Fast model-based design of large stroke dielectric elastomer membrane actuators biased with pre-stressed buckled beams

Abstract

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.