Air Flow Sensor Sampling Timing for Fast Corrected A/D Conversion
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Solution Overview
Problem
Conventional air flow measurement systems in internal combustion engines struggle to accurately measure air flow direction and rate due to nonlinear input and output characteristics of analog-to-digital converters, leading to inefficiencies in sampling periods, especially under high-frequency pulsation conditions.
Innovation Solution
An air flow measurement apparatus that includes an air flow detector, a reference voltage generator, an analog multiplexer, and a signal processing unit, where the sampling timing of the air flow voltage signal is interposed between successive sampling timings of reference voltage signals, allowing for reduced sampling periods and improved accuracy by applying correction processing using temperature and reference voltage data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the A/D converter sequentially converts multiple analog voltage signals including reference voltages, then conversion error is reduced through correction processing, but the sampling period increases
Solution Approach 1:
The patent applies correction values to the TAD output data in advance to pre-compensate for conversion errors. By calculating correction values based on reference voltages and applying them beforehand, the system reduces the need for extensive sequential sampling and correction processing, thereby shortening the overall sampling period while maintaining high measurement precision.
2Measurement precision
If the sampling frequency is increased to follow high-frequency air flow pulsation, then measurement accuracy is improved, but the complexity of the signal processing system increases
Solution Approach 1:
The patent changes the parameters of the TAD (such as reference voltages Vmin, Vmax, Vc) to optimize its input-output characteristics. By adjusting these parameters and applying corresponding correction values, the system can accurately track high-frequency air flow pulsation without requiring excessively complex signal processing circuits, thus improving measurement accuracy while controlling system complexity.
3Measurement precision
If the TAD conversion characteristics are made linear through correction processing, then conversion error is reduced, but the number of processing steps increases
Solution Approach 1:
The patent extracts the correction function from the main signal processing path and implements it as a separate correction circuit that processes TAD output data. By taking out the correction processing as an independent module that applies pre-calculated correction values, the system achieves linear conversion characteristics without significantly increasing the number of processing steps in the main measurement path.
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
The apparatus effectively reduces sampling periods and enhances accuracy in measuring air flow, enabling the system to follow changes in air flow under high-frequency pulsation, thereby improving the precision of air flow measurement in internal combustion engines.
Implementation Method 1
heat of a heat generating element is dissipated by the air flow, and the air flow is measured by using the principle that there is a correlation between the amount of dissipated heat and the amount of the air flow
Implementation Method 2
A temperature control circuit controls the temperature of the heat generating element so that the temperature of the heat generating element can be greater than an intake air temperature by a predetermined value
Implementation Method 3
an air flow detector having an air flow sensor for detecting air flow through a passage; an analog-to-digital converter for converting an output signal of the air flow sensor into digital data
Data Source
AI summary
An air flow measurement apparatus includes an air flow sensor for outputting an air flow signal indicative of detected air flow, a reference voltage generator for outputting reference voltage signals, a multiplexer for sequentially selecting the signals in a predetermined order, an A/D converter for converting the signals into digital data in an order selected by the multiplexer, and a signal processing unit for applying correction processing to air flow voltage data corresponding to the air flow signal using reference voltage data corresponding to the reference voltage signals. The signal processing unit has a sampling timing setting section for determining sampling timings at which the A/D converter samples the signals in such a manner that the sampling timing at which the air flow signal is sampled is interposed between the sampling timings at which successive two of the reference voltage signals are sampled.