Coordinated control method for turbocharged diesel engines having exhaust gas recirculation

A compression ignition engine system comprising:

• an exhaust gas recirculation (EGR) passage including an EGR valve connecting an intake manifold and exhaust manifold of the engine, said EGR valve responsive to an EGR valve control signal for regulating the amount of exhaust gas flowing into said intake manifold;
• a variable geometry turbocharger (VGT) including a compressor connected to a turbine, the compressor in communication with the intake manifold and the turbine in communication with the exhaust manifold, said turbine responsive to a Turbocharger signal for regulating the intake manifold pressure;
• a mass airflow sensor located upstream of said compressor for providing a compressor mass airflow signal (W.sub.a);
• an intake manifold pressure sensor located in said intake manifold for providing an intake manifold pressure signal (P.sub.1);
• an engine control unit including memory and a dynamic controller, said memory including a table of desired intake manifold pressure values (P.sub.1 *) and desired compressor flow values (W.sub.a *) indexed by engine speed and fueling rate said table of values corresponding to desired values for the air-fuel ratio and burnt gas fraction at each value of the requested engine fueling rate and engine speed, said dynamic controller adapted to receive as inputs said intake manifold pressure signal and said mass airflow signal and transmit as outputs said EGR valve control signal and said turbocharger signal as a function of the weighted sum of the differences between P.sub.1 and P.sub.1 *, and between W.sub.a and W.sub.a *.

In a compression ignition engine system having an exhaust gas recirculation (EGR) passage including an EGR valve connecting an intake manifold and exhaust manifold of the engine, said EGR valve responsive to an EGR valve control signal for regulating the flow of exhaust gas into said intake manifold, and a variable geometry turbocharger (VGT) including a compressor connected to a turbine, the compressor in communication with the intake manifold and the turbine in communication with the exhaust manifold, said turbine responsive to a turbocharger signal for regulating the intake manifold pressure, an engine control unit for regulating the airflow into said engine, said engine control unit comprising:

• memory for storing feedback gains and desired engine operating values;
• and
• a feedback controller for generating said EGR valve control signal and said turbocharger signal, said feedback controller programmed to:
• retrieve from said memory a desired intake manifold pressure value (P.sub.1 *) and a desired compressor flow rate (W.sub.a *) said P.sub.1 * and W.sub.a * corresponding to desired values for the air-fuel ratio and burnt gas fraction at each value of the requested engine fueling rate (W.sub.f (t)) and engine speed (N(t));
• receive a pressure signal (P.sub.1) indicative of the actual intake manifold pressure;
• receive a compressor flow value (W.sub.a) indicative of the actual compressor flow rate;
• determine controller weights g.sub.1, g.sub.2, h.sub.1, and h.sub.2 ;
• determine proportional and integral feedback gains k.sub.p and k.sub.i ;
• generate said EGR valve control signal (X.sub.egr) and said turbocharger signal (X.sub.vgt) as a function of g.sub.1, g.sub.2, h.sub.1, h.sub.2, P.sub.1 *, P.sub.1, W.sub.a, W.sub.a *, k.sub.p and k.sub.i and
• transmit X.sub.egr to said EGR valve to regulate the compressor flow rate;
• and
• transmit X.sub.vgt to said turbocharger turbine to regulate the intake manifold pressure.