Flow Measuring Device Pulsation Error Correction
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Solution Overview
Problem
Thermal flowmeters experience measurement accuracy issues due to pulsation errors in air flow rate measurements, particularly at low rotation speeds or heavy engine loads, leading to inaccuracies in fuel injection control.
Innovation Solution
A system that processes the sensed flow rate signal to calculate a correction amount for pulsation errors, which is then added or subtracted from the original signal to correct for pulsation errors, thereby improving measurement accuracy without altering the sensor's basic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermal flowmeter is used to measure air flow rate, then the flow rate can be directly sensed, but measurement accuracy deteriorates due to pulsation errors
Solution Approach 1:
A correction value calculation unit is introduced as an intermediary component that processes the raw flow rate signal, calculates pulsation correction values based on the nonlinear relationship between flow rate and sensor output, and applies corrections to eliminate pulsation errors. This mediator resolves the contradiction by adding a signal processing layer that compensates for the thermal flowmeter's inherent measurement inaccuracies under pulsating flow conditions.
2Measurement precision
If the sensor output voltage is directly used without correction, then the measurement system remains simple, but measurement accuracy decreases due to pulsation errors
Solution Approach 1:
The system performs preliminary calculation of pulsation correction values based on pre-established nonlinear characteristic data before the final measurement output is generated. By pre-calculating correction values using stored master characteristic curves and applying them to raw sensor signals, the system improves measurement accuracy without requiring complex real-time processing, thus resolving the contradiction between measurement precision and device complexity.
3Measurement precision
If a variable filter is used to reduce pulsation error, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The invention replaces complex mechanical or electronic variable filtering systems with a computational correction approach. Instead of using physical filters to remove pulsation components, the system uses digital signal processing to calculate and apply correction values based on the known nonlinear characteristics of the thermal flowmeter. This substitution resolves the contradiction by achieving pulsation error reduction through software-based correction rather than hardware-based filtering.
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 reduces measurement errors caused by pulsation without deteriorating the sensor's output characteristics, allowing for more accurate air flow rate measurements and improved fuel efficiency in internal combustion engines.
Implementation Method 1
a system of measuring an air flow rate by converting a heating current flowing through the heat resistive element into a voltage, wherein the heating current is controlled so as to maintain a constant temperature difference between a temperature of the heat resistive element whose heat is taken away in accordance with the air flow rate and a temperature of air to be measured as flow rate
Implementation Method 2
a system of measuring an air flow rate by converting a heating current flowing through the heat resistive element into a voltage, wherein the heating current is controlled so as to maintain a constant temperature difference between a temperature of the heat resistive element whose heat is taken away in accordance with the air flow rate and a temperature of air to be measured as flow rate
Data Source
Figure 1~2
Figure 3~4b
Figure 5a~6b
AI summary
The invention relates to a flow measuring device (4) which has a sensor element (11) for outputting a nonlinear signal according to a flow rate. The device (4) comprises: a first signal processing system for obtaining a first signal by filtering the nonlinear signal output from the sensor element (11), thereafter correcting a sensitivity of the filtered signal; a second signal processing system for obtaining a second signal by linearizing the nonlinear signal from the sensor element (11), thereafter filtering the linearized signal and correcting a sensitivity of the filtered signal, and then nonlinearizing the linearized signal with a corrected sensitivity; an amplifier for amplifying a differential signal between the first and second signals; and a correcting section for correcting the nonlinear signal by using the amplified differential signal.