Knock Determination Using Weighted Frequency Band Synthesis
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Solution Overview
Problem
Existing knock determination systems for internal combustion engines face challenges in accurately distinguishing knocking vibrations from noise superimposed on vibration waveform components of various frequency bands, leading to incorrect knock detection due to varying noise timing and synthesis methods.
Innovation Solution
A knock determining device that extracts vibration waveform components of multiple frequency bands, determines noise intensity for each band, and synthesizes them using weighting coefficients to reduce noise influence, enabling accurate knock detection by generating a composite vibration waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vibration waveform components of multiple frequency bands are extracted and simply synthesized to determine knock, then the knock determination covers a broad frequency range, but noise superimposed on any frequency band contaminates the composite waveform making knock distinction difficult
Solution Approach 1:
The patent applies local quality by assigning different weighting coefficients to vibration waveform components in different frequency bands based on their individual noise characteristics. Specifically, the noise determination unit evaluates noise levels in each frequency band separately, and the synthesis unit applies weighted coefficients that reflect the noise conditions of each band, thereby optimizing the signal-to-noise ratio locally in each frequency region rather than treating all bands uniformly.
Solution Approach 2:
The patent changes parameters by dynamically adjusting the weighting coefficients applied to vibration waveform components based on determined noise characteristics. The system modifies the synthesis parameters (weighting coefficients) according to the noise determination results, allowing the composite waveform synthesis to adapt to varying noise conditions in different frequency bands and time periods, thus improving knock detection accuracy under different operating conditions.
2Reliability
If noise determination is performed for each frequency band and knock determination is prohibited when noise is detected, then noise contamination is avoided, but actual knock occurrences are missed
Solution Approach 1:
The patent applies local quality by evaluating noise characteristics in each frequency band separately and applying localized weighting coefficients rather than globally prohibiting knock determination. The noise determination unit assesses each frequency band independently, and the synthesis unit applies different weighting coefficients to different bands based on their individual noise levels, allowing knock detection to proceed in clean frequency regions while suppressing noisy regions.
Solution Approach 2:
The patent applies partial action by partially synthesizing vibration waveform components from different frequency bands with appropriate weighting rather than completely excluding bands with detected noise. The system performs partial synthesis using only the reliable portions of the signal, applying weighting coefficients that reflect the confidence level in each frequency band's contribution, thus maintaining knock detection capability while reducing noise impact.
3Measurement precision
If vibration waveform components are synthesized with weighting according to noise intensity, then noise influence is reduced, but the synthesis process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the vibration waveform signal into multiple frequency bands using band-pass filters, and separately determining noise characteristics for each band. This segmentation allows the system to process and evaluate each frequency region independently, identifying noise sources in specific bands without being affected by other bands, thereby enabling targeted noise reduction through frequency-selective weighting.
Solution Approach 2:
The patent applies preliminary action by performing noise determination and calculating appropriate weighting coefficients for each frequency band before synthesizing the composite vibration waveform. The noise determination unit evaluates noise characteristics in advance, and the synthesis unit pre-calculates weighting coefficients based on these evaluations, so that when the composite waveform is synthesized, the noise reduction is already built into the weighting scheme, streamlining the overall process.
Data Source
AI summary
An output signal of a knock sensor is filtered with a plurality of band-pass filters to extract vibration waveform components of a plurality of frequency bands (f1-f4). Weighting coefficients (G1-G4) which multiply the vibration waveform component of each frequency band are established in such a manner as to be a small value as a noise intensity of each frequency band becomes larger. Thereby, the vibration waveform component of a plurality of frequency bands is synthesized by weighting according to an influence of a noise intensity of each frequency band. Even when the noise is superimposed on the vibration waveform component of any of the frequency bands, it becomes possible to reduce the influence of the noise and to synthesize the vibration waveform component of each frequency band, and an accurate knock determination can be performed based on the composite vibration waveform.