Orientation measurements for drift correction

Patent metadata

Field	Value
Publication number	US-9395447-B2
Application number	US-201414567697-A
Country	US
Kind code	B2
Filing date	Dec 11, 2014
Priority date	Dec 11, 2014
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

Technology for measuring orientation is described. Signals can be received from a signal source having a known location via at least two antennas of the interferometer that are separated by a predefined distance. A delay between receiving the signals from the signal source at the at least two antennas of the interferometer can be calculated. A line of bearing (LOB) of the interferometer with respect to the signal source can be determined based on the delay between receiving the signals at the at least two antennas from the signal source. The orientation of the interferometer can be measured in a global coordinate system using the LOB of the interferometer with respect to the signal source.

First claim

What is claimed is:

1. A method for measuring an orientation at a navigation device, the method comprising:
receiving signals from a signal source having a known location via at least two antennas of the navigation device, wherein the at least two antennas are oriented at substantially the same angle and separated by a predefined distance;
calculating a delay between receiving the signals from the signal source at the at least two antennas;
determining a line of bearing (LOB) of the at least two antennas with respect to the signal source based on the delay between receiving the signals at the at least two antennas from the signal source; and
measuring the orientation of the at least two antennas in a global coordinate system using the LOB, wherein the orientation is used to reduce drift at the navigation device by updating a previous orientation of the at least two antennas of the navigation device.

2. The method of claim 1 , wherein the navigation device is an inertial navigation system (INS).

3. The method of claim 1 , further comprising measuring the orientation of the at least two antennas of the navigation device using a plurality of LOBs for the at least two antennas of the navigation device with respect to a plurality of signal sources.

4. The method of claim 1 , wherein the at least two antennas of the navigation device comprise elements of an interferometer or a phase array that is used to determine the delay between receiving the signals from the signal source.

5. The method of claim 1 , wherein the delay between receiving the signals from the signal source is at least one of a phase delay or a group delay.

6. The method of claim 1 , wherein the navigation system operates within a self-propelled guided weapon or a vehicle.

7. The method of claim 1 , wherein the delay between the signals being received at the at least two antennas from the signal source is represented by c·Δt, wherein c is the speed of light and Δt is a difference between times of arrival for the signals that are received from the signal source.

8. The method of claim 7 , wherein c·Δt is equal to d·cos(α), wherein d represents the predefined distance between the at least two antennas and α represents the LOB of the at least two antennas with respect to the signal source.

9. The method of claim 7 , wherein an accuracy of the delay is represented by

c
·
Δ

⁢

⁢

t
accuracy

=

λ

2
⁢

⁢
π

·

1
SNR

,

wherein c is the speed of light, Δt accuracy is the accuracy of the delay, λ is a wavelength of a transmitter radiation and SNR is a Signal-to-Noise ratio at the at least two antennas.

10. The method of claim 7 , wherein c·Δt is equal to

D
2

+

d
2

/
4

+

Dd
·

cos
⁡

(
α
)

-

D
2

+

d
2

/
4

-

Dd
·

cos
⁡

(
α
)

,

wherein D represents a distance from the at least two antennas to the signal source, d represents the predefined distance between the at least two antennas, and a represents the LOB of the at least two antennas with respect to the signal source.

11. The method of claim 7 , wherein c·Δt is equal to {right arrow over (d)}·{circumflex over (D)} or

d
⇀

·

R
⇀

-

r
⇀



R
⇀

-

r
⇀



,

wherein {right arrow over (d)} represents a vector connecting effective positions of the at least two antennas, {circumflex over (D)} represents a unit vector of the LOB, {right arrow over (R)} represents a position of the signal source, and {right arrow over (r)} represents a location of a midpoint between the at least two antennas.

12. A method for measuring orientation, the method comprising:
receiving signals from a signal source having a known location via at least two antennas of an interferometer that are separated by a predefined distance;
calculating a delay between receiving the signals from the signal source at the at least two antennas of the interferometer;
determining a line of bearing (LOB) of the at least two antennas with respect to the signal source based on the delay; and
measuring the orientation of the at least two antennas in a global coordinate system using the LOB of the at least two antennas with respect to the signal source.

13. The method of claim 12 , further comprising measuring the orientation of the at least two antennas via an inertial navigation system (INS), wherein the INS navigates one of a vehicle or a self-propelled guided weapon.

14. The method of claim 13 , furthe

Assignees

• Raytheon Co

Inventors

• Dolgin Benjamin
• Law Sarah E
• Attridge Joanne M
• Pratap Preethi
• Fisher David C

Classifications

• G01C21/165

  combined with non-inertial navigation instruments · CPC title

• G01S19/49

  whereby the further system is an inertial position system, e.g. loosely-coupled · CPC title

• G01S19/41 Primary

  Differential correction, e.g. DGPS [differential GPS] · CPC title

• G01S3/46 Primary

  using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems · CPC title