Closed loop emission control in turbocharged Diesel engines

During the last decades Diesel engine control has been based on a set of static control strategies that basically guaranteed the air mass flow while imposing the injection settings. Although software calibration is set in order to satisfy the emission requirements in the certification cycle, no active control is performed at the engine emission level. The modification of the certification procedures, which could eventually include the
verification of random cycles, threatens the wellestablished control and calibration approach. Model based control techniques, along with on-board emission sensors, may be used for an effective control of the engine out emissions, by means of a coordinated control over the fuel and air paths. Present paper illustrates the application of an active NOx control to an automotive turbocharged diesel engine. The control concept is able to satisfy the emission level references coping with variations in the driving conditions and compensating unit-to-unit dispersion and environmental conditions.