Engine Misfire Detection via Frequency-Domain Noise Correction
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Solution Overview
Problem
Existing engine control systems face challenges in accurately detecting cylinder misfires due to the overlap of combustion and harmonic noise with the same frequency as the misfire signal, especially at high engine speeds, making it difficult to distinguish between noise and signal using standard digital filters.
Innovation Solution
A method and system that determine and apply specific combustion and harmonic noise correction factors based on current engine operating conditions to isolate and remove engine combustion and harmonic noise from sensor signals, allowing for effective misfire detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If standard digital filters are used to remove noise from misfire detection signal, then noise reduction is achieved, but the misfire signal is also removed because both noise and signal are at the same frequency
Solution Approach 1:
The patent segments the noise removal process into multiple frequency components using Fast Fourier Transform (FFT). Instead of treating the signal as a single frequency component, the method divides it into discrete frequency bins, allowing selective manipulation of specific frequency components. This segmentation enables the filter to target noise at specific frequencies without affecting the misfire signal at adjacent frequencies.
Solution Approach 2:
The patent applies local quality by creating a frequency-dependent filtering approach where different frequency components receive different treatment. The filter selectively attenuates noise frequencies while preserving signal frequencies based on their specific frequency characteristics. This localized frequency-domain processing allows the system to maintain signal integrity while removing noise.
2Power
If engine speed increases, then power output increases, but the amplitude of harmonic noise increases proportionally reducing signal-noise capability
Solution Approach 1:
The patent introduces the Fast Fourier Transform (FFT) as an intermediary that transforms the time-domain signal into the frequency domain. This transformation serves as a mediator that separates the mixed signal and noise components into distinct frequency bins, allowing the system to process and filter specific frequency components independently. The FFT intermediary enables the system to maintain signal-noise capability across varying engine speeds by providing a frequency-domain view that reveals the distinct spectral characteristics of signal and noise.
3Device complexity
If simple digital filters are used for noise removal, then device complexity is reduced, but the ability to distinguish signal from noise at the same frequency is lost
Solution Approach 1:
The patent transitions from time-domain filtering to frequency-domain filtering, adding a frequency dimension to the signal processing approach. By applying Fast Fourier Transform, the system converts the one-dimensional time signal into a two-dimensional representation (frequency vs. amplitude), enabling selective filtering based on frequency characteristics. This dimensional transformation provides the additional degree of freedom needed to distinguish and separate signal from noise that occupy the same time domain but have different frequency signatures.
Data Source
AI summary
A method and system for determining combustion and harmonic noise correction factors for current operating conditions corresponding to the actual vehicle and applying the combustion and harmonic noise correction factors to a sensor signal, thereby removing engine combustion and harmonic noise from the sensor signal and leaving a misfire data signal in the sensor signal.