行走時由氣流引發之壓電懸臂樑不穩定振動之能量擷取裝置

高齡化社會中，對於穿戴式監測系統的需求與日俱增，然而有限的電池壽命以及更換不易等問題大幅降低此項工作的便利性，因此，若能在操作環境中，成功擷取尚未被利用的邊界能量，透過換能器將其轉換成可靠且長久的電力來源，便可望為此問題之解決方案，故期望開發一操作於使用環境中之擷能裝置以供給可攜式感測器所需之電能。本研究利用可撓之壓電材料PVDF (Polyvinylidene fluoride)作為懸臂樑，於自由端附載偏心之圓柱體 (Bluff body)，藉由流場流經後產生之週期性升力使其持續振動而輸出交流電。由實驗結果可以得知，最大風速下 (U=9 m/s)其自由端位移可以到達4 mm之振幅，並於匹配阻抗下 (R=1 MΩ)產生1.18 V之閉迴路電壓，此時所對應之輸出功率為1.4 μW。另一方面，本研究亦實現了一可置於鞋中之嵌入式能量擷取裝置，將壓電擷能單元放置於壓克力製作之嵌入式機構，利用步行時巨大的作用力將氣體由鞋墊之出氣口擠壓進入流道中，因而產生振動達到於操作環境中進行能量擷取之目的。

關鍵字

壓電；能量擷取；圓柱形；渦列引致振動；鞋中嵌入式

並列摘要

Aging society urges the needs of stand-alone wearable monitoring system in recent years. However, limited life-span of battery and the difficulty to replace it have made the job considerably inconvenient. One desirable solution is to harvest energy from the environment and transfer it into reliable and durable electric power source by transducers. With this in mind, this research expects to develop a power harvesting device supplying electricity for monitoring system in the operational environment. The research utilizes a flexible piezoelectric cantilever beam (Polyvinylidene fluoride, PVDF) with dissymmetric arranged cylindrical bluff body attaching to its free end as a power harvesting unit. The periodical lift force will be generated when the flow passes the free end inducing vibration and also the output voltage of the cantilever beam. A tip displacement can be reached as large as 4 mm under flow speed of 9.8 m/s and the output voltage can be achieved to be 1.18V subjected to an external electrical resistance of 1 MΩ, with the corresponding power of 1.4 μW. Moreover, the research realizes a shoe embedded power harvesting device. The stepping power of walking will push air stream from the outlet of insole into flow channel made of acryl and excite the power harvesting unit placed inside the chamber which eventually scavenges power from the operational environment.

並列關鍵字

Piezoelectric ； power harvesting ； cylinder ； vortex induced vibration ； shoe mounted

參考文獻

[1] A. Khaligh, P. Zeng, X. Wu and Y. Xu, "A hybrid energy scavenging topology for human-powered mobile electronics," Industrial Electronics 34th Annual IEEE Conference, pp.448,453, 10-13 Nov. 2008.

[2] D. E. Lieberman, M. Venkadesan, W. A. Werbel, A. I. Daoud, S. D’Andrea, I. S. Davis and Y. Pitsiladis, “Foot strike patterns and collision forces in habitually barefoot versus shod runners,” Nature, vol.463, no.7280, pp. 531-535, 2010.

[3] R. T. Borno, J. D. Steinmeyer and M. M. Maharbiz, “Charge-pumping in a synthetic leaf for harvesting energy from evaporation-driven flows,” Physics Letters, vol.95, no.1, 2009.

[4] Y. Naruse, N. Matsubara, K. Mabuchi, M. Izumi and S. Suzuki, “Electrostatic micro power generation from low-frequency vibration such as human motion,” Journal of Micromechanics and Microengineering, vol.19, no.9, 2009.

[5] T. Krupenkin and J. A. Taylor, “Reverse electrowetting as a new approach to high-power energy harvesting,” Nature communications, 2, pp. 448, 2011.

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行走時由氣流引發之壓電懸臂樑不穩定振動之能量擷取裝置

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