Dynamic analysis of dielectric elastomer membrane for actuation in soft fish robots

Soft robots often show overwhelming performances. In the present work, mathematical formulations have been derived for nonlinear dynamic analysis of axial stretch in convex tapered dielectric elastomer considering temperature dependent material properties. The present formulation is based on the Gent model of hyperelasticity and the standard rheological model. The fish tail is modeled as bimorph dielectric elastomer actuator (DEA) for propulsion of soft fish robot. Based on the obtained axial stretch of the active layer, flapping movements of fish tail have been determined. The dependency of frequency, temperature, viscoelasticity, and taper effects on the dynamic performance in the active layer of bimorph DEA is studied. Investigation of time-dependent actuation, phase portraits, Poincare maps, bifurcation diagrams, and hysteresis loop associated in this system is carried out. The results reveal that at lower temperature more actuation is attained. At low frequency, time-dependent data show very small amplitude. With the increase in height taper, it is declared that the actuation increased. Thus, it is also observed that taper effects have significant role on the axial stretch. Subsequently, with the obtained stretch, deflection of bimorph DEA is determined through mathematical formulation in order to predict the bending actuation of fish tail.