Investigation of Multimodal Electret-Based MEMS Energy Harvester With Impact-Induced Nonlinearity

This paper presents an electret-based MEMS energy harvester synergizing the advantages of multi-modal structure and impact mechanism for broad operating bandwidth. The device with a volume of 295 mm(3) comprises an electret-based primary subsystem for power generation and an electrode-free auxiliary subsystem for frequency tuning. The tiny auxiliary subsystem helps to induce close resonances with comparable outputs at low excitations, as well as introduces impact-based nonlinearity to drive the first resonant peak upward and further approach the second one at elevated excitations. The experimental results demonstrate that at an excitation of 12.8 m/s(2), the 3-dB bandwidth of the first peak is increased from 20.4 to 60.4 Hz and a low frequency ratio of 1.15 between the two peaks is achieved. The two degree-of-freedom resonant structure with impact-based nonlinearity is systematically investigated through an equivalent circuit representation. An electrical equivalent circuit model of the proposed device with impact mechanism is derived. The circuit simulation confirms the nonlinear behavior of the system, and reveals the mechanism of peak shifting and bandwidth enhancing dynamics.