Air Flow Meter Pulsation Correction via AC Signal Rectification
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Solution Overview
Problem
Air flow meters face challenges in measuring air flow rates with high accuracy in environments where air pulsation is increased, particularly in internal combustion engine vehicles with reduced cylinders and enhanced exhaust gas recirculation systems.
Innovation Solution
An air flow meter design that includes a flow rate detection element in a sub-passage, a calculation unit, a signal extraction unit, a first correction unit that outputs a correction amount based on the half-wave rectified AC component, and a coupling unit that subtracts this correction amount from the output signal to improve measurement accuracy during increased pulsation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional flow rate measurement device is used in an intake passage, then it can measure air flow rate under normal conditions, but measurement accuracy deteriorates when air pulsation increases due to EGR and reduced cylinder configurations
Solution Approach 1:
The invention extracts the AC component representing air pulsation from the output signal and uses half-wave rectification to generate a correction amount that converts the harmful pulsation effect into a useful correction value. This correction amount is then subtracted from the original output signal to eliminate measurement errors caused by pulsation, thereby improving measurement accuracy in high pulsation environments
Solution Approach 2:
The invention implements a feedback mechanism where the AC component extracted from the output signal is processed through half-wave rectification to generate a correction amount. This correction amount is fed back to adjust the original measurement signal, creating a closed-loop system that continuously compensates for pulsation-induced measurement errors and maintains high accuracy under varying pulsation conditions
Data Source
AI summary
The present disclosure provides an air flow meter capable of measuring a flow rate of air in a main passage with high accuracy even in an environment where pulsation of air in the main passage increases. The air flow meter includes a flow rate detection element, a calculation unit 121, a signal extraction unit 122, a first correction unit 123, and a coupling unit 124c. The flow rate detection element is installed in a sub-passage that takes air from the main passage and returns the air to the main passage, and outputs a detection signal DS corresponding to a flow rate of the air flowing through the sub-passage. The calculation unit 121 generates a detected flow rate Qo as an output signal corresponding to the flow rate of the air flowing through the main passage based on the detection signal DS. The signal extraction unit 122 extracts an AC component Qhpf of the detected flow rate Qo which is an output signal. The first correction unit 123 outputs a first correction amount Q1 that corresponds to a half-wave rectified wave of the AC component Qhpf and increases according to an increase in a pulsation amplitude ratio of the AC component Qhpf. The coupling unit 124c subtracts a correction amount CA based on the first correction amount Q1 from the detected flow rate Qo as the output signal.