Lambda Probe Resistance Correction for Temperature Measurement
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Solution Overview
Problem
Existing methods for determining the temperature of a jump lambda probe using its internal resistance are inaccurate due to dependencies on exhaust gas lambda value, aging, and heating effects, limiting the precision of exhaust gas composition control in internal combustion engines.
Innovation Solution
A method that corrects the measured ohmic resistance of a jump lambda probe by accounting for physical and chemical parameters such as lambda value, aging, and probe body temperature, using correction factors and adaptation values to determine an absolute temperature, allowing for precise temperature calculation under various conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the internal resistance of the measuring element is used to determine temperature, then temperature monitoring is achieved, but measurement precision deteriorates due to dependencies on lambda value, aging, and heating effects
Solution Approach 1:
The patent applies parameter changes by introducing multiple correction factors that adjust the measured resistance value based on varying operational parameters. Specifically, a lambda-dependent correction factor accounts for exhaust gas composition variations, an aging-dependent correction factor compensates for sensor degradation over time, and a heating-dependent correction factor adjusts for thermal effects during resistance measurement. These parameter-based corrections transform the single-parameter resistance measurement into a multi-parameter compensation system, thereby maintaining measurement precision across different operating conditions.
2Reliability
If only measured values from specified mixture ranges are processed, then measurement reliability improves, but productivity deteriorates due to limited frequency of valid measurements
Solution Approach 1:
The patent resolves this contradiction by changing the parameter approach from filtering measurements to correcting measurements. Instead of discarding measurements outside specified mixture ranges, the system applies a lambda-dependent correction factor that validates and adjusts resistance measurements across the full range of lambda values. This parameter transformation allows continuous measurement processing while maintaining reliability through mathematical correction rather than selective filtering, thereby maximizing measurement frequency without sacrificing accuracy.
3Measurement precision
If a lambda-dependent correction value is applied to the measured value, then measurement precision improves for mixture composition, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-determining and storing correction factors in lookup tables during the manufacturing phase. The lambda-dependent correction factors, aging-dependent correction factors, and heating-dependent correction factors are all calculated and stored in advance based on characterized sensor behavior under various conditions. During operation, the control unit simply retrieves the appropriate correction factors from these pre-computed tables based on current sensor readings and operating parameters, rather than performing complex real-time calculations. This preliminary preparation significantly reduces computational complexity while maintaining high measurement precision.
Solution Approach 2:
The patent introduces intermediary correction factors as mediating elements between the raw resistance measurement and the final temperature calculation. These correction factors serve as intermediate variables that decouple the complex relationships between resistance, temperature, lambda value, aging, and heating effects. By introducing these intermediary parameters, the system transforms a complex multi-variable problem into a series of manageable correction steps, each handled by a dedicated correction factor that can be independently determined and applied.
4Measurement precision
If the probe is adjusted to a predetermined temperature through heating control, then measurement conditions are optimized, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by introducing a heating-dependent correction factor that allows accurate temperature measurement without maintaining the probe at a fixed predetermined temperature. Instead of controlling the heating element to maintain constant temperature, the system measures the resistance at the actual varying temperature and applies corrections that account for the heating state. This parameter transformation from temperature control to temperature compensation enables energy-efficient operation while maintaining measurement accuracy across varying thermal conditions.
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
Enables the use of all measured resistance values to determine an absolute temperature, improving accuracy and frequency of valid measurements, and ensuring precise exhaust gas composition control for effective catalytic converter operation.
Implementation Method 1
jump lambda probes based on the Nernst principle
Implementation Method 2
measuring element with a temperature-dependent ohmic resistance
Data Source
Figure 1~4
AI summary
The method involves measuring ohm resistance of a measuring element at a time point. A correction factor is determined from physical and/or chemical parameter of gases surrounding the measuring element at the time point of the measurement of the ohm resistance. The correction factor is predetermined for different values for the physical and/or chemical parameter of the gases. The correction factor is determined according to a preset formula. Adjustment of the measured ohm resistance is determined depending on the physical and/or chemical parameter of the measuring element.