Curve speed control system with adaptive map preview time and driving mode selection
View Patent ↗A system and method for detecting a road curve as a vehicle approaches the curve, automatically providing road curvature information and controlling vehicle speed. The system uses a locating device and a map database to know the vehicle's position. Depending on the speed of the vehicle, the system generates a curvature profile for different curvature data points at or around the curve in front of the vehicle. The system then generates a desired speed profile for the curvature points. The desired speed profile and the actual vehicle speed are compared to determine whether the vehicle is traveling too fast for the target speed at each profile point. The acceleration computation can be enhanced by providing a driver cornering mode input that the vehicle operator can select based on how aggressively the driver wants the system to act to slow down the vehicle.
1. A curve speed control system for controlling the speed of a vehicle traveling on a curve, said system comprising:
a map database storing information about road curves that the vehicle may be traveling through, said map database including a map database processor that includes curvature information about the curves;
a curvature profile processor responsive to the curvature information from the map processor and providing a curvature profile as a series of curvature data points from the curvature information of the curve, said curvature profile processor determining when to provide the curvature profile based on the vehicle speed;
a desired speed profile processor responsive to the curvature profile from the curvature profile processor, said desired speed profile processor providing a desired speed for each curvature profile point and providing a desired speed profile;
a driver mode selector that provides a driver mode value based on driver aggressiveness;
an acceleration profile processor that receives the desired speed profile from the desired speed profile processor, a vehicle speed signal and the driver mode value, said acceleration profile processor providing a performance index function based on the difference between the vehicle speed, the desired speed and the driver mode value; and
an acceleration command processor for providing an acceleration command that controls the speed of the vehicle based on the performance index function.
2. The system according to claim 1 wherein the curvature profile processor determines when to provide the curvature profile by a gap defined as the distance between the curvature data points as a derivative of the vehicle speed.
3. The system according to claim 1 wherein the driver mode value determines the number of the curvature data points that are used to calculate differences between the vehicle speed and the desired speed to provide the performance index function.
4. The system according to claim 3 wherein the performance index function is defined by the equation:
J
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
i
)
2
}
2
w
(
i
)
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
0
)
2
-
2
A
x
×
d
(
V
x
)
×
i
}
2
w
(
i
)
where J is the performance index function, K 1 and K 2 are a minimum index value and a maximum index value, respectively, that define the driver mode value, {circumflex over (V)} x is the desired speed, A x is the acceleration command, V x is the vehicle speed and w is a weighting function.
5. The system according to claim 4 wherein the acceleration command processor calculates the acceleration command as:
A
x
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
0
)
2
}
×
w
(
i
)
×
i
2
d
(
V
x
)
×
∑
i
=
K
1
K
2
w
(
i
)
×
i
2
.
6. The system according to claim 1 wherein the acceleration profile processor generates the performance index function using an optimal control principle that minimizes the sum of the speed differences between the vehicle speed and the desired speed.
7. The system according to claim 1 further comprising a GPS receiver providing a vehicle location signal to the map database processor.
8. The system according to claim 1 further comprising a vehicle speed sensor providing a vehicle speed signal, a yaw rate sensor providing a vehicle yaw rate signal and a steering angle sensor providing a vehicle steering angle signal, wherein the vehicle speed signal, the yaw rate signal and the steering angle signal are provided to the map processor to identify the curvature information.
9. The system according to claim 1 further comprising a braking module and an acceleration module, said acceleration command being provided to the braking module and/or the acceleration module so as to provide vehicle braking control or acceleration control depending on the value of the command.
10. The system according to claim 1 wherein a weighting function is applied to each data point in the acceleration profile processor.
11. The system according to claim 1 wherein the desired speed profile processor determines the desired speed for each data point based on driver comfort.
12. The system according to claim 11 wherein the desired speed for each data point is determined by the equation:
V
^
x
(
i
)
=
K
v
K
d
K
r
A
y
(
sin
θ
+
μ
cos
θ
)
cos
θ
-
μ
sin
θ
where {circumflex over (V)} x is the desired speed for each data point, K v is a gain factor related to the vehicle center of gravity, track width and roll characteristics, K d is a gain factor that is based on driver aggressiveness, K r is a factor based on road conditions, A y is vehicle lateral acceleration, μ is road surface coefficient of friction and θ is curve bank angle.
13. A curve speed control system for controlling the speed of a vehicle traveling on a curve, said system comprising:
a map database storing information about road curves that the vehicle may be traveling through, said map database including a map database processor that includes curvature information about the curves;
a locator device providing a vehicle location signal to the map database processor;
a curvature profile processor responsive to the curvature information from the map processor and providing a curvature profile as a series of curvature data points from the curvature information of the curve;
a desired speed profile processor responsive to the curvature profile from the curvature profile processor, said desired speed profile processor providing a desired speed for each curvature profile point and providing a desired speed profile;
a driver mode selector that provides a driver mode value based on driver aggressiveness;
an acceleration profile processor that receives the desired speed profile from the desired speed profile processor, a vehicle speed signal and the driver mode value, said acceleration profile processor providing a performance index function based on the difference between the vehicle speed, the desired speed and the driver mode value; and
an acceleration command processor for providing an acceleration command that controls the speed of the vehicle based on the performance index function.
14. The system according to claim 13 wherein the driver mode value determines the number of the curvature data points that are used to calculate differences between the vehicle speed and the desired speed to provide the performance index function.
15. The system according to claim 14 wherein the performance index function is defined by the equation:
J
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
i
)
2
}
2
w
(
i
)
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
0
)
2
-
2
A
x
×
d
(
V
x
)
×
i
}
2
w
(
i
)
where J is the performance index function, K 1 and K 2 are a minimum index value and a maximum index value, respectively, that define the driver mode value, {circumflex over (V)} x is the desired speed, A x is the acceleration command, V x is the vehicle speed and w is a weighting function.
16. The system according to claim 15 wherein the acceleration command processor calculates the acceleration command as:
A
x
=
∑
i
=
K
1
K
2
{
V
^
x
(
i
)
2
-
V
x
(
0
)
2
}
×
w
(
i
)
×
i
2
d
(
V
x
)
×
∑
i
=
K
1
K
2
w
(
i
)
×
i
2
.
17. The system according to claim 13 wherein the acceleration profile processor generates the performance index function using an optimal control principle that minimizes the sum of the speed differences between the vehicle speed and the desired speed.
18. The system according to claim 13 further comprising a vehicle speed sensor providing a vehicle speed signal, a yaw rate sensor providing a vehicle yaw rate signal and a steering angle sensor providing a vehicle steering angle signal, wherein the vehicle speed signal, the yaw rate signal and the steering angle signal are provided to the map processor to identify the curvature information.
19. The system according to claim 13 further comprising a braking module and an acceleration module, said acceleration command being provided to the braking module and/or the acceleration module so as to provide vehicle braking control or acceleration control depending on the value of the command.
20. The system according to claim 13 wherein a weighting function is applied to each data point in the acceleration profile processor.
21. The system according to claim 13 wherein the desired speed profile processor determines the desired speed for each data point based on driver comfort.