Knock signal analysis for gasoline engines based on discrete wavelet transform

For the increasing of knock detection precision, the application of discrete wavelet transform(DWT) in the analysis of gasoline engine knock signal was studied. First, the knock feature was extracted from gasoline engine cylinder block acceleration signals by using DWT. Then, the parameter for evaluating knock intensity based on the energy of DWT decomposition detail coefficient was put forward. According to the character of DWT decomposition detail coefficient energy step change when knock took place, the method of confirming the knock threshold value was brought out, and the effectiveness of the method was also tested. The research results build the foundation of applying DWT to accurate and real-time knock control of gasoline engine. Further more, gasoline engine can work at slight knock zone by spark advance control, and the performance of gasoline engine can also be improved.