A broadband bistable piezoelectric cantilever-based vibration energy harvester with nonlinear high power extraction

This work presents a nonlinear vibration energy harvester, which combines a nonlinear bistable broadband piezoelectric cantilever used to transduce ambient vibration energy, with synchronized capture for efficient harvesting over broadband sources. An accurate model of the bistable transducer, that augments the Butterworth van Dyke piezoelectric model to capture the external magnetic force added as a bias to the external vibrations, is presented. Its validity has been demonstrated through physical implementation and experimental validation against simulation of the mathematical model. For efficient extraction of the transduced energy, nonlinear extraction circuits, namely synchronous charge extraction (SCE) and parallel synchronized switch harvesting on inductor (SSHI), are employed. The switching in these circuits is implemented using a fully self-propelled, lowpower electronic breaker circuit, capable of detecting extrema in the waveform to perform switching. Both simulated and experimental power outputs from the bistable harvester have been presented, with the SCE and parallel-SSHI providing average outputs with more than one-hundred (100) fold increase over the harvested power reported in literature for the same input, and further, even more significant gains are observed for broadband excitations. For the above mentioned harvester, bistability is introduced through the use of two repelling magnets, one mounted on the cantilever tip and the other at a fixed location opposite it. Excitations that can overcome the repulsive magnetic force cause the cantilever to snap between its two equilibrium states, increasing amplitude and velocity of vibration, resulting in higher power outputs. This improved performance is observed whenever the cantilever operates in the bistable mode. Lower-amplitude excitations are unable to overcome