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Abstract



Coordinated model based throttle and turbo control


Downsizing and turbocharging is one way to meet the high demands on fuel consumption and performance on todays engines. The air-path system in a turbocharged spark ignited engine is a complex system and because the intake manifold pressure is tightly connected with the engine torque a consistent and robust control is needed. The control strategy utilizes two control loops, one wastegate actuator to control the intercooler pressure and one throttle actuator to control the intake manifold pressure. These pressures are coupled, making both actuators affect both pressures. Because of the time delay and the dynamics in the actuators and the system dynamics between the wastegate and the intercooler pressure the controller overreacts causing a pressure overshoot and sometimes oscillations. The oscillatory behavior is caused by both actuators trying to minimize their respective control error, affecting the others pressure. The delay in the system dynamics causes the two controllers to enter a state where they counteract each other. A compensation strategy is suggested, which estimates the intercooler pressure derivative and uses that to predict the future intercooler pressure. The compensation strategy shows good performance in simulations, reducing the overshoots and eliminating the oscillations.

Petter Carlsson

2013

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