Method for hill start assistance for motor vehicle
A method for hill start assistance for a motor vehicle and to an associated device that includes a clutch and a transmission between the clutch and driving wheels of the vehicle. The method determines the torque of the clutch for maintaining the vehicle in an immobile position based on a known engine torque, wherein the torque of the clutch is determined by taking into account a portion of the engine torque dedicated to operation of constituent mechanisms of the vehicle other than the clutch.
1. A hill start assistance method for a motor vehicle including a clutch and a transmission between the clutch and drive wheels of the vehicle, the method comprising:
holding the motor vehicle immobile on a hill;
determining via computation means of the vehicle a clutch torque (C emb ) to keep the vehicle immobile based on knowledge of an engine torque (C me );
estimating an equivalent torque C me,off as a quota of the engine torque dedicated to an operation of accessories of the vehicle,
determining the clutch torque (C emb ) by a system formed by Equation (2) and Equation (3):
ω
.
m
.
p
=
1
J
(
-
C
emb
+
C
me
-
C
me
,
off
)
+
K
1
(
ω
.
m
,
p
-
ω
.
m
)
Equation
(
2
)
C
.
emb
=
K
2
(
ω
.
m
,
p
-
ω
.
m
)
;
and
Equation
(
3
)
mobilizing the motor vehicle on the hill after a period of immobility, wherein
K1 and K2 are constants;
Equation (2) corresponds to a modified sum of the moments exerted on the transmission between the clutch and the drive wheels of the vehicle, for which a disturbance K 1 ({dot over (ω)} m,p −{dot over (ω)} m ) associated with the engine speed is added, and
Equation (3) establishes a link between the derivative of the clutch torque (C emb ) and the disturbance associated with the engine speed.
2. The method as claimed in claim 1 , wherein the equivalent torque C me,off associated with the accessories of the vehicle is estimated, by considering C me,off to be the residual value of the engine torque C me when:
the engine is declutched;
the engine speed is stabilized; and
in absence of any action on the vehicle's accelerator pedal.
3. The method as claimed in claim 1 , further comprising:
determining the clutch torque (C emb ) by using Equation (2) and Equation (3) as part of a Kalman observer.
4. The method as claimed in claim 1 , wherein the accessories of the vehicle include a mechanism selected from the group consisting of an assisted steering mechanism, an engine compartment fan, a passenger compartment fan, and an alternator.
5. A hill start assistance device for a motor vehicle, comprising:
a clutch;
a transmission between the clutch and drive wheels of the vehicle;
brakes; and
computation means,
wherein the computation means are configured to
determine a pressure applied to the brakes based on knowledge of an engine torque (C me ) to keep the vehicle immobile,
estimate an equivalent torque C me,off as a quota of the engine torque dedicated to an operation of accessories of the vehicle, and
determine the clutch torque (C emb ) to keep the vehicle immobile by a system formed by Equation (2) and Equation (3):
ω
.
m
,
p
=
1
J
(
-
C
emb
+
C
me
-
C
me
,
off
)
+
K
1
(
ω
.
m
,
p
-
ω
.
m
)
Equation
(
2
)
C
.
emb
=
K
2
(
ω
.
m
,
p
-
ω
.
m
)
,
wherein
Equation
(
3
)
K1 and K2 are constants,
Equation (2) corresponds to a modified sum of the moments exerted on the transmission between the clutch and the drive wheels of the vehicle, for which a disturbance K 1 ({dot over (ω)} m,p −{dot over (ω)} m ) associated with a speed of the engine, is added, and
Equation (3) establishes a link between the derivative of the clutch torque (C emb ) and the disturbance associated with the speed of the engine.
6. A motor vehicle, comprising a device as claimed in claim 5 .