Optimal Combustion Phasing Modeling and Control of a Turbulent Jet Ignition Engine

Combustion phasing control is very important for internal combustion engines to achieve a high thermal efficiency with low engine-out emissions. Traditional open-loop map-based control becomes less favorable in terms of calibration effort, robustness to engine aging, and especially control accuracy for turbulent jet ignition (TJI) engines due to the increased number of control variables over conventional spark-ignition engines. In this paper, a model-based feedforward controller is developed for a TJI engine. A feedback controller is designed based on the linear quadratic tracking control with output covariance constraint. Since the TJI main-chamber combustion is influenced by the prechamber one, the proposed controller optimizes the control variables in both combustion chambers. The proposed feedforward and feedback controller reduces standard deviation of combustion phase by more than 22% over a group of baseline controllers through a series of dynamometer engine tests.