Abstract Depending on its mounting orientation, the rotational piezoelectric harvester can be subjected to the centrifugal softening or stiffening effects, which may pose a positive or negative influence on the energy harvesting performance. This paper firstly presents the comprehensive comparison of the centrifugal softening and stiffening harvesters with a unified dimensionless analytical model. The analytical expressions of the optimum short-circuit and open-circuit rotational frequencies, the optimum resistances and the optimum centrifugal coefficients are derived to reveal the influence mechanism of the centrifugal effects. The proposed model is validated experimentally and used for case studies to compare the centrifugal softening and stiffening harvesters. Results illustrate that the centrifugal softening harvester has a superior energy harvesting performance at low rotational frequencies while the centrifugal stiffening harvester is better at high rotational frequencies. Furthermore, the peak power of the centrifugal softening harvester is higher while the frequency bandwidth of the centrifugal stiffening harvester is wider. In addition, it is found that the centrifugal stiffening harvester is more sensitive to the centrifugal coefficient. Based on the centrifugal stiffening effect, the self-tuning harvester can be achieved with a wide frequency bandwidth. Meanwhile, this requires that the centrifugal coefficient is precisely determined, and the fundamental natural frequency of the harvester without the centrifugal force should be low enough when operating at low rotational frequencies. Compared with the centrifugal stiffening effect, the centrifugal softening effect may be more suitable to be used in MEMS/NEMS applications since it can reduce the fundamental resonant frequency of the harvester during the rotation.

中文翻译：

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旋转能量收集中离心软化和硬化效应的分析和实验研究

摘要 根据安装方向的不同，旋转压电采集器会受到离心软化或硬化效应的影响，这可能对能量采集性能产生积极或消极的影响。本文首先介绍了离心软化和硬化收割机与统一的无量纲分析模型的综合比较。推导了最佳短路和开路转速、最佳阻力和最佳离心系数的解析表达式，揭示了离心效应的影响机制。所提出的模型经过实验验证并用于案例研究，以比较离心软化和硬化收割机。结果表明，离心软化收割机在低旋转频率下具有优异的能量收集性能，而离心硬化收割机在高旋转频率下性能更好。此外，离心软化收割机的峰值功率更高，而离心硬化收割机的频率带宽更宽。此外，发现离心硬化收割机对离心系数更敏感。基于离心硬化效应，可以实现宽频带宽的自调谐收割机。同时，这需要精确确定离心系数，在低转速下运行时，收割机无离心力的基本固有频率应足够低。