Electromechanical analytical model of shape memory alloy based tunable cantilevered piezoelectric energy harvester

The resonant frequency of electromechanical energy harvester should be tuned to ambient frequency so as to maximize the harvester power. In this paper, it is proposed to tune the natural frequency of the energy harvester by varying the martensite volume fraction (0–1) of shape memory alloy (SMA). It is found that the shifting of natural frequency is around 8–10% for first three modes of vibration. This paper presents the exact analytical solution for composite cantilevered energy harvester composed of piezoelectric energy harvester layer, substructure layer and SMA layer using the assumption of Euler–Bernoulli beam. The beam base displacement in transverse direction with small angular rotation is due to base excitation. The electromechanical coupled equations of response are derived and then reduced to harmonic behavior. The expressions for frequency response of voltage output, current output and power output are obtained. Finally, a parametric case study of composite cantilevered energy harvester with shape memory alloy and important behavior of the electromechanical coupled system for short circuit and open circuit behaviors are studied in detail.