Low-Frequency Piezoelectric Energy Harvesting From Coupled Longitudinal–Transverse Vibration of Two Magnetic Coupling-Based Orthogonal Beams

Vibration energy harvesting using piezoelectric transduction is becoming a promising alternative to electrochemical batteries for powering the low-powered wireless and portable electronic devices. Unlike typical cantilevered piezoelectric vibration energy harvesters (PVEHs), where the piezoelectric beam with a tip mass experienced the vibration excitation directly, low-frequency piezoelectric energy harvesting from coupled longitudinal–transverse vibration of two magnetic coupling-based orthogonal beams (LF-PVEH) is proposed in this article. An attractive feature of the proposed architecture was that the auxiliary beam tolerated the high-shock longitudinal vibration, and meanwhile, the motion of the auxiliary beam induced the transverse oscillation of piezoelectric beam parallel to the vibration direction via the magnetic coupling. To verify the principle feasibility and ascertain the effect of two magnetically coupled orthogonal beams on the dynamic behaviors and power generation characteristics of the LF-PVEH, theoretical analysis, numerical simulation, and experimental testing were conducted, respectively. The results showed when amplitude increased from 3 to 5 mm, the output maximum voltage increased no more. Besides, by increasing the proof mass
${m}1$
to 20 g, the corresponding resonance frequency of the LF-PVEH can be reduced to 8.5 Hz, and when the spatial distance
${L}_{y}$
is 10 mm, the optimal effective bandwidth of 8 Hz can be achieved to adapt to the broadband low-frequency vibration environments. The power testing shows that the maximum output power of LF-PVEH can reach 0.2 mW at 11 Hz with the optimal load resistance of 540
$\text{k}\Omega $
.