Patent ID: 7467040
Filing Date: 2008-12-16
Classification: F02D,G01L,G01M

Abstract:
1. A method for determining indicators of a combustion state of an internal-combustion engine, wherein a signal correlated with a combustion phenomenon is acquired in form of a series of samples, a frequency band correlated with the combustion is determined by carrying out a time-frequency analysis of the signal, a number k of frequencies belonging to the frequency band is selected comprising: a) after acquisition of a first sequence of N first samples: filtering the first sequence in said frequency band, by means of a band pass filter; and estimating at least k spectral components of the first sequence filtered by carrying out a discrete Fourier transform of the first filtered sequence; b) then, for each new sample nN+1, constructing a new sequence of N samples, from the samples of the first sequence except a first sample but with the new sample, filtering the new sequence in the frequency band, by means of a recursive band pass filter, estimating at least k spectral components of the new filtered sequence, by a discrete Fourier transform of the filtered new sequence, calculated by applying a circular shift property of the Fourier transform; and c) determining combustion state indicators from the estimated spectral components.