Spectral knock detection method and system therefor

Abstract

A spectral method, and corresponding system, for knock detection includes acquiring ( ) spectral energy associated with vibration caused by a knocking condition from a running engine. Preferably, a sampled data system ( ) acquires the spectral energy by converting an output from an accelerometer ( ) into data samples ( ) in a digital form. Then from the acquired spectral energy, a knock variable is derived from magnitudes of spectral components, representing a characteristic of a combustion chamber located within the running engine. In a preferred embodiment the knock variable is derived from magnitudes of spectral components related by ratios corresponding to Bessel function coefficients. The preferred embodiment includes a Digital Signal Processor ( ) applying a Fast Fourier Transform method ( ) to estimate a spectral content used to determine the knock variable. Then, a knock indication is provided ( ) when the knock variable exceeds a magnitude of a predetermined threshold ( ). Other embodiments include provision for providing a knock indication when a knock variable ( ) derived from magnitudes of individual spectral components corresponding to characteristic knock spectra associated with acquired spectral energy exceeds a magnitude of a trended time weighted version of the knock variable by a predetermined magnitude ( ).