Fine-Tuning the Resonant Frequency in Electromagnetic Vibration Energy Harvesting System

The electromagnetic vibration energy harvesting system is designed to extract energy from the vibrations, with its resonant frequency specifically tuned to match the primary vibration frequency of the energy source. However, the vibration frequency often deviates from resonant frequency under different operation/weather and installation circumstances. Such deviation can lead to a significant decrease in the collected output power. For example, a 1 Hz deviation in the vibration frequency results in a 51.3% decrease in induced voltage and a 76.3% decrease in output power. State-of-the-art wideband EVEH devices have either low output power or relatively large volume. Adopting a wideband EVEH is not a good choice. To address this issue, this paper proposes a new approach for fine-tuning the resonant frequency of EVEH by changing the structure of the spring. The details of the method is to add or remove bridge arms changing the rotation angle of the cantilever beams. The advantage of this method lies in the convenience of finely tuning the device's frequency while obtaining a larger output power. The results demonstrate that for the EVEH device designed at a resonant frequency of 60 Hz, the primary resonant frequency can vary from 58.5 to 59.5 Hz by nylon bridge arms. At resonant frequencies of 59 Hz and 0.5 g acceleration, the output voltage is increased by 77.1%. Output power reaches 15 mW, representing a 213.8% improvement.