A hummingbird-inspired dual-oscillator synergized piezoelectric energy harvester for ultra-low frequency

A new concept of vibration synergized energy harvesting is proposed for ultra-low frequency scenarios. A dual-oscillator synergized piezoelectric energy harvester (DOS-PEH), inspired by hummingbirds, is designed to demonstrate the new concept, both theoretically and experimentally. Mimicking the synergy mechanism of hummingbird muscles and wings, the DOS-PEH adopts a supporting oscillator (SO) and a buckled beam designated as the dominating oscillator (DO) to synergize the vibrations through magnetic coupling. SO engenders a hinge-support-like configuration at the beam midspan, by which DO exhibits three stable equilibrium positions while taking on four stable equilibrium states, including two second buckling modes that lower snapping force to facilitate snap-through oscillations. The non-contact magnetic force, introduced by SO, acts as a link that cohesively connects the dual oscillators. It enables continuous vibration transmission from the ambient environment, through SO, and ultimately to DO. A fresh bandwidth, extending from 2.5 to 10 Hz, of 7.5 Hz emerges under 0.4 g excitation. The DOS-PEH, in general, achieves the broadband, stable, and progressively improving voltage output across the ultra-low frequency range. Further, the output voltage of the DOS-PEH is about 70 times higher than that of the collision-based piezoelectric energy harvester (C-PEH), and the operational bandwidth is broadened to 136 %. It highlights the contribution of synergistic vibration to the ultra-low-frequency energy harvesting.