U.S. patent application number 10/353379 was filed with the patent office on 2004-07-29 for controller for controlling oxides of nitrogen (nox) emissions from a combustion engine.
This patent application is currently assigned to Visteon Global Technologies, Inc.. Invention is credited to Haskara, Ibrahim, Mianzo, Lawrence Andrew.
Application Number | 20040144082 10/353379 |
Document ID | / |
Family ID | 32736162 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040144082 |
Kind Code |
A1 |
Mianzo, Lawrence Andrew ; et
al. |
July 29, 2004 |
Controller for controlling oxides of nitrogen (NOx) emissions from
a combustion engine
Abstract
A controller for controlling oxides of nitrogen (NOx) emissions
from a combustion engine based on estimating a parameter for the
engine. The controller capable of adjusting cylinder temperature
based on the estimated parameter for controlling NOx emissions.
Inventors: |
Mianzo, Lawrence Andrew;
(Playmouth, MI) ; Haskara, Ibrahim; (Westland,
MI) |
Correspondence
Address: |
BROOKS KUSHMAN P.C.
1000 TOWN CENTER
TWENTY-SECOND FLOOR
SOUTHFIELD
MI
48075
US
|
Assignee: |
Visteon Global Technologies,
Inc.
728 Parklane Towers East, One Parklane Blvd.
Dearborn
MI
48126
|
Family ID: |
32736162 |
Appl. No.: |
10/353379 |
Filed: |
January 29, 2003 |
Current U.S.
Class: |
60/285 ;
60/301 |
Current CPC
Class: |
F02D 41/006 20130101;
Y02T 10/12 20130101; F02M 26/13 20160201; Y02T 10/40 20130101; Y02T
10/18 20130101; Y02T 10/47 20130101; F02M 26/01 20160201; F02D
13/0215 20130101; F02D 41/1462 20130101; F02D 35/024 20130101; F02D
41/0052 20130101; F02D 2250/36 20130101; F02D 35/026 20130101 |
Class at
Publication: |
060/285 ;
060/301 |
International
Class: |
F01N 003/00; F01N
003/10 |
Claims
What is claimed:
1. A method for controlling oxides of nitrogen (NO.sub.x) emissions
from a combustion engine, the method comprising, estimating at
least one parameter from the group of cylinder temperature and
cylinder fraction; detecting an engine operating point and
determining at least one desired value for the at least one
parameter based on the engine operating point; comparing the
estimated parameter to the at least one desired value for the at
least one parameter; and calculating an emissions control signal
that increases cylinder temperature when the estimated parameter is
below the desired value of the at least one parameter, and that
decreases cylinder temperature when the estimated parameter is
above the desired value of the at least one parameter.
2. The method of claim 1 further comprising estimating the at least
one parameter as a function of estimating cylinder pressure.
3. The method of claim 2 wherein the estimating function for
estimating cylinder pressure comprises detecting cylinder pressure
and estimating cylinder pressure as a function of the detected
cylinder pressure.
4. The method of claim 3 further comprising providing a cylinder
pressure model for estimating the cylinder pressure and providing a
cylinder temperature model for estimating cylinder temperature and
providing a cylinder fraction model for estimating cylinder
fraction.
5. The method of claim 4 wherein the emissions control signal is
for controlling at least one valve position for controlling an
amount of gas flow at a cylinder for controlling cylinder
temperature.
6. The method of claim 5 wherein the controlling comprises
adjusting an EGR valve position for controlling an amount of
exhaust gas flow at the cylinder.
7. The method of claim 5 wherein the controlling comprises
adjusting an exhaust valve position for controlling an amount of
exhaust gas flow at the cylinder.
8. The method of claim 7 wherein the controlling comprises
adjusting an intake valve position for controlling an amount of
intake air gas flow at the cylinder.
9. The method of claim 5 wherein detecting the engine operating
point comprises measuring engine speed and measuring engine
load.
10. The method of claim 9 further comprising determining an
acceptable amount of NO.sub.x based on the engine operating point
and estimating an amount of NO.sub.x emissions based on the at
least one estimated parameter, wherein the emissions control signal
is a function of the acceptable amount of NO.sub.x emissions and
the estimated amount of NO.sub.x emissions.
11. A controller for controlling oxides of nitrogen (NO.sub.x)
emissions from a combustion engine, the controller comprising, an
estimator configured for estimating at least one parameter from the
group of cylinder temperature and cylinder fraction; a detector
configured for detecting an engine operating point and determining
at least one desired value for the at least one parameter based on
the engine operating point; a comparator configured for comparing
the estimated parameter to the at least one desired value for the
at least one parameter; and a calculator configured for calculating
an emissions control signal that increases cylinder temperature
when the estimated parameter is below the desired value of the at
least one parameter, and that decreases cylinder temperature when
the estimated parameter is above the desired value of the at least
one parameter.
12. The controller of claim 11 wherein the estimator is further
configured for estimating the at least one parameter as a function
of cylinder pressure.
13. The controller of claim 12 wherein the estimator is configured
for further estimating cylinder pressure as the function comprising
detecting cylinder pressure and estimating cylinder pressure as a
function of the detected cylinder pressure.
14. The controller of claim 13 wherein the estimator further
comprises a cylinder pressure model for estimating the cylinder
pressure, a cylinder temperature model for estimating cylinder
temperature, and a cylinder fraction model for estimating cylinder
fraction.
15. The controller of claim 14 further comprising an emissions
control signal transmitter configured for adjusting the emissions
control signal for controlling at least one valve position for
controlling an amount of gas flow at a cylinder for controlling
cylinder temperature.
16. The controller of claim 15 wherein the emissions control signal
transmitter is further configured for adjusting the emissions
control signal for controlling an EGR valve position for
controlling an amount of exhaust gas flow at the cylinder.
17. The controller of claim 15 wherein the emissions control signal
transmitter is further configured for adjusting the emissions
control signal for controlling an exhaust valve position for
controlling an amount of exhaust gas flow at the cylinder.
18. The controller of claim 17 wherein the emissions control signal
transmitter is further configured for adjusting the emissions
control signal for controlling an intake valve position for
controlling an amount of intake air gas flow at the cylinder.
19. The controller of claim 15 wherein the detector is further
configured for detecting the engine operating point based on
measuring engine speed and measuring engine load.
20. The controller of claim 19 wherein the calculator is further
configured for determining an acceptable amount of NO.sub.x based
on the engine operating point and estimating an amount of NO.sub.x
emissions based on the at least one estimated parameter, wherein
the emissions control signal is a function of the acceptable amount
of NO.sub.x emissions and the estimated amount of NO.sub.x
emissions.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to controlling oxides of
nitrogen (NOx) emissions from a combustion engine based on
estimating a parameter for the engine.
[0003] 2. Background Art
[0004] As emission regulations become increasingly strict, the need
for accurate emission control strategies becomes more important.
For combustion engines, one important component of the generated
emissions comes from the exhaust gases produced during combustion,
and particularly from the oxides of nitrogen (NOx) contained in the
exhaust gases. The amount of NOx emissions are a function of the
cylinder temperature. By controlling the cylinder temperature, such
as by controlling exhaust gas residual, NOx production can be
controlled.
[0005] Past attempts for controlling NOx production have included
operations that measure an engine parameter and compare the
measured parameter to a predefined target for the measured
parameter. Based on a difference between the measured parameter and
the predefined target, these systems control the cylinder
temperature. One disadvantage with such systems is that the
measured parameters are difficult to measure with accuracy. As
such, the control strategies that rely on difficult to measure
parameters have a difficult time reflecting true conditions of the
measured parameters. In addition, even if the inaccuracies in the
measurements are forgiven, the predefined targets for the measured
parameters can become inaccurate over time from the aging, wearing,
and other inconsistencies in the engine.
SUMMARY OF THE INVENTION
[0006] The present invention overcomes the above-identified
deficiencies with a method for controlling oxides of nitrogen
(NO.sub.x) emissions based on estimating at least one parameter for
the engine and calculating an emissions control signal based on the
estimated parameter.
[0007] One aspect of the present invention relates to a method for
controlling oxides of nitrogen (NOx) emissions from a combustion
engine. The method comprises estimating at least one parameter from
the group of cylinder temperature and cylinder fraction, and
comparing the estimated parameter to a desired value for the
estimated parameter determined by detecting an engine operating
point. The comparison of the estimated parameter and the desired
value for the estimated parameter is used for calculating an
emissions control signal for controlling NOx emissions from the
engine. The control signal increases cylinder temperature when the
estimated parameter is below the desired value of the at least one
parameter and decreases cylinder temperature when the estimated
parameter is above the desired value.
[0008] Another aspect of the present invention relates to a
controller for controlling oxides of nitrogen (NOx) emissions from
a combustion engine. The controller comprises an estimator, a
detector, a comparator, and a calculator. The estimator is
configured for estimating at least one parameter from the group of
cylinder temperature and cylinder fraction. The comparator is
configured for comparing the estimated parameter to a desired value
for the estimated parameter determined by the detector detecting an
engine operating point. The calculator is configured for using the
comparison of the estimated parameter and the desired value for
calculating an emissions control signal for controlling NOx
emissions from the engine. The control signal increases cylinder
temperature when the estimated parameter is below the desired value
of the at least one parameter and decreases cylinder temperature
when the estimated parameter is above the desired value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates a controller for controlling emissions
from a combustion engine, in accordance with one aspect of the
present invention; and
[0010] FIG. 2 illustrates an estimator for use in the controller,
in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0011] FIG. 1 illustrates a controller 10 for controlling oxides of
nitrogen (NO.sub.x) emissions from a combustion engine 14. The
controller 10 can be used with any type of combustion engine, such
as, a variable valve time engine, a fixed valve timing engine, an
engine having internal exhaust gas recirculation, and an engine
having external exhaust gas recirculation.
[0012] One aspect of the present invention relates to the
controller 10 having an estimator 16 for estimating at least one
parameter for the engine 14. The parameter that is estimated is
referred to as the estimated parameter 18 and the value determined
for the estimated parameter 18 is the estimated value 20. As
described below, sometimes there can be more than one estimated
parameter 18 and corresponding estimated value 20.
[0013] The estimated parameter 18 is selected for in-cylinder
conditions that are predictive of NOx emissions, such as,
temperature, fraction, and pressure. Based on one of these
estimations, the engine 14 can be controlled to limit the amount of
NOx. The estimated value 20 can be used to control the engine 14
for limiting NOx or the estimated value 20 can be use to actually
predict NOx and the predicted amount of NOx can be used to control
the engine 14.
[0014] The estimator 16 can be any type of computer-readable or
programmable medium that is capable of modeling the engine 14 for
the purposes of estimating the estimated parameter 18. More
particularly, the estimator 16 can model the functioning of at
least one of the cylinder temperature, fraction, or pressure.
[0015] The controller 10 further comprises a detector 24 for
determining an acceptable value 26 for the estimated value 20. The
acceptable value 26 is determined based on the operating conditions
of the engine 14. More specifically, the acceptable value 26 can be
determined from an algorithm or look-up table that coordinates the
acceptable value 26 with the speed 28 and load 30 acting on the
engine 14.
[0016] The detector 24 is configured to detect an acceptable value
26 for each estimated value 20. As such, if the estimator 16
determines an estimated value 20 for each of the cylinder
temperature, cylinder fraction, and cylinder pressure, the detector
can determine an acceptable value 26 for each of the cylinder
temperature, cylinder fraction, and cylinder pressure. It can be
advantageous to estimate all three of these engine parameters so
that the effects of each parameter on the other parameters can be
understood and used to improve the accuracy of the estimated values
20.
[0017] The acceptable values 26 correspond with values for
temperature, fraction, and pressure that achieve tolerable NOx
emissions levels for the given operating point. In other words, NOx
emissions are related to one or a combination of in-cylinder
parameters for temperature, pressure, and fraction. If anyone or
more of these parameters are not at acceptable levels, then desired
levels of NOx emissions are not being achieved and engine operating
parameters need to be adjusted. There are a number of ways to
adjust the engine operating parameters, including controlling
exhaust gas residual, spark timing, valve timing, and gas flow. If
the estimated values 20 are greater or lower than the acceptable
values 26, then the controller 10 can adjust control of the engine
14 so that the estimated values 20 approach the acceptable values
26 and the desired NOx levels are achieved.
[0018] For example, if the estimated parameter 18 is cylinder
temperature and the estimated value 20 is greater than the
acceptable value 26 for the cylinder temperature, then the engine
14 is not running as desired. The engine 14 needs to be adjust so
that when the estimator next determines the estimated value 20 for
the cylinder temperature, the estimated value 20 is closer to the
acceptable value 26 for the cylinder temperature. Accordingly, more
or less exhaust gas can be recirculated to adjust the cylinder
temperature as needed.
[0019] The controller 10 still further comprises a comparator 34 to
quantify a difference between the estimated values 20 and the
acceptable value 26 for use in controlling the engine 14. The
comparator 34 determines if the estimated value 20 is greater than
or less than the acceptable value 26. The comparator 34 can also
compare the estimated values 20 to acceptable ranges instead of a
particular acceptable value 26. In either case, the object of the
comparator 34 is to quantify the level of control required to
adjust the estimated values 20 to values closer to the acceptable
values 26 so that the engine 14 can be controlled for limiting NOx
emissions.
[0020] The controller 10 still further comprises a calculator 38
for turning the results from the comparator 34 into an emissions
control signal 40 for controlling the engine 14. As NOx is best
controlled by adjusting combustion conditions in the cylinder, the
calculator 38 determines the emissions control signal 40 in a
manner that increases cylinder temperature when the estimated
values for the estimated parameters are below the acceptable values
and that decreases cylinder temperature when the estimated values
for the estimated parameters are above the acceptable values.
[0021] The controller 10 can still further comprise an emissions
control signal transmitter 44 for adjusting the emissions control
signal 50 to a particular engine component that affects the
estimated parameter. For example, the engine component can be a
valve 46, such as an EGR valve, an intake valve, an exhaust valve,
or an exhaust valve on a variable valve timing engine. By
controlling a position for the valve, the estimated parameters,
i.e., temperature, fraction, and/or pressure, can be adjusted.
[0022] The controller 10 can be used in any type of combustion
engine, such as, a variable valve time engine, a fixed valve timing
engine, an engine having internal exhaust gas recirculation, and an
engine having external exhaust gas recirculation.
[0023] With respect to external EGR systems, the transmitter 44 can
be configured for controlling the position of the EGR valve that
controls the amount of exhaust gas that is recirculated to the
intake port. With respect to internal EGR systems, the transmitter
44 can be configured to control the intake valve timing and the
exhaust valve timing. The intake valve timing can be controlled to
admit more intake air to the engine and/or the exhaust valve timing
can be controlled to allow more exhaust gas to escape from the
cylinders. Whether more intake gas is admitted or more exhaust gas
is allowed to escape, such control affects the combustion
conditions for the purposes of controlling NOx emissions.
[0024] FIG. 2 illustrates one configuration of the estimator 16
that can be implemented in conjunction with the controller 10 for
determining the estimated value 20 for the estimated in-cylinder
parameter 18. As described below, the estimator 16 includes a
cylinder temperature model 50 for estimating temperature, a
cylinder fraction model 52 for estimating cylinder fraction, and a
cylinder pressure model 54 for estimating cylinder pressure.
[0025] The estimated value 20 for the cylinder temperature is
referred to below as T.sub.cyl, the estimated value for the
cylinder pressure is referred to below as P.sub.cyl, and the
estimated value 20 for the cylinder fraction is referred to below
as F.sub.cyl. Based on estimating each of these in-cylinder
conditions, the controller 10 can adjust, if necessary, an engine
component 46 to achieve tolerable NOx emissions levels. In
addition, as described with more detail below, the estimator 16
includes intermediate models 58, 60, 62, 64, 66, and 68 for
receiving measurements and performing calculations that are needed
for the models 50, 52, and 54.
[0026] The cylinder temperature model 50 for the estimated
parameter 18 of cylinder temperature T.sub.cyl 72 is given by the
following equations:
{dot over
(T)}.sub.cyl=.function..sub.1(P.sub.cyl,F.sub.cyl,T.sub.cyl)
(1)
[0027] 1 T . cyl = 1 m cyl c v [ Q . w - P cyl V . cyl + m . i n h
i n + m . ex h ex + Q . ch - m . cyl u - m cyl ( u 1 - u 2 ) F .
cyl 1 ] ( 2 )
[0028] {dot over (T)}.sub.cyl 74 is the cylinder temperature rate
of change and obtained from Equation (1) based on a Function
f.sub.1 applied to a relationship of P.sub.cyl, F.sub.cyl, and
T.sub.cyl. From the cylinder temperature rate of change {dot over
(T)}.sub.cyl 74, the estimated cylinder temperate T.sub.cyl 72 is
known. According to one aspect of the present invention, the
relationship shown in Equation (1) can be rewritten as shown in
Equation (2) and used for obtaining the cylinder temperature
T.sub.cyl 72.
[0029] In Equation (2), c.sub.v is a specific heat of the mixture
of air and fuel in the cylinder and obtain as a function of engine
operating conditions and thermodynamic properties of working fluid;
u is the internal energy of the mixture of air and fuel and
obtained as a function of engine operating conditions and
thermodynamic properties of working fluid; u.sub.1 is the internal
energy of the combustion products and obtained as a function of
engine operating conditions and thermal properties of working
fluid; u.sub.2 is the internal energy of the charge product and
obtained as a function of engine operating conditions and
thermodynamic properties of working fluid; {dot over (Q)}.sub.w 76
is the rate of heat transfer through the cylinder wall and obtained
based on Equation (13) and intermediate model 56, as described
below, or as a function of a look-up table based on engine
operating parameters; h.sub.in is the enthalpy of the flow through
the intake valves and obtained from intermediate model 60 as a
function of engine operating conditions and thermodynamic
properties of working fluid; h.sub.ex is the enthalpy of the flow
through the exhaust valve and obtained as a function of engine
operating conditions and thermodynamic properties of working fluid;
{dot over (Q)}.sub.ch 78 is the combustion heat release rate and
obtained from Equation (10) and intermediate model 58, as described
below, or it can be determined as a function of a look-up table
based on engine operating parameters; {dot over (m)}.sub.in 80 is
the mass flow rate of air through the intake valves and obtained as
a measurement, estimation, or as a function of a look-up table
based on engine operating parameters; {dot over (m)}.sub.cyl 82 is
the cylinder mass rate of change and obtained from solving Equation
(9), as described below; m.sub.cyl 84 is the cylinder mass and
obtained from solving Equation (9), as described below; P.sub.cyl
88 is the cylinder pressure and obtained from Equation (6) and
model 54, as described below, or as a function of a look-up table
based on engine operating parameters; {dot over (V)}.sub.cyl 90 is
the cylinder volume rate of change and obtained from intermediate
model 62 as a function of engine geometry and crank angle
measurements; and {dot over (F)}.sub.cyl 92 is the burn mass
fraction rate of change and obtained from Equation (4) and model
52, as described below, or as a function of a look-up table based
on engine operating parameters.
[0030] The cylinder fraction model 52 for the estimated parameter
18 of cylinder fraction F.sub.cyl 94 is given by the following
equations:
{dot over
(F)}.sub.cyl=.function..sub.2(P.sub.cyl,F.sub.cyl,T.sub.cyl)
(3)
m.sub.cyl{dot over (F)}.sub.cyl1={dot over
(m)}.sub.inF.sub.icyl+{dot over (m)}.sub.exF.sub.cyle-{dot over
(m)}.sub.cylF.sub.cyl+min((m.sub.cyl(1-F.-
sub.cyl)).sub.SOC,(m.sub.i.function.AFR).sub.SOC){dot over
(x)}.sub.b (4)
[0031] {dot over (F)}.sub.cyl 92 is the cylinder fraction rate of
change and obtained from Equation (3) based on a Function f.sub.2
applied to a relationship of P.sub.cyl, F.sub.cyl, and T.sub.cyl.
From the cylinder fraction rate of change {dot over (F)}.sub.cyl
92, the estimated cylinder fraction F.sub.cyl 94 is known.
According to one aspect of the present invention, the relationship
shown in Equation (3) can be rewritten as shown in Equation (4) and
used for obtaining the cylinder temperature F.sub.cyl 94.
[0032] In Equation (4), {dot over (m)}.sub.inF.sub.icyl 98 is the
mass flow rate of the burned gas across the intake valves and
obtained according to Equation (7), as described below, or as a
function of a look-up table based on engine operating parameters;
{dot over (m)}.sub.exF.sub.cyle 100 is the mass flow rate of the
burn gas across the exhaust valves and obtained according to
Equation (8), as described below, or as a function of a look-up
table based on engine operating parameters; {dot over (m)}.sub.cyl
82 is the cylinder mass rate of change and obtained from Equation
(9), as described below; and the function min(.) evaluates to
(m.sub.ifAFR) at the start of combustion (SOC) if the mixture is
lean or (m.sub.cyl (1-F.sub.cyl)) at SOC, if the mixture is
stoichiometric or rich. The stoichiometric criteria refers to the
conditions when a sensor indicates that the chemical composition
between the air and fuel has optimal oxygen levels to burn all the
air, the rich designation means there is more fuel than the optimal
stoichiometric amount of fuel, and the lean designation means that
there is less fuel than the optimal stoichiometric amount of fuel.
This is done since only the part of the mixture that is
stoichiometric will burn completely, i.e., excess fuel is not
burned and if the fuel is lean, only the portion of unburned gas in
the cylinder stoichiometrically proportional to the fuel will
burn.
[0033] The cylinder pressure model 54 for the estimated parameter
18 of cylinder pressure P.sub.cyl 88 is given by the following
equations:
{dot over
(P)}.sub.cyl=.function..sub.3(P.sub.cyl,F.sub.cyl,T.sub.cyl)
(5)
[0034] 2 P . cyl = [ m . cyl m cyl + T . cyl T cyl + R 1 - R 2 R F
. cyl - V . cyl V cyl ] P cyl ( 6 )
[0035] {dot over (P)}.sub.cyl 102 is the cylinder pressure rate of
change and obtained from Equation (5) based on a Function f.sub.3
applied to a relationship of P.sub.cyl, F.sub.cyl, and T.sub.cyl.
From the cylinder pressure rate of change {dot over (P)}.sub.cyl
102, the estimated cylinder pressure P.sub.cyl 88 is known.
According to one aspect of the present invention, the relationship
shown in Equation (5) can be rewritten as shown in Equation (6) and
used for obtaining the cylinder pressure P.sub.cyl.
[0036] In Equation (6), m.sub.cyl 84 is the cylinder mass and
obtained from Equation (6) and intermediate model 64; {dot over
(m)}.sub.cyl 82 is the cylinder mass rate of change and obtained
from solving Equation (9) and intermediate model 64; T.sub.cyl 74
is the cylinder temperature and obtained from Equation (2), as
described below, or as a function of a look-up table based on
engine operating parameters; {dot over (T)}.sub.cyl 72 is the
cylinder temperature rate of change and obtained from solving
Equation (2) and model 50 or as a function of a look-up table based
on engine operating parameters; R is a gas constant and obtained on
R=F.sub.cyl R.sub.1+(1-F.sub.cyl)R.sub.2; R1 is the gas constant
for burned gas; R2 is the gas constant for unburned gas; {dot over
(F)}.sub.cyl 92 is the burn mass fraction rate of change and
obtained from solving Equation (4) and intermediate model 52 or as
a function of a look-up table based on engine operating parameters;
V.sub.cyl 90 is the cylinder volume and obtained from engine
geometry; {dot over (V)}.sub.cyl is the cylinder volume rate of
change and obtained from intermediate model 62 as a function of the
engine geometry and crank angle measurements 106 from intermediate
model 60.
[0037] As described above, some of the variables relate to
additional equations which are now described.
[0038] Equation (7) relates to the mass flow rate of the burned gas
across the intake valves and is given by the following
equation:
F.sub.icyl:=.sub.F.sub..sub.cyl.sub.i.function.{dot over
(m)}.sub..sub.in.sub.>0 .sup.F.sup..sub.i1.sup.i.function.{dot
over (m)}.sup..sub.in.sup.>0 (7)
[0039] F.sub.i 107 is the intake manifold fraction as determined
from intermediate model 60 and F.sub.cyl is the cylinder fraction
as determined from intermediate model 60.
[0040] Equation (8) relates to the mass flow rate of the burned gas
across the exhaust valves and is given by the following
equation:
F.sub.cyle:=.sub.F.sub..sub.cyl.sub.i.function.{dot over
(m)}.sub..sub.ex.sub..ltoreq.0
.sup.F.sup..sub.e.sup.i.function.{dot over
(m)}.sub..sub.ex.sup.>0 (8)
[0041] F.sub.e 109 is the exhaust manifold fraction as determined
from intermediate model 60 and F.sub.cyl is the cylinder fraction
as determined from intermediate model 60.
[0042] Equation (9) relates to the mass rate of change from the
conservation of mass, assuming the convention that flow rate is
positive into the cylinder, and represented according to the
following equation:
{dot over (m)}.sub.cyl={dot over (m)}.sub.in+{dot over (m)}.sub.ex
(9)
[0043] wherein {dot over (m)}.sub.in 80 is the mass of the air flow
rate through the intake valves and obtained from intermediate model
60 as a measurement or an estimation; {dot over (m)}.sub.ex 108 is
the mass of air flow rate through the exhaust valves and obtained
from intermediate model 60 as a measurement or estimation.
[0044] Equation (10) refers to the combustion heat release rate
{dot over (Q)}.sub.ch 78 and represented according to the following
equation and intermediate model 56: 3 Q . ch = m b t Q LHV ( 10
)
[0045] wherein Q.sub.LHV is the lower heating value of the fuel and
obtained as a function of engine operating parameters and fuel
property tables; m.sub.b 110 is the mass of the burned fuel and
obtained as the product of the mass fraction burned x.sub.b 112 and
the injected fuel m.sub.if 114 as determined by Equation (11), as
described below.
[0046] Equation (11) relates to the mass of the burned fuel m.sub.b
110 and represented according to the following equation:
m.sub.b=x.sub.bm.sub.if (11)
[0047] wherein: m.sub.if 114 is the injected fuel and obtained from
intermediate model 60 as a measurement or calculation of injected
fuel; and x.sub.b 112 is the product of the mass fraction burned
and obtained according to Equation (12) and intermediate model 58.
Equation (12) is determined according to the following equation: 4
x b = 1 - exp [ - a ( - 0 ) m + 1 ] ( 12 )
[0048] wherein: 0.sub.0 106 is the crank angle at the start of
combustion and measured by intermediate model 60; .DELTA..theta. is
the total combustion duration 118; and a and m are correlation
parameters.
[0049] Equation (13) refers to the variable rate of heat release
through the cylinder wall, {dot over (Q)}.sub.w 72, and represented
according to the following equation and intermediate model 56:
{dot over (Q)}.sub.w=hA(T.sub.cyl-T.sub.wall) (13)
[0050] wherein: h is the convective heat transfer coefficient and
obtained from heat transfer calculations; a is the surface area for
heat transfer and obtained from engine geometry; T.sub.wall is the
cylinder wall temperature and obtained from intermediate model 60
estimating or measuring coolant temperatures 120.
[0051] As described above, the equations (1) , (3), and (5) are
used for determining the estimated parameters 18 of temperature,
fraction, and pressure to determine the estimated values 20 for
temperature T.sub.cyl , 74 fraction F.sub.cyl 94, and pressure
P.sub.cyl 88. The models 50, 52, and 54 can include values
determined by the other models or the values that are included from
the other models can be substituted for with measured parameters,
look-up tables, or other algorithms
[0052] Each equation (1), (3), and (5) is not necessary for
controlling the engine 14, rather, only one of the estimated values
20 for fraction or temperature is needed for controlling the engine
14. The Equations (1), (2), and (3) can be rewritten, as shown
below, to illustrate the interaction of the three equations.
{dot over
(T)}.sub.cyl=.function..sub.2(P.sub.cyl,T.sub.cyl,F.sub.cyl (1)
{dot over (F)}.sub.cyl=.function..sub.3(P.sub.cyl,T.sub.cyl
,F.sub.cyl) (3)
{dot over
(P)}.sub.cyl=.function..sub.1(P.sub.cyl,T.sub.cyl,F.sub.cyl)
(5)
[0053] In addition, Equations (1), (3), and (5) can include
feedback correction functions g.sub.1 122, g.sub.2 124, and g.sub.3
126 for use in adjusting the estimations according to aging,
wearing, and other engine inconsistencies.
{dot over
(T)}.sub.cyl=.function..sub.1(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.1(error) (1)
{dot over
(F)}.sub.cyl=.function..sub.2(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.2(error) (2)
{dot over
(P)}.sub.cyl=.function..sub.3(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.3(error) (3)
[0054] The feedback correction functions g.sub.1, g.sub.2, and
g.sub.3 can be any type of correction function. As shown below, the
functions g.sub.1, g.sub.2, and g.sub.3 are determined from
intermediate model 66 and can be a value that is multiplied against
the error determined from a difference between an estimated value
20 and a measurement for the estimated value 20. As shown below,
the cylinder pressure P.sub.cyl is measured and generates the
feedback correction functions for g.sub.1, g.sub.2, and
g.sub.3.
{dot over
(T)}.sub.cyl=.function..sub.1(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.1(P.sub.cyl.sub..sub.--.sub.error)
{dot over
(F)}.sub.cyl=.function..sub.2(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.2(P.sub.cyl.sub..sub.--.sub.error)
{dot over
(P)}.sub.cyl=.function..sub.3(P.sub.cyl,T.sub.cyl,F.sub.cyl)+g.s-
ub.3(P.sub.cyl.sub..sub.--.sub.error)
g.sub.1(P.sub.cyl.sub..sub.--.sub.error)=k.sub.1(P.sub.cyl.sub..sub.--.sub-
.measured-P.sub.cyl.sub..sub.--.sub.estimated)
g.sub.2(P.sub.cyl.sub..sub.--.sub.error)=k.sub.2(P.sub.cyl.sub..sub.--.sub-
.measured-P.sub.cyl.sub..sub.--.sub.estimated)
g.sub.3(P.sub.cyl.sub..sub.--.sub.error)=k.sub.3(P.sub.cyl.sub..sub.--.sub-
.measured-P.sub.cyl.sub..sub.--.sub.estimated)
[0055] P.sub.cyl.sub..sub.--.sub.error 126 is determined by the
difference between a measured cylinder pressure
P.sub.cyl.sub..sub.--.sub.measured and the estimated cylinder
pressure P.sub.cyl. The P.sub.cyl.sub..sub.--.sub.error is
multiplied by a gain k.sub.1, k.sub.2, or k.sub.3. The gains can be
the same or different values.
[0056] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *