NOx Sensor Gain Correction for Aging Bias
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Solution Overview
Problem
NOx sensors in internal combustion engines experience a decrease in accuracy due to fouling and aging, leading to biased measurements that current compensation methods fail to adequately correct for, especially as they are influenced by varying conditions and sensor models.
Innovation Solution
A method and system that apply a gain correction factor determined by exposing sensors of different ages to known NOx concentrations, creating a data set to correct for both chronological age and drift, allowing for more accurate NOx concentration measurements by accounting for sensor model performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional NOx sensors are used without correction, then the device complexity is low, but the measurement precision deteriorates due to sensor aging and fouling
Solution Approach 1:
The patent applies preliminary action by pre-determining correction factors through controlled exposure of sensors to known NOx concentrations at different ages. These correction factors are calculated in advance and stored for later application, eliminating the need for real-time complex calculations and reducing system complexity while maintaining high measurement precision.
Solution Approach 2:
The patent introduces an intermediary element - the correction factor - that mediates between the raw sensor output and the actual NOx concentration. This intermediary compensates for sensor degradation without requiring direct modification of the sensor itself, simplifying the overall system while improving measurement accuracy.
2Measurement precision
If sensors are replaced frequently to maintain accuracy, then the measurement precision is maintained, but the loss of time and productivity increase due to maintenance operations
Solution Approach 1:
The patent applies parameter changes by modifying the interpretation of sensor readings through age-dependent correction factors rather than physically replacing the sensor. This changes the operational parameter from sensor hardware lifespan to software-based compensation, extending the effective service life of sensors while maintaining measurement precision.
3Measurement precision
If simple age-based correction is applied, then the device complexity remains low, but the measurement precision is insufficient due to varying sensor responses to different NOx concentrations
Solution Approach 1:
The patent applies segmentation by dividing the correction approach into discrete age groups and corresponding correction factors. Sensors are categorized into age segments, each with predetermined correction factors derived from exposure data. This segmented approach simplifies the correction process while capturing the non-linear degradation behavior across different sensor ages and NOx concentration levels.
Data Source
AI summary
A method, system, and apparatus are provided for improving accuracy of sensor readings reflecting measurements of at least one constituent in an engine exhaust. The sensor measurement is corrected or compensated for by applying to a gain correction factor to the reported sensor measurement. The gain correction factor is developed by determination of prior test sensor readings correlated with discrete sensor age levels, and with constituent concentrations to which those test sensors are exposed. By applying the determined gain correction factor to change the sensor's reported measurements, bias may be reduced and a more accurate measure of actual constituent levels is provided.