Method and apparatus to operate internal combustion engine employing an intake air compressor
View Patent ↗A method for controlling intake airflow in an internal combustion engine including an intake air compressor includes determining a first compressor boost signal based upon a predetermined intake manifold pressure command, determining a second compressor boost signal based upon a predetermined exhaust pressure limit, determining a compressor boost control command based upon the first compressor boost signal and a limit comprising one of a maximum boost setting and said second compressor boost signal, and controlling the intake air compressor in response to the compressor boost control command.
1. Method for controlling intake airflow in an internal combustion engine including an intake air compressor, comprising,
within a control module;
determining a first compressor boost signal based upon a predetermined intake manifold pressure command;
determining a second compressor boost signal based upon a predetermined exhaust pressure limit;
determining a compressor boost control command based upon the first compressor boost signal and a compressor boost limit comprising one of a maximum boost setting and said second compressor boost signal;
controlling the intake air compressor to operate at a position that controls flow of intake air to the internal combustion engine in response to the compressor boost control command; and
operating the internal combustion engine with the intake air compressor operating at the compressor boost control command, comprising maintaining exhaust pressure of the internal combustion engine at the predetermined exhaust pressure limit.
2. The method of claim 1 , wherein said intake air compressor is included in a variable-geometry turbocharger (VGT) and determining said second compressor boost signal comprises employing an inverse VGT model in feed-forward operation configured in accordance with the following relationship:
VGT
=
F
-
1
(
P
r
,
m
.
ex
RT
ex
P
ex
)
wherein VGT is a modeled VGT position signal,
P ex is exhaust gas pressure,
T ex is exhaust gas temperature,
R is ideal gas constant,
P
r
=
P
st
P
ex
is the pressure ratio across a turbine of the variable-geometry turbocharger,
P st is a turbine outlet pressure, and
{dot over (m)} ex is exhaust mass flowrate.
3. The method of claim 2 , wherein the exhaust mass flowrate {dot over (m)} ex includes compensation for dynamic transport delay.
4. The method of claim 3 , wherein the compensation for dynamic transport delay is determined in accordance with the following relationship:
m
.
ex
=
1
-
τ
2
s
1
+
τ
2
s
m
.
f
+
1
-
(
τ
1
+
τ
2
)
s
1
+
(
τ
1
+
τ
2
)
s
m
.
a
wherein τ 1 is air flow transportation delay,
τ 2 is combustion process delay,
τ 1 +τ 2 is mass airflow delay to turbine inlet,
{dot over (m)} f is mass fuel flow,
{dot over (m)} a is mass air flow.
5. The method of claim 2 , wherein determining said second compressor boost signal comprises a feedback loop including a signal correction to said modeled VGT position signal based on PID processing of the deviation of engine exhaust pressure from said predetermined exhaust pressure limit.
6. The method of claim 5 , wherein PID processing is suspended when engine exhaust pressure does not exceed said predetermined exhaust pressure limit.
7. The method of claim 1 , wherein said intake air compressor comprises a variable-geometry turbocharger (VGT) and determining said second compressor boost signal comprises employing an inverse VGT model in feed-forward operation configured in accordance with the following relationship:
VGT
=
Ω
-
1
(
P
r
,
m
.
ex
RT
ex
P
ex
f
1
(
P
r
)
)
wherein VGT is a modeled VGT position signal,
P ex is exhaust gas pressure,
T ex is exhaust gas temperature,
R is ideal gas constant,
P
r
=
P
st
P
ex
is the pressure ratio across a turbine of the variable-geometry turbocharger,
P st is a turbine outlet pressure,
{dot over (m)} ex is exhaust mass flowrate, and
f
1
=
{
2
γ
γ
-
1
(
P
r
2
m
-
P
r
m
+
1
m
)
PR
c
<
P
st
(
subsonic
)
(
2
m
+
1
)
1
(
m
-
1
)
2
γ
γ
-
1
m
-
1
m
+
1
P
st
≤
PR
c
(
choked
)
,
m
=
f
(
VGT
)
wherein γ is a specific heat ratio of the gas, and
m is a parameter which is a function of the modeled limit-based compressor boost signal.
8. The method of claim 1 , wherein said compressor boost limit comprises said second compressor boost signal when engine exhaust pressure exceeds said predetermined exhaust pressure limit.
9. The method of claim 1 , wherein said compressor boost limit comprises said maximum boost setting when engine exhaust pressure does not exceed said predetermined exhaust pressure limit.
10. Method for limiting intake boost pressure in an internal combustion engine including an intake air compressor, comprising
within a control module;
providing a compressor boost signal;
determining an exhaust based compressor boost limit as a function of a predetermined exhaust pressure limit;
when engine exhaust pressure exceeds said predetermined exhaust pressure limit, determining a compressor boost control command as a function of the compressor boost signal, a minimum boost setting, and said exhaust based compressor boost limit;
when engine exhaust pressure does not exceed said predetermined exhaust pressure limit, determining the compressor boost control command as a function of the compressor boost signal, said minimum boost setting, and a maximum boost setting;
controlling the intake air compressor to operate at a position that controls flow of intake air to the internal combustion engine in response to the compressor boost control command; and
operating the internal combustion engine with the intake air compressor operating at the compressor boost control command, comprising maintaining exhaust pressure of the internal combustion engine at the predetermined exhaust pressure limit.
11. The method of claim 10 , wherein said intake air compressor is included in a variable-geometry turbocharger (VGT) and determining said exhaust based compressor boost limit comprises employing an inverse VGT model in feed-forward operation configured in accordance with the following relationship:
VGT
=
F
-
1
(
P
r
,
m
.
ex
RT
ex
P
ex
)
wherein VGT is a modeled VGT position signal,
P ex is exhaust gas pressure,
T ex is exhaust gas temperature,
R is ideal gas constant,
P
r
=
P
st
P
ex
is the pressure ratio across a turbine of the variable-geometry turbocharger,
P st is a turbine outlet pressure, and
{dot over (m)} ex is exhaust mass flowrate.
12. The method of claim 11 , wherein determining said exhaust based compressor boost limit comprises a feedback loop including a signal correction to said modeled VGT position signal based on PID processing of the deviation of engine exhaust pressure from said predetermined exhaust pressure limit.
13. The method of claim 10 , wherein said intake air compressor comprises a variable-geometry turbocharger (VGT) and determining said second compressor boost signal comprises employing an inverse VGT model in feed-forward operation configured in accordance with the following relationship:
VGT
=
Ω
-
1
(
P
r
,
m
.
ex
RT
ex
P
ex
f
1
(
P
r
)
)
wherein VGT is a modeled VGT position signal,
P ex is exhaust gas pressure,
T ex is exhaust gas temperature,
R is ideal gas constant,
P
r
=
P
st
P
ex
is the pressure ratio across a turbine of the variable-geometry turbocharger,
P st is a turbine outlet pressure,
{dot over (m)} ex is exhaust mass flowrate, and
f
1
=
{
2
γ
γ
-
1
(
P
r
2
m
-
P
r
m
+
1
m
)
PR
c
<
P
st
(
subsonic
)
(
2
m
+
1
)
1
(
m
-
1
)
2
γ
γ
-
1
m
-
1
m
+
1
P
st
≤
PR
c
(
choked
)
,
m
=
f
(
VGT
)
wherein γ is a specific heat ratio of the gas, and
m is a parameter which is a function of the modeled limit-based compressor boost signal.
14. The method of claim 13 , wherein determining said exhaust based compressor boost limit comprises a feedback loop including a signal correction to said modeled VGT position signal based on PID processing of the deviation of engine exhaust pressure from said predetermined exhaust pressure limit.
15. Method for controlling intake airflow in an internal combustion engine including a variable-geometry turbocharger (VGT), comprising,
within a control module;
providing a first VGT position signal;
determining a second VGT position signal comprising
employing an inverse VGT model in feed-forward operation to determine a modeled VGT position signal based upon a predetermined exhaust pressure limit, and
employing a feedback loop including a signal correction to said modeled VGT position signal based on PID processing of the deviation of engine exhaust pressure from said predetermined exhaust pressure limit;
determining a VGT position control command based upon the first compressor boost signal and a limit comprising said second compressor boost signal when engine exhaust pressure exceeds said predetermined exhaust pressure limit and a maximum boost setting when engine exhaust pressure does not exceed said predetermined exhaust pressure limit;
controlling variable-geometry turbocharger (VGT) to operate at a position that controls flow of intake air to the internal combustion engine in response to the VGT position control command; and
operating the internal combustion engine with the VGT operating at the VGT position control command, comprising maintaining exhaust pressure of the internal combustion engine at the predetermined exhaust pressure limit.