Air Flow Rate Meter Pulsation Error Correction
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Solution Overview
Problem
Conventional air flow rate meters struggle to accurately correct pulsation errors in distorted waveforms with harmonics, as they rely on maximum and minimum values that do not account for the changing harmonic components of engine pulsation waveforms, leading to inadequate signal correction.
Innovation Solution
An air flow rate meter that detects when the output signal from the flow rate detection element exceeds a predetermined threshold, generates a pulse signal, and corrects the output signal using this pulse signal to address the pulsation error, effectively processing the distorted waveform including harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output signal is clamped based on maximum and minimum values, then the pulsation error is reduced for simple waveforms, but the measurement precision deteriorates for distorted waveforms with harmonics
Solution Approach 1:
The patent applies dynamics by transitioning from a static clamping method (fixed clamp values based on max/min) to a dynamic correction method where the correction amount is continuously adjusted based on the instantaneous output signal value. The correction amount is determined as a function of the output signal, allowing the system to adapt to changing waveform characteristics including harmonics, thereby maintaining measurement precision across different operating conditions.
2Device complexity
If a fixed clamp value is used for signal correction, then the device complexity is reduced, but the measurement precision deteriorates when harmonic components change
Solution Approach 1:
The patent applies parameter changes by making the correction amount a variable parameter that depends on the output signal value rather than using a fixed clamp value. The correction amount is determined as a function of the output signal, allowing it to change dynamically according to the waveform characteristics. This enables accurate correction of distorted waveforms with varying harmonic components while maintaining reasonable circuit complexity through functional dependency.
3Ease of operation
If maximum and minimum values are used to determine clamp values, then the ease of operation is improved, but the measurement precision deteriorates for waveforms with changing harmonic components
Solution Approach 1:
The patent applies feedback by using the output signal itself to determine the correction amount. The correction circuit continuously monitors the output signal value and adjusts the correction amount accordingly, creating a feedback mechanism that adapts to changing waveform characteristics. This feedback approach maintains measurement precision for distorted waveforms while keeping the operation simple, as the system automatically adjusts based on the signal characteristics without requiring external intervention.
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 reduces pulsation errors by correcting the output signal based on the detected threshold, enabling the air flow rate meter to accurately measure waveforms with harmonics, improving measurement accuracy and handling the physical phenomena occurring in the flow rate detection element.
Implementation Method 1
a heating element (8) that heats the air flow
Implementation Method 2
temperature sensors (7, 9) arranged on the upstream side and the downstream side of the heating element (8), respectively, in a flow rate detection element (1) that measures an air flow rate
Data Source
AI summary
An air flow rate meter includes a signal detector and a pulse generator. The signal detector is configured to detect that an output signal from the air flow rate detection element has passed a predetermined threshold. The pulse generator generates a pulse signal by using an output signal from the signal detector as a trigger. An output signal from the air flow rate detection element is corrected based on an output of the pulse generator.