Study on gasoline engine knock indicators based on wavelet transform and rough set

In order to improve the knock diagnosis accuracy, knock tests were carried out on a gasoline engine, and the slight knock characteristics from vibration signals of the gasoline engine were extracted by wavelet transform method. Making use of sub-band signals which were generated by wavelet transform of vibration signals as the style signals, 23 time-domain parameters were studied by using rough set theory, and the redundant relationship of the various parameters for describing the knock characteristic was revealed. Finally, the best parameters combination of peakto- peak value, mean amplitude and mean value was put forward as the knock indicators. The result shows that the indicators obtained by rough set theory can diagnose slight knock combustion, and the diagnostic accuracy is better than single indicator determination knock method.