Centripetal acceleration determination, centripetal acceleration based velocity tracking system and methods

Patent metadata

Field	Value
Publication number	US-9309004-B2
Application number	US-201314032375-A
Country	US
Kind code	B2
Filing date	Sep 20, 2013
Priority date	Sep 21, 2012
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

The flight of an aircraft is characterized in terms of Earth-based reference system data for a first position and a second position of the aircraft that are separated by a time increment. A centripetal acceleration of the aircraft is determined based on the Earth-based reference system data for the positions in conjunction with the time increment. A rate of rotation is established corresponding to the time increment in an aircraft-based reference system. Aircraft airspeed is determined based on the centripetal acceleration and the rate of rotation. A turn can be detected as characterized by a change in track angle from a prior GPS packet compared to a new packet. Aircraft turns can be detected based on a change in track angle in GPS packets. Compensation can be applied to a gyro based on centripetal acceleration such that the gyro more accurately responds to the Earth gravity axis.

First claim

What is claimed is:

1. A method for determining an airspeed of an aircraft in flight during a turn, said method comprising:
characterizing the flight of the aircraft in terms of Earth-based reference system data for a first position and a second position of the aircraft that are separated by a time increment;
determining a centripetal acceleration of the aircraft based on the Earth-based reference system data for the first and second positions in conjunction with the time increment;
establishing a rate of rotation corresponding to the time increment in an aircraft-based reference system; and
determining the airspeed based on the centripetal acceleration and the rate of rotation.

2. The method of claim 1 wherein characterizing uses the Earth-based reference system data as GPS data that is generated by a GPS system that is carried by the aircraft.

3. The method of claim 2 wherein the GPS data comprises a first GPS packet for the first position and a second GPS packet for the second position.

4. The method of claim 3 wherein determining the airspeed uses no more than the GPS data and the rate of rotation as input values.

5. The method of claim 3 wherein the GPS data for each of the first and second GPS packets is characterized as a groundspeed vector including a magnitude and a track angle.

6. The method of claim 3 wherein the GPS data for each of the first and second GPS packets is characterized by a north component and an east component of groundspeed.

7. The method of claim 1 , further comprising:
resolving a difference between the Earth-based reference system data for a first groundspeed vector at the first position and a second groundspeed vector at the second position into northing components and easting components and determining the centripetal acceleration based on a change in the northing component from the first position to the second position, a change in the easting component from the first position to the second position and the time increment.

8. The method of claim 7 further comprising:
representing the northing component change as ΔV N , the easting component change as ΔV E , the time difference as Δt, and determining the centripetal acceleration, α, as


α


=

(

Δ
⁢

⁢

V
N

Δ
⁢

⁢
t

)

2

+

(

Δ
⁢

⁢

V
E

Δ
⁢

⁢
t

)

2

.

9. The method of claim 7 , further comprising:
determining a vertical velocity acceleration;
comparing the vertical velocity acceleration to a groundspeed-heading change acceleration; and
selecting one of a two dimensional acceleration vector or a three dimensional acceleration vector for the centripetal acceleration based on the comparison.

10. The method of claim 1 wherein determining the airspeed uses the expression:
V=α/ω
where V is the airspeed, α is the centripetal acceleration and ω is the rate of rotation.

11. The method of claim 1 wherein determining the rate of rotation includes monitoring an output of a rate gyro onboard the aircraft which is indicative of changes in a yaw orientation of the aircraft.

12. The method of claim 11 wherein monitoring the output of the rate gyro includes reading a plurality of outputs of the rate gyro during the time increment and averaging the plurality of outputs to serve as the rate of rotation.

13. The method of claim 1 wherein establishing the rate of rotation includes reading a heading gyro to determine a first heading for the first position and a second heading for the second position and determining the rate of rotation based on a difference between the first position heading and the second position heading in conjunction with the time increment.

14. The method of claim 1 , further comprising:
prior to said characterizing, providing a GPS system that is carried by the aircraft which GPS system outputs GPS data as a series of GPS packets for selective use as the Earth-based reference system data such that a first packet is selected from the series in association with the first position and a second packet is selected from the series subsequent to the first packet and the second packet is associated with the second position.

15. The method of claim 14 , further comprising:
saving at least a portion of the series of GPS packets in a rolling buffer for selection of at least the first packet therefrom based on a comparison to a current packet that terminates the series of GPS packets.

16. The method of claim 14 , further comprising:
applying a packet selection interval to the series of GPS packets such that the first selected packet and the second selected packet are spaced apart by a predetermined number of unused packets.

17. The method of claim 14 , further comprising:
applying a packet selection interval to the series of GPS packets such that the first selected packet and the second selected packet are spaced apart by at least a predetermined amount of time.

18. The method of claim 14 , further comprising:
applying a packet selection interval to the series of GPS packets having a duration that is based on a rounding error in the GPS data such that the first selected packet and the second selected packet are spaced apart in time by at least a predetermined amount of time.

19. The method of claim 1 , further comprising:
at least one of (i) displaying the airspeed and (ii) providing the airspeed to a control system of the aircraft.

20. An apparatus for determining an airspeed of an aircraft in flight during a turn, said apparatus comprising:
a GPS receiver for characterizing the flight of the aircraft in terms of

Assignees

• Merlin Technology Inc

Inventors

• Mercer John E

Classifications

• G01S19/39

  the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO · CPC title

• G01P7/00

  Measuring speed by integrating acceleration (measuring travelled distance by double integration of acceleration G01C21/16) · CPC title

• G01P5/00

  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 title

• B64D43/02 Primary

  for indicating aircraft speed or stalling conditions · CPC title

• G01P15/14

  by making use of gyroscopes (gyroscopes per se G01C19/00) · CPC title