System and method in data-driven vehicle dynamic modeling for path-planning and control
Operation and motion control, by a vehicle's ADAS or AD features, is improved in ways suitable to EVs having higher driving and handling performance. The vehicle dynamic model for high rates of lateral acceleration (e.g., sharp cornering or taking curves having a small radius of curvature as faster speeds) is improved by one or more of optimizing time cornering stiffness with a sigmoid function and/or altering front/rear steering angle to account for roll steer and compliance steer, based on vehicle testing. Indicators for lane departure warning or collision warning, evasive steering, or emergency braking are therefore reliably extended to allow higher performance maneuvers.
1. An apparatus, comprising:
a transceiver configured to receive signals from a controller area network (CAN) bus coupled to at least one device configured to capture motion information for at least one motion by an ego vehicle; and
an operation and motion controller configured to:
process the motion information relating to the at least one motion by the ego vehicle to determine lateral acceleration for the ego vehicle using a dynamic vehicle model, the dynamic vehicle model including a tire cornering stiffness adapted as a function of the determined lateral acceleration of the ego vehicle, and
activate a steering control with a braking or acceleration control based on the determined lateral acceleration of the ego vehicle,
wherein the tire cornering stiffness as the function of the determined lateral acceleration of the ego vehicle is a sigmoid function.
2. The apparatus according to claim 1 , wherein the tire cornering stiffness is determined from:
{
β
.
r
.
}
=
[
-
2
m
V
x
(
C
f
+
C
r
)
-
1
+
2
(
-
l
f
C
f
+
l
r
C
r
)
m
V
x
2
2
I
z
(
-
l
f
C
f
+
l
r
C
r
)
-
2
I
z
V
x
(
l
f
2
C
f
+
l
r
2
C
r
)
]
{
β
r
}
+
[
2
C
f
m
V
x
2
C
r
m
V
x
2
l
f
C
f
I
z
-
2
l
r
C
r
I
z
]
[
1
k
f
0
k
r
]
{
δ
f
A
y
}
,
where A y is the lateral acceleration of the ego vehicle, C f and C r are front and rear tire cornering stiffnesses, respectively, β is a side-slip angle of the ego vehicle and {dot over (β)} is a derivative of β with respect to time, r is a velocity of the ego vehicle in a yaw direction and {dot over (r)} is a derivative of r with respect to time, V x is a longitudinal component of the ego vehicle's velocity V, l f and l r are front and rear wheelbase lengths for the ego vehicle, respectively, m and I z are translational and rotational mass inertias for the ego vehicle, respectively, k r are optimization parameters determined by testing of the ego vehicle, and δ f is a front steering angle of the ego vehicle.
3. The apparatus according to claim 1 , wherein:
the dynamic vehicle model further includes a front steering angle and a rear steering angle adapted as a function of lateral acceleration of the ego vehicle; and
the front steering angle and the rear steering angle each include a term accounting for roll steering and compliance steering.
4. An ego vehicle comprising the apparatus according to claim 1 , the ego vehicle further comprising:
a motor configured to drive at least one of front or rear wheels of the ego vehicle;
a chassis supporting axles on which the wheels are mounted, the wheels coupled to a steering mechanism configured to control at least one of a front steering angle or a rear steering angle based on activation of the steering control; and
a brake actuator configured to actuate brakes for one or more of the wheels based on activation of the braking or acceleration control.
5. The ego vehicle according to claim 4 , wherein the ego vehicle is an electric vehicle and the motor is an electric motor.
6. An apparatus, comprising:
a transceiver configured to receive signals from a controller area network (CAN) bus coupled to at least one device configured to capture motion information for at least one motion by an ego vehicle; and
an operation and motion controller configured to:
process the motion information relating to the at least one motion by the ego vehicle to determine lateral acceleration for the ego vehicle using a dynamic vehicle model, the dynamic vehicle model including a cornering stiffness, a front steering angle, and a rear steering angle adapted as a function of the determined lateral acceleration of the ego vehicle, and
activate a steering control with a braking or acceleration control based on the determined lateral acceleration of the ego vehicle,
wherein the cornering stiffness is adapted by a sigmoid function of the determined lateral acceleration of the ego vehicle,
wherein the front steering angle and the rear steering angle each include a term accounting for roll steering and compliance steering, and
wherein the front steering angle δ f is given by:
δ f =δ f,kinematic +k f a y ,
where δ f,kinematic corresponds to kinematic steering of front wheels of the ego vehicle, a y is the lateral acceleration of the ego vehicle, and k f is an optimization parameter determined by testing of a design for the ego vehicle.
7. The apparatus according to claim 6 , wherein k f a y accounts for roll steering and compliance steering of the front wheels of the ego vehicle.
8. The apparatus according to claim 6 , wherein the rear steering angle δ r is given by:
δ r =k r a y ,
where k r is another optimization parameter determined by testing of the design for the ego vehicle.
9. The apparatus according to claim 8 , wherein k r a y accounts for roll steering and compliance steering of rear wheels of the ego vehicle.
10. The apparatus according to claim 6 , wherein the cornering stiffness is determined from:
{
β
.
r
.
}
=
[
-
2
m
V
x
(
C
f
+
C
r
)
-
1
+
2
(
-
l
f
C
f
+
l
r
C
r
)
m
V
x
2
2
I
z
(
-
l
f
C
f
+
l
r
C
r
)
-
2
I
z
V
x
(
l
f
2
C
f
+
l
r
2
C
r
)
]
{
β
r
}
+
[
2
C
f
mV
x
2
C
r
mV
x
2
l
f
C
f
I
z
-
2
l
r
C
r
I
z
]
[
1
k
f
0
k
r
]
{
δ
f
A
y
}
,
where C f and C r are front and rear tire cornering stiffnesses, respectively, β is a side-slip angle of the ego vehicle and {dot over (β)} is a derivative of β with respect to time, r is a velocity of the ego vehicle in a yaw direction and {dot over (r)} is a derivative of r with respect to time, V x is a longitudinal component of the ego vehicle's velocity V, l f and l r are front and rear wheelbase lengths for the ego vehicle, respectively, m and I z are translational and rotational mass inertias for the ego vehicle, respectively, k r are optimization parameters determined by testing of the ego vehicle, and δ f is the front steering angle of the ego vehicle.
11. The apparatus according to claim 6 , further comprising:
a motor configured to drive at least one of front or rear wheels of the ego vehicle;
a chassis supporting axles on which the wheels are mounted, the wheels coupled to a steering mechanism configured to control at least one of the front steering angle or the rear steering angle based on activation of the steering control; and
a brake actuator configured to actuate brakes for one or more of the wheels based on activation of the braking or acceleration control.
12. A method, comprising:
receiving signals from a controller area network (CAN) bus coupled to at least one device configured to capture motion information for at least one motion by an ego vehicle;
processing the motion information relating to the at least one motion by the ego vehicle to determine lateral acceleration for the ego vehicle using a dynamic vehicle model, the dynamic vehicle model including tire cornering stiffness adapted as a function of the determined lateral acceleration of the ego vehicle; and
activating a steering control with a braking or acceleration control based on the determined lateral acceleration of the ego vehicle,
wherein the tire cornering stiffness as the function of the determined lateral acceleration of the ego vehicle is a sigmoid function.
13. The method according to claim 12 , wherein the tire cornering stiffness is determined from:
{
β
.
r
.
}
=
[
-
2
m
V
x
(
C
f
+
C
r
)
-
1
+
2
(
-
l
f
C
f
+
l
r
C
r
)
m
V
x
2
2
I
z
(
-
l
f
C
f
+
l
r
C
r
)
-
2
I
z
V
x
(
l
f
2
C
f
+
l
r
2
C
r
)
]
{
β
r
}
+
[
2
C
f
mV
x
2
C
r
mV
x
2
l
f
C
f
I
z
-
2
l
r
C
r
I
z
]
[
1
k
f
0
k
r
]
{
δ
f
A
y
}
,
where A y is the lateral acceleration of the ego vehicle, C f and C r are front and rear tire cornering stiffnesses, respectively, β is a side-slip angle of the ego vehicle and {dot over (β)} is a derivative of β with respect to time, r is a velocity of the ego vehicle in a yaw direction and {dot over (r)} is a derivative of r with respect to time, V x is a longitudinal component of the ego vehicle's velocity V, l f and l r are front and rear wheelbase lengths for the ego vehicle, respectively, m and I z are translational and rotational mass inertias for the ego vehicle, respectively, k r are optimization parameters determined by testing of the ego vehicle, and δ f is a front steering angle of the ego vehicle.
14. The method according to claim 12 , wherein:
the dynamic vehicle model further includes a front steering angle and a rear steering angle adapted as a function of lateral acceleration of the ego vehicle; and
the front steering angle and the rear steering angle each include a term accounting for roll steering and compliance steering.
15. The method according to claim 14 , wherein the front steering angle δ f is given by:
δ f =δ f,kinematic +k f a y ,
where δ f,kinematic corresponds to kinematic steering of front wheels of the ego vehicle, a y is the lateral acceleration of the ego vehicle, and k f is an optimization parameter determined by testing of a design for the ego vehicle.
16. The method according to claim 15 , wherein k f a y accounts for roll steering and compliance steering of the front wheels of the ego vehicle.
17. The method according to claim 14 , wherein the rear steering angle δ r is given by:
δ r =k r a y ,
where a y is the lateral acceleration of the ego vehicle, and k r is an optimization parameter determined by testing of a design for the ego vehicle.
18. The method according to claim 17 , wherein k r a y accounts for roll steering and compliance steering of rear wheels of the ego vehicle.
19. The method according to claim 12 , further comprising:
driving at least one of front or rear wheels of the ego vehicle with a motor;
supporting axles on which the wheels are mounted on a chassis, the wheels coupled to a steering mechanism configured to control at least one of the front steering angle or the rear steering angle based on activation of the steering control; and
actuating brakes for one or more of the wheels based on activation of the braking or acceleration control.
20. The method according to claim 19 , wherein the ego vehicle is an electric vehicle and the motor is an electric motor.