ITERATIVE ADAPTIVE AIR/FUEL RATIO CONTROL

This paper addresses the air-fuel (A/F) ratio control of an SI engine with a wide-range lambda sensor whose time constant may change during operation. For the feedback control of the A/F ratio, an internal model controller (IMC) is employed. Based on the concept of iterative feedback tuning (IFT), the current value of the sensor time constant needed for the adaptation of the IMC-controller is found by doing well-predefined experiments on the closed-loop control system. The effectiveness of this method is demonstrated with simulations and real experiments on an engine test bench.