“…In order to extract the fault feature information from vibration signals, various signal processing methods have been used in the field of fault detection [7,8], such as empirical mode decomposition (EMD) [9], wavelet transform (WT) [10], and their improved methods [11][12][13][14], sparse decomposition [15,16], manifold learning [17], deep learning [18], spectral kurtosis(SK) [19], and envelope analysis [20][21][22][23][24]. These methods realize fault detection from the time domain, frequency domain, or time-frequency domain.…”