AUTOMATIC DESIGN AND PARAMETRIZATION OF A MODEL-BASED CONTROLLER APPLIED TO THE AF-RATIO CONTROL OF A DIESEL ENGINE

The feedback control of the air-to-fuel (AF) ratio in diesel engines offers several advantages over the traditional control of exhaust gas recirculation (EGR) with the measured air mass flow. Because of the large transport delay involved in the feedback loop of the AF-ratio controller, a simple PI controller would not be sufficiently accurate to guarantee an adequate response of the system. Therefore a model-based approach is proposed for the design of the controller. Since the engine behaves differently in the different operating points within the operating range, a controller is designed that is capable of perceiving these changes and of tracking the desired setpoint reliably under varying operating conditions. Two approaches are investigated. First, an H∞ controller is designed in a grid of operating points and parametrized. Second, an internal model controller is developed with a simplified model of the plant. The efficiency of the two methods is tested in a driving cycle and compared with the conventional EGR controller.