Effect of Repulsive Magnetic Poles on the Natural Frequency and the Bandwidth of a Vibration Energy Harvester

Vibration energy harvesting has emerged as a promising source of sustainable power for wireless sensor networks. This paper describes the effect of alike magnetic pole repulsion on the natural frequency and operational bandwidth of a cantilever-based vibration energy harvester. Experimental result shows that the magnetic repulsive force produced by two horizontally oriented magnets was able to reduce the natural frequency of a cantilever by up to 35% as compared to a typical cantilever beam oscillated under normal conditions. Changing the orientation of one of the magnets to a vertical position reduces the magnetic repulsive force, resulting in a higher natural frequency, transmissibility and maximum amplitude than the horizontal orientation. The magnetic repulsive force effect also resulted in a significant increase in the operational bandwidth of the cantilever beam, recording different natural frequencies for different base acceleration magnitudes. For every 0.1 g increase in base acceleration value, the two horizontally oriented magnet configurations recorded an increase of 0.9 Hz in natural frequency, whereas an average increase of 0.6 Hz was recorded for the latter configuration.