Low frequency energy harvesting with a variable potential function under random vibration

This paper presents the study of a low frequency vibration energy harvester by applying a variable double potential function under Gaussian white noise. The energy harvester is composed of a piezoelectric cantilever with a magnetic tip and a second cantilever, this one perpendicular to the piezoelectric cantilever, that also has a magnetic tip. This differs from traditional designs where a fixed magnet opposes the piezoelectric cantilever. Three coupled differential equations represent a model of the nonlinear coupled system. The power spectral density and root mean square of the output voltage are obtained for various base excitation levels. The simulations are validated using experimental results. The optimal distance, where maximum output is generated, is found at the transition distance from mono-to bi-stable regions. Unlike the traditional fixed magnet design where the optimal distance changes with the noise level, in the proposed design the optimal distance remains the same regardless of the noise intensity. This is because of a variable potential function that enables effective conversions of potential and kinetic energies. The effect of different parameters of the system on the output voltage and power is investigated. The results show that the proposed structure can improve the efficiency of vibration harvesting in the low frequency range regardless of excitation levels.