Attitude determination exploiting geometry constraints

• US 7,292,185 B2
• Filed: 10/04/2005
• Issued: 11/06/2007
• Est. Priority Date: 10/04/2005
• Status: Active Grant

• Current Assignee: Hemisphere GNSS(USA) Incorporated
• Original Assignee: CSI Wireless Incorporated
• Inventors: Whitehead, Michael L., Davis, Cary, Scott, Dale R.
• Primary Examiner(s): Issing; Gregory C.
• Application Number:
  US11/243,112
• Publication Number:
  US 20070075896A1
• Time in Patent Office: 763 Days
• Field of Search: 342/357.11
• US Class Current: 342/357.36
• CPC Class Codes: G01S 19/53 Determining attitude

Abstract

A method and system for determining at least one attitude angle of a rigid body. The method comprising: receiving a plurality of Global Navigation Satellite System (GNSS) satellite signals with a plurality of antennas; establishing at least one pair of antennas such that each antenna of the plurality of antennas is included in at least one antenna pair; computing single- or double-difference phases corresponding to one or more GNSS satellites for each of the pairs of antennas; and constructing a single Differential Carrier Phase Attitude (DCPA) equation based on known geometry constraints of each of the pairs of antennas. The method also includes determining a solution for the DCPA equation based on a cost function, the solution yielding at least one integer ambiguity value and the at least one attitude angle.

Claims

1. A system for determining at least one attitude angle of a rigid body comprising:

a plurality of antennas disposed on the rigid body, said plurality of antennas exhibiting known relative geometries and receptive to a plurality of Global Navigation Satellite System (GNSS) satellite signals, said plurality of antennas partitioned into at least one baseline pair of antennas exhibiting a known physical geometry such that each antenna of said plurality of antennas is included in at least one antenna pair;

a receiver in operable communication with said plurality of antennas and configured to receive said GNSS satellite signals therefrom;

said receiver configured to;

a) compute single- or double-difference carrier phases corresponding to one or more GNSS satellites for each of said at least one pair of antennas,

b) construct a single Differential Carrier Phase Attitude (DCPA) equation based on constraints from said known relative geometries of each of said pairs of antennas,

c) loop over and sequentially increment at least one coarse attitude angle,

d) solve for an integer ambiguity vector that minimizes a residual error vector E when said coarse angle is substituted into the DCPA equation,

e) for each integer ambiguity vector of step d) determine at least one refined attitude angle that minimizes a least-squares cost function with a cost function based upon the DCPA equation, and

f) repeat steps c-e and save to computer memory any ambiguity vector that results in the cost function having a value that is less than a previous cost function value.

2. The system of claim 1 wherein said plurality of antennas includes at least three antennas.

3. The system of claim 1 wherein the at least one attitude angle corresponds to at least one of heading, pitch, or roll angles.

4. The system of claim 1 wherein said cost function is based on at least one of a degree to which selected ambiguity fronts intersect or a degree to which said selected ambiguity fronts correspond to said known geometry constraints.

5. The system of claim 1 wherein said solution is achieved employing at least one of a least-squares method or a Kalman filter.

6. The system of claim 1 further including a gyroscope configured to provide attitudes processed along with the differential carrier phase observations to enhance said solution.

7. The system of claim 1 further including a gyroscope configured to provide attitudes to a Kalman filter, wherein said Kalman filter is configured to estimate bias errors and scale errors in said attitudes from said gyroscope, and then reduce or remove these errors from said attitudes from said gyroscope.

8. A system for determining at least one attitude angle of a rigid body comprising:

a plurality of antennas disposed on the rigid body, said plurality of antennas exhibiting known relative geometries and receptive to a plurality of Global Navigation Satellite System (GNSS) satellite signals, said plurality of antennas partitioned into at least one baseline pair of antennas exhibiting a known physical geometry such that each antenna of said plurality of antennas is included in at least one antenna pair;

a receiver in operable communication with said plurality of antennas and configured to receive said GNSS satellite signals therefrom;

said receiver being configured to;

a) compute singe- or double-difference carrier phases corresponding to one or more GNSS satellites for each of said at least one pair of antennas,

b) construct a Differential Carrier Phase Attitude (DCPA) equation based on constraints from said known relative geometries of each of said pairs of antennas,

c) select a subset of integer ambiguities containing at least one integer ambiguity, but not containing the entire set of integer ambiguities,

d) loop over and sequentially increment at least one integer corresponding to at least one ambiguity of the subset,

e) using at least one of said incremented integer ambiguities, solve for at least one coarse attitude angle,

f) solve for an integer ambiguity vector that minimizes the residual error vector E when said coarse angle is substituted into the DCPA equation,

g) for each integer ambiguity vector of step f) determine at least one refined attitude angle that minimizes a least-squares cost function with said cost function based upon the DCPA equation, and

h) repeat steps c-g, and save to computer memory any ambiguity vector that results in the cost function having a value that is less than a previous cost function value.