Knock Determination Apparatus Cylinder Noise Separation
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Solution Overview
Problem
The existing knock determination methods using in-cylinder pressure sensors are susceptible to noise from gas column vibration, leading to inaccurate knock determination due to varying median values and dynamic range issues, making it difficult to set a reliable threshold for each cylinder.
Innovation Solution
A knock determination apparatus that separates noise and knock components using integrated intensity, correcting the knock determination threshold value to match target integrated intensity across cylinders, thereby stabilizing knock levels and reducing adaptation steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in-cylinder pressure sensor output signals are used for knock determination, then knock detection capability is achieved, but measurement precision deteriorates due to noise from gas column vibration and electric noise
Solution Approach 1:
The frequency spectrum is segmented into multiple frequency bands, with different bands assigned to different cylinders. This segmentation allows each cylinder's knock determination to focus on its specific frequency range, effectively separating knock signals from gas column vibration noise that occurs at different frequencies for each cylinder.
Solution Approach 2:
Each cylinder is assigned a specific frequency band tailored to its characteristics, creating local quality differences in the frequency domain. This allows the system to optimize knock detection for each cylinder individually while suppressing cylinder-specific noise components through frequency-selective analysis.
2Adaptability or versatility
If relative knock determination threshold values are used, then adaptability to different operating conditions is improved, but measurement precision deteriorates due to variation of median values among cylinders
Solution Approach 1:
The system changes the parameter basis for threshold determination from relative values (based on median intensity) to absolute values (based on integrated intensity across specific frequency bands). This parameter change allows establishment of consistent absolute threshold values that work across all cylinders and operating conditions, eliminating the variation problem inherent in relative threshold approaches.
3Device complexity
If in-cylinder pressure sensor is used instead of knock sensor, then device complexity is reduced, but measurement precision deteriorates due to smaller dynamic range and higher noise susceptibility
Solution Approach 1:
The system transitions from time-domain analysis to frequency-domain analysis, adding a dimensional transformation to the signal processing approach. By analyzing signals in the frequency domain and assigning specific frequency bands to different cylinders, the system can extract knock signals while suppressing noise, thereby improving measurement precision without changing the sensor type.
Data Source
Figure 1
Figure 2
Figure 3~4B
AI summary
A knock determination apparatus for an internal combustion engine (10) calculates a knock intensity based on an output signal of an in-cylinder pressure sensor (26) in a gate range for knock determination. When the calculated knock intensity is larger than a knock determination threshold value, the knock determination apparatus determines that knock has occurred. Further, the knock determination apparatus calculates an integrated intensity which is an integrated value of knock intensities that are equal to or larger than a knock intensity at a point of 97% or more in a target knock level among knock intensities that are calculated at the respective cycles during continuous N cycles in the same cylinder. Furthermore, the knock determination apparatus corrects a knock determination threshold value so that the difference between the calculated integrated intensity and a target integrated intensity becomes small.