Periodic time-varying model-based predictive control with input constraints for air-fuel ratio control in IC engines

Abstract

In multi-cylinder internal-combustion (IC) engines, the concerned air-fuel ratio is the one of the mixed exhaust gases from these cylinders. However, imbalance in air and fuel paths between cylinders exists. That demands for modifying fuel injection of individual cylinders for high-performance air-fuel ratio control. This paper applies the model-based predictive control technology to air-fuel ratio control through modifying fuel injection command for individual cylinders. Input constraints are accounted for and the controller action is solution to a constrained optimisation problem. Since the model is linear periodic time-varying and with bottom dead centre (BDC) scale, the designed control strategy is also BDC-scaled and periodic. The control strategy is validated via experiments, and experimental results show that the control performance is related to constraint limits.