Nonlinear Observer-Based Control of Load Transitions in Homogeneous Charge Compression Ignition Engines

This paper presents a model-based nonlinear feedback controller designed to regulate the crank angle at 50% fuel burned $(\theta_{CA50})$ for a gasoline homogeneous charge compression ignition engine model during load transitions. The regulation of the combustion timing is based on manipulating the charge temperature through internal dilution, which is achieved by controlling the lift of a secondary opening of the exhaust valve, also known as the rebreathing lift. The nonlinear feedback controller developed is based on a positive semidefinite Lyapunov function using a simplified control model which contains only the cycle-to-cycle temperature dynamics. The nonlinear feedback controller depends on measurement of the combustion timing $\theta_{CA50}$ and estimation of the temperature at intake valve closing. Closed-loop simulation of the full-order engine model shows that the nonlinear feedback controller, along with a nonlinear observer, is able to regulate the combustion timing $\theta_{CA50}$ by stabilizing the temperature dynamics during load transitions. The closed-loop system with the observer-based feedback controller is shown to be robust to some classes of model uncertainty and measurement noise through simulation and an estimate of the region of attraction.