Engine control signal processing system with frequency analysis by fourier transform algorithm

摘要

Only predetermined frequency components included in an ion current flowing between an ignition plug and the ground are extracted from the ion current by means of a low pass filter and a high pass filter as a knock detection signal, that is, a signal used for knock detection. This knock detection signal is then subjected to A/D-conversion in an A/D-converter to generate A/D-converted values which are subsequently supplied to a processing unit employed in a digital signal processor. In the processing unit, the A/D-converted values are subjected to a discrete Fourier transform (DFT) frequency analysis. Knock determination based on data obtained from the DFT frequency analysis results in information indicating the operating state of the internal combustion engine. That is, in the frequency analysis of the A/D-converted values obtained as a result of the A/D-conversion of predetermined frequency components of the ion current, a peculiarity such as the occurrence of a knock or the superposition of noise on the signal is clearly recognized.