Widening the bandwidth of vibration energy harvester by automatically tracking the resonant frequency with magnetic sliders

The mismatch between excitation and resonant frequencies, and the narrow bandwidth of the traditional vibration energy harvester, result in small amounts of generating power. This paper presents a novel automated resonant frequency tracking method by using a pair of cylindrical movable magnetic sliders. To increase the bandwidth, the slider can track the resonant frequency on the cantilever beam without manual intervention or additional energy input. The proposed method is validated experimentally by the sliding behavior of the sliders on a cantilever beam within magnetic slider vibration energy harvester (CBMS-VEH). The CBMS-VEH demonstrates 2.7 times increasing in bandwidth for low acceleration (<0.5 g) and low frequency (<10 Hz). Under different excitation frequencies, the relationship between the friction force on the slider and the tangential component of the slider gravity can be tuned to move the slider to specified positions for further widening the bandwidth. The comparative experiments with conventional cantilever beam-mass vibration energy harvester (CBM-VEH) indicate that the resonant frequency tracking method of CBMS-VEH works in the wider range of the energy-harvesting bandwidth (6-9 Hz). Finally, we have successfully demonstrated the great potential of this method in powering low-power electronics, such as digital clocks and LEDs.