线绳驱动转速提升式低频俘能器的设计与研究

DEVELOPMENT OF A LOW-FREQUENCY HARVESTER BASED ON A ROPE-DRIVEN ROTOR WITH ROTATION SPEED UP-REGULATION FUNCTION

俘获周围环境中丰富的低频机械能对减少废旧电池数量、实现自维持传感器、降低传感器网络的使用和维护成本等具有重要意义,但传统的振动型俘能器对低频机械能的俘获效果不佳.为了有效收集周围环境中的低频机械能,本文提出一种线绳驱动、具备转速提升功能的电磁式俘能器,首先借助线绳驱动转轴结构将低频振动转换为双向旋转运动,再通过刚度自动改变的拨片和磁齿轮将双向旋转运动转换为转速更高的单向旋转运动,从而提高输出功率.对所提出的俘能器建立了机电耦合动力学模型,并通过样机制作和实验测试证实了理论模型的正确性.实验研究表明,在激励幅值40 mm和激励频率2 Hz的条件下,通过本文设计制作的2.5倍转速提升功能的磁齿轮,可将线绳驱动电磁式俘能器的最大输出功率增加至7.82 mW,比对应的无磁齿轮提升转速的线绳驱动电磁式俘能器的最大输出功率(3.22 mW)高约143%.在相同的激励条件下,制作的俘能器的交流电能经过桥式整流器转换为直流后,可在1.2 s内将220μF储能电容器的电压从0 V提升至1.5 V.在低频、不规则的振动激励下,所制作的俘能器仍可提供0.35 m W的输出功率,为设计高性能低频俘能器提供一条可行的解决方案.

Harvesting the ubiquitous low-frequency mechanical energy for power generation can reduce the number of expired batteries, achieve self-sustained sensors, and cut down the costs for deploying and maintaining the sensor networks. However, the conventional vibrational energy harvesters(VEHs) perform poorly in exploiting low-frequency mechanical energy due to the mismatch between the excitation frequency and the working frequency of the conventional VEHs. To effectively harvest the low-frequency mechanical energy from the surrounding environment, we report herein a rope-driven electromagnetic harvester with a magnetic gear for enhancing the rotation speed and then improving the output power. By transforming low-frequency vibrations to bi-directional rotation via a rope-driven shaft and then converting the bi-directional rotation of the shaft to uni-directional rotation of a driven wheel with enhanced speeds through a stiffness-variable plectrum and a magnetic gear, the proposed motion-transmission system can achieve highspeed rotation under low-frequency vibrations. Based on the motion-transmission system, an electromagnetic energy harvester was designed and fabricated by embedding magnets into the driven wheel and arranging coils in the proximity of the wheels. A theoretical model for the proposed harvester was developed and then validated by experimental test.When excited at 2 Hz with an amplitude of 40 mm, the maximum output power of the proposed harvester reaches 7.82 mW with the aid of the magnetic gear with a transmission ration of 10:4, corresponding to 143% improvement as compared with that of the harvester without the magnetic gear(3.22 mW). Under the same excitation condition, the proposed harvester can increase the voltage of a 220 μF capacitor from 0 V to 1.5 V in 1.2 s via a standard rectifier to convert its alternating current(AC) output into direct current(DC) output. In addition, the proposed harvester can provide0.35 m W electric power under low-frequency and irregular vibration excitation. Therefore, the proposed design may be a feasible strategy for developing high-performance low-frequency energy harvesters.