Design of an Antagonistic Bistable Dielectric Elastomer Actuator Using the Bergstrom-Boyce Constitutive Viscoelastic Model

摘要

Dielectric Elastomer Actuators (DEA) has great potential for low cost, high performance robotic and mechatronic devices. However, the reliability of these actuators remains an important issue when used in continuous strain applications. To improve actuators reliability, DEAs can be used in a binary or bistable manner where actuators flip between two stable positions, thus maintaining one of two equilibrium states without any electrical energy input. This paper presents an antagonistic bistable DEA concept using a single, planar polymer film that can lead to compact high force multilayered actuators. The system is made bistable by the addition of carbon fiber leaf springs designed to maximize actuator strain output. The strong viscoelastic nature of the chosen polymer film significantly affects the system’s output force and is accounted for in the Bergstrom-Boyce material model. The model shows good agreement with experimental stress relaxation curves and is used to set the leaf springs’ force curve. Experimental results have shown that the acrylic polymer film’s (VHB 4905) strong viscoelastic nature limits the actuator speed at ∼ 0.9 mm/s; at higher speeds, the leaf springs cannot be matched with the proposed concept. The study also demonstrates that the proposed antagonistic actuator configuration is an interesting solution to provide reliable bistable actuation for compact structures and that developing polymer films with low viscoelasticity is key for optimal performance.