Electromechanical coupling in cylindrical dielectric elastomer actuators

This paper presents a model for the electromechanically coupled dynamic behavior of dielectric elastomer actuators (DEA). The main goal is to develop a lumped, dynamic model which can be used for the optimization of actuator design in specific applications as well as for the synthesis of high precision, model-based feedback control algorithms. A mass-biased membrane actuator with an annular geometry is chosen as a reference case to introduce the modeling concept. The mechanical model extends standard linear visco-elasticity through the introduction of a nonlinear hyperelastic Ogden element. Electromechanical coupling is implemented through the Maxwell stress concept. The DEA model is then experimentally calibrated and validated for both quasi static and dynamic loading conditions. It can be shown that both mechanical preloading and electric actuation can be reproduced over a relevant range of masses and frequencies.

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Linear-Quadratic Regulator for Control of Multi-Wall Carbon Nanotube/Polydimethylsiloxane Based Conical Dielectric Elastomer Actuators

Actuators ◽

10.3390/act9010018 ◽

2020 ◽

Vol 9 (1) ◽

pp. 18

Author(s):

Titus Mulembo ◽

Waweru Njeri ◽

Gakuji Nagai ◽

Hirohisa Tamagawa ◽

Keishi Naito ◽

...

Keyword(s):

Carbon Nanotube ◽

Rise Time ◽

Electromechanical Coupling ◽

Linear Quadratic Regulator ◽

Fast Response ◽

Dielectric Elastomer ◽

Soft Robotics ◽

Artificial Muscles ◽

Linear Quadratic ◽

Dielectric Elastomer Actuators

Conventional rigid actuators, such as DC servo motors, face challenges in utilizing them in artificial muscles and soft robotics. Dielectric elastomer actuators (DEAs) overcome all these limitations, as they exhibit complex and fast motions, quietness, lightness, and softness. Recently, there has been much focus on studies of the DEAs material’s non-linearity, the non-linear electromechanical coupling, and viscoelastic behavior of VHB and silicone-based conical DEAs having compliant electrodes that are based on graphite powder and carbon grease. However, the mitigation of overshoot that arises from fast response conical DEAs made with solid electrodes has not received much research focus. In this paper, we fabricated a conical configuration of multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) based DEAs with a rise time of 10 ms, and 50% peak overshoot. We developed a full feedback state-based linear-quadratic regulator (LQR) having Luenberger observer to mitigate the DEAs overshoot in both the voltage ON and OFF instances. The cone DEA’s model was identified and a stable and well-fitting transfer function with a fit of 94% was obtained. Optimal parameters Q = 70,000, R = 0.1, and Q = 7000, R = 0.01 resulted in the DEA response having a rise time value of 20 ms with zero overshoot, in both simulations and experiments. The LQR approach can be useful for the control of fast response DEAs and this would expand the potential use of the DEAs as artificial muscles in soft robotics.

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Electromechanical coupling in dielectric elastomer actuators

Sensors and Actuators A Physical ◽

10.1016/j.sna.2007.05.029 ◽

2007 ◽

Vol 138 (2) ◽

pp. 384-393 ◽

Cited By ~ 196

Author(s):

Michael Wissler ◽

Edoardo Mazza

Keyword(s):

Electromechanical Coupling ◽

Dielectric Elastomer ◽

Dielectric Elastomer Actuators

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A Simple Dynamic Characterization Method for Thin Stacked Dielectric Elastomer Actuators by Suspending a Weight in Air and Electrical Excitation

Actuators ◽

10.3390/act10030040 ◽

2021 ◽

Vol 10 (3) ◽

pp. 40

Author(s):

Kentaro Takagi ◽

Yuya Kitazaki ◽

Kota Kondo

Keyword(s):

Elastic Modulus ◽

Forced Vibration ◽

Electromechanical Coupling ◽

Great Difficulty ◽

Dielectric Elastomer ◽

Local Deformation ◽

Dynamic Elastic Modulus ◽

Electrical Excitation ◽

Dynamic Characterization ◽

Dielectric Elastomer Actuators

This paper proposes a simple but effective method for characterizing dielectric elastomer actuators (DEAs), especially for thin stacked DEAs, which are promising for haptic devices but which measure the dynamic elastic modulus with great difficulty. The difficulty of the measurement of such a thin stacked DEA arises from the friction and local deformation of the surface between the DEA and a contact, as shown in this paper. In the proposed method, a DEA is vertically suspended and a weight is attached to it. The proposed method requires no contact with the surface of a DEA and uses only a weighting mass. Experimental results demonstrated the proposed method can estimate almost essential constants, such as the dynamic elastic modulus (Young’s modulus and damping time constant), the electrical constants (permittivity and resistivity), and the coefficient of electromechanical coupling, through the forced vibration induced by voltage actuation.

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Instability in Nonlinear Oscillation of Dielectric Elastomers

Journal of Applied Mechanics ◽

10.1115/1.4030075 ◽

2015 ◽

Vol 82 (6) ◽

Cited By ~ 13

Author(s):

Jian Zhu

Keyword(s):

Nonlinear Oscillation ◽

Electromechanical Coupling ◽

Haptic Feedback ◽

Dynamic Instability ◽

Dielectric Elastomer ◽

Dielectric Elastomers ◽

Critical Amplitude ◽

Dielectric Elastomer Actuators ◽

Coupling Dynamic ◽

Static Instability

A membrane of a dielectric elastomer oscillates when subject to AC voltage. Its oscillation is nonlinear due to large deformation and nonlinear electromechanical coupling. Dynamic instability in dielectric elastomers—the oscillation with an unbounded amplitude—is investigated in this paper. The critical amplitude of AC voltage for dynamic instability varies with the frequency of AC voltage and reaches a valley when the superharmonic, harmonic, or subharmonic resonance is excited. Prestretches can improve dielectric elastomer actuators' capabilities to resist dynamic instability. The critical deformation at the onset of dynamic instability can be much larger than that at the onset of static instability. Oscillation of dielectric elastomers can be used for applications, such as vibration shakers for haptic feedback, soft loudspeakers, soft motors, and soft pumps. We hope that the current analyses can improve the understanding of dynamic behavior of dielectric elastomers and enhance their stability and reliability.

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Finite-Strain Models of Actuation: Prestretch and Elasticity Parameters

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.61.91 ◽

2008 ◽

Vol 61 ◽

pp. 91-100

Author(s):

Guggi Kofod

Keyword(s):

Electromechanical Coupling ◽

Finite Strain ◽

Dielectric Elastomer ◽

Simple System ◽

Elastic Model ◽

Direct Effects ◽

Dielectric Elastomer Actuators ◽

Ogden Model ◽

Hyper Elastic ◽

First Time

The cuboid actuator is presented as a simple system for evaluation of the properties of dielectric elastomer actuators. The Ogden model as a component of this theory is evaluated and parameters for VHB 4910 found in literature are compared. The model is presented and evaluated with both intensive and extensive variables. For the first time direct effects of the width prestretch on electromechanical coupling are clearly presented. Also, the importance of choosing proper parameters for the hyper-elastic model is made clear via example.

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