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Construction of Knock Detection Logic by Pattern Recognition Using Short-time Fourier Transform

Article of Honda R&D Technical Review Vol.24 No.1

Summary

The project discussed in this paper focused on the frequency attenuation characteristic of knock and mechanical noise in order to develop a more accurate method of distinguishing between the two phenomena. Short-time Fourier transform (STFT), which makes it possible to identify changes in frequency over time, was studied as a method of analyzing this characteristic. The duration of knocking is 80-90 deg in terms of crank angle. The frequencies of the multiple vibration modes that knock generates decline as time elapses, with attenuation greater in the high-frequency vibration modes, until finally only the 1, 0th mode remains. Mechanical noise occurs over a wide frequency band, and its attenuation is rapid. Based on these results, the concept of time was introduced in order to help enable the attenuation of the frequencies to be identified, and a knock detection logic that judges knock on the basis of pattern recognition was developed. This logic is able to distinguish knock and mechanical noise with a high degree of accuracy even when the timing and frequency of the two phenomena match. As a result, it has been possible to increase robustness in relation to mechanical noise in comparison to conventional knock detection systems that judge knock based on the intensity of the frequency at which it occurs, helping to ensure stable functioning of the system even when mechanical noise occurs. This has made it possible to set the threshold value for judgment of knock lower than is the case in conventional systems, contributing to the reduction of knock noise.

Reference

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Author (organization or company)

Kenji AKIMOTO(Automobile R&D Center)、Hirotaka KOMATSU(Automobile R&D Center)、Atsushi KURAUCHI(Automobile R&D Center)

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