换向激励式压电振动俘能器

Piezoelectric vibration harvester with excitation direction conversion

为提高在低频、宽带、高强度及大振幅振动环境下的可靠性,提出一种换向激励式压电振动俘能器,它由拾振器和换能器组成。换能器的振动方向垂直于拾振器振动方向(环境振动方向),振动方向的转换通过磁力换向结构实现,换向结构使响应振幅不随外部激励的增加而一直增加,从而提高可靠性。建立了俘能器的动力学模型,通过数值仿真和实验获得了相关参数对其输出特性的影响。仿真和实验结果表明:激励频率小于20 Hz时,该两自由度系统存在两阶谐振频率使输出电压达到峰值,一阶为拾振器谐振频率,二阶为换能器谐振频率。随着拾振簧片长度和拾振质量的增加,一阶谐振频率升高,所对应的输出电压基本不变;二阶谐振频率基本不变,所对应的输出电压逐渐升高;工作频带变宽。当外部激励振幅达到阈值时,换能器的响应振幅被有效控制,输出电压不再随之增加,最佳负载电阻为540 kΩ,此时输出功率最大为0.4 mW。实际应用中可通过改变俘能器的结构参数调整谐振频率及输出电压,将响应振幅控制在安全区域内,以适应低频、宽带、高强度及大振幅的工作环境。

To achieve adaptability to low frequency,wide bandwidth,high amplitude,and other vibration environments,a piezoelectric vibration harvester with excitation direction conversion(PVHEDC)is proposed;it constitutes a vibration collector and transducer.Due to the commutation structure,the vibration direction of the transducer is perpendicular to the ambient vibration direction,limiting the response amplitude.The dynamic model of the PVHEDC was established,and the influence of relevant parameters on its output characteristics was obtained via simulation and experiments.As a result,two natural frequencies were observed considering a low-frequency environment,which are the natural frequencies of the vibration collector and transducer,respectively,causing the output voltage of the PVHEDC to peak.With increasing length and proof mass of the elastic beam,fn1 gradually decreased,while fn2 remained unchanged,with the former corresponding to an essentially unchanged output voltage and the latter corresponding to an increased output voltage.Meanwhile,the bandwidth broadened.The experiment results show that when the external excitation amplitude increases to a certain value,the output voltage no longer increases,and the amplitude of the PVHEDC is effectively controlled.The achieved maximum output power is 0.4 mW for the optimal external load resistance of 540 kΩ.In practice,the above parameters influence the resonant frequency of the PVHEDC and its corresponding output voltage and limit the response amplitude,allowing adaptation to lowfrequency,broadband,high-intensity,and large-amplitude working environments.