| 摘要: | 本論文研究提出一個可以擴增光強度動態量測範圍及具有強光保護效果的暉光儀設計。這個創新暉光儀使用光電倍增管(Photomultiplier Tube, PMT)檢測到的光子計數值做為回饋去控制光電倍增管的高壓電，以補償光強度的變化並維持光子計數值恆定。當光子計數值被控制到保持恆定時，因高壓電與光強度成反比，故可從高壓電數值推算出光強度。使用曲面擬合方法將數學模型擬合至實驗數據，藉由使用此模型，可從光子計數值與高壓電計算出光強度。透過光強度及預設光子計數值，可計算出前饋高壓電的補償數值，然後以之調整高壓電，前饋光電倍增管特性補償控制即完成。另一方面，回饋控制包含比例積分線性控制以消除數學模型誤差的影響，使量測光子計數值更接近預設光子計數值。我們以校正平台進行實驗測試以確認此創新儀器可以達到設計目標。新儀器除了擴增線性動態範圍(從450 pW到4500 pW)外，同時還維持了高靈敏度(最大誤差1.69 pW，標準偏差0.73 pW)。
為了校正與測試前述的創新暉光儀設計，本論文研究亦開發建構了一個光電倍增管的校正平台，可幫助科學家量測並建立光子計數值與光強度的關係曲線。此校正平台使用一個創新的10倍光衰減器使光功率計能夠用來校正光電倍增管，以令校正平台的解析度遠大於光功率計的解析度。首先，透過模擬驗證了此校正系統的可行性，然後實現了系統設計，其中包括光學設計、電路設計和軟體演算法。以此平台實際進行量測取得光子計數值與光強度的數據，並以量測數據建立光子計數值與光強度的特性曲線。;This research proposed a design of the innovative airglow instrument, which can extend the measure range of the light intensity, and also have the influence of strong light protection. The innovative instrument uses the photomultiplier tube to detect the photon count, then by the photon count to feedback and control the high voltage of the photomultiplier tube to reimburse for the change in light intensity and remain the photon count fixed. While the photon count is controlled to maintain fixed, the light intensity is inversely proportional to the high voltage, and then the light intensity can be reckoned from the high voltage. The photon count is the function from the light intensity and the high voltage, representing the characteristic surface of the photomultiplier tube. The experimental data can be used system identification algorithm to establish its mathematical model of quadratic polynomial equation. On the characteristic surface of the photomultiplier tube, the feedforward control function is the high voltage calculated from the photon count and the light intensity, and the function of the light intensity calculated by the photon count and the high voltage. Substituting the measured photon count and measured hight voltage into the light intensity function can calculate the measured light intensity. Substituting the measured light intensity and the preset photon count into the feedforward control function can calculate the feedforward compensation high voltage and feed it into the high voltage power regulator. The loop completes the feedforward control compensation of the photomultiplier tube. In addition to the photomultiplier tube characteristic compensation feedforward control loop, the feedback control can also be parallel connected with a PI linear feedback control loop to remove the effect of system identification model errors to let the measured photon count more similar to the preset photon count.
In order to calibrate and test the innovative airglow instrument design, this study also developed and constructed a photomultiplier tube calibration platform. The calibration platform can help the researcher to measure and establish the photon count corresponding to the light intensity characteristic curve. The calibration platform by an 10-fold optical attenuator to let the optical power meter can increase 10 time resolution to calibrate photomultiplier tube. This study proposed a preliminary validation of the simulation data, and then constructed the calibration platform, including optical, circuit, and software design. Finally, the calibration platform is verified by the experimental data, and the light intensity corresponding to the photomultiplier tube characteristic curve is established. By using the calibration platform, the photomultiplier tube characteristic compensation feedforward control algorithm with/without linear feedback control has been tested. The data shows that the new designed instrument can not only expand the linear dynamic range (Form 450 pW to 4500 pW) and but also increase the sensitivity (Maximum error is 1.69 pW, standard deviation is 0.73 pW). |
