Reductant Tank Sensor Diagnostic Method
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Solution Overview
Problem
Existing sensor systems for reductant tanks in aftertreatment systems face challenges in accurately diagnosing sensor defects, such as gain and offset errors, which can lead to incorrect dosing of reductants, affecting NOx emission control and potentially causing damage to the dosing module or premature shutdown.
Innovation Solution
A computer-implemented method and system that diagnose sensor performance by comparing sensor-estimated dosing values with commanded reductant feedback, determining positive or negative gain and offset defects, and sending diagnostic decisions to monitoring devices based on threshold values, ensuring the sensor operates within acceptable calibration ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tank-level sensors are used to monitor reductant levels, then the dosing system can control NOx emissions, but the sensors may develop gain and offset errors leading to incorrect dosing decisions
Solution Approach 1:
The system uses feedback from multiple tank-level sensors and compares their readings against expected tank level trajectories based on dosing history. When sensor readings deviate from expected values beyond threshold offsets, the system identifies potential gain or offset errors and adjusts dosing commands accordingly, maintaining reliable NOx control despite sensor inaccuracies
Solution Approach 2:
The system dynamically changes dosing parameters by adjusting dosing commands based on diagnosed sensor defects. When gain errors are detected, the system modifies dosing rates to compensate; when offset errors are detected, the system adjusts dosing thresholds. This allows continuous operation with degraded sensors while maintaining emission control reliability
2Measurement precision
If the system continuously monitors sensor performance and diagnoses defects, then dosing accuracy is maintained, but system complexity increases
Solution Approach 1:
The controller performs multiple functions using the same sensor infrastructure: it monitors tank levels for dosing control, tracks sensor readings over time for drift detection, compares multi-sensor readings to diagnose gain/offset errors, and adjusts dosing commands based on diagnostic results. This multi-functionality maintains dosing accuracy without adding separate dedicated diagnostic hardware systems
Solution Approach 2:
The system uses its own operational data (dosing history, tank level trajectories) to self-diagnose sensor defects. By comparing expected tank level changes based on commanded dosing against actual sensor readings, the system automatically identifies sensor gain and offset errors without external calibration equipment or manual intervention, maintaining accuracy while avoiding complex external diagnostic systems
Data Source
AI summary
A system for diagnosing a sensor of an exhaust aftertreatment system may include receiving a first tank level value from a sensor. A plurality of reductant dosing command values over a period of time are received. A dosed reductant value is determined responsive to the plurality of reductant dosing command values reaching a threshold integrated value. A second tank level value is received from the sensor responsive to the dosed reductant value reaching the threshold integrated value. A sensor-estimated dosing value is determined based on the difference between the first tank level value and the second tank level value. The sensor may be diagnosed as performing outside of an acceptable calibration range based on the difference between the sensor-estimated dosing value and the dosed reductant value.