Normalized Knock Intensity Determination Based on the Knock Sensor Analysis to Have a Fixed Detection Threshold at Different Operating Conditions

Abstract

Processing the knock sensor's signal is the most common approach for knock detection in series production vehicles. Filtration, rectification, and integration in a defined knock window (KW) are main steps to compute the standard knock intensity (SKI). The SKI strongly depends on the engine operating conditions. In this study, a novel model is proposed based on the knock sensor analysis to determine the normalized knock intensity (NKI) with much less dependency on the operating conditions, cylinder numbers (CNs), and KW. Implementing the proposed normalization model, a fixed detection threshold can be used for knock detection at all operating conditions. To verify the model, an accurate knock detection method based on cylinder pressure analysis is utilized, which comprises intensity calculation and a novel technique for detection threshold determination. Experimental results at all operating conditions show a square of correlation coefficient greater than 0.7 when the knock intensity from the presented model is compared with the reference cylinder pressure based method. In addition, the model detects all heavy knocking cycles and there is no wrongly detected knocking combustion.