Time-frequency analysis of multiple resonances in combustion engine signals

This paper presents time}frequency analysis of multiple resonances in combustion chamber pressure signals and corresponding structure-born sound signals of the cylinder block of a combustion engine considering only one combustion cycle. Since the Wigner distribution proved itself as a good tool for these kinds of signals, the requirement which we imposed here was to produce a sum of the Wigner distributions of the signal components separately, but without cross-terms using only one signal realization. A distribution having this property can be achieved using the S-method. Based on this property of the method, we investigate a procedure to estimate the instantaneous frequencies that are functions of temperature within the combustion chamber and the energies of the components that are used for knock detection. The calculation delay is smaller than the duration of one combustion cycle. This can provide an e$cient and accurate combustion control of spark-ignition car engines. The procedure is demonstrated on several simulated and experimental signals. ( 1999 Elsevier Science B.V. All rights reserved.