NLQR Control of High Pressure EGR in Diesel Engine

The tightening of the diesel pollutant emission regulations has made the performances obtainable from steady-state map controls, commonly employed in Internal Combustion Engine management, unsatisfactory. To overcome these limitations a NonLinear Quadratic Regulator (NLQR) system for the High Pressure Exhaust Gas Recirculation (HP-EGR) loop of a turbocharged diesel engine has been developed to control the intake O
₂
concentration and the Intake MAnifold Pressure (IMAP). This model-based control approach exploits the prediction of two dynamic Recurrent Neural Networks (RNN) to compute the command actions for the HP-EGR valve and VGT (Variable Geometry Turbocharger) rack position. Engine speed, engine load, HP-EGR and VGT valves positions together with the intake O
₂
concentration and IMAP feedbacks are the inputs used by the RNN to compute the predictions. In order to select the next HP-EGR and VGT control actions the effect of different command combinations, retrieved from a discretized action space, are evaluated through a quadratic objective function to be minimized. Two different transient profiles have been used to test the designed control system against the steady-state map approach. The developed control system has shown a satisfactory performance improvement over the map control. Therefore it is suitable for the subsequent assessment on the real engine.