- 學位論文
混合陣列式壓電振子應用於能量擷取之實驗驗證
An Experimental Investigation of Mixed Type of Array of Piezoelectric Oscillators used for Energy Harvesting
摘要
本文利用理論分析及實驗驗證，將混合陣列式系統應用於壓電振動能量擷取之特性進行深入研究及探討。 原始壓電能量擷取器始終存在兩個缺點，第一為低功率面積密度、第二為偏離共振頻時輸出大幅降低。前者由於設備尺寸限制而難以突破，後者需使用複雜的頻率協調技術才能加以改善。有鑑於此，本研究團隊致力於開發陣列式壓電系統，試圖有效提升系統功率及其頻寬。 傳統的陣列式系統(全串聯或全並聯系統)雖然於許多方面都有所提升，但我們發現，傳統陣列式系統，有效功率增幅與頻寬均勻擴增，兩種效果無法同時存在。其主因為傳統/單一的陣列配置具有峰值集中現象，系統的峰值被集中於壓電片最大或最小共振頻附近，此現象導致頻寬無法於所需範圍內均勻分布，進而使得有效頻寬變得狹窄。有鑑於此，我們有個新的想法，若我們能結合不同的單一陣列，並利用開關適時切換其組合，進而達到在所需範圍內，每個組合峰值皆能均勻分布，有助於在有效功率增幅同時均勻擴增頻寬，經過一番努力後，混合陣列式系統油然而生。 本文首先利用等效阻抗法導出系統搭配標準電路之解析解。接著找出系統最佳配置方式，探討系統最佳阻抗並做出阻抗搭配結論。最後利用四根強耦合振子進行實驗驗證，並利用實驗數據，探討系統功率增幅及其寬頻效果；除了實驗結果與理論相當吻合外，混合陣列式系統於四根振子下，功率增幅為單根振子的3.4倍，寬頻效果為傳統陣列式系統的5.7倍；最重要的是，混合陣列式系統完全改善傳統陣列式缺點，達到有效功率增幅與均勻擴增頻寬同時存在的效果。 重要的是，混合陣列式系統完全改善傳統陣列式缺點，達到有效功率增幅與均勻擴增頻寬同時存在的效果。
並列摘要
The thesis aims to experimentally investigate the mixed type of array of piezoelectric oscillators used for energy harvesting. There are two inherent drawbacks for energy harvesting based on the use of a single piezoelectric oscillator. The first one is the low power area density and the second is the pronounced power reduction at off-resonance. The former is hard to be improved due to limitations in the size of devices and the latter requires sophisticated techniques of frequency tuning. This motivated the research group led by Professor Shu to develop arrays of piezoelectric energy harvesters for power boosting and bandwidth improvement. While this approach has enjoyed great success in many aspects, it is found that power enhancement and bandwidth enlargement cannot be achieved simultaneously in a single array configuration. This is because the peaks of harvested power are not uniform within the frequency range of interest. As a result, the effective bandwidth is shortened. To resolve it, an idea is to develop an array system which is able to switch the connection from parallel to series and vice versa. Thus, it is expected that both harvested power and bandwidth can be further improved. The present thesis first proposed the use of equivalent load impedance to derive the analytic estimate of harvested power for the mixed parallel/series connection of piezoelectric oscillators. Secondly, the optimal array configurations and the optimal load impedance are discussed. Finally, the experimental validation is carried out based on the use of 4 different strongly coupled piezoelectric oscillators. The results are found to be in good agreement with the theory. In addition, the peak power of the array of mixed type is roughly 3.4 times higher than that based on the use of a single oscillator. The bandwidth of the mixed array is also improved up to 5.7 times wider than that using a single array configuration.