The model is validated through a series of experiments in

This paper is organized as follows. In Section 2, we introduce the modeling framework to predict the undulations of the tail and the voltage output of the piezoelectrics. In Section 3, we demonstrate the accuracy of the model through a series of experiments in which the BRD 7389 excitation is parametrically varied. In Section 4, we discuss the practical implementation of the approach through the ad-hoc experimental setup. Conclusions are summarized in Section 5.
2. Modeling
2.1. Underwater base excitation
The passive biomimetic fish tail used in this study is equivalent to that designed in Ref. [9], see Fig. 1. To simplify the analysis and compensate for imperfections in the realization of the clamp, we model the thick portion of the tail that is not covered by the piezoelectrics and is adjacent to the base as a rigid pendulum, connected to the rest of the structure through a torsional spring. As displayed in Fig. 2, we place the origin of the material abscissa x in correspondence of the torsional spring of stiffness κ and focus on the base excitation of a beam with varying geometrical and physical properties. The base excitation is controlled through the rotation θB(t), so that the x-axis rotates with respect to the otherwise quiescent fluid and the elastic deflection is measured along the rotating z-axis.