Engine Knock Analysis and Detection Using Time-Frequency Analysis

We have performed an extensive study of cycle-to-cycle variation of engine knock and its occurrence in order to have a better understanding of engine knock. Experimental studies show the randomness of knock as well as its frequency varying nature. We propose using time-frequency based signal detection method to improve knock detection since this method can track frequency variations in the measured signals. The fundamental idea behind time-frequency analysis is to be able to understand and describe how the spectral content of a signal is changing in time. Classical signal analysis has traditionally dealt with time and frequency separately. Such individual descriptions are good in situation where spectral content of signals do not change with time; however, there are often signals that have time-varying spectral content such as engine knock. It is shown that one gains more information about knock signals using time-frequency analysis method. In addition, we have developed an improved knock detection algorithm using time-frequency detection method. The experimental studies performed on a 3.5 l V-6 engine using the proposed detection method show a significant improvement in signal-to-noise ratio (SNR) and the Receiver operating characteristic (ROC).