Method for estimating wind

• US 6,807,468 B2
• Filed: 07/30/2002
• Issued: 10/19/2004
• Est. Priority Date: 07/30/2002
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Campbell, Charles R.
• Primary Examiner(s): BEAULIEU, YONEL
• Application Number:
  US10/207,156
• Publication Number:
  US 20040024500A1
• Time in Patent Office: 812 Days
• Field of Search: 701/14, 701/3, 701/4, 701/7, 701/200, 701/213
• US Class Current: 701/14
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01P 3/50 for measuring linear speed G01P3/56 takes precedence
• CPC Class Codes: G01P 5/00 Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft application of speed-measuring devices for measuring volume of fluid G01F
• CPC Class Codes: G01P 5/02 by measuring forces exerted by the fluid on solid bodies, e.g. anemometer
• CPC Class Codes: G01P 5/16 using Pitot tubes , e.g. Machmeter

Abstract

Attitude, ground velocity, and acceleration inputs from an aircraft Inertial Navigation System (INS) and/or a Global Positioning System (GPS) instrument on board the aircraft, are used to estimate wind velocity relative to the aircraft and/or the ground in three dimensions. A wind velocity in the third dimension is assumed to be zero. In an exemplary embodiment, one or more of a) atmospheric density, b) speed of sound, C) air temperature, d) thrust of the aircraft, e) aerodynamic force coefficients of the aircraft, and f) mass of the aircraft, are used in conjunction with the inputs from the INS/GPS instrument(s) to estimate the wind velocity. Air temperature can be used, for example, together with an ambient air pressure and/or a known altitude of the aircraft to indicate an atmospheric density.

Claims

1. A method for estimating, at a first object in a fluid, a velocity of the fluid relative to a second object, comprising:

determining an acceleration of the first object relative to the second object;

determining a dynamic pressure of the fluid on the first object;

determining a thrust vector of the first object relative to the second object; and

estimating the velocity of the fluid relative to the second object in three dimensions, based on the determined acceleration, the determined dynamic pressure, the determined thrust vector and an assumption that a speed of the fluid along a single dimension and relative to the second object is zero.

2. The method of claim 1, wherein the step of estimating the velocity of the fluid comprises:

combining force equations and a velocity equation to form an over-constrained set of equations, wherein the velocity equation indicates an assumed zero speed of the fluid along the third dimension relative to the second object, and the force equations include the determined acceleration, the determined dynamic pressure, and the determined thrust vector.

3. The method of claim 2, wherein the step of estimating the velocity of the fluid comprises:

solving the over-constrained set of equations via a weighted least squares fit, wherein the weighting determines relative influence of the force equations versus the velocity equation on the fluid velocity estimate.

4. The method of claim 3, comprising:

adjusting the weighting to increase influence of the velocity equation and decrease influence of the force equations on the fluid velocity estimate, as a degree of certainty that the speed of the fluid along the third dimension is zero, decreases.

5. The method of claim 3, comprising:

adjusting the weighting based on a distance between the first object and the surface of the earth.

6. The method of claim 1, further comprising:

determining an orientation of the first object with respect to a velocity of the first object relative to the fluid, based on a velocity of the first object relative to the second object, an orientation of the first object with respect to the second object, and the determined velocity of the fluid relative to the second object.

7. The method of claim 1, wherein:

the velocity of the fluid relative to the second object is a three-dimensional vector;

the acceleration is a three-dimensional vector; and

the thrust vector is a three-dimensional vector.

8. The method of claim 7, wherein the velocity of the fluid relative to the second object is determined based on a mass of the first object, a reference area of the first object, and aerodynamic coefficients of the first object.

9. The method of claim 8, wherein the aerodynamic coefficients include an aerodynamic coefficient along each axis of the first object.

10. The method of claim 1, wherein the steps of determining the acceleration, determining the dynamic pressure, and determining the thrust vector are performed based on acceleration, dynamic pressure, and thrust data gathered when the first object has a steady state pitch angle of attack relative to the fluid and a steady state yaw angle of attack relative to the fluid.

11. The method of claim 1, wherein the second object has a fixed position relative to the earth.

16. A device for estimating, at a first object in a fluid, a velocity in three dimensions of the fluid relative to a second object, comprising:

a computer arranged to perform the steps of claim 1.

17. The device of claim 16, comprising:

at least one of an Inertial Navigation System and a Global Positioning System, connected to the computer to provide a position of the first object relative to the second object.

18. The device of claim 16, wherein the computer is arranged to perform the step of claim 2.

19. The device of claim 16, wherein the computer is arranged to perform the step of claim 3.

20. The device of claim 16, wherein the computer is arranged to perform the step of claim 4.

21. The device of claim 16, wherein the computer is arranged to perform the step of claim 5.

12. A method for estimating air velocity of a vehicle, comprising:

determining a parameter associated with the vehicle; and

determining a weighting factor to weight force equations and a velocity equation in an equation set, based on the determined parameter; and

solving the weighted equation set to estimate the air velocity of the vehicle.

13. The method of claim 12, wherein the parameter indicates a probability of vertical velocity of the air with respect to a surface of the earth.

14. The method of claim 13, wherein the parameter corresponds to an altitude of the vehicle above a surface of the earth.

15. The method of claim 13, wherein the vehicle comprises an engine and the force equations describe thrust force of the engine and aerodynamic forces acting on the vehicle.

28. A device for estimating, at a first object in a fluid, a velocity in three dimensions of the fluid relative to a second object, comprising:

a computer arranged to perform the steps of claim 12.

22. A method for estimating, at a first object in a fluid, a velocity of the fluid relative to a second object, comprising:

estimating the velocity of the fluid relative to the second object in three dimensions, based on a determined acceleration of the first object relative to the second object, a determined dynamic pressure of the fluid on the first object, a determined thrust vector of the first object relative to the second object, and an assumption that a speed of the fluid along a single dimension and relative to the second object is zero.

23. The method of claim 22, wherein the step of estimating the velocity of the fluid comprises:

combining force equations and a velocity equation to form an over-constrained set of equations, wherein the velocity equation indicates an assumed zero speed of the fluid along the third dimension relative to the second object, and the force equations include the determined acceleration, the determined dynamic pressure, and the determined thrust vector.

24. The method of claim 23, wherein the step of estimating the velocity of the fluid comprises:

solving the over-constrained set of equations via a weighted least squares fit, wherein the weighting determines relative influence of the force equations versus the velocity equation on the fluid velocity estimate.

25. The method of claim 23, wherein the step of estimating the velocity of the fluid comprises:

solving the over-constrained set of equations, wherein the equations are weighted to determine relative influence of the force equations versus the velocity equation on the fluid velocity estimate.

26. The method of claim 25, comprising:

adjusting the weighting to increase influence of the velocity equation and decrease influence of the force equations on the fluid velocity estimate, as a degree of certainty that the speed of the fluid along the third dimension is zero, decreases.

27. The method of claim 25, comprising:

adjusting the weighting based on a distance between the first object and the surface of the earth.