A direction-adaptive ultra-low frequency energy harvester with an aligning turntable

Ultra-low frequency vibrations in the ambient environment contain abundant sustainable energy. However, their time-varying and random direction nature poses a prominent challenge for the design of effective energy harvesters. This paper proposes a direction-adaptive ultra-low frequency energy harvester with an aligning turntable to ensure a systematic alignment between the pendulum swinging plane and the excitation direction. The aligning turntable is easily rotated by overcoming friction, thus reducing the deviation angle till zero. Experimental results verify the output power enhancement from several milliwatts to over 1 W owing to the alignment process. Moreover, setting resonance frequency with large amplitude vibration can significantly shorten the alignment time. Decreasing the pendulum swinging natural frequency contributes to a slower alignment process but enhances the system stability.