用於轉輪動能獵取之電磁式發電元件開發

SYSTEM ANALYSIS OF AN ELECTROMAGNETIC GENERATOR FOR HARVESTING ENERGY FROM A ROTATING WHEEL VIA A WEIGHTED PENDULUM

王郁仁(Yu-Jen Wang)

指導教授 ： 宋震國

國立清華大學/工學院/動力機械工程學系/博士(2011年)

https://doi.org/10.6843/NTHU.2011.00430

摘要

動能獵取技術可將環境中的動能轉換為電能，以取代傳統電池之電化學供電方式，作為低耗電產品的供電來源，如：壓力與溫度感測元件。無線胎壓計 (Tire pressure monitoring system, TPMS) 可用來偵測車輪胎壓，有效地減少因胎壓不足所造成的事故。在美國、歐洲與亞洲的部分地區，正在考慮藉立法將TPMS列為汽車必備品。然而，目前TPMS的壓力感測元件皆採用電池作為電力供應來源，其缺點包含電池的壽命有限以及對於環境的污染。因此，本研究致力於開發可應用於TPMS的發電元件。
本研究所設計的配重單擺利用多個配重產生電能，並應用於旋轉輪胎動能獵取上。一般而言，單一單擺無法於各種頻率皆產生大角度擺動。本研究開發共振頻率可自我調整之配重單擺技術，使得該結構可於各種車速之下皆能保持共振模態並以高轉換效率將動能轉換成電能。此一設計模型已被建立，其數值分析結果與實驗比較，不論是擺動角度與速度都僅只有微小的差異，且配重單擺的非線性行為也被詳細討論。配重單擺結合電磁發電機制可產生數百微瓦的能量，發電機制的物理模型由法拉地定律與勞倫茲力所產生的電磁阻尼力都已被考慮在此一模型當中，其數值分析與實驗結果的比較已完成，並具有良好的一致性。此外，為了提昇電磁發電效率，本文更提出創新環狀賀巴陣列(Circular Halbach array)磁路設計，能夠減少40 % 的線圈使用。
相關實驗與驗證方式，包含配重單擺擺動角度量測與發電量測皆已建立完成，並驗證本研究所提出之理論的正確性，藉由實驗結果驗證本研究所完成微型獵能器雛形品可於200~500 rpm之轉輪轉速之下，產生200~400微瓦之發電量，足以作為無線胎壓計供電之使用。

關鍵字

能量獵取元件 ； 共振頻率自我調整元件 ； 配重單擺 ； 微型發電機

並列摘要

Harvesting kinetic energy from environment is particularly suitable to replace the traditional electro-chemical type batteries as a power source of low-power electronics, such as pressure sensors and thermometers. Tire pressure monitoring system (TPMS) is a key device in preventing a flat tire, which is one of the most frequent causes of car accidents. In U.S.A., European Union and a number of Asian countries are currently considering the implementation of TPMS-related legislation. The existing TPMS are powered by a battery, but there are drawbacks to these batteries, such as their limited durability and pollution of the environment. For this reason, this thesis is aimed at developing a power generator for TPMS
This study designed a weighted pendulum to harvest energy from a rotating wheel, which consisted of a pendulum and one or more weights. As an energy harvester applied in TPMS, a normal pendulum cannot oscillate with a large angle at any wheel speed. In this study, the well-weighted pendulum helped the pendulum to adjust its natural frequency to meet the wheel rotation frequency. Therefore, the well-weighted pendulum is able to oscillate at various wheel speeds with a large angle and angular velocity. The kinetic energy produced was converted into electrical energy by electromagnetic induction, and a numerical study revealed that the well-weighted pendulum generated power of hundreds micro-Watts. The numerical results obtained from the analytical model of the well-weighted pendulum were in good agreement with the experimental results in both the swing angle and the power generation. The models of power generation were derived by using Faraday's law of induction and Lorentz force law, which were followed by the numerical solutions performed to verify the correctness with experiments. Moreover, for enhancing the electromagnetic efficiency, a novel circular Halbach array disk has been presented to lighten 40 % of the coil layers in the power generation compared with the normal multipolar disk. To investigate the dynamic behavior and power generation of the weighted pendulum, a car wheel emulator was constructed. At an optimum external resistance, the power output of the well-weighted pendulum was approximately 300 to 550 micro-Watts at about 200 to 500 rpm. This performance demonstrated that this has the potential to replace the battery in TPMS.

並列關鍵字

Energy harvesting device ； Frequency-adjusting device ； Weighted pendulum ； Micro-power generator

參考文獻

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