Variable Nozzle Turbocharger Controller Pressure Overshoot
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Solution Overview
Problem
Conventional supercharging pressure control systems experience significant overshooting of exhaust pressure when shifting from rich combustion mode to lean combustion mode in NOx occlusion-reduction catalysts, leading to hardware protection issues and degraded drivability and fuel consumption.
Innovation Solution
An engine controller with an exhaust flow rate adjustment mechanism, utilizing a deviation computation section, proportional control term computation section, and integral control term computation section to adjust the operation amount of the exhaust flow rate, initializing the integral control term at the mode shift and varying gains based on combustion modes to mitigate overshooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the waste gate valve and VNT vane are closed to control supercharging pressure, then supercharging pressure control is improved, but exhaust pressure overshooting occurs when shifting from rich to lean combustion mode
Solution Approach 1:
The system performs preliminary action by detecting the combustion mode shift from rich to lean mode and proactively adjusting the operation amount of the exhaust flow rate adjustment mechanism before significant pressure overshooting occurs. The control unit computes a corrected operation amount that prevents excessive closing of the waste gate valve and VNT vane, thereby avoiding harmful exhaust pressure spikes while maintaining precise supercharging pressure control.
2Object-affected harmful factors
If the target supercharging pressure is reduced to prevent overshooting, then exhaust pressure control is improved, but drivability and fuel consumption deteriorate
Solution Approach 1:
The system applies dynamics by making the operation amount of the exhaust flow rate adjustment mechanism variable based on combustion mode. During rich combustion mode, the system uses standard PI control for optimal performance. When transitioning to lean combustion mode, the system dynamically corrects the operation amount to prevent overshooting. This dynamic adaptation maintains both drivability and fuel consumption performance while preventing harmful pressure spikes.
3Object-affected harmful factors
If the minimum valve opening degree is increased to prevent overshooting, then exhaust pressure control is improved, but responsiveness to accelerator pedal operation deteriorates
Solution Approach 1:
The system changes parameters by adjusting the operation amount of the exhaust flow rate adjustment mechanism based on combustion mode detection. Rather than fixing the minimum valve opening degree, the system computes a corrected operation amount that varies with combustion mode. This allows the waste gate valve and VNT vane to operate at optimal opening degrees for both responsiveness and overshooting prevention, as the operation amount is continuously optimized based on real-time combustion conditions.
Data Source
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AI summary
A supercharging pressure control system that controls supercharging pressure in a diesel engine with a supercharger includes: a deviation computation section that computes a deviation between actual supercharging pressure and target supercharging pressure; a proportional control term computation section that computes a proportional control term used to change an operation amount of a variable nozzle turbo vane in proportion to the deviation; an integral control term computation section that computes an integral control term being used to change the operation amount of the variable nozzle turbo vane in proportion to time integration of the deviation; and an operation amount computation section that adds the proportional control term and the integral control term to compute the operation amount. The integral control term computation section initializes the time integration of the deviation to a specified value and computes the integral control term at a time point at which a combustion mode of an NOx occlusion-reduction catalyst starts being shifted from a rich combustion mode to a lean combustion mode.