Time-frequency analysis of multiple resonances in combustion engine signals

This paper presents time-frequency analysis of multiple resonances in combu stion chamber pressure signals and corresponding structure-born sound signa ls of the cylinder block of a combustion engine considering only one combus tion cycle. Since the Wigner distribution proved itself as a good tool for these kinds of signals, the requirement which we imposed here was to produc e a sum of the Wigner distributions of the signal components separately, bu t without cross-terms using only one signal realization. A distribution hav ing this property can be achieved using the S-method. Based on this propert y of the method, we investigate a procedure to estimate the instantaneous f requencies that are functions of temperature within the combustion chamber and the energies of the components that are used for knock detection. The c alculation delay is smaller than the duration of one combustion cycle. This can provide an efficient and accurate combustion control of spark-ignition car engines. The procedure is demonstrated on several simulated and experi mental signals. (C) 1999 Elsevier Science B.V. All rights reserved.