Exhaust Gas Sensor Deviation Analysis Thresholds
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Solution Overview
Problem
Existing methods for evaluating and correcting characteristic curves of exhaust gas sensors, particularly two-point lambda probes, fail to reliably distinguish between tolerable and intolerable deviations, leading to inaccurate pollutant emission control and potential malfunctions, which can result in high emissions or incorrect corrective measures.
Innovation Solution
Specifying thresholds to assess deviations and differentiate responses, allowing for precise correction of tolerable deviations while triggering alternative reactions for intolerable ones, such as limiting corrections or setting status information, to ensure robust error detection and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant characteristic curve offset or temperature-related deviation is compensated for, then constant lambda control is enabled, but implausibly high correction needs may indicate defective probes or malfunctions
Solution Approach 1:
The method implements feedback by continuously monitoring the corrected deviation and comparing it against predefined thresholds. When the deviation exceeds the threshold, the system triggers a diagnostic routine to detect malfunctions. This feedback mechanism ensures that only valid corrections are applied, maintaining reliable lambda control while preventing incorrect corrections from defective probes.
Solution Approach 2:
The method performs preliminary action by determining the corrected deviation before applying the correction to the characteristic curve. This preliminary calculation allows the system to assess whether the correction is plausible by comparing it against thresholds, and only then proceed with the actual correction, preventing incorrect corrections from being applied.
2Adaptability or versatility
If the actual lambda characteristic curve is shifted to account for aging effects, then continuous lambda control is possible, but the accuracy of regulation decreases when deviation from reference characteristic increases
Solution Approach 1:
The method applies parameter changes by dynamically adjusting the characteristic curve based on the determined deviation. The system modifies the reference characteristic curve parameters (offset, slope, curvature) to match the actual sensor behavior, enabling continuous lambda control while maintaining regulation accuracy through adaptive parameter updates.
Solution Approach 2:
The method replaces mechanical adjustment mechanisms with electronic parameter modification. Instead of physical adjustments to the sensor, the system electronically corrects the characteristic curve parameters through software algorithms, enabling precise adaptation to aging effects while maintaining control accuracy.
3Ease of manufacture
If two-point control with control to lambda=1 is used, then two-point lambda probes can be used, but target lambda can only be pre-controlled and not controlled in lean or rich operating modes
Solution Approach 1:
The method introduces dynamics by enabling the system to adaptively adjust the target lambda value based on operating conditions. The control system dynamically modifies the characteristic curve parameters in response to sensor feedback and operating mode requirements, allowing two-point probes to achieve continuous lambda control across different operating modes rather than being limited to fixed lambda=1 control.
Data Source
Figure 1
AI summary
The invention relates to a method and device for analysing the deviation (18) from at least one reference value in at least one portion of a characteristic plot of values from an exhaust gas sensor mounted in an exhaust passage. A robust method for correcting a characteristic plot to ensure reliable pollutant optimisation is achieved by specifying at least one threshold for assessing the deviation (18), which forms a criterion for distinguishing between a tolerable correction requirement and a non-tolerable correction requirement.