Design and simulation of a frequency self-tuning vibration energy harvester for rotational applications

In order to broaden the operating frequency bandwidth of the vibration energy harvester (VEH), a novel frequency self-tuning VEH is proposed for rotating applications. Under the rotating excitation, the proposed VEH can simultaneously adjust two parameters that affect the resonant frequency by centrifugal force, which is the key to realize frequency self-matching of the VEH in a certain frequency range. The two parameters are the axial force and effective length of the piezoelectric beam. A frequency tuning mass was designed to effectively adjust the axial force of the piezoelectric beam, and a nonlinear spring was designed to accurately control the effective length of the piezoelectric beam. The proposed VEH was simulated with ANSYS. The simulation results show that there is only one frequency matching point in a certain rotation frequency range when the centrifugal force only changes the axial force of the piezoelectric beam, which is the reason why the reported self-tuning VEH can not achieve frequency self-matching within a certain frequency range. When the centrifugal force simultaneously changes the axial force and the effective length of the piezoelectric beam, the frequency self-matching can be realized in a certain frequency range instead of only one frequency point. Simulation data analysis shows that the proposed VEH can achieve frequency self-matching in the range of 10–20 Hz through easy spring design.