Rough Road Detection via Frequency Domain Signal Normalization
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Solution Overview
Problem
Existing engine misfire detection systems often generate false alerts due to rough road conditions, which can mimic the engine speed changes caused by actual misfires, leading to unnecessary system adjustments.
Innovation Solution
A rough road detection system that includes an engine speed module, feature space module, normalization module, and rough road module, which generates a normalized signal based on engine speed and frequency domain analysis to determine if a rough road condition exists, thereby disabling the engine misfire detection system when necessary to prevent false alerts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If misfire detection systems rely on changes in engine speed to detect engine misfire events, then misfire detection capability is improved, but false misfire events are generated due to rough roads
Solution Approach 1:
The patent segments the engine speed signal into multiple frequency components using spectral analysis. By dividing the signal into distinct frequency bands and analyzing each component separately, the system can identify the specific frequency signature of misfire events while filtering out rough road disturbances that occur at different frequencies.
Solution Approach 2:
The patent transitions from analyzing engine speed in the time domain to analyzing it in the frequency domain. This dimensional change allows the system to distinguish between misfire events and rough road conditions by examining the spectral characteristics and frequency distribution of speed variations, enabling more accurate detection.
2Reliability
If misfire detection system is disabled when rough roads are detected, then false misfire events are reduced, but misfire detection capability is lost
Solution Approach 1:
The patent changes the detection parameters by using frequency domain analysis instead of simple time domain speed changes. By monitoring specific frequency components and their characteristics, the system can maintain high detection sensitivity while being immune to rough road conditions that produce different frequency signatures.
Solution Approach 2:
The patent introduces frequency domain transformation as an intermediary step between raw engine speed measurement and misfire detection. This intermediary analysis layer extracts meaningful features from the speed signal while filtering out noise from rough roads, enabling continuous operation without disabling the detection system.
3Measurement precision
If normalization value is varied in accordance with engine speed signal, then detection accuracy under different operating conditions is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamic normalization where the normalization value changes based on the current engine operating conditions and speed. This dynamic adjustment allows the detection thresholds and parameters to adapt to different operational states, maintaining high accuracy across varying conditions without requiring multiple fixed detection systems.
Data Source
AI summary
A rough road detection system includes an engine speed module, a feature space module, a normalization module, and a rough road module. The engine speed module generates an engine speed signal based on a crank signal. The feature space module generates a feature space signal based on the engine speed signal. The normalization module generates a normalized signal. The normalized signal is based on the feature space signal and a normalization value that varies in accordance with the engine speed signal. The rough road module determines whether a rough road condition exists based on the normalized signal.