Field-based torque steering control

Patent metadata

Field	Value
Publication number	US-9618938-B2
Application number	US-201514814856-A
Country	US
Kind code	B2
Filing date	Jul 31, 2015
Priority date	Jul 31, 2015
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A system includes a computer programmed to determine, along a nominal path to be traversed by a vehicle, a potential field representing a driving corridor for the vehicle. The computer is further programmed to identify a position of the vehicle relative to the potential field at a current time, and apply a torque to q steering column of the vehicle. The torque is based at least in part on the position. The potential field includes an attractive potential that guides the vehicle to remain within the corridor.

First claim

The invention claimed is:

1. A system comprising:
a computer including a processor and a memory, the memory storing instructions executable by the processor such that the computer is programmed to:
determine, along a nominal path to be traversed by a vehicle, a potential field representing a driving corridor for the vehicle, the potential field including an attractive potential that guides the vehicle to remain within the corridor;
identify a first position of the vehicle relative to the potential field at a current time;
calculate a torque to apply to a steering column based at least in part on the first position relative to the potential field; and
apply the torque to the steering column of the vehicle.

2. The system of claim 1 , wherein the computer is programmed to increase the attractive potential as a first distance from the first position to the nominal path increases.

3. The system of claim 2 , wherein a first relationship between the attractive potential and the first distance is quadratic.

4. The system of claim 1 , wherein the potential field is defined such that the nominal path is at a proximate center of the potential field, along a direction of travel.

5. The system of claim 1 , wherein the computer is further programmed to:
identify a second position relative to the potential field, the second position indicating a projected future position of the vehicle a first predetermined time period after the current time, wherein determining the torque to be applied to the steering column of the vehicle is based at least in part on the second position.

6. The system of claim 5 , wherein the applied torque is determined based in part on a first direction of travel of the vehicle and a first velocity of the vehicle, and the computer is further programmed to calculate the second position to be equal to the first position plus a first displacement equal to the product of the first velocity and the first predetermined time period along the first direction of travel.

7. The system of claim 1 , wherein the potential field further includes a repulsive potential, the repulsive potential guiding the vehicle away from an object within a predetermined distance of the nominal path.

8. The system of claim 7 , wherein the computer is further programmed to:
calculate the repulsive potential based on a second distance of the vehicle from the object.

9. The system of claim 8 , wherein the repulsive potential increases as the second distance decreases.

10. The system of claim 7 wherein the potential field is a sum of the attractive potential field and the repulsive potential field.

11. The system of claim 1 , wherein the computer is further programmed to:
calculate a negative gradient

-

∇

U

(
x
)

=

-

DU

(
x
)

=

-

[

∂
U

∂

x
1

⁢

(
x
)

,

∂
U

∂

x
2

⁢

(
x
)

]

T

;

and
determine the torque in part based on the negative gradient;
wherein U (x) is the potential field at a location x on a two dimensional plane.

12. The system of claim 11 , wherein the computer is further programmed to:
determine the torque

τ
⁡

(
t
)

=

K
p

⁢

F
⁡

(

x

t
+
L

)

+

K
d

⁢

ⅆ

ⅆ
t

⁢

F
⁡

(

x

t
+
L

)

;

wherein:
F(x t+L ) is the negative gradient of the potential field at a projected future location x t+L ;
t is a current time;
L is a predetermined time period;
K p is a proportional gain; and
K d is a derivative gain.

13. A method comprising:
determining, by a computer, along a nominal path to be traversed by a vehicle, a potential field representing a driving corridor for the vehicle, the potential fie

Assignees

• Ford Global Tech Llc
• Univ Michigan Regents

Inventors

• Olson Edwin
• Galceran Enric
• Eustice Ryan M
• Mcbride James Robert

Classifications

• B62D6/04

  responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel · CPC title

• B62D1/283 Primary

  for unmanned vehicles · CPC title

• G05D2201/0213

  Physics · mapped topic

• G05D1/0212 Primary

  with means for defining a desired trajectory (involving a plurality of land vehicles G05D1/0287) · CPC title

• B62D15/025 Primary

  Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation (B62D1/28 takes precedence) · CPC title