We present a portable, stacked and tri-stable energy harvester based on the unique geometrical structure of L-shaped beams and the nonlinearity of magnetic force to harness low-frequency and low-level excitations. In this device, multiple L-shaped piezoelectric beams are connected in a head-to-tail manner. Such a special stacked structure reduces the natural frequency of the system while realizing the series connection of multiple piezoelectric sheets in a limited space, thus improving the acquisition efficiency. Additionally, magnetic coupling endows the harvester with tri-stability and consequently enhances the bandwidth responses in low-frequency environments. The mathematical model is developed, and the static behaviors are explored by the bifurcation theory. Furthermore, the complex dynamic frequency method combined with the arc length method is conducted to investigate the dynamic responses with different parameters. Sinusoidal excitation experiments on the prototype verify the rationality of the mathematical model and the low-frequency broadband capability of the harvester. In the experiments, the designed harvester can reach a maximum output power of 1.49 mW at the low excitation amplitude of 0.4 g, and the magnet coupling significantly enhanced the electrical responses. The human motion tests demonstrate that the designed harvester has the potential to convert biomechanical energy into electrical energy for continuous powering of wireless devices.

中文翻译：

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堆叠式三稳态压电能量收集器的低频能量收集


我们提出了一种便携式、堆叠式、三稳态能量收集器，基于 L 形梁的独特几何结构和磁力的非线性，以利用低频和低水平的激励。在该装置中，多个L形压电梁以头尾相连的方式连接。这种特殊的堆叠结构降低了系统的固有频率，同时实现了有限空间内多个压电片的串联，从而提高了采集效率。此外，磁耦合赋予采集器三稳定性，从而增强低频环境中的带宽响应。建立了数学模型，并通过分岔理论探索了静态行为。此外，采用复动态频率法与弧长法相结合来研究不同参数下的动态响应。样机上的正弦激励实验验证了数学模型的合理性和采集器的低频宽带能力。实验中，设计的采集器在0.4 g的低激励幅度下可以达到1.49 mW的最大输出功率，并且磁体耦合显着增强了电响应。人体运动测试表明，设计的采集器有潜力将生物机械能转化为电能，为无线设备持续供电。