Knocking Detection Using Pressure-Windowed Frequency Analysis
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Solution Overview
Problem
Existing knocking detection methods in internal combustion engines fail to accurately select the time range for setting the knocking and reference time windows, leading to inaccurate detection of knocking occurrence, which affects the control of ignition timing and engine efficiency.
Innovation Solution
A method that sets specific time windows based on the maximum inner pressure time in a combustion cycle, transforming oscillation waveforms into frequency domain expressions, and calculating representative values to determine knocking occurrence, ensuring accurate correlation between knocking and non-knocking periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the knocking time window is set to match the combustion period of the combustion chamber, then the detection range covers the entire combustion process, but the detection accuracy decreases because the time window includes periods with minimum knocking risk
Solution Approach 1:
The patent divides the combustion period into multiple time windows based on inner pressure characteristics. Specifically, it identifies the maximum inner pressure time point and creates distinct time windows: a first time window from ignition timing to maximum inner pressure time, and a second time window from maximum inner pressure time to a predetermined time thereafter. This segmentation allows selective analysis of high-risk periods, improving detection accuracy while reducing unnecessary monitoring of low-risk periods.
2Quantity of substance
If the reference time window is set to include the non-combustion period, then the window captures periods without knocking, but the detection accuracy decreases because it includes periods with minimum knocking risk that do not represent true baseline conditions
Solution Approach 1:
The patent applies local quality by selecting reference time windows with specific characteristics - they are set to periods within the combustion cycle that have minimum knocking risk but still represent active combustion conditions. The reference time window is determined based on inner pressure characteristics to ensure it captures representative baseline combustion data without including high-risk knocking periods, thus providing a more accurate reference for comparison.
3Productivity
If earlier ignition timing is used to improve engine efficiency, then the thermal efficiency increases, but the knocking frequency increases due to abnormal combustion in the combustion chamber
Solution Approach 1:
The patent implements feedback control by continuously monitoring inner pressure during combustion, detecting knocking occurrences, and using this information to adjust ignition timing. The system calculates knocking indices based on comparisons between actual combustion data and reference data, then feeds this information back to control the ignition timing, dynamically optimizing the balance between efficiency and knocking prevention based on real-time combustion conditions.
Data Source
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Figure 3A~3B
AI summary
A knocking detection method includes: a step of obtaining an oscillation waveform generated by combustion in the combustion chamber; a step of setting a first time window preceding a maximum inner pressure time at which an inner pressure of the combustion chamber is at maximum in a single combustion cycle and a second time window immediately after the maximum inner pressure time, and transforming each of a first waveform portion included in the first time window and a second waveform portion included in the second time window into an expression-domain expression, of the oscillation waveform; and a step of extracting a first peak at which amplitude of the frequency domain expression of the first waveform portion is at maximum in the first frequency windows and a second value at which the amplitude of the frequency domain region of the second waveform portion is at maximum in the second frequency window and determining whether knocking has occurred on the basis of the second peak value and the first peak value.