Lambda Probe Offset Correction for Engine Exhaust Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for operating internal combustion engines with exhaust gas purifying devices face challenges in achieving high converting efficiency due to inaccuracies in the first lambda probe's signal, leading to deviations in fuel-air mixture composition, which result in poorer catalytic converter performance and potential oscillations when trying to correct these errors.
Innovation Solution
A method that determines the oxygen filling state of the catalytic converter using both lambda probes, adjusts the offset value based on the second lambda signal's thresholds, and integrates this information to correct the first lambda signal, ensuring accurate oxygen storage levels and preventing errors over time, thereby maintaining stoichiometric ratios for efficient purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a higher regulation speed is used to correct the first lambda probe error, then the correction speed is improved, but regulation oscillations occur which lead to poorer converting efficiency of the catalytic converter
Solution Approach 1:
The patent applies preliminary action by determining the offset value of the first lambda probe during a predefined initialization phase before normal operation begins. This pre-correction of the lambda probe offset eliminates the need for continuous high-speed regulation during operation, thereby avoiding oscillations while maintaining fast initial correction. The offset determination is performed once beforehand using the second lambda probe as reference, and then applied continuously to correct the first lambda probe readings without causing instability.
2Loss of time
If the first lambda probe signal is used directly for control, then the response time is improved, but the measurement accuracy deteriorates due to offset errors
Solution Approach 1:
The patent implements feedback by continuously comparing the first lambda probe signal with the offset value that was determined during initialization. The corrected lambda value (original signal minus offset) is used for control decisions. This feedback mechanism maintains measurement accuracy by compensating for the probe's inherent offset error while preserving the fast response characteristics of the first lambda probe, as the correction is applied in real-time without adding significant delay.
Solution Approach 2:
The offset value acts as an intermediary that mediates between the inaccurate first lambda probe signal and the control system. By introducing this intermediate correction parameter determined during initialization, the system transforms the biased raw signal into an accurate control signal without requiring continuous reference to the second lambda probe, thus maintaining both speed and accuracy.
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
This approach allows for rapid and accurate correction of the first lambda probe's errors without causing controller oscillations, ensuring high converting efficiency and effective pollutant removal from the exhaust gas by maintaining optimal oxygen storage levels in the catalytic converter.
Implementation Method 1
a first lambda probe arranged upstream of the catalytic converter in the exhaust gas stream and a second lambda probe arranged downstream of the catalytic converter in the exhaust gas stream, so that the oxygen content of the exhaust gas can be determined at the respective position upstream or downstream of the catalytic converter
Implementation Method 2
The catalytic converter has an oxygen storage or respectively operates as such. This means that when a lean exhaust gas is present—i.e., in the case of an oxygen excess at combustion of λ greater than one—oxygen transitions from the exhaust gas into the oxygen accumulator and is intermittently stored therein
Data Source
AI summary
A method for operating an internal combustion engine includes the steps of determining an oxygen filling state of an oxygen storage of a catalytic converter by way of a first lambda signal provided by a first lambda probe and an offset value, the first lambda probe being arranged in an exhaust gas stream upstream of the catalytic converter; when a second lambda signal provided by a second lambda probe arranged in the exhaust gas stream upstream of the catalytic converter falls below a lower lambda signal threshold, setting the oxygen filling state to a first value corresponding to an empty oxygen storage and/or when the second lambda signal exceeds a upper lambda signal threshold setting the oxygen filling state to a second value corresponding to a full oxygen storage; immediately thereafter regulating the oxygen filling state during at least one regulation time period to a target filling state; and after expiration of the regulation time period adjusting the offset value by way of the second lambda signal.