Low-Pass Filter Combustion Signal Processing for Engine Control
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Solution Overview
Problem
Existing devices for processing pressure-measurement signals in internal combustion engines to determine the instant of start of combustion are costly, time-consuming, and difficult to implement in traditional engine control computers.
Innovation Solution
A device that employs a low-pass filter to generate a filtered signal, subtracts it from the original signal to obtain a difference signal, and compares this difference signal with a predetermined threshold to determine the instant of start of combustion, using either digital or analog means for simple and reliable processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wavelet transformation is used to process the pressure-measurement signal, then the instant of start of combustion can be detected, but the computing time is considerable and the device is costly
Solution Approach 1:
The patent extracts only the essential feature needed for detection by comparing the pressure signal with a reference signal to generate a difference signal. Instead of applying complex wavelet transformation, it extracts the deviation from reference combustion characteristics, which is sufficient to detect the instant of start of combustion while avoiding excessive computing time
Solution Approach 2:
The patent replaces expensive complex processing (wavelet transformation) with simple, inexpensive operations (filtering and comparison). The solution uses basic digital signal processing functions that are computationally cheap and can be implemented in traditional engine control computers without requiring advanced processing power
2Measurement precision
If wavelet transformation is used to process the pressure-measurement signal, then the instant of start of combustion can be detected, but the device is difficult to install in traditional engine control computers
Solution Approach 1:
The patent substitutes complex mathematical transformation (wavelet analysis) with simpler signal processing operations (filtering and comparison). This replacement makes the system compatible with traditional engine control computers that have limited processing capabilities, while still achieving reliable detection of the combustion start instant
Solution Approach 2:
The patent changes the approach from frequency-domain analysis (wavelet transformation) to time-domain comparison (difference signal analysis). By working directly with the pressure signal in its original domain and comparing it with reference characteristics, the system achieves detection with simpler parameters and operations suitable for traditional control computers
3Adaptability or versatility
If the pass band of the low-pass filter is broadened, then a second instant of start of combustion can be detected, but the filter may allow more noise
Solution Approach 1:
The patent makes the filter characteristics dynamic by adjusting the pass band width based on the detected combustion event. After detecting the first instant of start of combustion, the system broadens the pass band to enable detection of a second combustion event. This dynamic adaptation allows the system to balance noise filtering with the ability to detect multiple combustion events
Solution Approach 2:
The system uses feedback from the detection process to adjust filter parameters. When a combustion event is detected, the system modifies the pass band of the low-pass filter to enable detection of subsequent events. This feedback mechanism allows the filter to adapt its characteristics based on the combustion state, enabling versatile detection while managing noise through controlled parameter adjustment
Data Source
AI summary
A device for processing a signal of pressure measurement of an internal combustion engine combustion chamber. The device obtains, by a low-pass filter of the pressure measuring signal, a filtered signal, subtracts the filtered signal from the pressure measuring signal to obtain a difference signal, compares the difference signal to a predetermined threshold value, and determines a combustion starting time as a time at which the difference signal reaches the predetermined threshold value.