Application of the Time-Frequency Selection of the Vibration Signal for Misfire Sensing in Diesel Engines

The paper presents a new method of misfire identification for a Diesel engine, based on results of parameterizations of a time-frequency a(t, f) map of an engine vibration signal. The Joint Time-Frequency Analysis (JTFA) methods have been proposed as a tool for a time-frequency selection of a vibration signal. An algorithm of the method has been outlined and an example application of a synchronous averaged Short Time Fourier Transform (STFT) for extracting vibration signal components related to combustion process has been shown. Parameterization of a(t, f) map gives measures covariable with misfire in a cylinder of an internal combustion engine. The method and analyses of the chosen characteristics and parameters were used in on-line diagnostics of the combustion process lack, what gave the necessary bases for application of the new method in OBD system. It might be helpful to use and improve the strategy of the combustion process control in the engine at on-line conditions and to assure the reliability of the diagnostic decisions being put in the OBD strategy control (misfire monitor basing on the vibration signal analysis). The method can be used in present (OBD II) and future (OBD III) engine diagnostics systems, it might be used also in on-board measuring systems. Its application will also result in the control of engine processes in the point of view of the environment protection from engine exhaust gas emission.