Control of thermal ignition in gasoline engines

In this paper a model based controller is designed to regulate the crank angle of 50% fuel burned (CA50) and the air to fuel ratio (AFR) in the exhaust manifold of a gasoline engine during fuel step changes. The regulation of the combustion timing is based on manipulating the charge temperature through the internal and external dilutions which are achieved by controlling the lift of a secondary opening of the exhaust valve, also known as rebreathing lift (RBL), and the exhaust gas recirculation (EGR) valve. The paper includes a brief introduction of the engine model followed by its experimental validation during fuel step changes which are considered as disturbances for the control problem. A two-input two-output controller is designed for the linearized model and simulations of closed loop response with the controller applied to the nonlinear model are presented. Finally, an equivalent reduced order controller is derived to facilitate implementation on a dynamometer facility.