Christian Winge Vigild

A λ Control Observer with Fault Correction

Abstract At the present, long term stoichiometric Air/Fuel Ratio (AFR) control of an SI engine is maintained by using a switching HEGO sensor and a gain scheduled, high gain PI controller. Because of its inexpensive and primitive design and the engine time delay, this loop has a very low effective bandwidth. It seldom exceeds 2 Hz. This is altogether too small for accurate transient air/fuel ratio control. This paper presents a new λ (normalized air/fuel ratio) control methodology based on a time delay observer. This technique makes possible a significant increase of the lambda control bandwidth while at the same time incorporating an integration term so that stationary AFR errors are reduced to zero.