A low-frequency multidirectional piezoelectric vibration energy harvester using a universal joint structure

Vibration energy harvesting using piezoelectric mechanism has attracted much attention for powering wireless sensors over the last decade. This paper proposes a low-frequency multidirectional piezoelectric vibration energy harvester (LM-PVEH) using a universal joint structure. Unlike conventional PVEHs, LM-PVEH utilized a pendulum instead of a proof mass in a typical piezoelectric beam and employed a universal joint to indirectly pluck the piezoelectric beam, ensuring the beam was only subjected to compressive stress. With the multidirectional rotation characteristic of the universal joint, the harvester efficiently scavenged multidirectional energy. To verify the feasibility of principle and investigate the effect of structural parameters on the power generation performance of LM-PVEH, theoretical analysis and experimental test were conducted. The results demonstrated that LM-PVEH exhibited different power-generating characteristics in various vibration directions. The resonant frequency of LM-PVEH could be efficiently tuned by adjusting proof mass and mass distance to accommodate low-frequency environments. The proposed harvester achieved a maximum power of 4.99 mW with the load resistance of 300 kΩ at 7.3 Hz. The LM-PVEH could power 100 LEDs, a temperature sensor, and a transmitting module. Additionally, the successful demonstration of powering a calculator from human motion highlights the practical application of the proposed harvester.