Amplitude-modulated piezoelectric rotational energy harvester with magnetically induced membrane vibration and cavity-orifice coupling

An amplitude-modulated piezoelectric rotational energy harvester based on a magnetically induced membrane–vibrator coupling mechanism is proposed to achieve stable and high-efficiency energy conversion under fluctuating rotational environments. The harvester utilizes a two-stage indirect excitation mechanism, where (Stage I) the rotating magnet array generates a periodic magnetic attraction to drive the flexible membrane, and (Stage II) the induced membrane vibration is transmitted through a cavity–orifice coupling to excite multiple piezoelectric vibrators simultaneously. This design enables unidirectional strain application, prevents excessive deformation of the piezoelectric elements, and improves the durability and reliability of the system. Theoretical modeling and experimental validation demonstrate that the proposed AM-PREH achieves an optimal power output of 57.6 mW at 900 rpm, corresponding to the impedance-matched condition, and can efficiently power typical low-power electronic devices. The cavity–orifice coupling and multi-vibrator activation significantly enhance energy harvesting performance. Owing to its mechanical robustness and scalable modular configuration, the AM-PREH shows strong potential for self-powered sensing and structural health monitoring applications in rotational machinery systems.