Control of Air Fuel Ratio in SI Engine Using Optimization

The air fuel ratio (AFR) control is one of the effective methods to reduce emission and fuel consumption in spark ignition (SI) engines. Due to the hard nonlinearities existing in the engine dynamics model, a nonlinear controller should be designed for AFR control. In this Paper, an optimization-based nonlinear control law is developed for injected fuel mass flow to maintain AFR in the stoichiometric value. Simulation results show that the AFR in the controlled system is very close to the desired value, unlike the uncontrolled system in which the AFR has intensive fluctuations.