限幅激励式压电发电机性能分析与试验

Structure and Performance of Piezoelectric Generator with Amplitude Limit

为提高旋转式压电发电机的可靠性及有效带宽,提出一种限幅激励式压电发电机,利用凸轮激励压电振子使其发生幅值可控的单向变形。从理论和试验两方面研究凸轮升程与升角、激振力及弹簧刚度等对发电机输出性能的影响规律。研究结果表明,利用移动凸轮限幅激励压电振子可获得无明显峰值、较平坦的电压幅频特性曲线;其他条件相同时,降低凸轮升程有助于降低最大输出电压、拓宽有效转速带宽,凸轮升角(30°~45°)增加对最大输出电压无影响、但可拓宽有效转速带宽,增加激振力可拓宽某一输出电压所对应的有效带宽,复位和缓冲弹簧刚度对有效转速带宽及转速值都有一定的影响,当复位弹簧刚度50 N/m、缓冲弹簧刚度20 N/m、激励距离8 mm、凸轮升程2 mm、升角为40°时,输出电压大于30 V所对应的有效转速范围为0~537.6 r/min,故通过合理匹配系统参数可有效提高发电机的可靠性及有效带宽;存在最佳电阻使发电机输出功率达到最大值,最佳电阻70 kΩ、转速392 r/min时的输出功率为10.88 mW。

In order to improve the reliability and effective bandwidth of rotary piezoelectric generators,a piezoelectric energy harvester with amplitude limit is proposed and the characteristic of different spring stiffness、excitation distance、cam lift and lift angle was evaluated through theoretical analysis,simulations,and experiments.Research results show that exciting the piezoelectric by moving cam,a flat voltage amplitude-frequency characteristic curve without significant peaks can be obtained.Under other parameters given,the effective speed bandwidth increases as the lift decreases but the maximum output voltage also decreases;The cam angle increases(30°-45°)has no affect to the maximum output voltage,but it can broaden the speed bandwidth effectively;Reducing the excitation distance can increase the excitation force,thereby increasing the horizontal amplitude of the cam and the reliability of the generator can be effectively improved by properly matching the stiffness of the rebound spring and the buffer spring.When buffer spring’s stiffness is 50 N/m,rebound spring’s stiffness is 20 N/m,cam lift is 2 mm,lift angle is 40°,excitation distance is 8 mm,there is a loading resistance 70 kΩto maximize the output power,and the output power reaches 10.88 mW when the rotary speed is 392 r/min and the power generation performance of the energy harvester can be improved.