Delay Compensated Air/Fuel Control for Engine Response
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Solution Overview
Problem
Closed loop fuel/air control systems using universal exhaust gas oxygen sensors are hindered by significant time delays, leading to destabilization and sluggish response speeds, which compromise catalyst efficiency and drivability, especially under aggressive driving conditions.
Innovation Solution
A closed loop fuel control system incorporating a Smith Predictor feedback control loop and a transient fuel control filter to compensate for time delays and engine temperature variations, adjusting the fuel control signal to maintain accurate fuel regulation and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop fuel/air control is implemented using a UEGO sensor, then measurement precision of fuel/air ratio is improved, but time delay in the exhaust gas path destabilizes the control system resulting in sluggish response speed
Solution Approach 1:
The Smith Predictor implements preliminary action by using a process model to predict the future state of the system and compensate for the time delay in advance. The predictor calculates what the fuel/air ratio will be at a future time based on current control actions and system dynamics, allowing the controller to act as if there were no delay, thereby maintaining fast response speed while using the precise UEGO sensor measurements
2Measurement precision
If closed loop fuel/air control is implemented using a UEGO sensor, then measurement precision of fuel/air ratio is improved, but time delay in the exhaust gas path destabilizes the control system
Solution Approach 1:
The Smith Predictor compensates for time delay by predicting future system states, allowing the controller to maintain stability despite the delayed feedback from the UEGO sensor. The predictor uses a process model to calculate the expected fuel/air ratio at future time points, enabling the controller to make adjustments that maintain stability while utilizing the precise sensor measurements
3Speed
If delay compensation is implemented to increase response speed, then response speed is improved, but complexity of the control system increases
Solution Approach 1:
The Smith Predictor implements feedback by continuously comparing the actual UEGO sensor measurements with the predicted future values from the process model. The difference between measured and predicted values feeds back to correct the control actions, enabling fast response speed through delay compensation while managing system complexity through a structured feedback mechanism that builds upon the existing PID controller
Data Source
AI summary
A fuel control approach that compensates for time delays to increase exhaust gas sensor feedback response speed.