可调频旋磁激励式压电发电机的设计与试验

Structure and performance of rotating piezoelectric generator with tunable frequency

为提高旋转式压电发电机的安全性与有效带宽,提出一种可调频旋磁激励式压电发电机,并从理论、仿真与试验三个方面对发电机的工作特性进行了研究。建立了压电梁在端部外载荷作用下的刚度/频率偏移模型,并通过仿真获得了刚度、动磁铁数量对发电机响应特性的影响规律。结果表明,压电梁刚度随端部拉/压力的增大而线性增大/减小,固有频率相应地提高且趋于平缓/降低且速率增大,而动磁铁数量将影响发电机的谐振峰数量与放大比。在此基础上进行了相关试验,试验表明,压电梁受拉伸/压缩都将提高发电机的固有频率并降低输出电压幅值,且受压时减幅更大;此外,动磁铁数量除仿真中影响因素外对发电机的固有频率也具有一定影响;通过改变动磁铁数量与调节量,实现了发电机固有频率在39.2～112Hz内的调整,最大频率偏移为185.7%。

To improve the security of a rotary piezoelectric generator and broaden the effective frequency band,a rotating piezoelectric generator with tunable frequency was studied and its performance was evaluated through theoretical analysis,simulations,and experiments.Natural frequency offset and stiffness offset models were first established,and the effects of stiffness and the number of rotating magnets on the response performance of a generator were determined through a simulation.The analytical results show that the stiffness of the generator linearly increased with axial tension and linearly decreased with axial compression.In addition,the natural frequency increased and became steady with axial tension but decreased at a fast rate with axial compression.Based on the fact that the number of rotating magnets affects the number of resonant peaks as well as the amplitude ratio of the generator,aprototype rotating piezoelectric generator was fabricated and tested.The test results reveal that the natural frequency of the generator increases and that generated voltage decreases depending on whether the piezoelectric beam is stretched or compressed,with the latter having agreater influence on voltage reduction.In addition,the number of rotating magnets affects the natural frequency of the generator.By changing the number of rotating magnets and conducting pre-stretching and pre-compression,the natural frequency of the generator can be adjusted to within a range of 39.2-112 Hz with a maximum frequency shift of 185.7%.