Engine Control Decoupling Fuel Mass Correction from Boost Pressure Limitation
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Solution Overview
Problem
Torque-oriented control methods for internal combustion engines can lead to unstable behavior during shifting under load and acceleration due to the dynamic interaction between boost pressure-dependent torque limitations and fuel mass corrections, resulting in oscillating target torque and inefficient speed control.
Innovation Solution
Dynamic decoupling of fuel mass correction from boost pressure-dependent limitations by using a delay element, such as a filter, or a flat weighting curve, and decoupling efficiency calculation from LDA limiting torque using a PT1 filter to stabilize the speed control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a steep transition weighting curve is used for fuel mass correction, then fuel efficiency is improved, but control stability deteriorates due to oscillating target torque
Solution Approach 1:
The patent segments the control system into distinct functional blocks: a first control unit that calculates target torque based on accelerator pedal position, and a second control unit that calculates fuel mass based on target torque. This segmentation allows independent optimization of each control function and prevents oscillations from propagating between them.
Solution Approach 2:
The patent extracts the fuel mass calculation from the torque control loop by introducing a separate fuel mass control unit. This extraction breaks the harmful feedback loop where torque limitations caused by steep weighting curves would otherwise create oscillations. The fuel mass is now determined independently rather than being dynamically coupled to torque limitations.
2Reliability
If boost pressure-dependent torque limitation is applied, then engine protection is improved, but speed control stability deteriorates during transient operations
Solution Approach 1:
The patent applies preliminary action by calculating and limiting the target torque in advance based on boost pressure conditions before the actual torque application. The first control unit determines a limited target torque that accounts for LDA curve constraints, preventing the engine from entering unstable operating regions in the first place rather than reacting to instabilities after they occur.
Solution Approach 2:
The patent introduces an intermediary control structure where the limited target torque from the first control unit serves as the input to the second control unit. This intermediary variable decouples the boost pressure-dependent limitations from the fuel mass calculation, allowing the system to maintain protection while avoiding the oscillation-prone direct coupling.
Data Source
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AI summary
The invention relates to a method and an assembly for operating an internal combustion engine. In the method, a correction of the fuel mass is dynamically decoupled from the calculation of the charging-pressure-dependent limitation.