Award Date

May 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Committee Member

Kwang Kim

Second Committee Member

Brendan O'Toole

Third Committee Member

Mohamed Trabia

Fourth Committee Member

Jaeyun Moon

Fifth Committee Member

David James

Number of Pages

248

Abstract

Electroactive polymer (EAP) materials are a novel soft electromechanical device that exploits the inherent electrical and mechanical advantages of flexible polymer materials. Within this groundbreaking field there are various actuator and sensor devices that have been developed for a variety of applications, from medical devices to artificial biological systems. This research focuses on electrohydraulic actuators, which are comprised of a flexible conductive medium, a dielectric fluid, and a compliant film material to encapsulate the dielectric fluid. This specific study centers around the electrohydraulic EAP actuator known as the Hydraulically Amplified Self-Healing Electrostatic (HASEL) actuator, first introduced by the Keplinger group of Intelligent System/Max Planck Institute in 2018. This actuation device utilizes two traditional actuation mechanisms, electrostatic actuation and hydraulic actuation, in a unique way to develop artificial muscles. As a state-of-the-art device, further research is required to fully understand the driving mechanisms, thus pushing HASELs and other electrohydraulic devices to the forefront of robotic and mechatronics technology.This research study investigates the actuator mechanism by theoretical and experimental means, in the form of an analytical model, finite element modeling, and an in-depth materials characterization study. The analytical and experimental investigations are then connected via dimensional analysis. Finally, a proof-of-concept robotic device is introduced as a means to illustrate the versatility of this unique actuator. The analytical model is developed using Lagrange’s method to determine the equation of motion and is used as a jumping-off point for understating the activation mechanism of HASEL actuators and other electrohydraulic actuators. The finite element model propels the analytical equation forward by describing the system in detail. Unlike current models from literature, the finite element model in this study predicts the dynamic performance of the actuation system based on the materials and input electric field. The model can provide output displacement, fluid motion, and other electrical properties in relation to the time-based application of the electric field. To further understand the actuator mechanism and the accompanying materials, a materials characterization study was conducted. This experimental process examined the material properties and actuation performance of eight different actuation materials to compare their effectiveness in this actuation device. The theoretical results and experimental results are then connected by using dimensional analysis, wherein, eight distinct Π groups are determined and indicate the parameters important to the overall actuation mechanism. From this analysis, the Washington-Kim (WK) group is developed, and it describes the electro-mechano-hydraulic behavior based on various parameters and describes their contributions to the actuator output. Finally, this study concentrates on the development of a proof-of-concept biomimetic device, the Hybrid Robotic Snake Platform. This unique exploratory device mimics the locomotion of a snake to traverse various terrains. To make a more robust and durable robotic device while maintaining flexibility, the platform is a hybrid of soft actuators and rigid body linkages. The platform was fabricated using rapid additive manufacturing processing techniques and uses an onboard control system. Furthermore, the development of this platform is informed by the theoretical and experimental results and indicates the feasibility of electrohydraulic actuators in a variety of applications. In summary, this research work builds a framework that explores the functionality and effectiveness of these novel actuators.

Keywords

COMSOL Multiphysics; Dimensional Analysis; Electroactive Polymers (EAPs); Electrohydraulic Actuation; HASEL Actuators; Soft Robotics

Disciplines

Mechanical Engineering

File Format

pdf

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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