Abstract
Due to their unique combination of features such as large deformation, high compliance, lightweight, energy efficiency, and scalability, dielectric elastomer (DE) transducers appear as highly promising for many application fields, such as soft robotics, wearables, as well as micro electro-mechanical systems (MEMS). To generate a stroke, a membrane DE actuator (DEA) must be coupled with a mechanical biasing system. It is well known that nonlinear elements, such as negative-rate biasing springs (NBS), permit a remarkable increase in the DEA stroke in comparison to standard linear springs. Common types of NBS, however, are generally manufactured with rigid components (e.g., steel beams, permanent magnets), thus they appear as unsuitable for the development of compliant actuators for soft robots and wearables. At the same time, rigid NBSs are hard to miniaturize and integrate in DE-based MEMS devices. This work presents a novel type of soft DEA system, in which a large stroke is obtained by using a fully polymeric dome as the NBS element. More specifically, in this paper we propose a model-based design procedure for high-performance DEAs, in which the stroke is maximized by properly optimizing the geometry of the biasing dome. First, a finite element model of the biasing system is introduced, describing how the geometric parameters of the dome affect its mechanical response. After conducting experimental calibration and validation, the model is used to develop a numerical design algorithm which finds the optimal dome geometry for a given DE membrane characteristics. Based on the optimized dome design, a soft DEA prototype is finally assembled and experimentally tested.
Highlights
In recent years, dielectric elastomer (DE) transducers have attracted the interest of several researchers due to their unique mix of features [1]
We propose a novel approach that allows optimization of the design of the polymeric dome negative-rate biasing springs (NBS) for DE actuator (DEA)
Such hysteresis is commonly observed in NBS-DEA systems and is a direct consequence of the same mechanism which leads to the large stroke performance
Summary
Dielectric elastomer (DE) transducers have attracted the interest of several researchers due to their unique mix of features [1]. Some examples of DE-based soft robots prototypes presented in recent literature include bioinspired crawling robots [25], miniature underwater vehicles [26], soft tentacle arms [27], and translucent swimming robots [28] In all those types of systems, the actuation is made possible by the softening effect that a DE membrane undergoes upon electrical activation, which results in a stroke from the undeformed to the deformed configuration. The impossibility of using currently available types of NBS in those application fields unavoidably restricts the high potential of DE technology To overcome this limitation, innovative NBS elements need to be developed such that, when coupled with a DE membrane, provide large strokes without affecting the compliance and flexibility of the overall actuator system.
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