旋轉式徑向磁力於壓電振能擷取之研究

Abstract

本文提出一種藉由磁力激振在旋轉環境下之壓電能量擷取裝置。此裝置適用於智能軸承健康監測傳感器的自主供電。該裝置由壓電懸臂樑組成，固定於滾珠軸承結構的外圈上並接上標準能量擷取電路。透過旋轉磁鐵沿徑向激振懸臂樑端點磁鐵，產生非接觸式磁力激振，壓電懸臂樑的振動能量得以擷取。基於磁力相互作用和傅立葉技術的分析，開發一個理論框架，從提出的理論中得到一些觀察結果。首先，磁鐵距離與旋轉半徑的比率較小可使壓電懸臂樑產生更穩定的頻率響應；其次，選擇較高共振頻率的壓電振動子可以產生更密集的頻率響應；第三，選擇較大機械阻尼的壓電振子可以實現減少頻率響應的波紋，隨後透過實驗證實這些觀察結果。最後，研究滾珠軸承結構外圈隨機振動引起的干擾效應，發現會使頻率響應的波紋以及功率顯著降低。

The thesis proposes a piezoelectric device capable of harvesting energy form rotary magnetic plucking dynamics. It is intended for self-powering sensors used in the health monitoring of smart bearings. The device consists of a piezoelectric cantilever beam fixed on the outer ring of a ball-bearing structure and attached to the standard energy harvesting circuit. A tip magnet is excited along the radial direction by a rotating magnet. Energy is therefore harvested by vibration due to non-contact magnetic plucking. A theoretical framework is developed based on the analysis of magnetic interaction and the use of the Fourier technique. There are several observations drawn from the proposed theory. First, the smaller ratio of magnetic distance to the radius revolution gives the more stable rotary frequency response. Second, the choice of high resonance of a piezoelectric oscillator gives dense rotary frequency response. Third, the reduction of ripples in rotary frequency response can be achieved by requiring larger mechanical damping. These observations are subsequently confirmed by experiment. Finally, the effect of the noise induced by the random vibration of the outer ring of a ball-bearing structure is studied. It is found that the ripples in the rotary frequency response are reduced at the significant cost of harvested power.