A bistable electromagnetic micro-power generator using FR4-based folded arm cantilever

• A bistable electromagnetic micro-power generator using FR4-based folded arm cantilever. Bistability is incorporated into the system dynamics by repulsive magnetic force at one end of the cantilever.
• Half power bandwidth widened up to 5 Hz (15% of peak power frequency) due to bistability.
• Peak load power of 22 μW was achieved at a frequency of 35 Hz and 0.5 g acceleration.
• It is demonstrated numerically and experimentally that in low acceleration low frequency vibration environment, a shallower potential energy profile is suitable to ensure cross-well oscillation of the harvester, which is beneficial for energy harvesting.

This paper discusses a wideband, bistable vibrational micro-power generator using a folded cantilever beam. At an acceleration of 0.5 g (35 Hz frequency) the device generated a peak power of 22 μW across an optimum resistive load of 1 kΩ. The half-power bandwidth of the nonlinear bistable device was increased by 5 Hz (15% of the peak power frequency) with respect to the linear counterpart. The choice of FR4 as the structural material and the utilization of a folded cantilever design are aimed at achieving a low operational frequency within a relatively small footprint. The bistable mechanism which is introduced into the system by means of a magnetic force between a pair of repulsively positioned NdFeB permanent magnets was analytically modelled, numerically simulated and successfully validated with experimental results. The wideband frequency response is further experimentally modified by adjusting the gap between the repulsive magnets. The effect of the depth of the bistable potential well on the performance of the vibration energy harvester at low to medium accelerations is also validated numerically and experimentally.