Transient lean burn air-fuel ratio control using input shaping method combined with linear parameter-varying control

Abstract

Transient air-fuel ratio control for lean burn engines is critical to achieve desired fuel economy and meet federal emission regulations. Unlike conventional SI engines, lean burn engines are no longer operating in a narrow band around stoichiometry resulting in a very challenging air-fuel ratio tracking problem. An approach to combine an input shaping method together with a linear parameter varying (LPV) feedback controller is proposed to solve the transient air-fuel ratio tracking problem. In the work of Zhang et al. (2005), a feedback LPV air-fuel ratio controller has been designed to regulate the air-fuel ratio at steady state engine operating conditions, reduce the variability of the closed-loop system, reject disturbances and guarantee robustness and stability. In this paper, an input shaping method is proposed to reduce the cost of feedback, and thereby enhance the air-fuel ratio tracking performance during engine transient operations. The prefilter is designed based on the closed-loop dynamics resulting from the LPV design. A systematic input shaping prefilter design process is developed. The designed prefilter successfully extends the closed-loop air-fuel ratio tracking bandwidth. Simulation results are used to demonstrate the effectiveness of the input shaping prefilter. Moreover, the designed prefilter is structurally simple and computationally efficient