本論文主要目的是研究旋轉機械齒輪系統在變轉速的情況下，齒輪發生磨損、斷齒、不平衡等故障時，使用希爾伯特-黃轉換方法分析其非線性、非穩態訊號，以提取其故障特徵。首先將訊號透過集成經驗模態分解法分解，並進行後處理過程，得到數個的固有模態函數，使用正常化希爾伯特變換方法、一般化跨零點方法、Direct Quadrature方法，三種不同的方法計算每一個固有模態函數的瞬時頻率，將瞬時頻率計算結果利用馬達轉速進行無因次單位頻率正規化，使固有模態函數去除轉速的因子後，選取具有意義的固有模態函數，將其得到的無因次單位瞬時頻率和瞬時振幅作時間-頻率-能量分布圖，並對時間積分作頻率-能量圖，即為邊際頻譜圖，從四種實驗類型之頻譜圖中有效的找出對應之故障特徵，以辨別出四種故障類型。

The main purpose of this paper is to study the fault features of gear system, such as gear wearing, teeth broken, gear unbalance, under variable rotation speed. The Hilbert-Huang Transform (HHT) method is utilized to analyze the nonlinear and non-stationary vibration signals. The signals are decomposed into a number of Intrinsic Mode Function (IMF) through the Ensemble Empirical Mode Decomposition (EEMD) and the Post-Processing of EEMD. The three different methods of calculating the instantaneous frequencies, Normalized Hilbert Transform (NHT) method, Generalized Zero-Crossing (GZC) method, and Direct Quadrature (DQ) method, are employed to determine the instantaneous frequencies of IMFs. The dimensionless frequency-time-energy distributions of IMFs is then obtained through dimensionless frequency normalization, so that the factor of shaft rotation speed can be extracted. The characteristic dimensionless frequencies of different fault types can be identified in the marginal spectrum of the information-contained IMFs.

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