NOx Sensor Fault Diagnosis via Oxygen Comparison
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing exhaust aftertreatment systems for internal combustion engines face challenges in accurately diagnosing faulty NOx sensors due to the complexity of estimating NOx levels, which can lead to inaccurate emission readings and system performance degradation.
Innovation Solution
The system employs oxygen sensors at different locations within the exhaust aftertreatment system to compare oxygen levels, using a threshold-based method to determine sensor faultiness, and optionally includes a virtual sensor to estimate oxygen content based on engine operation data, allowing for passive or intrusive diagnostic tests to identify faulty sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NOx sensor diagnosis is performed using complex NOx estimation models, then diagnostic capability is improved, but system complexity and measurement accuracy deteriorate due to model inaccuracies
Solution Approach 1:
The patent uses oxygen concentration as an intermediary parameter to diagnose NOx sensor faults. Instead of directly measuring or estimating NOx levels using complex models, the system measures oxygen concentration (which is easier to measure accurately) and uses it as a proxy to infer NOx sensor performance. The oxygen concentration serves as a mediator that correlates with NOx levels through the exhaust aftertreatment process, enabling indirect diagnosis without complex NOx estimation models.
Solution Approach 2:
The patent replaces complex computational models and algorithms for NOx estimation with a simpler measurement-based approach using oxygen sensors. Instead of relying on mechanical/computational estimation systems that require multiple inputs and complex processing, the system substitutes this with direct oxygen concentration measurements that provide sufficient diagnostic information through comparison with expected values from aftertreatment models.
2Measurement precision
If multiple sensors are used to monitor oxygen levels at different locations, then diagnostic accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The patent divides the exhaust aftertreatment system into multiple monitoring zones by placing oxygen sensors at different locations (upstream and downstream of the SCR catalyst). Each sensor monitors oxygen levels in its specific zone, allowing the system to detect changes in oxygen concentration as exhaust gas flows through the aftertreatment system. This segmentation enables precise localization of sensor faults by comparing readings from different segments.
Solution Approach 2:
The oxygen sensors perform multiple functions: they monitor oxygen concentration for emission control, provide diagnostic information for NOx sensor fault detection, and enable determination of SCR catalyst performance. By using a single sensor type for multiple purposes, the system achieves high measurement precision without proportionally increasing complexity.
Data Source
AI summary
A method includes: interpreting first oxygen data acquired by a first nitrous oxide (NOx) sensor indicative of a first amount of oxygen in an exhaust flow at a location in or proximate to an exhaust aftertreatment system, wherein the exhaust aftertreatment system is in exhaust gas receiving communication with an engine; estimating an amount of oxygen in the exhaust flow entering the exhaust aftertreatment system from the engine based on engine operation data; and, determining that the NOx sensor is faulty based on determining that a difference between the first amount of oxygen and the estimated amount of oxygen is greater than a threshold value.