Piezoceramic based wideband energy harvester using impact-enhanced dynamic magnifier for low frequency vibration
Piezoceramic materials (such as PZT) have excellent piezoelectric properties and have been extensively used in vibration energy harvesting. Conventional piezoceramic-based energy harvesters (SDOF systems) are only efficient near their 1st resonance, and their 2nd resonance is generally ignored due to the higher frequency and comparatively lower response level. A properly designed dynamic magnifier can be used in a 2-DOF system to increase the effective bandwidth of the device by reducing the frequency gap between the 1st and 2nd resonances. The output is therefore improved by increasing the strain produced in the piezoelectric cantilever. Nevertheless, such a device cannot effectively harvest energy from vibrations at a frequency below 30 Hz. We present a piezoceramic-based wideband low-frequency vibration energy harvester that exploits the mechanical impact of the mass of a flexible dynamic magnifier on a harvester base stopper. This mechanical impact delivers a large secondary force to a piezoceramic cantilevered secondary beam, resulting in an increased strain and also triggering a non-linear frequency up-conversion mechanism that increases both the output power and the bandwidth of the operating frequency. A prototype energy harvester with a mass ratio of μ=5.8 and a stopper distance of d=0.5 mm generated a peak power with a maximum of 449 μW delivered to an optimal load of 30 kΩ at a frequency of 17 Hz, and the half-power bandwidth was found to be 15 Hz (from 9 Hz to 24 Hz) at 1 g of acceleration, indicating that the device is capable of efficiently harvesting energy from a broad range of low-frequency random vibrations as well as shocks.
