Method for controlling an internal combustion engine using model based VGT/EGR control
A method for controlling an internal combustion engine using model based control, the engine including a variable geometry turbocharger (VGT) driven in response to a VGT command signal and/or an exhaust gas recirculation (EGR) valve driven in response to an EGR valve command signal to recirculate exhaust to an engine intake manifold.
1. A method for controlling an internal combustion engine, the engine including an exhaust gas recirculation (EGR) valve driven in response to an EGR valve command signal, the method comprising:
generating a desired EGR valve discharge coefficient based at least in part on a set of engine parameters;
generating the EGR valve command signal using the desired EGR valve discharge coefficient and a Discharge Coefficient to EGR Valve Position model; and
transmitting the EGR valve command signal to the EGR valve.
2. The method of claim 1 further comprising:
determining a desired EGR mass flow rate; and
determining an actual EGR mass flow rate,
wherein the set of engine parameters includes the desired EGR mass flow rate and the actual EGR mass flow rate.
3. The method of claim 1 further comprising:
determining EGR valve position; and
determining actual EGR valve discharge coefficient based at least in part on the EGR valve position,
wherein the set of engine parameters includes the actual EGR valve discharge coefficient.
4. The method of claim 3 wherein the actual EGR valve discharge coefficient is determined using the EGR valve position and an EGR Valve Position to Discharge Coefficient model comprising a lookup table.
5. The method of claim 3 wherein the actual EGR valve discharge coefficient is determined using the EGR valve position and an EGR Valve Position to Discharge Coefficient model comprising a mathematical algorithm.
6. The method of claim 3 wherein the EGR valve position is determined using a sensor coupled to the EGR valve.
7. The method of claim 3 wherein the EGR valve position is determined using the EGR valve command signal and an EGR valve delay model.
8. The method of claim 1 wherein the Discharge Coefficient to EGR Valve Position model comprises a lookup table.
9. The method of claim 1 wherein the Discharge Coefficient to EGR Valve Position model comprises a mathematical algorithm.
10. The method of claim 1 wherein the desired EGR valve discharge coefficient is generated using
DISC_des
=
DISC_act
+
[
DISC_act
Megr_act
]
[
Megr_des
-
Megr_act
]
wherein DISC_des is the desired EGR valve discharge coefficient, DISC_act is an actual EGR valve discharge coefficient, Megr_act is an actual EGR mass flow rate, and Megr_des is a desired EGR mass flow rate.
11. A method for controlling an internal combustion engine, the engine including a variable geometry turbocharger (VGT) driven in response to a VGT command signal, the method comprising:
generating a desired turbine pressure ratio based at least in part on a set of engine parameters;
generating the VGT command signal using a VGT position model having a set of inputs, wherein the set of inputs includes the desired turbine pressure ratio and an actual intake mass flow rate; and
transmitting the VGT command signal to the VGT.
12. The method of claim 11 wherein generating the desired turbine pressure ratio comprises:
generating a first turbine pressure ratio corresponding to a desired intake mass flow rate;
generating a second turbine pressure ratio corresponding to a desired EGR mass flow rate; and
setting the desired turbine pressure ratio equal to the greater of the first and second turbine pressure ratios.
13. The method of claim 11 further comprising optimizing the VGT command signal prior to transmitting the VGT command signal to the VGT.
14. The method of claim 13 wherein optimizing the VGT command signal further comprises:
determining when the VGT command signal violates at least one of an intake mass flow criterion and a turbine power criterion; and
modifying the VGT command signal to increase intake mass flow when the VGT command signal violates at least one of the intake mass flow criterion and the turbine power criterion.
15. The method of claim 11 wherein the VGT position model comprises at least one of a lookup table and a mathematical algorithm.
16. The method of claim 11 wherein the VGT position model comprises a three dimensional lookup table.
17. A method for controlling an internal combustion engine, the engine including a variable geometry turbocharger (VGT) driven in response to a VGT command signal, the engine further including an exhaust gas recirculation (EGR) valve driven in response to an EGR valve command signal to recirculate exhaust to an engine intake manifold, the method comprising:
determining a set of engine parameters including desired EGR mass flow rate, actual EGR mass flow rate, desired intake mass flow rate, and actual intake mass flow rate;
generating a desired EGR valve discharge coefficient and a desired turbine pressure ratio based at least in part on one or more members of the set of engine parameters;
generating the EGR valve command signal using the desired EGR valve discharge coefficient and a Discharge Coefficient to EGR Valve Position model;
generating the VGT command signal using the desired turbine pressure ratio, the actual intake mass flow rate and a VGT position model;
transmitting the EGR valve command signal to the EGR valve; and
transmitting the VGT command signal to the VGT.
18. The method of claim 17 wherein the Discharge Coefficient to EGR Valve Position model comprises a lookup table.
19. The method of claim 17 wherein the Discharge Coefficient to EGR Valve Position model comprises a mathematical algorithm.
20. The method of claim 17 wherein the desired EGR valve discharge coefficient is generated using
DISC_des
=
DISC_act
+
[
DISC_act
Megr_act
]
[
Megr_des
-
Megr_act
]
wherein DISC_des is the desired EGR valve discharge coefficient, DISC_act is an actual EGR valve discharge coefficient, Megr_act is the actual EGR mass flow rate, and Megr_des is the desired EGR mass flow rate.