双自由度压电振动能量采集器的力-电输出特性分析

Force-electrical output characteristic analysis of piezoelectric vibration energy harvester with two degrees of freedom

在单自由度悬臂梁压电振动能量采集器模型基础上增加一个弹性放大器,构造形成了具有双自由度的压电振动能量采集器。利用ANSYS有限元软件建立了双自由度压电能量采集器的有限元力-电耦合模型,数值分析了模型中各参数(如质量比、阻尼比以及负载电阻等)对系统力特性(速度、加速度等)和电输出特性(电压、电流、输出功率等)的影响。研究结果表明:大的质量比和小的阻尼比能够提高压电悬臂梁能量采集器的输出功率,并能拓展其工作频带;短路谐振状态下的匹配电阻能够使能量采集器产生较大的输出电流,而开路谐振状态的匹配电阻能够使能量采集器产生较大的输出电压。研究结果还表明:对于尺寸为50.8mm×31.8mm×0.26mm的悬臂梁基板和50.8mm×31.8mm×0.14mm的压电晶体构成的双自由度系统,在基础加速度40m/s2、频率38Hz的外界振动激励下,系统在负载电阻短路和开路状态下的最大输出功率分别达到4 386.5和4 263.4mW,是单自由度系统的10倍。双自由度系统的频带宽度达到10Hz,是单自由度系统的5倍。

Two degrees of freedom（TDOF）piezoelectric vibration energy harvester（PEVH）was constructed via the addition of a single degree of freedom（SDOF）cantilever piezoelectric vibration energy harvester and an elastic amplifier.The relevant finite element force-electric coupling model was established by ANSYS software,and the effects of the model parameters（such as the mass ratio,the damping ratio,and load resistance,etc.）on the system vibration characteristics and electrical output characteristics were studied in detail.The dimensions of the cantilever substrate and the piezoelectric plates are 50.8 mm×31.8mm×0.14 mm and 50.8mm×31.8mm×0.26 mm,respectively.The results have shown that a larger mass ratio and a smaller damping ratio can both improve the output power and broaden the working frequency band of the TDOF,and a suitable matching resistor under short-circuit resonant condition can make the TDOF system produce larger output current,while one under open-circuit resonant condition can produce larger output voltage.The maximum power outputs of the TDOF system are4 386.5mW and 4 263.4mW with the load resonance under short-circuit condition and open-circuit condition when the base vibration frequency is 38 Hz with acceleration amplitude 40m/s2,respectively,which is ten times of the SDOF system.The results have also shown that the band width of the TDOF system is 10 Hz,which is five times of the SDOF system.