the PVC middle cylinder under a range of input voltages (0.1–1.0 V) with 0.1 Hz frequency

Figure 19

Experimental force results with eight polymer actuators measured from the PVC middle cylinder under a fixed 1.0 V input voltage with a variable frequency range (0.1–1.0 Hz)

Figure 20

Experimental force output results with eight polymer actuators measured from the PVC middle cylinder under a range of input voltages (0.1–1.0 V) with a fixed 1.0 Hz frequency

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