Dynamics of pneumatically coupled visco-hyperelastic dielectric elastomer actuators: Theoretical modeling and experimental investigation

Dielectric elastomers represent a class of electroactive polymers that are capable of undergoing large reversible deformations when driven electrically. Pneumatically connected DE (PCDE) actuator is one of the prevalently used configurations, wherein an electrically driven DE membrane is connected to another passive DE membrane via an intervening air column. This paper outlines the development of a theoretical model, well-supported by experimental observations, for analyzing the dynamic electromechanical response of PCDE actuators. The underlying energetics of the model is developed in the setting of the Hamilton's principle taking into account the effects of membrane pre-stretch, initial inflation pressure, membrane viscoelasticity, and time-dependent electric loading. An idea of pseudo air-spring, responsible for the transfer of deformation from the active to passive sides of the actuator, is introduced and the analytical expressions are developed for the coupling function. Both pressurized and depressurized states are considered in the analysis. The developed nonlinear dynamic model is then used for building insights into several influential parameters, such as initial inflation pressure, time-dependent (DC and AC) electric actuation, height of the confined air column, volume of the intervening chamber, etc. The proposed model predicts the transfer efficiency of about 80% between the active and the passive membranes. The predictive capability of the theoretical model is established through comparisons with the experimental observations. The proposed investigation can find its potential use in the design and analysis of interconnected DE actuators subjected to a dynamic electromechanical actuation.