Sensor Control Device for NOx Concentration Anomaly Diagnosis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor control devices cannot accurately diagnose failures where input signals from amplification circuits assume anomalous values in an intermediate range between ground and drive voltage, due to deterioration or improper mounting of amplification circuit components.
Innovation Solution
A sensor control device with two amplification sections and a control section that compares equivalent values from both sections to determine anomalies within a predetermined overlap range, using difference calculation and integrated value analysis to detect signal system failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two amplification circuits with different amplification factors are used to expand the detection range, then the detection accuracy of NOx concentration is improved, but the ability to diagnose failures in the intermediate range between GND and drive voltage deteriorates
Solution Approach 1:
The patent applies preliminary action by performing anomaly diagnosis on amplification circuit output signals before final NOx concentration calculation. The control section acquires equivalent values from both amplification circuits, determines if they fall within the anomaly diagnosis range (overlap portion), and compares them to detect failures. This preliminary diagnostic step ensures that intermediate range failures are identified before affecting the final measurement, resolving the contradiction between expanded detection range and failure diagnosis capability.
2Measurement precision
If the amplification factor is increased to detect low concentration signals, then the sensitivity for low concentration detection is improved, but the detection range for high concentration signals deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the detection system into two parallel amplification circuits with different amplification factors. The first amplification circuit uses a first amplification factor for detecting low concentration signals, while the second amplification circuit uses a second amplification factor for detecting high concentration signals. The control section selectively uses outputs from either circuit based on the current concentration level, enabling both high sensitivity for low concentrations and appropriate range for high concentrations.
Solution Approach 2:
The patent applies universality by designing the amplification circuit system to perform multiple functions: the first amplification circuit handles low concentration detection with high sensitivity, the second amplification circuit handles high concentration detection with appropriate range, and both circuits simultaneously provide diagnostic capability through equivalent value comparison. This multi-functional design resolves the trade-off between sensitivity and detection range.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An object is to perform accurate diagnosis of a failure in which an input signal from an amplification circuit assumes an anomalous value in an intermediate range between GND and Vcc. When at least one of a first NOx concentration Ip2W based on the output OP1 of a first differential amplification circuit 210 and a second NOx concentration Ip2N based on the output OP2 of a second differential amplification circuit 220 falls within an anomaly diagnosis range ZN, the difference D between the first NOx concentration Ip2W and the second NOx concentration Ip2N is obtained, and the difference D is stored in a difference accumulation buffer BF such that 16 values of the difference D continuously sampled up to the present are stored. The integrated value (difference integral value) Dint of the difference D is obtained. When the difference integrated value Dint becomes equal to or greater than a predetermined value Di0, a diagnosis result of "anomalous" is provided.