Knocking Detection Threshold Adjustment for Miller Cycle Engines
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Solution Overview
Problem
Internal combustion engines face challenges in reliably detecting knocking due to interference from external or control signals, leading to potential engine damage and inefficiencies, especially when operating in the Miller cycle with variable inlet valve closure times.
Innovation Solution
The method involves using a knocking sensor to evaluate sensor signals within a shorter measurement time window, adjusting the threshold value with a variable interference factor based on the relative inlet valve closure time, and employing adaptive mechanisms to filter out external noise, ensuring accurate and robust knocking identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If knocking sensors are used to detect acoustic signals caused by knocking, then knocking detection capability is improved, but false detection increases due to external or control signals from other sources
Solution Approach 1:
The measurement process is segmented into specific crank angle intervals (e.g., 10° to 40° after top dead center) where knocking is most likely to occur. By dividing the measurement window and applying different evaluation criteria to different segments, the system can distinguish knocking signals from interference signals that occur at different times in the engine cycle.
Solution Approach 2:
Different evaluation thresholds and criteria are applied to different crank angle intervals based on the local characteristics of knocking versus interference signals. The system adjusts the measurement sensitivity locally in time and cylinder space, using cylinder-specific reference values and adaptive thresholds that account for the specific operating conditions and interference patterns of each cylinder.
2Object-affected harmful factors
If inlet valve closure is advanced in Miller cycle operation, then knocking is reduced through lower charge temperature, but interference with knocking detection increases due to valve closure occurring within the measurement window
Solution Approach 1:
The system performs preliminary identification of inlet valve closure timing relative to the measurement window before evaluating knocking signals. By anticipating when valve closure interference will occur based on the configured valve timing, the system can pre-adjust the evaluation strategy, such as excluding contaminated time intervals or adapting thresholds, to maintain accurate knocking detection despite the known interference.
Solution Approach 2:
The measurement and evaluation parameters are made dynamic and adaptive rather than fixed. The system continuously adjusts measurement windows, thresholds, and evaluation criteria based on real-time operating conditions including variable valve timing positions, engine load, and speed. This dynamic adaptation allows the system to maintain detection accuracy across varying Miller cycle configurations where valve closure timing changes.
3Reliability
If adaptive mechanisms are used to filter external noise, then false positives are reduced, but system complexity increases
Solution Approach 1:
The system performs self-calibration by automatically learning and adapting to its specific operating environment. Through continuous operation, the adaptive mechanisms automatically identify patterns of interference signals versus genuine knocking signals based on the specific engine characteristics, sensor locations, and operating conditions. This self-learning capability reduces false positives without requiring complex manual configuration or external calibration equipment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively filters out external noise, reduces false positives and negatives, and maintains reliable knocking identification even with variable inlet valve closure times, preventing engine damage and inefficiencies.
Implementation Method 1
detect acoustic signals caused by knocking
Implementation Method 2
by actuating the inlet valves assigned to the cylinder identified as knocking the temperature of the charge of this cylinder is lowered
Data Source
AI summary
A method and control device for automatically identifying knocking in an internal combustion engine, wherein, in a predefined measurement time frame, a signal of the knocking sensor is received and evaluated with respect to a criterion for detecting knocking. A basic threshold value predefined for the identification of knocking is modified by a predefined variable interference factor, which depends on a relative point in time at which an inlet valve of at least one of the cylinders closes in relation to a predefined reference point. A signal based on the sensor signal is only identified as knocking if it reaches at least the modified basic threshold value.