Air Flow Meter EMI Noise Mitigation via Estimated Range Validation
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Solution Overview
Problem
Existing air flow quantity measuring apparatuses for internal combustion engines are prone to sensing errors due to electromagnetic interference (EMI) noise, which affects the accuracy and reliability of air flow quantity measurements.
Innovation Solution
An air flow quantity measuring apparatus that includes an air flow meter, an air flow quantity sensing means, an air flow quantity estimating means, and an air flow quantity determining means. The air flow quantity determining means determines the measurement value based on whether the sensed value is within or out of an estimated air flow quantity range, mitigating the impact of EMI noise by using the estimated value as the measurement when the sensed value is outside the range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the ECU converts the pulse frequency signal into the air flow quantity directly, then the conversion time period is shortened, but the sensing accuracy deteriorates due to EMI noise overlap
Solution Approach 1:
The air flow quantity estimating means performs preliminary estimation of the air flow quantity range based on engine operational state before the final determination. This preliminary action allows the system to prepare expected value ranges in advance, enabling rapid comparison and decision-making when EMI noise is detected, thus maintaining both fast conversion and accurate sensing.
Solution Approach 2:
The system implements feedback by comparing the sensed air flow quantity against the estimated range and adjusting the measurement value accordingly. When EMI noise causes the sensed value to fall outside the estimated range, the system feedbacks by using the estimated value instead, creating a self-correcting mechanism that maintains accuracy while preserving conversion speed.
2Speed
If the ECU uses the sensed value directly as the measurement value, then the response speed is improved, but the reliability deteriorates due to EMI noise interference
Solution Approach 1:
The system performs preliminary estimation of the air flow quantity range based on engine operational state before final measurement determination. This allows the system to have pre-computed reference ranges ready for immediate comparison, enabling fast response while maintaining reliability through preliminary validation.
Solution Approach 2:
The estimated air flow quantity range acts as an intermediary between the raw sensed value and the final measurement value. This intermediary layer filters out EMI noise by comparing sensed values against expected ranges, allowing the system to maintain fast response speeds while ensuring reliability through intermediate validation.
3Reliability
If the system adds an air flow quantity estimating means to detect EMI noise, then the measurement reliability is improved, but the device complexity increases
Solution Approach 1:
The air flow quantity estimating means serves multiple functions: it estimates air flow quantity for normal operation, detects EMI noise by comparing sensed values against estimated ranges, and provides fallback values when noise is detected. This multi-functionality allows a single component to improve reliability without proportionally increasing complexity.
Solution Approach 2:
The system changes parameters dynamically by adjusting which value (sensed or estimated) is used as the measurement value based on the comparison between sensed air flow quantity and estimated range. This parameter switching approach improves reliability while maintaining relatively simple system architecture through logical rather than physical complexity.
Data Source
AI summary
A flow meter outputs a frequency signal, which corresponds to an air flow quantity of intake air to be supplied to an engine. In an engine control unit, when a sensed value of the air flow quantity, which is obtained based on the frequency signal, is within an estimated air flow quantity range, which is estimated based on an operational state of the engine, the sensed value of the air flow quantity is determined as a measurement value of the flow meter. In contrast, when the sensed value of the air flow quantity is out of the estimated air flow quantity range, a median of the estimated air flow quantity range is determined as the measurement value of the flow meter.