Injector waveform analysis and engine fault diagnosis based on frequency space subdivision in wavelet transform

Abstract

Although traditional waveform analysis in time domain plays an important role in realizing engine non-disintegration fault diagnosis, this method fails to make an accurate fault diagnosis when fault waveform and normal waveform are very close. To solve this problem, a new method based on frequency space subdivision (FSS) in wavelet transform (WT) is proposed and applied in this paper. Meanwhile, a processing approach of engine data stream is introduced, which makes further waveform analysis possible. This method is applied to an injector-pulse-width waveform analysis. As for the No. 12 fault analysis, firstly a biorthogonal wavelet base with good characteristics is selected, then three-layer wavelet decomposition is used to analyze injector-pulse-width in both time domain and frequency domain, and finally the accurate fault band is located through calculation of the sum of the difference between fault and normal wavelet coefficients. The result obtains that the fault comes from the oxygen sensor, which is completely coincident with the experimental fault hypothesis. Injector-pulse-width waveform of No.1, 8, 11 and 19 faults are also analyzed similarly. The results show that the proposed waveform analysis method improves the accuracy of the engine fault diagnosis. This method provides a supplement for the known non-disintegration engine fault diagnosis and supplies a good reference for fault diagnosis of the other large machines.