Ammonia Sensor Accuracy Correction for Exhaust Gas Humidity
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Solution Overview
Problem
Ammonia sensors face accuracy issues when measuring NH3 concentration in exhaust gases containing water and oxygen, leading to inaccurate readings.
Innovation Solution
A system and method that utilize an NH3 sensor, an air humidity sensor, and a controller to determine the NH3 concentration by generating signals from these sensors, calculating an air/fuel ratio, and using a calibration table to correct for humidity and fuel ratio deviations, thereby accurately measuring NH3 levels in exhaust gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an NH3 sensor is used to monitor exhaust gases, then NH3 concentration can be detected, but the sensor accuracy deteriorates in the presence of water and oxygen
Solution Approach 1:
The patent introduces intermediate parameters (humidity level from air humidity sensor, air/fuel ratio from airflow and fuel injection signals) that mediate between the harmful environmental factors and the NH3 sensor reading. These intermediates are used to calculate a deviation value that corrects the raw sensor signal, effectively filtering out the interference from water and oxygen through a computational intermediary layer.
Solution Approach 2:
The patent changes the measurement parameters by incorporating additional measured variables (humidity, air/fuel ratio) and transforming the raw NH3 sensor signal through mathematical correction using a calibration table. This parameter transformation converts the inaccurate raw reading into a corrected NH3 concentration value that compensates for environmental interferences.
2Measurement precision
If additional sensors and correction calculations are added to improve NH3 measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The controller performs multiple functions: it reads the NH3 sensor signal, reads airflow and fuel injection signals to calculate air/fuel ratio, reads humidity from the air humidity sensor, looks up deviation values in a calibration table, and calculates the corrected NH3 concentration. By making the controller multi-functional, the patent avoids adding separate dedicated devices for each function, thereby limiting the increase in device complexity.
Solution Approach 2:
The system uses existing sensors (airflow sensor, fuel injection signals, air humidity sensor) that are already part of the engine management system to provide the additional information needed for correction. Rather than adding entirely new sensing systems, the patent makes the existing system serve the additional function of providing correction parameters, reducing overall system complexity.
Data Source
AI summary
Systems and methods for determining an NH3 concentration in exhaust gases from an engine are provided. In one exemplary embodiment, a method includes generating a first signal from an NH3 sensor fluidly communicating with the exhaust gases. The method further includes generating a second signal from an air humidity sensor disposed proximate to an air intake manifold of the engine indicating a humidity level. The method further includes determining an air/fuel ratio associated with the engine. The method further includes determining an NH3 deviation value in a calibration table based on the second signal and the air/fuel ratio, utilizing a controller. The method further includes determining an NH3 concentration value based on the first signal and the NH3 deviation value, utilizing the controller. The NH3 concentration value is indicative of the NH3 concentration in the exhaust gases. The method further includes storing the NH3 concentration value in a memory device, utilizing the controller.