Identification of material parameters of a tubular dielectric elastomer actuator for a cardiac assist device

The recent development of Dielectric Elastomer Actuators (DEA) requires a new approach to the description of hyperelastic material when the architectures are more complex than a film of material. In this paper, we propose a new technique of identification of the model parameters based on the comparison between measurements and results from an analytical modelling for a cylindrical DEA. This method allows to obtain an accurate description of the behavior of the actuator compared to results obtained with hyperelastic parameters determined with a classic approach.

Evaluation of dielectric elastomers to develop materials suitable for actuation

Morgan Almanza, Jonathan André Jean-Marie Chavanne, Yoan René Cyrille Civet, Thomas Guillaume Martinez, Yves Perriard

Electroactive polymers based on dielectric elastomers are stretchable and compressible capacitors that can act as transducers between electrical and mechanical energies. Depending on the targeted application, soft actuators, sensors or mechanical-energy harvesters can be developed. Compared with conventional technologies, they present a promising combination of properties such as being soft, silent, light and miniaturizable. Most of the research on dielectric elastomer actuators has focused on obtaining the highest strain, either from technological solutions using commercially available materials or through the development of new materials. It is commonly accepted that a high electrical breakdown field, a low Young's modulus and a high dielectric constant are targets. However, the interdependency of these properties makes the evaluation and comparison of these materials complex. In addition, dielectric elastomers can suffer from electromechanical instability, which amplifies their complexity. The scope of this review is to tackle these difficulties. Thus, first, two physical parameters are introduced, one related to the energy converted by the dielectric elastomer and another to its electromechanical stability. These numbers are then used to compare dielectric elastomers according to a general and rational methodology considering their physicochemical and electromechanical properties. Based on this methodology, different families of commercially available dielectric elastomers are first analyzed. Then, different polymer modification methods are presented, and the resulting modified elastomers are screened. Finally, we conclude on the trends enabling the choice of the most suitable modification procedure to obtain the desired elastomer. From this review work, we would like to contribute to affording a quick identification method, including a graphic representation, to evaluate and develop the dielectric materials that are suitable for a desired actuator.

2021

Control-oriented modeling and analysis of tubular dielectric elastomer actuators dedicated to cardiac assist devices

Yoan René Cyrille Civet, Ning Liu, Thomas Guillaume Martinez, Yves Perriard, Armando Matthieu Walter

This paper deals with the control-oriented modeling of a multilayered dielectric elastomer actuator based tube. The actuator is clamped at both sides and performs a radial displacement. The hyperelastic deformation and the viscoelastic performance, together with the electro-mechanical coupling are considered in the model. With the chosen Yeoh’s model for the Helmholtz free energy function, we aim to model the snapthrough effect of this tubular actuator at high applied voltage. Simulation results of the nonlinear dynamic model are later compared with experimental ones in order to identify unknown parameters of the dielectric elastomer, especially to fit the snapthrough effect and the high frequency performance. With proper identification process, our model has a good accuracy to fit the physical system (more than 90.27% for a ramp input and more than 82.7% for a step input) and is ready for the future controller design.

2022

Evaluation of dielectric elastomers to develop materials suitable for actuation

Morgan Almanza, Jonathan André Jean-Marie Chavanne, Yoan René Cyrille Civet, Thomas Guillaume Martinez, Yves Perriard

2021