Catalyst Transfer Function Gain Estimation via Air-Fuel Modulation

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Solution Overview

Problem

Existing methods for determining catalyst degradation in vehicles are intrusive, prone to noise, and may degrade emissions, making it difficult to assess catalyst efficiency and emissions compliance.

Innovation Solution

A method that determines a catalyst's transfer function within a specified frequency range using feedback engine air-fuel ratio control, allowing for non-intrusive degradation assessment through small air-fuel ratio variations, rather than specialized perturbations, thereby improving catalyst efficiency and emissions monitoring.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a one-time change to the engine's air fuel ratio is made to assess catalyst degradation, then catalyst degradation level can be indicated, but engine exhaust emissions are degraded due to rich or lean exhaust gases breaking through the catalyst

Engineering Contradiction:

Improvecatalyst degradation assessmentVSAvoidexhaust emissions

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies periodic action by using continuous small air-fuel ratio variations instead of a single large step change. The system repeatedly modulates the air-fuel ratio within normal operating ranges during feedback control, allowing multiple observations to be made without causing emission breakthrough. This periodic modulation enables robust statistical analysis of catalyst response while maintaining emissions compliance.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the parameter of air-fuel ratio modulation from large step changes to small continuous variations. By operating within a specified frequency range and using smaller amplitude variations, the system maintains the catalyst within its efficient operating window, preventing emission breakthrough while still obtaining sufficient signal to assess degradation. This parameter optimization resolves the contradiction between measurement needs and emissions control.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a one-time change to the engine's air fuel ratio is made to assess catalyst degradation, then catalyst degradation level can be indicated, but the assessment is limited by noise in the system and few observations

Engineering Contradiction:

Improvecatalyst degradation assessmentVSAvoidestimated results

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system uses periodic air-fuel ratio modulations at specified frequencies to generate multiple observations over time. By continuously applying small variations and measuring the catalyst response repeatedly, the system accumulates sufficient data points to perform statistical analysis and filter out noise, thereby improving the reliability of degradation assessment.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent employs feedback control using downstream oxygen sensors to monitor the catalyst response to air-fuel ratio variations. This feedback mechanism allows the system to continuously adjust and refine measurements, distinguish between normal system noise and actual catalyst degradation signals, and improve the reliability of the assessment through real-time monitoring and analysis.

Inventive Principle:

Principle #23Feedback

3Object-generated harmful factors

If small air-fuel ratio variations are used to assess catalyst degradation, then emissions are not degraded and driver noticeability is minimized, but the measurement may be more susceptible to noise

Engineering Contradiction:

Improveexhaust emissionsVSAvoidmeasurement robustness

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Inventive Principle:

Principle #23Feedback

4Productivity

If precise engine air-fuel ratio control is applied to improve catalyst efficiency, then catalyst conversion efficiency is improved, but it becomes necessary to determine whether the catalyst is degraded to maintain emissions compliance

Engineering Contradiction:

Improvecatalyst conversion efficiencyVSAvoidcatalyst degradation monitoring

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent makes the existing feedback control system multi-functional by enabling it to perform both emissions control and catalyst degradation assessment. The same downstream oxygen sensors and air-fuel ratio control mechanisms used for maintaining catalyst efficiency are also utilized to evaluate catalyst health. This eliminates the need for separate dedicated diagnostic hardware, reducing overall system complexity while maintaining both functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9359967B2Method for identification of a threshold-level catalyst

Publication Date: 2016.06.07 FORD GLOBAL TECH LLC

AI summary

Systems and methods for estimating catalyst transfer function gain are disclosed. In one example, an air-fuel ratio forcing function is applied to a catalyst. Air-fuel ratios upstream and downstream of the catalyst are manipulated to determine a transfer function gain of the catalyst. The transfer function gain may be a basis for indicating the presence or absence of catalyst degradation.