Gain-scheduled model-based feedback control of the air/fuel ratio in diesel engines

This paper investigates the adoption of an innovative closed-loop control of the air/fuel ratio (AFR) in modern diesel engines. The in-cylinder AFR is in fact a critical quantity responsible for the formation of NOxNOx and particulate matter emission.Two approaches are investigated for the design of a gain-scheduled AFR controller, that are based on the internal model control structure and on the H∞H∞ design method. In addition, two feedforward controllers are investigated for improving the tracking quality of the system.In terms of tracking performance and driveability, the proposed AFR controllers at least match the series production EGR controller. However, due to the fact that an AFR controller uses information obtained after the combustion process, it can also deal with the drift of sensors and actuators involved in the control loop.