Detection of misfire and knock in spark ignition engines by wavelet transform of engine block vibration signals

摘要

The high-frequency components of engine block vibration signals during misfire and normal combustion show clear differences of duration and scale by wavelet analysis—continuous wavelet transform (CWT). A new factor, combustion noise intensity ('CNI_(CWT)'), has been defined, which has been derived from the CWT scalogram. It has been shown that CNI_(CWT) can detect misfire more accurately than fast Fourier transform power spectral density. Similarly, it has been found that CNI_(CWT) can also be applied to knock detection. The durations of both knock and misfire detection overlapped each other at the same wavelet scale 8; misfire, normal and knock cycles can be indicated on the same histogram by CNI_(CWT). Moreover, knock and misfire detection can be combined to one CNI_(CWT) computation.