Individual Air-Fuel Ratio Balancing Control for Multi-Cylinder SI Engines: Modeling and Validation

The three phase catalyst is popularly employed in modern engines for exhaust control and its catalytic efficiency is determined by the Air-Fuel ratio (A/F). In this paper, individual A/F control problem is addressed for a multi-cylinder SI engine, of which one exhaust pipe is shared by many cylinders. Firstly, an overlap model to describe the dynamics from individual fuel injection to A/F value of mixing point at the exhaust pipe is introduced. In this model, the imbalance between cylinders in A/F is presented by unknown offsets in individual fuel injection. Then the unknown offset free Model Predictive Control (MPC) scheme is designed based on this model. Finally, both the model and the controller are validated by a car-used six-cylinder SI engine.