Statistical Engine Knock Detection

A knock detection circuit that is based on the signal of an accelerometer installed on the engine block of a spark ignition automotive engine has a bandpass filter with a certain frequency as a parameter to be calibrated. A new statistical method for the determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The method uses both the cylinder pressure and block vibration signals. The knock detectability, which is an individual cylinder attribute at a certain frequency, is verified via a statistical hypothesis test for testing the equality of two mean values, i.e. mean values of the amplitudes for knocking and non-knocking cycles. Signal-to-noise ratio is associated in this Chapter with the value of t - statistic. The frequency with the largest signal-to-noise ratio (the value of t - statistic) is chosen for implementation in the engine knock detection circuit.