微型壓電元件應用於寬頻旋轉系統之研究

Abstract

本研究將微型壓電能量擷取器應用於旋轉式能量擷取架構並利用氣膠沉積技術及金屬-微機電製程技術製作出約一厘米尺寸的壓電能量擷取元件。根據所參考的理論模型，利用磁鐵旋轉給予貼在壓電元件端點的磁鐵一磁斥力，壓電元件受外力作用後呈現週期性的阻尼震盪且在不同的驅動轉速下，元件在低轉速區間皆能夠有較高的輸出功率，有別於在垂直震盪的量測時，元件僅能夠在共振頻下輸出最大的功率。而在實驗操作上，壓電元件將進行三種量測。首先以垂直震盪的方式將元件操作於其共振頻率上並量測其輸出，再來是藉由調變馬達轉速，量測元件在不同轉速下的輸出表現並探討其輸出在低轉速及高轉速之間的關係且改變驅動磁鐵與元件間的距離，觀察其輸出變化，並將其輸出的能量接上一個低功耗的無線藍芽模組進行溫度感測，以確認旋轉式能量擷取器在實際應用中的可行性。最後再參考前者的作動方式，將壓電元件結合3D列印的軸承結構進行輸出表現的量測，以實現在旋轉式架構上的自供電能量擷取系統。

This study proposes a broadband rotational energy harvesting setup by using micro piezoelectric energy harvester (PEH). Based on the theoretical model, when driven in different rotating speed, the PEH can output relatively high power which exhibits the phenomenon of frequency up-conversion transforming the low frequency of rotation into the high frequency of resonant vibration. It aims to reach a self-powered device used in the applications, like smart tire, smart bearings, and health monitoring on rotational machines. The experimental setup consists of a bimorph piezoelectric cantilever beam fabricated by metal-mems process in the size of 6 mm x 9 mm with a tip magnet and a same sized magnet on a revolving motor. Energy is harvested by the vibration of beam excited by non-contact repelling magnetic force. Through the excitation of the rotary magnetic repulsion, the cantilever beam presents periodically damped oscillation. The output performance of PEH is measured under three types of testing bench including a vertical base oscillation, a rotational excitation and a bearing prototype structure. Besides, the distance between two magnets is also investigated to improve the output power and the stability of the device. Furthermore, the demonstration of a self-powered BLE wireless temperature sensor with only the power from the MEMS PEH harvesting from the rotational excitation has also been done to prove the feasibility of the MEMS PEH in real applications.