Multi-Gas Sensor Control for Ammonia Detection Accuracy
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Solution Overview
Problem
The accuracy of ammonia concentration detection in urea SCR systems is compromised due to variations in oxygen concentration, particularly during sharp changes, leading to calculation errors and decreased detection precision.
Innovation Solution
A sensor control method that includes an oxygen concentration computation step, a corrected concentration computation step, an oxygen concentration change rate computation step, and an ammonia concentration setting step, where the ammonia concentration is set based on a predetermined correction permission condition involving oxygen concentration change rates and reference values to minimize detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If corrected ammonia concentration is calculated based on output signal of ammonia sensor section and oxygen concentration, then influence of oxygen concentration is reduced, but when oxygen concentration varies sharply, calculation errors increase and detection accuracy decreases
Solution Approach 1:
The patent applies dynamics by making the correction process adaptive rather than static. The correction permission determination dynamically adjusts whether correction is applied based on real-time oxygen concentration change rates. When oxygen concentration changes sharply (high change rate), correction is suspended to avoid erroneous corrections. When oxygen concentration is stable (low change rate), correction is applied to compensate for oxygen interference. This dynamic approach resolves the contradiction between reducing oxygen influence and maintaining accuracy during sharp oxygen variations.
Solution Approach 2:
The patent changes the parameter of correction application from a fixed state to a variable state based on oxygen concentration change rate. By introducing the oxygen concentration change rate as a controlling parameter, the system determines whether to apply correction dynamically. This parameter change allows the system to switch between correction and non-correction modes, resolving the contradiction between needing correction for accuracy and avoiding correction during sharp oxygen changes.
2Measurement precision
If ammonia sensor section output is corrected using oxygen concentration, then ammonia detection accuracy is improved under stable conditions, but followability to rapid oxygen concentration changes deteriorates
Solution Approach 1:
The patent makes the correction process dynamic by introducing time-based control through oxygen concentration change rate monitoring. The system adapts its correction behavior in real-time: applying correction when oxygen concentration is stable (improving accuracy) and suspending correction when oxygen concentration changes sharply (maintaining followability). This dynamic switching resolves the contradiction between improving accuracy under stable conditions and maintaining response speed during rapid changes.
Solution Approach 2:
The patent maintains continuous monitoring of oxygen concentration and its change rate, ensuring the system is always ready to switch between correction and non-correction modes. This continuous observation allows the system to maintain both accuracy and followability by continuously adapting the correction application based on current oxygen concentration conditions, rather than using discrete or intermittent correction.
3Object-affected harmful factors
If corrected ammonia concentration is always applied, then oxygen concentration influence is suppressed, but detection accuracy decreases during sharp oxygen concentration variations
Solution Approach 1:
The patent extracts the harmful effect of oxygen concentration influence selectively rather than continuously. By introducing the correction permission determination based on oxygen concentration change rate, the system takes out (removes) the correction process only when oxygen concentration changes sharply. This selective extraction of the correction mechanism resolves the contradiction between suppressing oxygen influence and avoiding accuracy degradation during sharp oxygen variations.
Solution Approach 2:
The patent applies preliminary anti-action by monitoring oxygen concentration change rate before applying correction. The system predicts potential accuracy degradation by detecting sharp oxygen concentration changes in advance and preemptively suspends correction. This preliminary detection and preventive suspension of correction resolves the contradiction between suppressing oxygen influence and maintaining accuracy during sharp variations.
Data Source
AI summary
In a multi-gas sensor control apparatus 1, the concentrations of ammonia, NO2, and NO contained in a gas under measurement are computed as a result of execution of gas concentration computation processing by a CPU 61 of a microcomputer 60. In the gas concentration computation processing, depending on whether or not a correction permission condition is satisfied (S200), the CPU 61 switches its operation between an operation of storing the latest corrected ammonia concentration as a value of “NH3 concentration (this time)” (S170) and an operation of storing a value of “NH3 concentration (reference)” as a value of “NH3 concentration (this time)” (S210). The multi-gas sensor control apparatus 1 can suppress a decrease in the accuracy of detection of the ammonia concentration performed through use of a multi-gas sensor 2.