Engine Misfire Detection via Spectral Analysis and Cylinder Pressure
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Solution Overview
Problem
Current techniques for misfire and air-fuel ratio (AFR) imbalance detection in internal combustion engines face limitations due to variable valve actuation, combustion phasing variations, and cylinder deactivations, leading to power drops, reduced fuel efficiency, and higher emissions.
Innovation Solution
A system and method using spectral analysis of multi-harmonics, including sliding discrete Fourier transform (SDFT), finite impulse response (FIR) filter, and Kalman filter, to diagnose misfire and AFR imbalance conditions, with complex modulation shifting harmonics to DC for reduced computational and memory usage, enabling fast and accurate diagnosis across all possible cylinder combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection techniques are used, then misfire and AFR imbalance can be detected, but detection accuracy is reduced due to variable valve actuation, combustion phasing variations, and cylinder deactivations
Solution Approach 1:
The patent applies dynamics by making the detection system adaptable to varying engine operating conditions through real-time analysis of cylinder pressure traces. The system dynamically adjusts to variable valve actuation and cylinder deactivation by continuously monitoring and analyzing pressure variations during different engine modes, enabling accurate misfire and AFR imbalance detection across all operating conditions.
Solution Approach 2:
The patent changes the detection parameters by analyzing multiple features of cylinder pressure traces including peak pressure, pressure rise rate, and integrated area under the curve. By monitoring multiple parameters simultaneously and comparing them across cylinders, the system can distinguish between normal variations due to valve actuation or cylinder deactivation and actual misfire or AFR imbalance conditions.
2Reliability
If comprehensive diagnosis of all cylinder combinations is performed, then complete misfire and AFR imbalance detection is achieved, but computational complexity and processing time increase
Solution Approach 1:
The patent segments the diagnosis process into distinct analytical steps: first extracting individual cylinder pressure traces, then calculating key parameters for each cylinder, comparing parameters across cylinders, and finally determining misfire or AFR imbalance conditions. This segmentation allows comprehensive diagnosis of all cylinder combinations while managing computational complexity through systematic breakdown of the analysis process.
Solution Approach 2:
The patent applies partial action by focusing analysis on specific diagnostic parameters most indicative of misfire and AFR imbalance rather than analyzing all possible pressure trace features. By selecting and analyzing only the most relevant parameters (peak pressure, pressure rise rate, integrated area), the system achieves reliable detection without excessive computational burden.
3Measurement precision
If standard DFT analysis is used, then spectral analysis can be performed, but spectral leakage occurs reducing measurement accuracy
Solution Approach 1:
The patent applies preliminary action by applying a window function to the cylinder pressure trace data before performing Fast Fourier Transform analysis. This preprocessing step reduces spectral leakage by tapering the signal at the boundaries, thereby improving the accuracy of spectral analysis for detecting misfire and AFR imbalance conditions without requiring changes to the fundamental DFT methodology.
Data Source
AI summary
A system for detecting and controlling misfire and/or AFR imbalance conditions in cylinders of an internal combustion engine having a plurality of cylinders is disclosed.