Dielectric Elastomer Actuators (DEAs) are known for their outstanding properties such as low weight, high energy density and self-sensing capability. Compared to conventional magnetic actuators, they are manufactured from generally inexpensive and widely available polymer materials, making the technology particularly attractive for developing actuator systems that are potentially low-cost and serve a wide range of applications. This advantage can be further enhanced by developing scalable and standardized system designs that use identical parts in order to reduce product variation and enable high volumes in a mass production process. Following this approach, this paper introduces a low-profile and compact linear actuator design, which provides a configurable force and stroke transmission in order to serve different load-profiles without changing shape and dimension of the DEA itself. The design is based on rectangular-shaped, in-plane operating DEAs coupled to a unibody linkage mechanism, which is likewise flat and based on compliant joints and rigid links. A negative rate stiffness mechanism enables to increase the performance output of the actuator system in terms of cyclic converted energy in quasi-static operation. By configuring the lever ratios of the input and output sides accordingly, it can either behave stroke-magnifying or force-magnifying. Thus, as an example, a system with negative and one with positive transmission ratio are realized and characterized with respect to their force and their stroke behavior.
In recent years, dielectric elastomers (DEs) have found novel applications in the field of soft robotics, where compliant and compact actuators with high energy densities are needed. Rolled DEs can be effectively used to achieve muscle-like actuators for soft robots, eliminating the need for external motors while providing at the same time a lightweight structure with self-sensing capabilities. In this paper, we propose a large deformation, energy-based model for rolled DEs which permits to describe the actuator behavior in a lumped-parameter fashion. The model is intended for control and self-sensing applications. After presenting the model equations, a parameter identification is performed and discussed based on experimental data.
In this work we present a new concept for scalable and tightly rolled dielectric elastomer actuators (DEA). The proposed solution is motivated by the need for designing soft, high energy density, and compact actuators for soft robotics and artificial muscle applications. Each rolled DEA is made starting from a 50 μm thin silicone film (Wacker Elastosil 2030) with flexible carbon-black based electrodes screen-printed on one side. Two of those printed films are first stacked and subsequently tightly rolled, leading to the final DEA design. At first, the systematic development of the rolled DEA concept is presented. Electrical and mechanical contacts are provided by off-the-shelf wire end ferrules. The roll manufacturing process is described subsequently. Finally, an experimental evaluation of mechanical and electrical characteristics of the developed DEAs is performed. Our measurements show a change of blocking force of 0.18 N under constant load conditions and we predict a stroke of 2.5% at 2 N.
Dielectric Elastomers (DEs) represent a class of soft electro-mechanical transducers, which is promising compared to conventional actuation technologies due to features such as lightweight, high energy efficiency, and low operational noise. Despite several prototypes have been proposed in the recent literature, only very few of them have been commercialized yet. To further DE technology towards real-life applications, it is of great importance to quantify the long-term performance of theses transducers in terms of electrical and mechanical fatigue under controllable environmental conditions. In order to investigate these properties, this paper introduces a modular electro-mechanical testing device that is designed in order to determine the long-term and fatigue characteristics of rectangular shaped DE actuator (DEA) membranes working under in-plane loading conditions. Each module permits to arbitrarily program mechanical stroke and applied voltage, and also enables simultaneous testing of five samples. Quantities of measurement are force and current. The modules are placed inside of a climate chamber which provides testing environments with constant temperature and humidity. To ensure uninterrupted 24/7-operation, the setup provides safety-equipment with remote control and remote monitoring. First test results are presented in this work.
Dielectric Elastomer Actuators (DEAs) represent a promising alternative technology for common small- and micro-drives, due to their lightweight, high energy density, high design flexibility, and silent operations. In order to obtain a stroke, membrane DEAs need to be preloaded with mechanical biasing elements. The use of negative stiffness mechanisms results in a relatively large stroke, in comparison with conventional biasing systems based on masses or linear springs. Centrally loaded, pre-stressed buckled beams show this negative stiffness behavior in a well-defined range. In particular, their force-displacement characteristics is highly nonlinear and depends on the beam geometry and axial pre-compression.
This paper provides a fast model-based design approach for large stroke DEA systems biased with pre-stressed and centrally loaded buckled beams. The method is based on a Finite Element model of a buckled beam, implemented in COMSOL Multiphysics®. Large deformations are considered in order to accurately design compact DEA systems with highly compressed beams. Stroke optimization is achieved by combining nonlinear beam elements with linear spring mechanisms. This method allows the calculation of the required beam geometry and pre-compression in order to achieve the desired characteristics of the preloading mechanism. The proposed methodology is validated by numerous simulations.
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