US2007294017A1PendingUtilityA1
Method for estimating clutch engagement parameters in a strategy for clutch management in a vehicle powertrain
Est. expiryJun 20, 2026(expired)· nominal 20-yr term from priority
F16D 2500/70264F16D 2500/7082F16D 2500/3165F16D 48/06F16D 2500/70605
48
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Cited by
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Claims
Abstract
A method is disclosed for estimating clutch engagement characteristics of a friction clutch system in a vehicle powertrain. A dynamic model of the system is used under conditions that cause clutch slipping. Algebraic equations defining a functional relationship between clutch torque and an engagement angle have characteristic parameters that are estimated using a non-linear least squares technique. A non-linear least squares technique iteratively minimizes the difference between a measured output clutch disk speed and an output clutch disk speed from the system dynamic model for the same inputs until a small insignificant error is reached. Parameter estimates are used to compile an estimated clutch engagement characteristic.
Claims
exact text as granted — not AI-modified1 . A method for controlling clutch engagement of a friction clutch system in a vehicle powertrain, the powertrain having an engine and a power transmission, the clutch system including a clutch actuator under the control of a vehicle operator, the actuator being movable between a clutch open position and a clutch closed position in accordance with a clutch position variable to establish and disestablish a power flow path from the engine to a powertrain power output element through the transmission, the method comprising the steps of:
developing a dynamic model of the driveline under conditions that cause clutch slipping; determining an engine torque request in response to vehicle speed requests by the vehicle operator; determining a target engine torque; the dynamic model and an initial functional relationship of the clutch position variable and clutch torque defining differential algebraic equations with known parameters that determine an initial clutch engagement characteristic as the clutch position variable changes between an initial clutch slip state value and a clutch engaged state value; and computing a final estimated clutch engagement characteristic following clutch wear during a clutch operating time history using estimated parameters for the dynamic model and the functional relationship whereby optimal clutch engagement quality is maintained.
2 . The method set forth in claim 1 including the step of minimizing in an iterative fashion an error between measured clutch speed and a computed clutch speed determined by using the dynamic model for the same input variables, the final clutch engagement characteristic being determined when the error between the measured and the computed clutch speed is insignificant.
3 . The method set forth in claim 2 wherein the difference between the measured clutch speed and a clutch speed determined by using a set of estimated parameters is minimized iteratively with a non-linear least squares technique until a final set of estimated parameters is obtained.
4 . The method set forth in claim 1 wherein the dynamic model and the functional relationship define the following differential algebraic expressions:
ω
.
e
=
-
β
e
J
e
ω
e
-
1
J
e
T
cl
+
1
J
e
T
e
(
1
)
ω
.
c
=
-
β
c
J
c
ω
c
-
1
J
c
T
l
+
1
J
c
T
cl
(
2
)
T
cl
=
a
0
(
1
-
α
)
3
+
a
1
3
α
(
1
-
α
)
2
+
a
2
3
α
2
(
1
-
α
)
+
a
3
α
3
(
3
)
where,
ω e =Engine speed, measured from experiment;
ω c =Clutch/Mainshaft speed, measured from experiment;
β e =Crankshaft friction coefficient;
T e =Engine torque, measured from vehicle;
T cl =Torque transmitted by the clutch, estimated;
J e =Engine inertia;
T 1 =Load torque at wheel;
β c =Mainshaft and wheel friction coefficient;
J c =Inertia of the mainshaft; and
α=Angle of engagement.
5 . The method set forth in claim 2 wherein the dynamic model and the functional relationship define the following differential algebraic expressions:
ω
.
e
=
-
β
e
J
e
ω
e
-
1
J
e
T
cl
+
1
J
e
T
e
(
1
)
ω
.
c
=
-
β
c
J
c
ω
c
-
1
J
c
T
l
+
1
J
c
T
cl
(
2
)
T
cl
=
a
0
(
1
-
α
)
3
+
a
1
3
α
(
1
-
α
)
2
+
a
2
3
α
2
(
1
-
α
)
+
a
3
α
3
(
3
)
where,
ω e =Engine speed, measured from experiment;
ω c =Clutch/Mainshaft speed, measured from experiment;
β e =Crankshaft friction coefficient;
T e =Engine torque, measured from vehicle;
T cl =Torque transmitted by the clutch, estimated;
J e =Engine inertia;
T 1 =Load torque at wheel;
β c =Mainshaft and wheel friction coefficient;
J c =Inertia of the mainshaft; and
α=Angle of engagement.
6 . The method set forth in claim 3 wherein the step of estimating a final clutch engagement characteristic comprises using estimated values for parameters for the differential algebraic equations;
determining errors between measured clutch speed and clutch speed indicated by the estimated clutch engagement characteristic at various time samples; computing the sum of the squares of the errors to define an error function; and minimizing the error function in an iterative fashion until it does not change significantly.
7 . The method set forth in claim 5 wherein the step of minimizing the error function comprises computing a partial derivative of the error function with respect each of multiple parameters of a previously computed clutch engagement characteristic;
computing a corresponding engagement characteristic using a previously computed engagement characteristic and partial derivatives of the error functions; computing a new error function using the new parameters; and comparing the new error function to a previously computed error function to determine whether the new error function is not significantly less than the previously computed error function,
8 . The method set forth in claim 6 wherein the step of minimizing the error function includes repeating the error function computation if the value of the new error function is not less than the value of the previously computed error function by an insignificant amount.
9 . A speed-based method for controlling clutch engagement characteristics for a friction clutch in a powertrain for a wheeled vehicle, the friction clutch having a displaceable actuator element that is movable by a vehicle operator between a clutch open position to a clutch closed position as a power flow path from an engine to vehicle traction wheels is established and disestablished, the method comprising the steps of:
developing a driveline system dynamic model when the friction clutch is slipping, the model and a functional relationship based on clutch torque and displacement of the actuator element defining a clutch engagement characteristic; determining an engine torque request in response to a difference between a measured actual vehicle speed and a predetermined target vehicle speed; determining a target engine torque; the clutch engagement characteristic including a known set of parameters; and estimating a clutch engagement characteristic during a period following clutch wear to maintain optimum clutch engagement quality.
10 . The method set forth in claim 9 wherein the dynamic model and the functional relationship comprise:
ω
.
e
=
-
β
e
J
e
ω
e
-
1
J
e
T
cl
+
1
J
e
T
e
(
1
)
ω
.
c
=
-
β
c
J
c
ω
c
-
1
J
c
T
l
+
1
J
c
T
cl
(
2
)
T
cl
=
a
0
(
1
-
α
)
3
+
a
1
3
α
(
1
-
α
)
2
+
a
2
3
α
2
(
1
-
α
)
+
a
3
α
3
(
3
)
where:
ω e =Engine speed, measured from experiment;
ω c , =Clutch/Mainshaft speed, measured from experiment;
β e =Crankshaft friction coefficient;
T e =Engine torque, measured from vehicle;
T cl =Torque transmitted by the clutch, estimated;
J e =Engine inertia;
T 1 =Load torque at wheel;
β c =Mainshaft and wheel friction coefficient;
J c =Inertia of the Mainshaft; and
α=Angle of engagement.
11 . The method set forth in claim 9 wherein the estimated clutch engagement characteristic is computed following wear of the clutch in a time period later in a clutch operating history than an initial time period, the estimated clutch engagement characteristic being computed by using a new set of parameters and a least squares error function based on a difference between actual clutch speed values and calculated clutch speed values for given actuator element displacements.
12 . The method set forth in claim 10 wherein:
estimating the clutch engagement characteristic includes computing a least squares error function for clutch speeds at multiple actuator element displacements; computing partial derivatives of the least squares error function; computing new clutch speeds at the multiple actuator element displacements using a new set of parameters and the partial derivatives of the least squares error function; comparing a least square error function using the set of parameters previously determined to a current least squares error function; and repeating the clutch engagement characteristic calculation at multiple time samples until the difference in the least squares error functions is insignificant.Join the waitlist — get patent alerts
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