Hybrid magnetic coupling and impact enhanced low, adjustable and broadband piezoelectric vibration energy harvesting

Ambient vibrations from human activities, vehicle, and grid transmission lines’ motion are low frequency, broadband, and random, which brings challenges in piezoelectric vibration energy harvester (PVEH) design. Nonlinear technology including magnetic coupling and impact has their limitation such as no broadband behavior in low excitation level. This paper proposed a hybrid magnetic coupling and impact enhanced broadband PVEH. For upward broadband, the impact design is adopted to provide overload protection for the piezoelectric cantilever beam while achieving frequency expansion with hardening stiffness. For downward broadband, the magnetic coupling enhancement is introduced, and the high voltage area gradually extends to the low frequency range. The frequency tuning mechanism brought about by the magnetically coupled axial force which helps to achieve frequency matching and energy harvesting to the ambient vibration. An inverted beam with large U-shaped mass block is adapted in PVEH to achieve low resonant frequency and high power output. The simulation of the lumped parameters model indicates the effect of impact and magnetic parameters on the broadband and output voltage characteristics. The proposed PVEH can achieve bidirectional broadband expending and high output power compared with conventional PVEH. The optimized PVEH can achieve 8.96 V (pure impact), 10.69 V (hybrid) as peak voltage and 1.004 mW (pure impact), 1.91 mW (hybrid) as average power under 0.5 g acceleration, 10 Hz fixed frequency excitation. Compared to the conventional linear design, the broadband performance of proposed PVEH in this paper can realize 8.5–14.1 Hz (56 %, pure impact) and 7.7–15.81 Hz (81 %, hybrid) respectively under acceleration of 0.5 g.