Model-based feedback control of the air-to-fuel ratio in diesel engines based on an empirical model

This paper discusses the application of a modelbased feedback control loop for the air-to-fuel (AF) ratio instead of the standard exhaust gas recirculation (EGR) control loop that utilizes the hot-film air-mass meter (HFM) as control variable. A comparison between the model-based controller that contains information about the plant dynamics and the standard EGR controller is carried out. In terms of performance and driveability the results of the AF ratio controller match those of a standard EGR controller. Moreover, with this new configuration, production tolerances and drift of sensors and actuators, such as the HFM and the injectors, can be detected and compensated. The starting point for the controller design is an empirical linear engine model with the EGR valve control signal as input signal and the AF ratio as the output signal.