Abstract
The object of this paper is to develop a new method to deal the influence of air and fuel dynamics on A/F ratio control. In order to control the A/F ratio accurately and to improve the exhaust emission of SI engine, the author has developed a nonlinear compensator for fuel film and a close-loop observer for manifold pressure estimation, which construct the transient AFR control model of SI engine. Compared with the conventional open-loop observer, the close-loop observer effectively prevents the transient A/F ratio control from the influence of sensor noise, response delay and the influence of engine model error. And in general this observer requires less calibration time and accuracy because of it's inherent robustness. Experiment approves that this control method gives accurate A/F ratio control on transient and stationary conditions.