NOx Sensor Compensation for Transient Exhaust Conditions
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Solution Overview
Problem
Existing NOx sensors face challenges in accurately measuring nitrogen oxide concentrations during transient engine conditions due to temperature fluctuations, which require temporary cessation of NOx concentration measurement and can result in erroneous readings.
Innovation Solution
A method that adjusts NOx concentration readings based on transient engine exhaust conditions, including changes in exhaust gas flow rate, temperature, and O2 concentration, using correction values to continuously monitor NOx levels without direct temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If temperature detection is implemented by measuring internal resistance of the gas concentration measurement cell, then temperature can be detected without additional temperature sensing components, but NOx concentration measurement must be temporarily ceased
Solution Approach 1:
The patent implements time-multiplexed measurements where the measurement cell alternates between resistance measurement mode (for temperature detection) and NOx concentration measurement mode. This periodic switching allows both functions to be performed using the same cell without requiring additional sensors, directly resolving the contradiction between device complexity and measurement continuity.
Solution Approach 2:
The gas concentration measurement cell is made multi-functional by enabling it to serve both as a temperature sensor (through resistance measurement) and as a NOx concentration sensor. This universal usage eliminates the need for separate temperature sensing components while maintaining the ability to measure both parameters, addressing the contradiction between device complexity and measurement capability.
2Device complexity
If time-multiplexed measurements are used for temperature and NOx concentration, then both parameters can be measured with a single cell, but erroneous NOx readings occur during transient conditions
Solution Approach 1:
The patent performs resistance measurement (temperature detection) before NOx concentration measurement during transient conditions. This preliminary action allows the system to detect temperature changes first and apply appropriate corrections to the subsequent NOx readings, preventing erroneous measurements during transient engine operations.
Solution Approach 2:
The system uses the temperature information obtained from resistance measurement to correct the NOx concentration readings. This feedback mechanism compensates for temperature-induced measurement errors, maintaining measurement precision even when using time-multiplexed measurements with a single cell.
3Temperature
If constant voltage or constant current is applied to measure internal resistance, then temperature can be calculated, but NOx concentration measurement is interrupted
Solution Approach 1:
The patent implements rapid periodic switching between resistance measurement and NOx concentration measurement modes. This periodic action minimizes the time the cell is not measuring NOx concentration while still obtaining temperature data, reducing measurement loss time through efficient time management.
Solution Approach 2:
The resistance measurement is performed as a brief, rapid step before transitioning to NOx concentration measurement. By rushing through the temperature detection phase quickly, the system minimizes the interruption time for NOx monitoring while still obtaining necessary temperature correction data.
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
Enables continuous monitoring of NOx concentrations during transient conditions, reducing errors by using correction values derived from engine operating parameters, thereby maintaining accurate readings.
Implementation Method 1
temperature detection of the sensor is implemented by measuring internal resistance of a gas concentration measurement cell, as internal resistance is temperature dependent
Implementation Method 2
The NOx concentration is measured by detecting a current through the measurement cell that changes proportionally to the concentration of NOx
Data Source
AI summary
Various systems and methods are described for controlling an engine in a vehicle during engine operation, the engine having an exhaust and a NOx sensor coupled in the engine exhaust. One example includes correcting the NOx sensor to account for transients in exhaust gas flow, such as transients in exhaust gas flow rate. Such transients may cause NOx sensor temperature to deviate from a desired value as the sensor heater is unable to maintain temperature during such transients. In this way, even during such transients, accurate NOx readings are still available.