Piezoelectric Energy Harvesting Lab Report

Introduction
Vibration based energy harvesting has been investigated by several researchers over the last few years and cantilever beams with piezoelectric material layers are employed in electronic circuits as piezoelectric energy harvester due to its simple configuration. With the advancement in the electronics, interest in piezoelectric wireless sensors has increased manifold and various researches has been conducted to optimize the harvested energy for the proper and efficient functioning of the electronic circuits. Although piezoelectric energy harvesting is most promising one as self-contained power source but the major limitation is the generation of sufficient amount of energy for the autonomous operation of the portable device over
However, contribution of higher order terms increase with the increase in amplitude of the input excitation. In practice, a truncated version of the Volterra representation is used, and quite often involves only the first few orders of the Volterra kernels which leads to the limited convergence. To solve duffing type nonlinear equation a simple convergence criterion is given by [22]. The criterion defined by equation (11) provides a simple estimate of the upper magnitude of the input excitation level required for the convergence of first order Volterra series
PZT-5A layer is poled along the thickness direction result in transverse (d31) operation mode. Such configuration is chosen since it enables the condition of low frequency to be fulfilled. The design of the piezoelectric cantilever is selected by taking in to consideration it low acceleration (<= 1g) and low excitation frequencies (10- 70Hz) [23]. These conditions are correspond to common environmental vibrations. Neodymium magnetic proof mass of density 7500Kg/mm3 and dimension 20 x 10 x 8 mm3 fixed at the tip of the beam approximated as point mass. A magnet of same properties is fixed at distance d from the piezoelectric cantilever beam tip. When d is sufficiently large the effect of magnetic repulsive force between two poles become negligible. As the d decrease the effect of magnetic repulsive force increase as shown in Figure 3. In the absence of any magnetic force the first natural frequency of beam is found to be 48.3614 Hz that is similar to the linear frequency (48.4 Hz) calculated by [24]. The magnetic force leads to cubic nonlinearity in the stiffness of the piezoelectric beam result in monostable or bistable system depending on the distance d. Monostable and bistable region can be found from linear frequency plot of Equation (1) as shown in Figure 5. For the convergence of first