Modelling and characterization of dielectric elastomer stack actuators

Abstract

This paper aims to establish and evaluate an electrical and mechanical model for dielectric elastomer stack actuators. Based on the structure of an electrically interconnected actuator a simplified electrical and mechanical network is deduced. The electrical model results in a low-pass filter. The model is evaluated by measurements of the electrical impedance and contact, electrode and parallel resistances. Measurement results show good agreement of the model with the electrical behaviour of the real actuator over a wide frequency range, from below 0.1 Hz to above 10 kHz. The mechanical modelling is split into dynamic and static behaviour. The dynamic mechanical behaviour is modelled as a mechanical equivalent network using fractional elements. The static mechanical model uses the uniaxial compressive modulus of the actuator material to describe the static characteristic. The combination of static and dynamic models allows a realistic prediction of the static and dynamic deflection of the actuators under an applied electrical voltage. This electro-mechanical model has been validated in a frequency range of 4 Hz to 4 kHz.

Mechanics of dielectric elastomers: materials, structures, and devices

“…The actuators in stacking or multi-layer configuration were shown to provide larger forces in parallel and nearly linear contractile response in the thickness direction, as indicated in Fig. 4f (Brochu and Pei, 2010;Haus et al, 2013;Tutcuoglu and Majidi, 2014). Carpi et al (2005) designed a contractile DE actuator of helical stack configuration, which was capable of 5% strain under an electric field of 14 V per μm.…”

“…Some analytical efforts have been devoted to this problem, but most of them were limited to small strains (Tian et al, 2012). Although numerous DE structures and devices have been successfully modeled and analyzed, DE actuators with self-healing capability , increasing sophistication in stacking or even hierarchical configurations (Haus et al, 2013) require more theoretical effort to address the underlying challenges that impede the practical application of these smart materials in artificial muscles.…”

Dielectric Elastomers as EAPs: Models

“…6 are usually a good description of the electrical behavior of the actuator, as long as the length to width ratio (x 0 to y 0 ) of the active area is between 1/3 and 3 (Haus et al 2013). For most applications, the model in Fig.…”

“…For most applications, the model in Fig. 6a is sufficient, as the leakage current through the dielectric is typically negligible, as R p is typically in the range above 10 GΩ (Haus et al 2013). For low frequencies (( 0:1 Hz) or energy harvesting applications, the influence of R p may still have to be considered.…”

Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation

“…For DE transducers, the stack of DE membranes and electrodes that form the variable capacitance (hereafter called "active membrane") can be deformed in an equi-biaxial fashion according to one of the following methods: 1) by inflating the active membrane that usually has an initial circular shape 13,14 2) by expanding the active membrane through a number of clamps that are equally spaced along the membrane perimeter and that move according to prefixed trajectories 10 ; 3) by compressing the active membrane with a uniform pressure 15 .…”