Engine Misfire Detection Using Filtered Crank Acceleration
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Solution Overview
Problem
Existing methods for detecting engine misfire events in vehicles, particularly in plug-in hybrid electric vehicles (PHEVs) lacking torque converters or using locked torque converter clutches, struggle to accurately detect misfires due to resonance effects and high combustion variation, leading to performance and reliability issues.
Innovation Solution
A method utilizing a high pass filter to mitigate resonance and combustion randomness effects, calculating root mean square (RMS) engine acceleration based on filtered acceleration, and implementing corrective actions upon detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing detection methods are used in PHEVs lacking torque converters or using locked torque converter clutches, then the detection system is simpler, but misfire detection accuracy deteriorates due to resonance effects and high combustion variation
Solution Approach 1:
A filter is introduced as an intermediary component between the acceleration signal and misfire detection. The filter processes the raw acceleration signal to remove resonance effects and combustion variation noise, enabling accurate misfire detection in PHEVs without complex hardware modifications.
Solution Approach 2:
The patent changes the parameter of acceleration signal processing by applying filtering operations. This transforms the raw acceleration signal into a filtered signal that highlights misfire characteristics while suppressing unwanted resonance and combustion variation effects.
2Measurement precision
If filtering is applied to mitigate resonance and combustion randomness effects, then misfire detection accuracy is improved, but computational complexity increases
Solution Approach 1:
The filter serves as a computational intermediary that performs the complex task of signal processing. By implementing the filter in software or firmware, the system achieves accurate misfire detection without adding complex hardware, thereby managing computational complexity effectively.
Solution Approach 2:
The patent replaces mechanical solutions (such as torque converters) with a computational/filtering approach. Instead of using mechanical components to physically isolate resonance, the system uses digital filtering to achieve the same effect computationally.
3Reliability
If resonance effects and combustion variation are present, then the detection system is simpler, but misfire detection reliability deteriorates
Solution Approach 1:
The filter acts as a mediator that separates the useful misfire signal from unwanted resonance and combustion variation. This intermediary processing step ensures reliable misfire detection by systematically removing interfering signals before the detection decision is made.
Solution Approach 2:
The filtering process changes the signal parameters by selectively attenuating frequency components associated with resonance and combustion variation while preserving misfire-related components. This parameter transformation improves detection reliability without requiring complex hardware modifications.
Data Source
AI summary
Examples described herein provide a method that includes calculating an engine speed based at least in part on a crank sensor signal received from a crank sensor of the engine at periodic intervals defined by a crank rotation. The method further includes calculating an engine acceleration based at least in part on the engine speed. The method further includes generating, using a filter, a filtered engine acceleration for the periodic intervals based at least in part on the engine acceleration. The method further includes calculating a root mean square (RMS) engine acceleration based at least in part on the filtered engine acceleration for the periodic intervals. The method further includes detecting an engine misfire event based at least in part on the RMS engine acceleration. The method further includes implementing a corrective action for the vehicle in response to detecting the engine misfire event.