Compliant quasi-zero stiffness device for vibration energy harvesting and isolation

Using a small piezoelectric device to extract energy from low frequency (< 5 Hz) and ultra-low level (< 0.05 g) vibration environments is a very challenging task. The device with quasi-zero stiffness (QZS), widely used in vibration isolation, could be a good candidate for a low frequency energy harvester. However, the conventional QZS devices with complex frames are not very suitable for small-scale harvesters operating in low vibration conditions. To solve these problems, we propose a compact W-shaped compliant mechanism with the direct QZS. Both static and dynamic models have been established to investigate the performance. A compact prototype is fabricated for testing. The experimental results are in good agreement with numerical predictions and demon-strate a good energy harvesting performance under the excitation level below 0.02 g. The normalized power density can even reach 2.3 mW/cm3g2 under the excitation level of 0.007 g at 3.5 Hz. This device can also serve as a compact low-frequency vibration isolator with the transmissibility of -20 dB at 10 Hz. Overall, this compact QZS device shows a great potential to scalable applications of low-frequency energy harvesting and vibration isolation.