Lambda Sensor Dead Time Estimation via Delay Compensation
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Solution Overview
Problem
Existing methods for determining the end of a period in exhaust gas cleaning devices with lambda probes are imprecise due to signal delays and noise, leading to incorrect identification of the period end.
Innovation Solution
The method corrects the end of the period by accounting for the time constant of the delay, which is determined from the signal value's progression, thereby compensating for signal delays and noise, ensuring a more precise determination of the period end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a difference value is used to determine the end of the period when the signal value falls below or exceeds the variable value, then the period end can be identified, but the determination becomes imprecise due to signal noise and delays
Solution Approach 1:
The patent applies preliminary action by determining the time constant of the delay before using it to correct the period end determination. The control unit first characterizes the delay behavior of the lambda probe signal by determining the time constant from signal progressions, then uses this pre-determined time constant to compensate for delays in subsequent period end measurements. This preliminary characterization enables more accurate period end identification despite signal noise and transmission delays.
2Object-affected harmful factors
If the difference value is selected sufficiently large to avoid noise interference, then signal noise is reduced, but the end of the period is recognized after the actual end due to delay
Solution Approach 1:
The patent implements feedback by using the determined time constant to correct the period end determination. The control unit monitors the signal value progression, determines the time constant from the signal's temporal behavior, and then uses this feedback information to compensate for the delay inherent in the lambda probe signal transmission. This feedback mechanism allows the system to recognize the actual period end more accurately despite the delay caused by using a sufficiently large difference value to filter noise.
3Ease of operation
If the signal value is tracked with variable value to identify period end, then period identification is enabled, but incorrect identification occurs due to signal delays in transmission
Solution Approach 1:
The patent applies parameter changes by introducing the time constant as a new parameter to characterize and compensate for signal delays. Instead of simply tracking the variable value and difference value, the control unit determines the time constant from the signal's temporal progression and uses this parameter to correct the period end identification. This additional parameter transformation enables accurate period end determination despite delays in signal transmission from the lambda probe.
Data Source
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AI summary
The invention relates to a method for operating an exhaust gas purifying device (1), comprising at least one catalyst (2) for filtering exhaust gas and at least one lambda sensor (5, 6) arranged in the exhaust gas, wherein an end of a time period (t0,t1) assigned to a maximum or minimum of a delayed signal value (lambda) supplied by the lambda sensor (5,6) is determined in that a variable value tracks the signal value (lambda) and, if the signal value (lambda) falls short of or exceeds the variable value by a specific difference value (Deltalambda), the end of the time period (t0,t1) is determined. According to the invention, the end of a time period (t0,t1) is corrected on the basis of the time constant (tau) of the delay. The invention further relates to an exhaust gas purifying device (1).