Lambda Controller Oxygen Balance for Catalytic Converter
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Solution Overview
Problem
Existing lambda control systems in internal combustion engines react slowly, leading to undesired emission breakthroughs due to inaccurate determination of the catalytic converter's oxygen state and its correlation with conversion performance, resulting in suboptimal catalytic converter operation.
Innovation Solution
A method and device that determine a balanced oxygen quantity in the catalytic converter after a sign change in the difference value of the rear oxygen sensor's output signal, using this information to adjust the manipulated variable of the rear lambda control circuit, thereby improving lambda control by considering the oxygen balance and state of the catalytic converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional lambda control systems with front and rear oxygen sensors are used, then the system structure is simple and easy to implement, but the system reacts slowly leading to undesired emission breakthroughs
Solution Approach 1:
The patent applies preliminary action by determining the oxygen quantity balance in advance before emission breakthroughs occur. The control system continuously calculates the balance between oxygen introduced into and discharged from the catalytic converter, enabling predictive control adjustments that prevent deviations rather than merely reacting to them, thus improving response speed without requiring complex additional hardware
Solution Approach 2:
The patent introduces an intermediary computational approach by using the oxygen quantity balance as a mediator variable. This balance serves as an intermediate parameter that connects the front and rear oxygen sensor signals, allowing the control system to infer the catalytic converter's internal oxygen state without directly measuring it, thereby improving control speed while maintaining manageable system complexity
2Measurement precision
If the current oxygen state of the catalytic converter is determined with great accuracy using complex models, then the lambda control precision is improved, but the device complexity and computational requirements increase significantly
Solution Approach 1:
The patent extracts only the essential information needed for control by focusing solely on the oxygen quantity balance between input and output. Instead of implementing complex comprehensive models of catalytic converter behavior, the system extracts and utilizes only the net oxygen accumulation, discarding unnecessary modeling complexity while maintaining sufficient precision for lambda control
Solution Approach 2:
The patent simplifies the problem by changing the parameter representation from complex oxygen storage capacity models to a straightforward oxygen quantity balance calculation. This parameter transformation converts a potentially complex state estimation problem into a simple differential calculation based on front and rear sensor signals, achieving high precision with minimal complexity
3Productivity
If the manipulated variable is adjusted frequently to maintain optimal lambda, then the exhaust gas purification efficiency is improved, but the risk of oscillation and instability increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the oxygen quantity balance and using this information to adjust the manipulated variable. The control system incorporates the balance information into the lambda control loop, creating a feedback mechanism that automatically stabilizes the system by counteracting deviations before they lead to oscillations, thereby maintaining both high purification efficiency and control stability
Solution Approach 2:
The patent applies beforehand cushioning by using the oxygen quantity balance to anticipate and cushion against potential lambda deviations. By detecting imbalances in advance, the system can make preemptive adjustments to the manipulated variable, cushioning the control system against future oscillations and instability while maintaining continuous optimization of purification efficiency
Data Source
Figure 1
AI summary
In the lambda control method for an internal combustion engine (3) having at least one catalytic converter (19) which is arranged in an exhaust system (17) of the internal combustion engine (3), the exhaust system (17) having a front lambda control circuit (5) and a rear lambda control circuit (9) with at least one rear oxygen sensor (15) arranged downstream of the catalytic converter (19), an output signal of the rear oxygen sensor (15) being processed by the rear lambda control circuit (9), a difference value from a rear set point lambda value being formed, and a manipulated variable which acts on the set point lambda value of the front lambda control circuit (5) being output, there is provision that after the change in sign of the difference value for a time interval since the change in sign a balanced quantity of oxygen is determined from the quantity of oxygen which has been input into and output from the catalytic converter (19), and the manipulated variable of the rear lambda control circuit (9) is additionally selected as a function of the balanced quantity of oxygen. In addition, in a device for carrying out the method there is provision that a device (13) for determining a balanced quantity of oxygen of the catalytic converter (19) from the quantity of oxygen which has been input into and output from the catalytic converter (19) is used, and that after the change in sign of the difference value for a time interval after the change in sign the balanced quantity of oxygen is determined and the rear lambda control circuit (9) is configured to determine the manipulated variable additionally as a function of the balanced quantity of oxygen.