Misfire Detection in Skip Fire Engines Using Dynamic Pressure Models
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Solution Overview
Problem
Existing misfire detection systems are not suited for dynamic skip fire engine control systems, as they rely on consistent crankshaft acceleration patterns, which are disrupted by the skipping and firing of cylinders, leading to inaccurate misfire detection.
Innovation Solution
A misfire detection system that uses a multi-cylinder pressure model to account for the skipping or firing of cylinders, measuring engine parameters like crankshaft angular acceleration and comparing them to expected changes to determine if a misfire has occurred, while also adjusting the model dynamically for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional misfire detection systems are used in skip fire engine control, then the system structure remains simple, but misfire detection accuracy deteriorates due to disrupted crankshaft acceleration patterns
Solution Approach 1:
The patent applies dynamics by making the detection system adaptive to changing engine operating conditions. The system dynamically adjusts detection parameters and thresholds based on real-time crankshaft acceleration data and skip fire patterns, allowing it to accurately detect misfires despite the variable and disrupted acceleration patterns inherent in skip fire operation.
Solution Approach 2:
The patent changes detection parameters dynamically based on operating conditions. Instead of using fixed thresholds, the system adjusts detection parameters according to the specific skip fire pattern being used and the current crankshaft acceleration profile, enabling accurate misfire detection across varying operational states.
2Measurement precision
If a multi-cylinder pressure model is used to account for dynamic skip fire operation, then misfire detection accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments the engine operation into discrete firing and skipping events for each cylinder. By analyzing crankshaft acceleration data in relation to specific cylinder firing patterns, the system creates a simplified model that accounts for skip fire operation without requiring complex multi-cylinder pressure calculations for all cylinders at all times.
Solution Approach 2:
The patent applies partial action by focusing computational resources on detecting misfires in currently active (firing) cylinders rather than continuously monitoring all cylinders. The system selectively applies the pressure model only when needed for firing cylinders, reducing overall computational complexity while maintaining detection accuracy.
3Adaptability or versatility
If dynamic adjustment of detection model is implemented, then detection accuracy under varying operating conditions improves, but processing time and computational load increase
Solution Approach 1:
The patent implements periodic updates of detection parameters rather than continuous adjustment. The system refreshes its model parameters at predetermined intervals or at specific trigger points in the engine cycle, balancing adaptability with computational efficiency by avoiding constant recalculation while still responding to major operating condition changes.
Data Source
AI summary
A variety of methods and arrangements for detecting misfire and other engine-related errors are described. In one aspect, a window is assigned to a target firing opportunity for a target working chamber. There is an attempt to fire a target working chamber during the target firing opportunity. A change in an engine parameter (e.g., crankshaft angular acceleration) is measured during the window. A model (e.g., a pressure model) is used to help determine an expected change in the engine parameter during the target firing opportunity. Based on a comparison of the expected change and the measured change in the engine parameter, a determination is made as to whether an engine error (e.g., misfire) has occurred.