Air Charge Estimation for Skip Fire Engine Control
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Solution Overview
Problem
Conventional air charge estimators in internal combustion engines are not well suited for skip fire controlled engines, as they fail to accurately predict cylinder air charge due to irregular and shifting firing sequences, leading to poor fuel injection and efficiency issues.
Innovation Solution
The development of methods and systems that estimate air charge by predicting manifold pressure based on current and anticipated firing sequences, actuator positions, and engine parameters, allowing for accurate fuel injection timing and improved air-fuel ratio regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional air charge estimators are used in skip fire controlled engines, then the device complexity is reduced, but the measurement precision of cylinder air charge deteriorates due to irregular and shifting firing sequences
Solution Approach 1:
The system performs preliminary actions by predicting future manifold pressure values and determining anticipated firing sequences before they occur. The controller predicts the firing sequence for a predetermined number of future engine cycles and uses this information to calculate anticipated manifold pressure values, which are then used to determine accurate air charge values for current and future combustion events.
Solution Approach 2:
The system dynamically adapts to changing engine operating conditions by continuously updating predictions of firing sequences and manifold pressure values. The controller modifies air charge calculations based on predicted variations in engine speed, load, and firing patterns, allowing accurate measurements despite dynamic changes in engine operation.
2Measurement precision
If accurate air charge estimation is achieved through prediction methods, then the measurement precision improves, but the loss of time increases due to computational requirements
Solution Approach 1:
The system performs preliminary calculations by predicting manifold pressure values and firing sequences in advance, before the actual combustion events occur. This allows the controller to prepare accurate air charge values ahead of time, reducing computational delays during critical fuel injection timing.
Solution Approach 2:
The system calculates air charge values for a predetermined number of future engine cycles in advance, performing more calculations than immediately needed. This excessive action ensures that accurate air charge values are available when required, trading computational effort in advance for reduced real-time processing requirements.
3Adaptability or versatility
If skip fire engine control is implemented for finer displacement control, then the adaptability improves, but the reliability of conventional air charge estimation deteriorates
Solution Approach 1:
The controller determines anticipated firing sequences for future engine cycles in advance, before the skip fire pattern is executed. This preliminary determination allows the system to predict manifold pressure variations caused by irregular firing sequences, maintaining reliable air charge estimation despite the adaptability introduced by skip fire control.
Solution Approach 2:
The system uses feedback from predicted manifold pressure values and actual engine operation to continuously refine air charge calculations. By comparing predicted versus actual conditions and adjusting subsequent predictions, the system maintains reliable air charge estimation even as skip fire patterns change engine behavior.
Data Source
AI summary
Methods, devices, estimators, controllers and algorithms are described for estimating working chamber air charge during engine operations. The described approaches and devices are well suited for use in dynamic firing level modulation controlled engines. Manifold pressure is estimated for a time corresponding to an induction event associated with a selected working cycle. The manifold pressure estimate accounts for impacts from one or more intervening potential induction events that will occur between the time that the manifold pressure is estimated and the time that the induction event associated with the selected working cycle occurs. The estimated manifold pressure is used in the estimation of the air charge for the selected working cycle. The described approach may be used to individually calculate the air charge for each induction event at any time that the engine is operating in a mode that can benefit from the individual cylinder air charge estimations.