Aftertreatment Sensor Tampering Detection via NOx Cross-Leg Comparison
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Solution Overview
Problem
Aftertreatment systems face challenges in detecting sensor tampering, such as NOx sensor displacement, which can lead to inaccurate reductant dosage and NOx slip, making it difficult to maintain compliance with environmental regulations.
Innovation Solution
A controller-based system that monitors NOx values and adjusts reductant dosing to detect sensor tampering by analyzing differences in NOx readings between sensors in different legs of the aftertreatment system, using an ammonia-to-NOx ratio override to identify sensor misplacement and generate notifications for maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensor tampering detection is implemented through complex monitoring systems, then detection capability is improved, but device complexity increases
Solution Approach 1:
The system uses feedback from NOx sensor readings to detect tampering. The controller continuously monitors NOx values from sensors in different legs and compares them against expected ranges and relationships. When discrepancies are detected (such as unexpected NOx levels or inconsistent readings between legs), the system generates a tampering indication. This feedback-based approach enables reliable detection without requiring complex additional hardware.
Solution Approach 2:
The aftertreatment system performs self-diagnosis for sensor tampering using its existing components. The controller leverages data already being collected for normal operation (NOx readings from multiple legs, reductant dosing information) to detect tampering conditions. This self-service capability eliminates the need for separate dedicated detection systems, maintaining reliability while minimizing added complexity.
2Measurement precision
If continuous monitoring of NOx values is performed to detect sensor displacement, then detection accuracy is improved, but energy consumption increases
Solution Approach 1:
The controller performs periodic evaluation of NOx sensor readings rather than continuous analysis. The system monitors NOx values continuously during normal operation but evaluates them for tampering conditions at specific intervals or under defined operating conditions. This periodic evaluation maintains detection accuracy for sensor displacement while significantly reducing the computational load and energy consumption compared to continuous analysis.
3Reliability
If multiple NOx sensors are deployed in different legs for comparison, then tampering detection reliability is improved, but manufacturing cost increases
Solution Approach 1:
The existing NOx sensors in the aftertreatment system serve dual purposes: they perform their primary function of measuring NOx emissions for compliance monitoring, and simultaneously provide data for tampering detection through cross-leg comparison. By making the existing sensors multi-functional, the system achieves reliable tampering detection without requiring additional sensor installations, thereby avoiding increased manufacturing costs.
Data Source
AI summary
A system, method, and apparatus for sensor tampering detection are provided. An aftertreatment system comprises a first leg comprising a first Selective Catalytic Reduction (SCR) system, a first doser, and a first NOx sensor, a second leg comprising a second SCR system, a second doser, and a second NOx sensor, and a controller. The controller determines satisfaction of enabling conditions. The controller doses reductant to the first and second SCR systems. The controller determines NOx values of the first SCR system and the second SCR system. The controller adjust the dosing of the first SCR system for a time period. The controller measures NOx values of the first SCR system and the second SCR system. The controller determines a difference between the third and first NOx values and a difference between the fourth and second NOx values. The controller generates an indication regarding whether the first NOx sensor is displaced.