EGR Flow Measurement Using Weighted Sensor Fusion
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Solution Overview
Problem
Existing exhaust gas recirculation systems face challenges in accurately measuring EGR flow rates, particularly at low flow rates, due to the limitations of venturi-type flow meters, which result in poor signal-to-noise ratios and inaccurate control of valves.
Innovation Solution
A method and system that utilize a venturi sensor for differential pressure measurements and an EGR valve position sensor to calculate EGR flow rates by determining a weighting factor based on the EGR valve effective area, combining position-based and pressure-based estimates to achieve accurate flow measurement across various flow regimes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a venturi sensor is used to measure EGR flow rate, then the measurement can be implemented with a simple structure, but the measurement precision deteriorates at low flow rates due to poor signal-to-noise ratio
Solution Approach 1:
The patent combines two different measurement approaches: position-based estimation (using EGR valve position sensor) and pressure-based estimation (using venturi differential pressure sensor). By merging these two methods and weighting their results based on operating conditions, the system achieves accurate measurement across both low and high flow rates while maintaining relatively simple device structure
Solution Approach 2:
The patent introduces an intermediary computational system that processes signals from both the position sensor and venturi sensor. This intermediary system calculates weighted combinations of both measurements, acting as a mediator that optimizes the overall measurement accuracy without requiring direct modification of the physical sensing elements
2Device complexity
If only position-based estimation is used to calculate EGR flow rate, then the system remains simple, but measurement precision is insufficient particularly at high flow rates
Solution Approach 1:
The patent implements a dynamic measurement system that adapts its measurement strategy based on operating conditions. The weighting factor dynamically adjusts the contribution of position-based versus pressure-based estimation depending on the EGR valve position and differential pressure readings, ensuring optimal accuracy across the full range of operating conditions
3Measurement precision
If only pressure-based measurement is used, then measurement can be obtained, but signal-to-noise ratio deteriorates at low flow rates leading to poor measurement precision
Solution Approach 1:
The patent applies beforehand cushioning by using position-based estimation to compensate for the poor signal-to-noise ratio of pressure-based measurement at low flow rates. The system proactively identifies low flow conditions and pre-adjusts the weighting to favor position-based estimation, cushioning against the measurement errors that would otherwise occur
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 enables precise control of EGR flow rates, improving engine efficiency and emission reduction by accurately measuring flow rates both at low and high flow conditions, overcoming the limitations of traditional venturi-type flow meters.
Implementation Method 1
a venturi sensor situated to take a differential pressure measurement relative to recirculated exhaust gas
Data Source
AI summary
A system and method for measuring an EGR flow rate for an engine having an EGR valve with a selectable EGR valve position and a venturi sensor situated to take a differential pressure measurement relative to recirculated exhaust gas includes determining an EGR valve effective area based on the EGR valve position, determining a weighting factor based on the effective area, calculating a first EGR flow estimate based on the effective area, and calculating a second EGR flow estimate based on the differential pressure measurement of the venturi sensor. A final EGR flow rate is determined based on the weighting factor, the first EGR flow estimate, and the second EGR flow estimate.