Energy harvesting from the tail beating of a carangiform swimmer using ionic polymer–metal composites

Abstract

In this paper, we study energy harvesting from the beating of a biomimetic fish tail using ionic polymer-metal composites. The design of the biomimetic tail is based on carangiform swimmers and is specifically inspired by the morphology of the heterocercal tail of thresher sharks. The tail is constituted of a soft silicone matrix molded in the form of the heterocercal tail and reinforced by a steel beam of rectangular cross section. We propose a modeling framework for the underwater vibration of the biomimetic tail, wherein the tail is assimilated to a cantilever beam with rectangular cross section and heterogeneous physical properties. We focus on base excitation in the form of a superimposed rotation about a fixed axis and we consider the regime of moderately large-amplitude vibrations. In this context, the effect of the encompassing fluid is described through a hydrodynamic function, which accounts for inertial, viscous and convective phenomena. The model is validated through experiments in which the base excitation is systematically varied and the motion of selected points on the biomimetic tail tracked in time. The feasibility of harvesting energy from an ionic polymer-metal composite attached to the vibrating structure is experimentally and theoretically assessed. The response of the transducer is described using a black-box model, where the voltage output is controlled by the rate of change of the mean curvature. Experiments are performed to elucidate the impact of the shunting resistance, the frequency of the base excitation and the placement of the ionic polymer-metal composite on energy harvesting from the considered biomimetic tail.

Ionic polymer–metal composite applications

“…[57][58][59][60] Recent applications of IPMC sensing capabilities span the measurement of force, flow, shear loading, curvature, structural health monitoring and energy harvesting. [61][62][63][64][65][66][67][68][69] IPMCs generate charges when experiencing a mechanical load or deformation. If the polymer is not deformed, the distribution of cations inside the polymer is uniform and no output voltage is detected.…”

Energy harvesting from underwater vibration of an annular ionic polymer metal composite

“…(14). Given the typical range of Young's modulus of IPMCs, which is between 200 and 600 MPa [8,16,[19][20][21]47], the in-vacuum fundamental frequency is expected to vary from 20 to 90 Hz, so that the corresponding underwater resonance should be from 2 to 9 Hz.…”

“…While the very first efforts on IPMC-based energy harvesting have focused on in-air vibrations [10,61], underwater energy harvesting has been recently studied by several authors, who have contributed to an improved understanding of the process of energy transduction in these materials [4,8,12,13,18,19,29]. Underwater flexural vibrations of an IPMC undergoing base excitation have been analyzed in [8].…”

“…To understand the scalability of this design, energy harvesting from a parallel IPMC array with a common base excitation has been investigated in [12]. In [19], the possibility of harvesting energy from the undulation of a fish tail using IPMCs has been investigated. In [29], fluttering heavy flags have been utilized to induce flexural vibrations of IPMCs and harvest energy from a steady water flow.…”

Free vibration analysis of a robotic fish based on a continuous and non-uniform flexible backbone with distributed masses

“…The literature of robotic fishes and bio-inspired robots has several examples of structures using flexible materials that bend to produce thrust, for maneuvering [4], [18], and even for energy harvesting [2]. However, few works analyze the normal frequency of vibration of the flexible structures employed as a way to maximize and optimize the use of energy.…”