Oxygen Storage Capacity Determination via Probe Step Response Correction
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Solution Overview
Problem
Existing methods for determining the oxygen storage capacity of emission control systems in internal combustion engines are prone to inaccuracies due to dynamic errors in exhaust gas analyzer probes, leading to incorrect evaluations of catalytic converter functionality and potential increased emissions.
Innovation Solution
The method involves determining the step response parameters of the exhaust gas analyzer probes to correct oxygen input and discharge, using a lambda characteristic calculation to account for probe delays and time constants, thereby improving the accuracy of oxygen and hydrocarbon gas storage capacity determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diagnostic methods are used to determine oxygen storage capacity, then the catalytic converter functionality can be monitored, but measurement inaccuracies occur due to dynamic errors in exhaust gas analyzer probes
Solution Approach 1:
The patent applies preliminary action by determining the step response parameters of the exhaust gas analyzer probes before using them for oxygen storage capacity measurements. The method characterizes the dynamic behavior (delays and time constants) of the probes in advance through step response analysis, then uses this characterization data to correct subsequent measurements. This preliminary characterization enables accurate compensation of dynamic errors in all future measurements, resolving the contradiction between reliable diagnostics and precise measurement.
2Reliability
If exhaust gas analyzer probes are used to monitor oxygen storage capacity, then catalytic converter aging can be detected, but probe delays and time constants cause asymmetric dynamic errors leading to false offset errors
Solution Approach 1:
The patent implements feedback by using the determined step response parameters (delays and time constants) to continuously correct the oxygen input and discharge calculations. The method creates a feedback loop where measurement data is processed through the characterized probe response model, and the corrected values are used for accurate oxygen storage capacity determination. This feedback mechanism eliminates false offset errors by constantly compensating for the asymmetric dynamic behavior of the probes.
3Productivity
If the engine is operated with rich-lean oscillation to maximize oxygen loading, then the oxygen storage capacity can be determined, but the dynamic response of probes causes inaccuracies in oxygen input determination
Solution Approach 1:
The patent applies parameter changes by utilizing the step response parameters (delays and time constants) as correction factors in the oxygen input calculation. Instead of using raw probe signals directly, the method transforms the measurement parameters through the characterized probe response model, adjusting for dynamic errors. This parameter transformation enables accurate oxygen storage capacity determination during rich-lean oscillation operations despite the dynamic behavior of the probes.
Data Source
AI summary
A method and a device for determining the oxygen storage capacity of an emission control system in an exhaust duct of an internal combustion engine. In a first phase, the internal combustion engine being operated using an air-fuel mixture having a rich air-to-fuel ratio, and in a second phase, the engine being operated at a lean air-to-fuel ratio; and an oxygen storage capacity of the emission control system being determined from an oxygen input into the emission control system during the second phase; and/or in order to determine a hydrocarbon gas storage capacity, the internal combustion engine being operated during the first phase at a lean air-to-fuel ratio, and operated in the second phase at a rich air-to-fuel ratio; and the hydrocarbon gas storage capacity being determined from the oxygen discharge from the emission control system during the second phase.