Compressive-mode piezoelectric energy harvesting in translational and rotational systems

Energy harvesting, as one of the best alternatives to batteries for powering wireless sensors, has been increasingly implemented in real-time condition monitoring of rotating machines and structures, such as wind turbines and wheel tires. The high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH) is a typical vibration-based energy harvester that possesses the characteristics of high power output and wide working bandwidth. Based on the HC-PEH, this paper aims to study its performance when applied in the rotational motion, where the gravity is the excitation of the system. In order to investigate the system analytically, we develop a theoretical model with consideration of the nonlinear stiffness, nonlinear damping, and nonlinear piezoelectricity. The approximate analytical solution of the system is obtained by using the harmonic balance method. In the experimental study, a 21.82-gram prototype is tested under two types of excitations: 1) under the translational harmonic vibrations via an electrodynamic shaker platform and 2) under a rotational excitation, between which the difference is mainly the centrifugal force. The simulation results of both the analytical solution for the rotational system and the modified analytical solution for the translational system closely render the experiment results. Additionally, the experiment results show that the HC-PEH performs better in the rotational system than that in the translational system under the same conditions. The maximum voltage is larger and the working bandwidth is wider in the rotational system. In the rotational experiment, a maximum power output of 16.52 mW is generated at 21.67 Hz with an external resistor of 40 KΩ.