A low-frequency unidirectional-strain-mode bistable piezoelectric vibration energy harvester via prestressing curved vibrators

Vibration energy harvesting using piezoelectric transduction becomes increasingly popular as a promising alternative to electrochemical batteries for powering low-power wireless and portable electronic devices. A low-frequency unidirectional-strain-mode bistable piezoelectric vibration energy harvester (USB-PVEH) is proposed to offer a viable solution to the possible damage caused by the bidirectional deformation of piezoelectric plates in this paper. The salient characteristics of the USB-PVEH were that bistable vibration energy harvesting was implemented via the unidirectional-strain piezoelectric vibrators which were constructed by prepressuring two initially-curved piezoelectric plates. Also, the deformation of pre-bent piezoelectric vibrators subjected to the unidirectional compressive strain wasn’t directly induced by the external vibration source but triggered indirectly by the elastic beam. To prove the structural feasibility and ascertain the influence of adjustable magnet installation parameters on the energy harvester, the theoretical investigation, simulation, fabrication and experimental testing were conducted. The results showed that the potential well structure in nonlinear magnetic force can be altered by adjusting installation parameters such as the horizontal distance, vertical distance and installation angle of the adjustable magnet, thereby modifying the dynamic performance of the energy harvester. Additionally, the USB-PVEH exhibited an optimal parameter combination (d = 14 mm, h = 6 mm, α = 67.5°), where the natural frequency was 16 Hz and the effective bandwidth was 19.6 Hz. Furthermore, the maximum output power of the USB-PVEH could reach 5.27 mW at 16 Hz with the optimal load resistance of 70 kΩ. Consequently, it is expected that the USB-PVEH can provide reference for the structural design of PVEH in high-amplitude environments.