Virtual NOx Sensor for Dynamic EGR Control
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Solution Overview
Problem
Existing exhaust-gas recirculation systems in diesel engines face challenges in accurately measuring and regulating nitrogen oxide (NOx) emissions under dynamic operating conditions, as NOx sensors provide time-delayed signals, making real-time control difficult.
Innovation Solution
A method that incorporates a virtual NOx sensor for adaptive control, using a combination of control means to simulate and adjust the exhaust-gas recirculation system, allowing for faster and more precise control of NOx values by integrating a NOx model, particulate model, and PID regulator, with the option to revert to real sensor data for calibration and learning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a real NOx sensor is used for control, then measurement of nitrogen oxide emissions is possible, but the control response is delayed due to sensor signal lag
Solution Approach 1:
The virtual NOx sensor calculates and provides preliminary NOx values based on engine operating parameters before the real sensor can deliver its delayed signal. This preliminary action enables the control system to react immediately to changing conditions while the real sensor data becomes available for validation and adaptation.
Solution Approach 2:
The virtual NOx sensor acts as an intermediary between the engine control system and the delayed real NOx sensor. It bridges the time gap by providing estimated NOx values calculated from engine parameters, allowing continuous control while the real sensor signal is delayed.
2Object-generated harmful factors
If exhaust gas recirculation rate is increased to reduce NOx emissions, then nitrogen oxide emissions decrease, but charge air temperature and charge pressure are affected
Solution Approach 1:
The system dynamically adjusts the exhaust gas recirculation rate based on real-time virtual NOx sensor readings and adaptation from the real NOx sensor, rather than using fixed recirculation rates. This dynamic control allows optimization of NOx reduction while managing charge air temperature and pressure effects.
Solution Approach 2:
The control system uses feedback from both the virtual NOx sensor (for immediate response) and the real NOx sensor (for adaptation) to continuously adjust the exhaust gas recirculation rate. This feedback mechanism enables the system to reduce NOx emissions while compensating for temperature and pressure changes in real-time.
3Measurement precision
If control is based on real NOx sensor signal, then direct measurement of nitrogen oxide is possible, but the time-delayed signal cannot indicate current nitrogen oxide value under dynamic conditions
Solution Approach 1:
The virtual NOx sensor performs preliminary calculations of NOx values based on engine operating parameters, providing immediate control information before the real sensor signal arrives. This preliminary action maintains high control speed under dynamic conditions while preserving the advantage of direct measurement through the real sensor for adaptation.
Solution Approach 2:
The virtual NOx sensor serves as an intermediary that provides current NOx value estimates to the control system, bridging the delay between actual NOx formation and the real sensor's delayed signal. This intermediary enables fast control response while the real sensor provides accurate measurement data for system adaptation.
Data Source
AI summary
The present invention relates to a method for adjusting a mass flow of an exhaust gas return of an internal combustion engine, taking into consideration a NOx behavior, wherein a controlling system provides a coupling of a virtual NOx determination with a real NOx control. Furthermore, an internal combustion engine with appropriate controlling means is proposed.