Fuel Control Delay Compensation for Engine Equivalence Ratio
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Solution Overview
Problem
Fuel control systems in internal combustion engines face challenges in accurately adjusting fuel injection to achieve a target equivalence ratio due to delays in exhaust gas oxygen sensor measurements and exhaust flow rates, leading to overshoot and undershoot in air/fuel mixture control.
Innovation Solution
A fuel control system that incorporates an equivalence ratio delay module, closed loop module, and feedback module to set a delayed base equivalence ratio request and determine closed loop corrections using proportional-integral control, accounting for sensor and transport delays, to adjust fuel injection based on real-time EGO sensor measurements and exhaust flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If real-time EGO sensor measurements are used for fuel control, then the responsiveness of fuel adjustment is improved, but measurement delays cause inaccuracy in achieving target equivalence ratio
Solution Approach 1:
The system performs preliminary actions by predicting the equivalence ratio based on historical data and engine operating conditions before the actual measurement is available. This prediction compensates for the sensor delay, allowing the control system to act proactively rather than reactively, thus maintaining both responsiveness and accuracy.
Solution Approach 2:
The system implements feedback by continuously comparing predicted equivalence ratio with actual sensor measurements once available, and using this information to refine future predictions. This closed-loop approach ensures that measurement delays do not accumulate errors and that the system maintains accuracy over time.
2Device complexity
If fuel injection is adjusted based on delayed sensor data, then the control system remains simple, but overshoot and undershoot occur in air/fuel mixture control
Solution Approach 1:
The system performs preliminary calculations to predict future equivalence ratio based on current engine state and historical sensor data. This allows the control system to adjust fuel injection in advance, compensating for known delays in the measurement and actuation chain, thereby preventing overshoot and undershoot without requiring complex real-time control algorithms.
Solution Approach 2:
The system changes parameters by dynamically adjusting the predicted equivalence ratio based on varying engine operating conditions such as load, speed, and temperature. This allows the simple control structure to adapt to different operating regimes and maintain precision without increasing device complexity.
3Measurement precision
If multiple control loops are implemented to account for delays, then the accuracy of equivalence ratio tracking is improved, but the control system complexity increases
Solution Approach 1:
The system segments the control problem into distinct components: a prediction module that handles the delay compensation, a fuel calculation module that determines injection quantity, and a control module that executes the adjustment. This segmentation allows each component to be optimized independently while maintaining overall system accuracy without excessive complexity.
Solution Approach 2:
The control system achieves multi-functionality by using a single integrated prediction and control algorithm that handles multiple control loops simultaneously. Rather than implementing separate physical control loops, the system uses software-based multi-functionality to achieve accurate equivalence ratio tracking while minimizing hardware and system complexity.
Data Source
AI summary
A delay module, based on a base request received for a first loop, sets a delayed base request for a second loop. A first period between the first and second loops corresponds to: a first delay period of an oxygen sensor; and a second delay period for exhaust to flow from a cylinder of an engine to the oxygen sensor. A closed loop module determines a closed loop correction for the second loop based on: the delayed base request for the second loop; a measurement from the oxygen sensor; the closed loop correction for the first loop; and the closed loop correction for a third loop. A second period between the second and third loops corresponds to the first delay period of the oxygen sensor. A summer module sets a final request for the second loop based on the base request plus the closed loop correction for the second loop.