Speed control method for vehicle approaching and traveling on a curve
A vehicle curve speed control system ( 10 ) adapted for use with a vehicle ( 12 ) having an operator ( 14 ), includes a map database ( 16 ) representing a current vehicle path, and a locator device ( 20 ) communicatively coupled to the database ( 16 ) and configured to determine the location of the vehicle ( 12 ) on the path. The system ( 10 ) further includes a controller ( 36 ) configured to identify approaching curve points of a curve ( 18 a ) in terms of curvature or radius, and determine a desired speed profile based on operator preference and/or vehicle characteristic input. An acceleration profile is determined, based on the current vehicle speed, and desired speed profile. An acceleration/deceleration command at the present control loop is modified towards achieving an optimal curve speed, and is delivered to either a brake or acceleration module ( 40,42 ) to automatically accelerate or decelerate the vehicle ( 12 ) accordingly.
1. A speed control system adapted for use with a vehicle having a steering wheel and operator, said system comprising:
a map database having at least one record, wherein the record presents at least one path, said path presenting a plurality of position points, wherein a portion of the points present adjacent curve points that define a curve;
a locator device communicatively coupled to the database, and configured to determine the location of the vehicle and match the location with a first of said points on the path, when the vehicle is located on the path;
a controller communicatively coupled to the device and database, and configured to identify an approaching curve point and determine an allowable curve point management speed; and
a steering angle module communicatively coupled to the controller, and configured to determine and communicate to the controller the current degree of rotation of the steering wheel,
said controller being configured to determine a desired curve point management speed based in part on the allowable curve point management speed and an operator preference or vehicle characteristic input, and further configured to determine the current vehicle speed,
said controller including an estimation module configured to estimate a future condition of the vehicle based on the current vehicle speed and degree of rotation, and presenting a closed loop system, wherein the controller is configured to compare the estimated future condition to the corresponding actual future condition, and modify the estimation module accordingly.
2. The system as claimed in claim 1 ,
said database including an allowable curve point management speed table, wherein each curve point is associated with an allowable curve point management speed,
said controller being further configured to retrieve the associated curve point management speed from the table.
3. The system as claimed in claim 1 ; and
a brake module communicatively coupled to the controller, and configured to decelerate the vehicle upon command,
said controller being further configured to achieve the current vehicle speed, and send a deceleration command signal to the brake module, when the current speed is greater than the desired curve point management speed.
4. The system as claimed in claim 1 ; and
an acceleration module communicatively coupled to the controller, and configured to accelerate the vehicle upon command,
said controller being further configured to determine the current vehicle speed, and send an acceleration command signal to the acceleration module, when the current speed is less than the desired curve point management speed.
5. The system as claimed in claim 4 ,
said vehicle including an internal combustion engine having a fuel intake,
said acceleration module being communicatively coupled to and configured to modify the fuel intake, so as to modify the amount or constituency of the fuel consumed by the engine.
6. The system as claimed in claim 1 ,
said controller being actuated utilizing a voice request/voice response or button press/voice response mechanism.
7. A method of vehicular curve management by a controller, wherein the vehicle includes a navigation system having a map database, said method comprising the steps of:
a) accessing and locating the current position of the vehicle upon a path in the database;
b) identifying a plurality of approaching curve points of a curve on the path;
c) determining a curve point radius and an allowable curve point management speed for each of said points, so as to determine an allowable curve speed profile; and
d) receiving an input relating to an operator preference or vehicle characteristic, and determining a desired curve point management speed for each of said points based on the allowable curve point management speed and input, so as to determine a desired curve speed profile for said plurality of approaching curve points.
8. The method as claimed in claim 7 , wherein the allowable curve point management speed, V x — critical , is calculated according to the equation:
V
x_critical
=
Rg
(
sin
θ
+
μ
cos
θ
)
cos
θ
-
μ
sin
θ
,
with θ being the bank angle of the curve at the curve point;
g being the acceleration due to gravity (9.81 m/s 2 );
R being the radius of curvature of the curve at the curve point; and
μ being the coefficient of friction between the surface and vehicle at the curve point.
9. The method as claimed in claim 7 , wherein the desired curve point management speed, V x — comfort , is calculated by the controller as a function of a vehicle characteristic or operator preference factor, a maximum lateral acceleration rate, the radius of curvature, and the coefficient of friction between the surface and vehicle at the curve point.
10. The method as claimed in claim 9 , wherein the desired curve point management speed, V x — comfort , is calculated according to the equation:
V
x_comfort
=
K
v
K
d
RA
y
(
sin
θ
+
μ
cos
θ
)
cos
θ
-
μ
sin
θ
,
with A y being an desired lateral acceleration rate;
K v being a desired factor pertaining to vehicular characteristics ; and
K d being a desired factor pertaining to operator preference.
11. The method as claimed in claim 7 ; and
(e) determining the current vehicle speed and position, and an acceleration profile, and generating an acceleration/deceleration command based on the acceleration profile and current speed.
12. The method as claimed in claim 11 ,
step (e) further including the steps of delivering the command to an acceleration or brake module, so as to automatically accelerate or decelerate the vehicle.
13. The method as claimed in claim 11 ; and
(f) receiving speed and positioning feedback, utilizing a control loop, and modifying the command, to achieve an optimal curve speed.
14. The method as claimed in claim 11 , wherein the acceleration or deceleration command is modified to achieve the optimal curve speed based on a minimum acceleration or deceleration rate.
15. The method as claimed in claim 11 , wherein the acceleration or deceleration command is modified to achieve the optimal curve speed based on a minimum speed differential.
16. The method as claimed in claim 15 , wherein the acceleration or deceleration command is modified to achieve the optimal curve speed, in accordance with the following algorithm:
A
x
=
∑
i
=
1
N
{
V
^
x_target
2
-
V
x
(
i
)
2
}
w
(
i
)
×
i
2
∑
i
=
1
N
w
(
i
)
×
i
2
wherein V x — target is the desired curve speed at a given curve point i,
V x (i) is a pre-determined estimated curve speed at the point, and
w(i) is a weighting factor at the point.