Abstract:

A method to extract the knock characteristic of the spark ignition engine was proposed based on the higherorder cumulants. The vibration signals were collected by an accelerometer mounted on the cylinder head of a 4cylinder spark ignition engine. A formula based on the higherorder cumulants was defined to calculate the knock intensity by analysis of the higherorder statistics characteristic of the signal. The proposed method was compared with the methods based on the Fourier transform and the wavelet transform, and it was found that the former needs less data points, and is capable of detecting the occurence of weaker knock. Combining with the sound intensity when the knock occurs, a knock intensity classification method was proposed after analyzing the higherorder statistics characteristic of the vibration signal under different engine operating conditions. Processing of the real vibration signals show the practicality of the proposed method.

Key words: power machinery and engineering, technology of instrument and meter, spark ignition engine, knock detection, higherorder statistics, knock intensity