Air-Fuel Ratio Feedback Control for Engine Transient Response
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Solution Overview
Problem
Existing air-fuel ratio feedback control methods face issues with overcorrection and delayed convergence due to the transient response of the air-fuel ratio sensor, particularly when the sensor's response is delayed or deteriorates.
Innovation Solution
A method that compares the air-fuel ratio sensor signal with a threshold value to determine when to update the manipulation signal, preventing excessive corrections and ensuring timely resumption of feedback control, even if the sensor's transient response is deteriorated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of time during which updating of the manipulated variable is prohibited is extended, then overcorrection is prevented even when the transient response of the air-fuel ratio sensor deteriorates, but convergence on the target air-fuel ratio is delayed when the transient response has not deteriorated
Solution Approach 1:
The prohibition period for updating the manipulated variable is made dynamic rather than fixed. The control device determines the prohibition period based on the transient response characteristics of the air-fuel ratio sensor, specifically using the response time measured during engine startup or after fuel injection resumption. This allows the system to adapt the prohibition duration to actual sensor performance, preventing overcorrection when response is slow while enabling timely updates when response is fast.
Solution Approach 2:
The control device changes the parameter of the prohibition period based on sensor response characteristics. By measuring the transient response time of the air-fuel ratio sensor and using this measurement to set the prohibition period, the system transforms a static parameter into a variable one that adapts to sensor condition, thereby resolving the contradiction between preventing overcorrection and maintaining fast convergence.
2Productivity
If feedback control is resumed immediately after fuel injection is resumed, then convergence speed is improved, but excessive increase in injection quantity correction occurs due to delayed sensor response
Solution Approach 1:
The control device performs preliminary measurement of the air-fuel ratio sensor's transient response time during engine startup or after fuel injection resumption. Based on this preliminary measurement, it pre-determines the appropriate prohibition period for updating the manipulated variable before actual feedback control begins. This preliminary characterization of sensor performance enables the system to set optimal control parameters in advance, preventing excessive correction while maintaining fast convergence.
Solution Approach 2:
The control device uses feedback from the air-fuel ratio sensor's actual response behavior to adjust the prohibition period. By continuously monitoring how quickly the sensor responds to changes in air-fuel ratio and using this information to set the update prohibition duration, the system creates a closed-loop adaptation mechanism that prevents excessive correction while enabling rapid convergence when conditions permit.
Data Source
AI summary
A feedback control of an air-fuel ratio of an internal combustion engine is performed in such a manner that when fuel injection is resumed from a condition where fuel injection is stopped due to deceleration running, air-fuel ratio feedback control is resumed once the output from an air-fuel ratio sensor indicates an air-fuel ratio less than or equal to a threshold value SL.