Obstacle avoidance method
View Patent ↗A method automatically controls a motor vehicle with wheels including at least two steered wheels. The method includes the following steps: the motor vehicle acquiring parameters relating to an obstacle avoidance trajectory, and a computer computing a provisional control instruction for an actuator for braking the steered wheels, based on the parameters and by way of a closed-loop controller. The method also includes the following steps: acquiring a lateral acceleration or a roll angle to which the motor vehicle is subject, and computing, in open-loop mode, a correction term or the provisional control instruction, based on the acquired lateral acceleration or roll angle.
1 . A control method for automated steering of a motor vehicle comprising wheels of which at least two wheels are steered wheels, the method comprising:
acquiring parameters of an avoidance path whereby the motor vehicle avoids an obstacle;
calculating, using a computer, a temporary control instruction that steers the steered wheels via a steering actuator, as a function of said parameters and by a closed loop controller;
acquiring a lateral acceleration or a roll angle experienced by the motor vehicle; and
calculating, using an open loop calculation, a correction term that corrects said temporary control instruction, as a function of the lateral acceleration or of the roll angle acquired,
wherein the correction term is calculated as a function of a coefficient of steering caused by a roll angle of a front wheelset of the wheels of the motor vehicle and/or of a coefficient of steering caused by the roll angle of the front wheelset of the wheels of the wheels of the motor vehicle.
2 . The control method as claimed in claim 1 , wherein the correction term is calculated as a function of a curvature of a road taken that the motor vehicle is traveling upon.
3 . A control method for automated steering of a motor vehicle comprising wheels of which at least two wheels are steered wheels, the method comprising:
acquiring parameters of an avoidance path whereby the motor vehicle avoids an obstacle;
calculating, using a computer, a temporary control instruction that steers the steered wheels via a steering actuator, as a function of said parameters and by a closed loop controller;
acquiring a lateral acceleration or a roll angle experienced by the motor vehicle; and
calculating, using an open loop calculation, a correction term that corrects said temporary control instruction, as a function of the lateral acceleration or of the roll angle acquired,
wherein the correction term is calculated as a function of a curvature of a road taken that the motor vehicle is traveling upon, and
wherein the correction term is equal to the sum of:
a product of a first variable multiplied by the lateral acceleration or by the roll angle, and
a product of a second variable multiplied by the curvature of the road that the motor vehicle is traveling upon.
4 . The control method as claimed in claim 1 , wherein the correction term is calculated as a function of at least one gain of the closed loop controller.
5 . The control method as claimed in claim 1 , wherein the correction term is calculated as a function of an understeer gradient.
6 . The control method as claimed in claim 5 , wherein the understeer gradient is calculated as a function of at least one gain of the closed loop controller.
7 . The control method as claimed in claim 1 , wherein the correction term is calculated by the following equation:
δ
Ffwd
=
[
(
l
f
+
l
r
)
(
1
-
k
δ
-
k
δ
ref
)
+
(
k
ψ
L
-
k
β
)
l
r
+
k
ψ
L
l
s
-
k
r
V
+
K
V
V
2
]
·
ρ
ref
-
[
(
1
-
k
δ
-
k
δ
ref
)
ε
1
-
(
1
-
k
δ
-
k
δ
ref
+
k
ψ
L
-
K
β
)
ε
2
]
·
ϕ
where:
l f , is a distance between a center of gravity and a front axle of the motor vehicle,
l r is a distance between a center of gravity and a rear axle of the motor vehicle,
V is a longitudinal velocity of the motor vehicle,
l s is a predetermined sighting distance,
ρ ref is a radius of curvature of a road that the motor vehicle is traveling upon,
ε 1 is a coefficient of steering caused by a roll angle of a front wheelset of the wheels of the motor vehicle,
ε 2 is a coefficient of steering caused by a roll angle of a rear wheelset of the wheels of the motor vehicle,
Φ is the roll angle,
Kv is an understeer gradient,
k δ ,k δref , k ΨL , k f , and k β are gains of the closed loop controller.
8 . A motor vehicle comprising:
a steering actuator for steering the steered wheels and a computer configured for controlling said actuators,
wherein the computer is programmed to implement the control method as claimed in claim 1 .
9 . A control method for automated steering of a motor vehicle comprising wheels of which at least two wheels are steered wheels, the method comprising:
acquiring parameters of an avoidance path whereby the motor vehicle avoids an obstacle;
calculating, using a computer, a temporary control instruction that steers the steered wheels via a steering actuator, as a function of said parameters and by a closed loop controller;
acquiring a lateral acceleration or a roll angle experienced by the motor vehicle; and
calculating, using an open loop calculation, a correction term that corrects said temporary control instruction, as a function of the lateral acceleration or of the roll angle acquired,
wherein the correction term is calculated as a function of an understeer gradient,
wherein the understeer gradient is calculated as a function of at least one gain of the closed loop controller, and
wherein the understeer gradient is calculated by the following equation:
K
V
=
(
l
r
(
1
-
k
δ
-
k
δ
ref
)
C
f
-
l
f
(
1
-
k
δ
-
k
δ
ref
+
k
ψ
L
-
k
β
)
C
r
)
·
m
l
f
+
l
r
,
where
m is a total mass of the motor vehicle,
C f is a cornering stiffness of a front wheelset of the wheels of the motor vehicle,
C r is a cornering stiffness of a rear wheelset of the wheels of the motor vehicle,
l f is a distance between a center of gravity and a front axle of the motor vehicle,
l r is a distance between a center of gravity and a rear axle of the motor vehicle, and
k δ , k δref , k ΨL , and k β are gains of the closed loop controller.