Method and apparatus for target relative guidance

Patent metadata

Field	Value
Publication number	US-10657832-B2
Application number	US-201916352675-A
Country	US
Kind code	B2
Filing date	Mar 13, 2019
Priority date	Oct 11, 2016
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

A system and method for navigating a vehicle comprising an image sensor in the absence of global positioning information is disclosed. In one embodiment, the method comprises accepting a user-selected target of an image produced by the imaging sensor, determining a difference between an optic flow due only to motion of the vehicle and the selected target of the image, determining a vehicle guidance command at least in part according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of a ground speed of the vehicle V g , and commanding the vehicle at least in part according to the vehicle guidance command. Another embodiment is evidenced by an apparatus having a processor and a communicatively coupled memory storing processor instructions for performing the foregoing operations.

First claim

What is claimed is:

1. A method of navigating a vehicle comprising an image sensor in the absence of global positioning information, comprising:
selecting and tracking a target within an image sequence produced by the imaging sensor;
determining a difference between an optic flow of the selected target due only to motion of the vehicle and the selected target of the image;
determining a vehicle guidance command at least in part according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of a ground speed of the vehicle; and
commanding the vehicle and imaging sensor at least in part according to the vehicle guidance command.

2. The method of claim 1 , wherein determining a difference between an optic flow due only to motion of the vehicle and the selected target of the image comprises:
determining an effect of motion of the imaging sensor on stationary objects in imaging sensor screen coordinates;
determining the optic flow at least in part from a rate of change of the screen coordinates of the stationary objects; and
de-rotating the determined optic flow to compute the optic flow due only to translation of the vehicle.

3. The method of claim 2 , wherein:
determining the vehicle guidance command at least in part according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of the ground speed of the vehicle comprises:
determining a heading rate of change command at least in part according to a rate of change in a bank angle of the vehicle, an estimate of an air speed of the vehicle and the estimate of the ground speed of the vehicle.

4. The method of claim 3 , further comprising:
determining an imaging sensor pan and tilt command according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of a ground speed of the vehicle.

5. The method of claim 4 , wherein determining an imaging sensor pan and tilt command according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of a ground speed of the vehicle comprises:
determining an imaging sensor pan and tilt command according to a rate of change in a bank angle of the vehicle, an estimate of the air speed of the vehicle and the estimate of the ground speed of the vehicle.

6. The method of claim 5 , wherein the heading rate of change command and the imaging sensor pan and tilt command are determined according to a control law:

(

u
ψ

u
K

u
λ

)

=

B

-
1

⁡

(

-
Ke

-

A
⁡

(

V
a

ϕ
.

)

)

wherein u ψ represents a commanded vehicle yaw angle rate, u κ represents a commanded imaging sensor pan angle rate, and u λ represents a commanded imaging sensor tilt angle rate, V a represents the vehicle air speed, {dot over (ϕ)} represents the vehicle bank angle rate, B represents an effect of the commanded signals on the screen coordinates and the pan angle, and K represents tuned gain parameters.

7. The method of claim 6 , wherein the heading rate of change command is determined according to

V
^

g
2

V
a

⁢

R
d

wherein {circumflex over (V)} g is an estimate of the ground speed of the vehicle and R d is a desired orbit radius of the vehicle.

8. The method of claim 7 , wherein computing the ground speed of the vehicle comprises computing a ground speed of the vehicle from the optic flow only due to translation of the vehicle.

9. The method of claim 7 , wherein computing the ground speed of the vehicle comprises computing the ground speed of the vehicle from the computed air speed of the vehicle and a wind estimate.

10. An apparatus for navigating a vehicle comprising an image sensor in the absence of global positioning information, comprising:
a processor;
a memory, communicatively coupled to the processor, the memory for storing instructions comprising instructions for:
determining a difference between an optic flow due only to motion of the vehicle and a user-selected target of an image produced by the imaging sensor;
determining a vehicle guidance command at least in part according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the image, and an estimate of a ground speed of the vehicle; and
commanding the vehicle at least in part according to the vehicle guidance command.

11. The apparatus of claim 10 , wherein the instructions for determining a difference between an optic flow due only to motion of the vehicle and the selected target of the image comprise instructions for:
determining an effect of motion of the imaging sensor on stationary objects in imaging sensor screen coordinates;
determining the optic flow at least in part from a rate of change of the screen coordinates of the stationary objects; and
de-rotating the determined optic flow to compute the optic flow due only to translation of the vehicle.

12. The apparatus of claim 11 , wherein:
the instructions for determining the vehicle guidance command at least in part according to the difference between the optic flow of the selected target due to motion of the vehicle and the selected target of the im

Assignees

• Insitu Inc

Inventors

• Rysdyk Rolf

Classifications

• G06T7/246

  using feature-based methods, e.g. the tracking of corners or segments · CPC title

• G06T7/20

  Analysis of motion (motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51) · CPC title

• G06T2207/10016

  Video; Image sequence · CPC title

• G06T2207/30252

  Vehicle exterior; Vicinity of vehicle · CPC title

• G06T2207/10032

  Satellite or aerial image; Remote sensing · CPC title