Dynamic Air-Fuel Ratio Control via Variable Safety Margin
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Solution Overview
Problem
Existing methods for controlling the air-fuel ratio in internal combustion engines based on exhaust gas composition are limited by constant safety margins, leading to inaccurate lambda value regulation and increased fuel consumption due to overcorrection for potential interference variables like probe temperature and aging.
Innovation Solution
A method that dynamically adjusts the safety margin based on the current accuracy of disturbance variables such as probe temperature, aging, and chemical poisoning, using evaluations of variance and calibration history to set the minimum necessary safety margin for precise lambda control and reduced fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant safety margin is applied to lambda threshold values to account for potential measurement inaccuracies, then component protection is ensured under all conditions, but fuel consumption increases due to excessive mixture enrichment
Solution Approach 1:
The patent applies dynamics by making the safety margin variable rather than constant. The control device dynamically adjusts the safety margin based on actual sensor signal characteristics and operating conditions. This allows the system to maintain reliable component protection when needed while reducing unnecessary fuel enrichment during normal operation, thereby resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The patent changes the parameter of safety margin from a fixed value to a variable parameter that adapts to operating conditions. By modifying the safety margin parameter based on sensor signal evaluation and disturbance variable assessment, the system achieves both reliable component protection and reduced fuel consumption, as the safety margin is only increased when actually needed.
2Reliability
If a large safety margin is used to compensate for characteristic curve inaccuracies, then lambda control reliability is improved, but lambda control precision deteriorates due to excessive mixture enrichment
Solution Approach 1:
The patent makes the safety margin dynamic, adjusting it in real-time based on actual sensor signal quality and operating conditions. This allows the system to maintain high lambda control reliability when measurement uncertainties are high, while achieving precise lambda control when sensor signals are accurate, thus resolving the contradiction between reliability and precision.
Solution Approach 2:
The patent applies local quality by evaluating sensor signal characteristics and disturbance variables at specific operating points. The safety margin is adjusted locally based on actual signal quality rather than applying a uniform margin across all operating conditions. This enables precise lambda control where signal quality is high while maintaining reliability where signal quality degrades.
3Reliability
If constant maximum safety margins are applied to all operating conditions, then the worst-case scenario is covered, but fuel consumption increases for the majority of operating conditions where less margin is needed
Solution Approach 1:
The patent transforms the static safety margin approach into a dynamic one that adapts to actual operating conditions. The control device continuously evaluates sensor signal characteristics and adjusts the safety margin accordingly. This ensures worst-case coverage is maintained when necessary while significantly improving fuel efficiency during normal operating conditions where less margin is required.
Solution Approach 2:
The patent changes the safety margin parameter from a constant maximum value to a variable parameter that reflects actual operating conditions. By modifying the safety margin parameter based on real-time sensor signal evaluation, the system achieves both worst-case reliability coverage and improved overall fuel efficiency across the operating range.
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 more accurate regulation of air-fuel ratios with reduced fuel consumption by tailoring the safety margin to the actual conditions, minimizing additional fuel use during component protection measures and enhancing overall lambda control precision.
Implementation Method 1
the relevant exhaust gas component is measured using a suitable exhaust gas sensor. In particular, the air-fuel ratio at which the engine operates is regulated by measuring the oxygen content of the exhaust gas using a lambda sensor in the exhaust tract.
Implementation Method 2
This sensor signal is converted into a lambda value using a stored characteristic curve or a corresponding calculation formula, and this value is then used for control.
Implementation Method 3
the probe temperature is determined from a stored characteristic curve as a function of the probe's internal resistance.
Implementation Method 4
the current correction voltage is then determined, which is added to the current probe voltage to obtain a corrected probe voltage.
Data Source
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AI summary
The invention relates to a method and to a regulating device for regulating an air-fuel ratio of an internal combustion engine (10), wherein an exhaust-gas composition of an exhaust gas of the internal combustion engine (10) is determined by virtue of an actual probe signal, which is dependent on the exhaust-gas composition, being detected by means of an exhaust-gas probe (22) and the exhaust-gas composition being determined as a function of the actual probe signal by means of a characteristic curve or a calculation rule, and wherein the determined exhaust-gas composition is compared with a setpoint value or a threshold value, the attainment or exceedance of which triggers a manipulation of the air-fuel ratio supplied to the internal combustion engine (10), wherein, in order to take into consideration at least one disturbance variable which affects the actual probe signal, a safety margin (ΔS) is defined which is applied to the characteristic curve or calculation rule, to the actual probe signal or to the setpoint value or threshold value. It is provided that an evaluation of a present accuracy of the at least one disturbance variable and/or of a present influence of the at least one disturbance variable on the probe signal is performed, and the safety margin (ΔS) owing to the at least one disturbance variable is defined as a function of the evaluation.