NOx Sensor Sensitivity Adjustment via Dual-Sensor Comparison
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Solution Overview
Problem
Existing methods for determining nitrogen oxide content in internal combustion engine exhaust gases are limited by sensitivity tolerances and cross-sensitivities of nitrogen oxide sensors, leading to inaccurate NOx concentration measurements.
Innovation Solution
A method involving the simultaneous comparison and adjustment of signals from two nitrogen oxide sensors, one upstream and one downstream of a nitrogen oxide reduction catalytic converter, to compensate for sensitivity tolerances and cross-sensitivities, ensuring both sensors have similar sensitivity to NO and NO2, and are calibrated during specific conditions to minimize the influence of hydrocarbons and ammonia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensitivity adjustment is performed based on comparison of two nitrogen oxide sensors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control device receives signals from both nitrogen oxide sensors, compares their outputs, and automatically adjusts the sensitivity of one sensor based on the comparison result. This closed-loop feedback mechanism eliminates manual calibration needs and compensates for manufacturing tolerances, thereby improving measurement precision while automating the complexity management
Solution Approach 2:
The invention uses a second nitrogen oxide sensor as a reference copy to calibrate the first sensor. By comparing the outputs of two identical sensor types and adjusting one based on the other, the system achieves mutual calibration without requiring external reference instruments, simplifying the overall calibration process while maintaining high precision
2Difficulty of detecting and measuring
If nitrogen oxide sensors are used to measure exhaust gas composition, then detection capability is improved, but cross-sensitivity to hydrocarbons and ammonia increases measurement error
Solution Approach 1:
The invention introduces a control device as an intermediary that processes signals from both sensors and applies correction algorithms. This intermediary layer filters out cross-sensitivity effects by comparing sensor outputs under controlled conditions and adjusting measurements to compensate for interference from hydrocarbons and ammonia
Solution Approach 2:
The system changes the operating parameters by comparing sensor outputs under specific exhaust gas conditions and dynamically adjusting sensor sensitivity. By performing comparisons and adjustments under controlled conditions where cross-sensitivity effects are minimized or characterized, the system compensates for these interference effects through sensitivity correction
Data Source
Figure 1
AI summary
The invention relates to a method for processing measured values from a first nitrogen oxide sensor (7), arranged upstream of a nitrogen oxide reduction catalyst (4) in the exhaust gas section (9) of a motor vehicle, and measured values from a second nitrogen oxide sensor (8), arranged downstream of the nitrogen oxide reduction catalyst (4) in the exhaust gas section (9) of the motor vehicle, in which measured values from the first and second nitrogen oxide sensors (7; 8) are recorded and compared with one another at least approximately at the same time. According to the invention, a sensitivity of the first nitrogen oxide sensor (7) and/or of the second nitrogen oxide sensor (8) is changed on the basis of the result of the comparison.