Evaluation and Development of Methods for Knock Detection Using Cylinder Pressure Data

There are several methods for determining the knock intensity using cylinder pressure data, evaluation and development of these methods by analyzing test bench datasets is the basic issue of this study. At first, the methods for knock intensity determination are investigated and optimal methods are introduced by comparing test results in the fixed conditions. After determining the knock intensity by an appropriate method,threshold values must be determined for identifying knock borderline. Several methods for determining threshold values in individual cycles or statistical parameters of multiple cycles are introduced.Two methods for determining knock intensity can be compared by assuming one of them as the reference method, the way for comparison and selection of optimal parameters for second method are represented.Note that important parameters for analyzing of transducers› data, such as digital filtering and Fast Fourier Transformation (FFT), are introduced. FFT determines the main oscillation frequencies and digital filtering omits undesired frequencies.Investigations of the test results show that knock is occurred in special frequencies because of acoustic vibration modes, some methods for determining of these frequencies are introduced. It should be mentioned that the main oscillation frequency due to knock is about 8 kHz. Exact determination of these frequencies is important for investigation of filtering and optimal transducer location.