Method and apparatus for differential global positioning system (DGPS)-based real time attitude determination (RTAD)

Patent metadata

Field	Value
Publication number	US-9829582-B2
Application number	US-201113236575-A
Country	US
Kind code	B2
Filing date	Sep 19, 2011
Priority date	Sep 19, 2011
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A differential global positioning system (DGPS) processor can include an almost fixed integer ambiguity (AFIA) module for generating in real-time a multiple dimensional state vector of integer ambiguities and multiple dimensional corrections. The AFIA module can use double difference (DD) measurements for pseudo-range (PR) and carrier phase (CP) pairs generated from at least three global positioning system (GPS) receivers. A DGPS processor can be included in a high data rate real time attitude determination (RTAD) system to achieve high heading accuracy with high integrity.

First claim

What is claimed is:

1. A differential global positioning system (DGPS) processor, comprising:
an almost fixed integer ambiguity (AFIA) module configured to generate, in real-time, a multiple dimensional state vector of integer ambiguities and multiple dimensional corrections using double difference (DD) measurements for pseudo-range (PR) and carrier phase (CP) pairs generated from at least three global positioning system (GPS) receivers, wherein, to generate the multiple dimensional state vector, the AFIA module is operative to (i) determine a difference between a double difference (DD) measurement error and a DD measurement vector for a defined number of GPS satellites in view and at least three GPS receivers, and (ii) divide the difference by an observation matrix for the PR and CP pairs, wherein the AFIA module is stored in a digital memory device or is implemented in a hardware circuit;
an attitude module configured to generate an attitude from the multiple dimensional state vector of integer ambiguities and multiple dimensional corrections, wherein the attitude module is stored in a digital memory device or is implemented in a hardware circuit;
a single difference (SD) module configured to generate at least two single difference observables, wherein a single difference observable is the difference between two receiver observables, wherein a receiver observable includes observable GPS data or a LOS unit vector for each receiver, wherein the SD module is stored in a digital memory device or is implemented in a hardware circuit; and
a DD module configured to generate at least two double difference observables, wherein a double difference observable is the difference between SD observables of two GPS satellites, wherein the DD module is stored in a digital memory device or is implemented in a hardware circuit,
wherein a number of single difference observables or a number of double difference observables is less than a number of GPS receivers used to generate observable GPS data.

2. The DGPS processor of claim 1 , wherein the multiple dimensional corrections are angle corrections for a set of roll, pitch, and/or yaw angles.

3. The DGPS processor of claim 1 , wherein the GPS receivers are rigidly fixed in known positions relative to each other.

4. The DGPS processor of claim 1 , further comprising:
a data selection module configured to receive GPS data and GPS-aided navigation data and selecting observable GPS data for at least three GPS receivers, wherein the GPS-aided navigation data combines GPS data of each GPS receiver with inertial measurement unit (IMU) data; and
a line-of-sight (LOS) module configured to generate a LOS unit vector for each GPS receiver from the observable GPS data for GPS satellites in view of the GPS receivers.

5. The DGPS processor of claim 1 , wherein the AFIA module is configured to generate a multiple dimensional observation matrix for at least two PR and CP measurement pairs.

6. The DGPS processor of claim 1 , wherein the double difference measurements is configured to utilize a CP measurement for carrier frequency selected from the group consisting of a single frequency and a narrow-lane (NL) frequency, where NL frequency sums at least two CPs measurements together.

7. A method for determining attitude data in real time, comprising:
under control of one or more computer systems configured with executable instructions:
generating, using one or more processors of the computer systems, in real time a multiple dimensional state vector of integer ambiguities and multiple dimensional corrections using double difference (DD) measurements for pseudo-range (PR) and carrier phase (CP) pairs generated from at least three global positioning system (GPS) receivers, wherein the multiple dimensional state vector is generated by: (i) determining a difference between a double difference (DD) measurement error and a DD measurement vector for a defined number of GPS satellites in view and at least three GPS receivers, and (ii) dividing the difference by an observation matrix for the PR and CP pairs;
generating, using the one or more processors of the computer systems, an attitude from the multiple dimensional state vector of integer ambiguities and multiple dimensional corrections;
generating at least two single difference (SD) observables, wherein a single difference observable is the difference between two receiver observables, wherein a receiver observable includes at least one of observable GPS data and a LOS unit vector for each receiver; and
generating at least two double difference (DD) observables, wherein a double difference observable is the difference between SD observables of two GPS satellites, wherein a number of single difference observables or a number of double difference observables is less than a number of GPS receivers used to generate observable GPS data.

8. The method of claim 7 , further comprising, prior to generating the multiple dimensional state vector:
receiving GPS data and GPS-aided navigation data for at least three GPS receivers, wherein the GPS-aided navigation data combines GPS data of each GPS receiver with inertial measurement unit (IMU) data;
selecting observable GPS data from the GPS data and the GPS-aided navigation data; and
generating a line-of-sight (LOS) unit vector for each GPS receiver from the observable GPS data for GPS satellites in view of the GPS receivers.

9. The method of claim 7 , wherein the relationship between the multiple dimensional state vector and the double difference (DD) measurements is represented by y=Hx+ε, where y is a DD measurement vector for n GPS satellites in view and m GPS receivers, H is an observation matrix, x is the multiple dimensional state vector, and ε represents the DD measurement error, represented by

y
=

[

DD

ϕ
,
f

2
,
1

⁡

(

n
-
1

,
1

)

DD

ρ
,
NL

2
,
1

⁡

(

n
-
1

,

Assignees

• Wu Benjamin
• Peck Stephen R
• Wu Shuwu
• Raytheon Co

Inventors

• Wu Benjamin
• Peck Stephen R
• Wu Shuwu

Classifications

• G01S19/55 Primary

  Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method · CPC title

• G01S19/53

  Determining attitude · CPC title

• G01S19/44

  Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method · CPC title

• G01S19/41

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

• G01S19/04

  providing carrier phase data · CPC title