EGR Flow Rate Estimation via Valve Area Learning
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Solution Overview
Problem
Existing internal combustion engine control systems face challenges in accurately estimating the EGR flow rate due to changes in EGR valve opening degree characteristics over time and variations in engine conditions, especially when EGR and intake/exhaust VVT are concurrently controlled, leading to reduced accuracy in air flow rate calculations.
Innovation Solution
An internal combustion engine EGR flow rate estimation apparatus that includes units for calculating intake air flow rate, volume efficiency correction, internal EGR ratio, desired EGR ratios, and EGR effective opening area, with an EGR valve opening degree calculation unit that learns the relationship between EGR valve opening degree and effective opening area to maintain accurate control, allowing collaboration between EGR valve and intake/exhaust VVT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional EGR flow rate calculation methods are used, then the system is simple to operate, but the EGR flow rate estimation accuracy deteriorates over time due to changes in EGR valve opening degree characteristics
Solution Approach 1:
The patent implements a feedback mechanism where the EGR flow rate calculation unit continuously calculates the EGR flow rate based on intake air flow rate and internal EGR ratio, and this calculated value is fed back to update the control strategy. The feedback loop allows the system to adapt to changes in EGR valve characteristics over time, maintaining accuracy without requiring complex hardware modifications.
Solution Approach 2:
The system uses its own operational data (intake air flow rate, valve timing control information) to self-correct and maintain accurate EGR flow rate estimation. The EGR flow rate calculation unit leverages existing sensor data and control parameters to continuously refine the EGR flow rate calculation, eliminating the need for additional dedicated sensors or complex external calibration systems.
2Productivity
If EGR and intake/exhaust VVT are concurrently controlled, then engine performance is improved, but the accuracy of air flow rate calculations deteriorates due to variations in engine conditions
Solution Approach 1:
The patent accounts for parameter changes by dynamically adjusting the volume efficiency correction coefficient based on valve timing control information. As the intake and exhaust valve timing parameters change during concurrent EGR and VVT control, the system updates the correction coefficient to reflect these changes, thereby maintaining accurate air flow rate calculations despite the varying engine conditions.
Solution Approach 2:
The system transitions from static to dynamic control by continuously updating the volume efficiency correction coefficient based on real-time valve timing control information. This dynamic approach allows the system to adapt to the changing engine conditions caused by concurrent EGR and VVT control, maintaining measurement accuracy throughout the operating range.
3Speed
If preliminary flow rate characteristics are provided for EGR valve control, then control response is fast, but the characteristics become inaccurate due to changes over time and individual unevenness
Solution Approach 1:
The system performs preliminary calculations by establishing the relationship between intake air flow rate, internal EGR ratio, and EGR flow rate in advance. These preliminary flow rate characteristics are stored and used as the basis for rapid control response. When control actions are needed, the system quickly retrieves and applies these pre-calculated characteristics without requiring complex real-time computations.
Solution Approach 2:
The system adapts the preliminary flow rate characteristics by applying corrections based on actual operating conditions. The EGR flow rate calculation unit adjusts the preliminary characteristics using real-time parameters such as intake air flow rate and internal EGR ratio, ensuring that the control remains both fast and accurate despite changes over time or individual unevenness in the EGR valve.
Data Source
AI summary
Based on an internal EGR ratio and desired external and internal EGR ratios, an EGR valve opening degree is feedback-controlled based on a desired EGR ratio, calculated in such a way as to perform correction so that a total EGR ratio becomes constant, and an EGR effective opening area obtained through learning of the relationship between an EGR valve opening degree and an effective opening area; thus, a correct characteristic of EGR valve opening degree vs. effective opening area can be maintained and hence it is made possible to absorb variations, changes with time, and even environmental conditions, while making an EGR valve and an intake/exhaust VVT collaborate with each other; therefore, an EGR flow rate can accurately be estimated.