Apparatus and method for estimating torque of engine clutch in hybrid electric vehicle
An apparatus and method for accurately estimating the transfer torque of an engine clutch provided between an engine and a motor in a hybrid electric vehicle, may include a forward estimation device configured for determining a first estimate of engine clutch transfer torque using engine torque information, a reverse estimation device configured for determining a second estimate of the engine clutch transfer torque using a drive system model including wheels, a transmission, and a motor and using wheel speed information, a weight determination device configured for determining a weight based on brake input by a driver and whether predetermined devices in the vehicle are operated, and an estimate combination determination device configured for determining a final estimate of the engine clutch transfer torque as a value combined by applying a weight to the determined first estimate and the determined second estimate.
1. An apparatus for estimating transfer torque of an engine clutch in a hybrid electric vehicle using a motor and an engine as drive sources the engine clutch being provided between the engine and the motor, the apparatus comprising:
a forward estimation device configured for determining a first estimate of engine clutch transfer torque using engine torque information;
a reverse estimation device configured for determining a second estimate of the engine clutch transfer torque using a drive system model including wheels, a transmission, and a motor and using wheel speed information;
a weight determination device configured for determining a feedforward weight and a feedback weight based on brake input by a driver and whether predetermined devices in the vehicle are operated; and
an estimate combination determination device configured for receiving the determined first estimate and the determined second estimate from the forward estimation unit and the reverse estimation unit and determining a final estimate of the engine clutch transfer torque as a value combined by applying the feedforward weight and the feedback weight to the determined first estimate and the determined second estimate, the final estimate being used in controlling the engine clutch.
2. The apparatus of claim 1 , wherein the forward estimation device is configured to determine the first estimate using nominal engine torque, engine speed, nominal engine clutch torque, and stored setting information as the engine torque information.
3. The apparatus of claim 2 , wherein
the forward estimation device is configured to determine the first estimate as a value obtained by adding the nominal engine clutch torque and an error estimate, and
the error estimate is determined from the nominal engine torque, the engine speed, the nominal engine clutch torque, and the stored setting information using a first equation and a second equation,
wherein
the
first
equation
is
ω
^
.
e
=
1
J
d
T
e
,
n
-
1
J
d
(
T
ec
,
n
+
T
~
^
ec
,
f
)
+
l
f
1
(
ω
e
-
ω
^
e
)
,
wherein
the
second
equation
is
T
~
^
.
ec
,
f
=
-
l
f
2
(
ω
e
-
ω
^
e
)
,
and
wherein:
{circumflex over ({tilde over (T)})} ec,f : Error estimate,
T e,n : Nominal engine torque,
T ec,n : Nominal engine clutch torque,
J d : Damper inertia value,
ω e : Engine speed,
l f1 : P gain of PI-type observer in forward estimation device,
l f2 : I gain of PI-type observer in forward estimation device,
{circumflex over ( )}: Estimate,
{tilde over ( )}: Error, and
{dot over ( )}: Differential value.
4. The apparatus of claim 1 , wherein the reverse estimation device is configured to determine the second estimate using wheel speed, actuator torque, actuator speed, vehicle load torque, transmission state information, and stored setting information.
5. The apparatus of claim 4 , wherein the reverse estimation device is configured to determine an engine clutch output shaft torque estimate using wheel acceleration obtained from the wheel speed, the vehicle load torque, and a vehicle inertia value selected among the stored setting information, and is configured to determine the second estimate using the engine clutch output shaft torque estimate, a motor torque, a motor speed, the transmission state information, and the stored setting information.
6. The apparatus of claim 5 , wherein
the transmission state information includes a gear ratio of a current transmission stage, a rotation speed of an input shaft fastened to a current transmission stage for power transmission, and a final reduction ratio depending on the fastened input shaft, and
the stored setting information for determining the second estimate includes a motor inertia value and an input shaft inertia value.
7. The apparatus of claim 6 , wherein the reverse estimation device is configured to determine the second estimate using a third equation and a fourth equation or using the third equation and a fifth equation depending on the input shaft fastened to the current transmission stage for power transmission,
wherein
the
third
equation
is
T
^
o
=
J
v
ω
.
w
+
T
v
,
wherein
the
fourth
equation
is
T
^
ec
,
r
=
-
T
m
+
J
m
ω
.
m
+
J
e
1
ω
.
c
1
+
T
^
o
i
t
1
i
f
1
,
wherein
the
fifth
equation
is
T
^
ec
,
r
=
-
T
m
+
J
m
ω
.
m
+
J
e
2
ω
.
c
2
+
T
^
o
i
t
2
i
f
2
,
and
wherein:
{circumflex over (T)} ec,r : Second estimate,
T m : Drive motor torque
T o : Output shaft torque,
T v : Vehicle load torque,
J m : Drive motor inertia value,
J e1 : Inertia value of first input shaft of transmission,
J e2 : Inertia value of second input shaft of transmission,
ω m : Drive motor speed,
ω e1 : Speed of first input shaft of the transmission,
ω e2 : Speed of second input shaft of the transmission,
i t1 and i t2 : Gear ratios depending on fastened input shafts,
i f1 and i f2 : Final reduction ratios depending on the fastened input shafts,
{circumflex over ( )}: Estimate,
{tilde over ( )}: Error, and
{dot over ( )}: Differential value.
8. The apparatus of claim 1 ,
wherein the estimate combination determination device is configured to determine the final estimate of the engine clutch transfer torque from a sixth equation using the feedforward weight and the feedback weight determined by the weight determination device,
wherein the sixth equation is
{dot over ( {circumflex over (T)} )}= L ff {dot over ( {circumflex over (T)} )} ec,r +L fb ( {circumflex over (T)} ec,f −{circumflex over (T)} ec ), and
wherein:
{circumflex over (T)} ec,f : First estimate,
{circumflex over (T)} ec,r : Second estimate,
L ff : Feedforward weight,
L fb :r Feedback weight,
{circumflex over (T)} ec : Final estimate of engine clutch transfer torque, and
{dot over ({circumflex over (T)})} ec,r : Differential value of second estimate.
9. The apparatus of claim 8 , wherein
the weight determination device is configured to determine the feedforward weight to be 0 when at least one of the predetermined devices in the vehicle is configured to be operated, and
the weight determination device is configured to determine the feedforward weight to be a smaller value and the feedback weight to be a larger value as a value of the brake input by the driver is increased.
10. The apparatus of claim 1 , wherein
the weight determination device is configured to determine the feedforward weight and the feedback weight to be applied to the first estimate and the second estimate, respectively, and
the feedforward weight and the feedback weight are determined from a seventh equation and an eighth equation,
wherein the seventh equation is
L ff =( I−D 8 )× D S ,
wherein the eighth equation is
L fb =( C−L ff )× K , and
wherein:
L ff : Feedforward weight,
L fb : Feedback weight,
D B : Normalized disturbance value determined to be value selected from between 0 and 1 in a response to brake input by driver
D S : Value determined to be 1 when no predetermined devices in vehicle are operated and to be 0 when at least one predetermined device in vehicle is operated,
C: Stored setting value, and
K: Predetermined gain.
11. The apparatus of claim 10 , wherein the normalized disturbance value is set to be a larger value as a value of the brake input by the driver is increased.
12. A method of estimating transfer torque of an engine clutch in a hybrid electric vehicle using a motor and an engine as drive sources, the engine clutch being provided between the engine and the motor, the method comprising:
determining a first estimate of engine clutch transfer torque using engine torque information;
determining a second estimate of the engine clutch transfer torque using a drive system model including wheels, a transmission, and a motor and using wheel speed information;
determining a weight based on brake input by a driver and whether predetermined devices in the vehicle are operated; and
receiving the determined first estimate and the determined second estimate from the forward estimation unit and the reverse estimation unit and determining a final estimate of the engine clutch transfer torque as a value combined by applying a weight to the determined first estimate and the determined second estimate, the final estimate being used in controlling the engine clutch.
13. The method of claim 12 , wherein the step of determining the first estimate includes determining the first estimate using nominal engine torque, engine speed, nominal engine clutch torque, and stored setting information as the engine torque information.
14. The method of claim 13 , wherein the step of determining the first estimate includes determining the first estimate as a value obtained by adding the nominal engine clutch torque and an error estimate, the error estimate being determined from the nominal engine torque, the engine speed, the nominal engine clutch torque, and the stored setting information using a first equation and a second equation,
wherein
the
first
equation
is
ω
^
.
e
=
1
J
d
T
e
,
n
-
1
J
d
(
T
ec
,
n
+
T
~
^
ec
,
f
)
+
l
f
1
(
ω
e
-
ω
^
e
)
,
wherein
the
second
equation
is
T
~
^
.
ec
,
f
=
-
l
f
2
(
ω
e
-
ω
^
e
)
,
and
wherein:
{circumflex over ({tilde over (T)})} ec,f : Error estimate,
T e,n : Nominal engine torque,
T ec,n : Nominal engine clutch torque,
J d : Damper inertia value,
ω e : Engine speed,
l f1 : P gain of PI-type observer in forward estimation device,
l f2 : I gain of PI-type observer in forward estimation device,
{circumflex over ( )}: Estimate,
{tilde over ( )}: Error, and
{dot over ( )}: Differential value.
15. The method of claim 12 , wherein the step of determining the second estimate includes determining the second estimate using wheel speed, motor torque, motor speed, vehicle load torque, transmission state information, and stored setting information.
16. The method of claim 15 , wherein the step of determining the second estimate includes determining an engine clutch output shaft torque estimate using wheel acceleration obtained from the wheel speed, the vehicle load torque, and a vehicle inertia value selected among the stored setting information, and determining the second estimate using the engine clutch output shaft torque estimate, the motor torque, the motor speed, the transmission state information, and the stored setting information.
17. The method of claim 16 , wherein
the transmission state information includes a gear ratio of a current transmission stage, a rotation speed of an input shaft fastened to a current transmission stage for power transmission, and a final reduction ratio depending on the fastened input shaft, and
the stored setting information for determining the second estimate includes a motor inertia value and an input shaft inertia value.
18. The method of claim 17 , wherein the step of determining the second estimate includes determining the second estimate using a third equation and a fourth equation or using the third equation and a fifth equation depending on the input shaft fastened to the current transmission stage for power transmission,
wherein
the
third
equation
is
T
^
o
=
J
v
ω
.
w
+
T
v
,
wherein
the
fourth
equation
is
T
^
ec
,
r
=
-
T
m
+
J
m
ω
.
m
+
J
e
1
ω
.
c
1
+
T
^
o
i
t
1
i
f
1
,
wherein
the
fifth
equation
is
T
^
ec
,
r
=
-
T
m
+
J
m
ω
.
m
+
J
e
2
ω
.
c
2
+
T
^
o
i
t
2
i
f
2
,
and
wherein:
{circumflex over (T)} ec,r : Second estimate,
T m : Drive motor torque
T o : Output shaft torque,
T v : Vehicle load torque,
J m : Drive motor inertia value,
J e1 : Inertia value of first input shaft of transmission,
J e2 : Inertia value of second input shaft of transmission,
ω m : Drive motor speed,
ω e1 : Speed of first input shaft of the transmission,
ω e2 : Speed of second input shaft of the transmission,
i t1 and i t2 : Gear ratios depending on fastened input shafts,
i f1 and i f2 : Final reduction ratios depending on the fastened input shafts,
{circumflex over ( )}: Estimate,
{tilde over ( )}: Error, and
{dot over ( )}: Differential value.
19. The method of claim 12 , wherein the step of determining the final estimate includes determining the final estimate of the engine clutch transfer torque from a sixth equation using the feedforward weight and the feedback weight determined by the weight determination device,
wherein the sixth equation is
{dot over ( {circumflex over (T)} )}= L ff {dot over ( {circumflex over (T)} )}+ L fb ( {circumflex over (T)} ec,f −{circumflex over (T)} ec ), and
wherein:
{circumflex over (T)} ec,f : First estimate,
{circumflex over (T)} ec,r : Second estimate,
L ff : Feedforward weight,
L fb : Feedback weight,
{circumflex over (T)} ec : Final estimate of engine clutch transfer torque, and
{dot over ({circumflex over (T)})} ec,r : Differential value of second estimate.
20. The method of claim 19 , wherein the step of determining the weight includes determining the feedforward weight to be 0 when at least one of the predetermined devices in the vehicle is operated and determining the feedforward weight to be a smaller value and the feedback weight to be a larger value as a value of the brake input by the driver is increased.
21. The method of claim 12 , wherein the step of determining the weight includes determining the feedforward weight and the feedback weight to be applied to the first estimate and the second estimate, respectively, the feedforward weight and the feedback weight being determined from a seventh equation and an eighth equation,
wherein the seventh equation is
L ff =(1− D B )× D S ,
wherein the eighth is
L fb =( C−L ff )× K , and
wherein:
L ff : Feedforward weight,
L fb : Feedback weight,
D B : Normalized disturbance value determined to be value selected from between 0 and 1 in a response to brake input by driver
D S : Value determined to be 1 when no predetermined devices in vehicle are operated and to be 0 when at least one predetermined device in vehicle is operated,
C: Stored setting value, and
K: Predetermined gain.
22. The method of claim 21 , wherein the normalized disturbance value is set to be a larger value as a value of the brake input by the driver is increased.