Decoupling EGR Valve and VGT Control Loops for Intake Flow
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Solution Overview
Problem
Current control systems for internal combustion engines are complex and require significant calibration efforts, with coupling between intake manifold pressure, EGR valve position, and fuel flow rate, making them inefficient for achieving targeted torque and power while controlling emissions.
Innovation Solution
A controller system that decouples EGR valve and VGT positions using a non-linear gain matrix to prioritize EGR valve control at low flow rates and low EGR valve positions, and exhaust pressure control at high flow rates and high EGR valve positions, optimizing charge and EGR flow management through feedback and feedforward mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If decoupling techniques are applied to achieve targeted intake flow parameters, then intake flow control precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the control system into two independent control loops: one for EGR valve position control and another for VGT position control. Each loop operates autonomously with its own setpoint and feedback mechanism, eliminating the need for complex mathematical transforms to decouple the interactions between EGR flow and turbocharger swallowing capacity.
Solution Approach 2:
The patent introduces separate setpoint generators for EGR valve position and VGT position that act as intermediaries between the desired intake flow parameters and the actual actuators. These setpoints are calculated independently based on target EGR flow and target fresh air flow, respectively, simplifying the control architecture.
2Manufacturing precision
If mathematical transforms are applied to decouple EGR valve and VGT position, then intake flow parameter control is improved, but calibration effort increases
Solution Approach 1:
The control strategy is segmented into independent EGR valve control and VGT control, each with its own setpoint calculation based on target flows. This segmentation eliminates the need for complex mathematical transforms and reduces calibration requirements to simple gain adjustments in each independent loop.
3Device complexity
If EGR valve and VGT positions are operated as serial controllers, then device complexity is reduced, but intake flow control precision deteriorates
Solution Approach 1:
Instead of serial control, the patent implements parallel independent control loops for EGR valve and VGT, where each actuator is controlled by its own setpoint derived from target flow parameters. This parallel segmentation maintains simplicity while achieving precise intake flow control.
Solution Approach 2:
The patent implements feedback control in both the EGR valve loop and VGT loop, where actual EGR flow and actual fresh air flow are measured and compared against target values, with corrections applied independently in each loop to maintain precise intake flow parameters.
Data Source
AI summary
A method for controlling charge flow in an internal combustion engine includes operating an engine having a VGT. The method includes determining a target and current charge flow and EGR flow. The method further includes determining an error term for the charge flow and the EGR flow, and determining an exhaust pressure feedback command in response to the error terms. The exhaust pressure feedback command is combined with an exhaust pressure feedforward command, and the VGT is controlled in response to the exhaust pressure feedback command. The method additionally includes determining the exhaust pressure feedback command in response to a current EGR valve position. The method further includes controlling an EGR flow rate with the EGR valve at relatively closed EGR valve positions, and controlling the EGR flow rate with exhaust pressure at relatively open EGR valve positions.