Humidity Sensor Monitoring via Oxygen Signal Offset
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Solution Overview
Problem
Monitoring ambient humidity sensors in combustion engines is challenging due to the lack of an obvious method for redundant determination, making it difficult to ensure accuracy and compliance with emission regulations, especially when using a single NOx sensor for NOx emissions calculation.
Innovation Solution
The method involves determining ambient humidity from oxygen measurements of NOx, lambda, or oxygen sensors by relating the offset of their signals to humidity variations during fuel cut-off conditions, allowing independent monitoring of the humidity sensor without the need for multiple humidity sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a humidity sensor is used to correct NOx emissions, then NOx emissions prediction accuracy is improved, but the reliability of the humidity sensor cannot be verified due to lack of independent monitoring
Solution Approach 1:
The patent uses oxygen sensors (lambda sensors, NOx sensors with oxygen measurement capability) as intermediary devices to indirectly monitor humidity sensor reliability. These sensors serve as mediators that provide alternative measurement paths for ambient humidity through oxygen concentration measurements, enabling cross-validation without requiring direct humidity measurement redundancy.
Solution Approach 2:
The patent replaces the need for mechanical/redundant humidity sensor systems with an electrical/electronic substitution approach. Instead of using multiple physical humidity sensors, the system substitutes humidity measurement with oxygen concentration measurement from existing sensors, converting the monitoring problem into an equivalent electrical signal comparison task.
2Reliability
If multiple humidity sensors are used for redundant determination, then humidity sensor reliability is improved, but system cost increases
Solution Approach 1:
The patent makes existing oxygen sensors perform a dual function: their primary function for oxygen/concentration measurement plus an additional function for humidity monitoring. By analyzing oxygen sensor readings under specific engine operating conditions (fuel cut-off phases), the system extracts humidity information from sensors already present in the vehicle, eliminating the need for separate humidity sensing hardware.
Solution Approach 2:
The system uses its existing sensor infrastructure to monitor itself. The oxygen sensors, already installed for emissions control, are utilized to provide self-diagnosis capability for the humidity sensor, creating a self-sufficient monitoring system that does not require external or additional dedicated monitoring components.
3Reliability
If oxygen sensors are used to determine ambient humidity, then humidity sensor monitoring is enabled, but additional processing complexity is introduced
Solution Approach 1:
The system performs preliminary filtering and selection of appropriate measurement phases before full processing. By identifying and isolating fuel cut-off phases where ambient air sampling occurs, the system pre-processes the data stream to extract only relevant measurement windows, reducing the complexity of continuous processing by focusing computation on specific, pre-identified time intervals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable monitoring of the humidity sensor independently, ensuring accurate NOx emissions prediction and compliance with emission regulations, while avoiding the cost of multiple humidity sensors.
Implementation Method 1
determination of the ambient humidity from the oxygen measurement of at least another sensor in the engine system
Data Source
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AI summary
The present invention provides for a method and device for monitoring an ambient humidity sensor in a combustion engine, where the monitoring of the ambient humidity sensor is made by comparing the ambient humidity measured by said humidity sensor and an ambient humidity determined from an oxygen measurement of at least another sensor in the engine system, such as a NOX, or Lambda and/or an oxygen sensor. Said comparison is made using an offset of the oxygen signal reading of said at least another sensor, in a fuel cut condition where the drift or offset of said another sensor is related to the variation of the ambient humidity.