Automatic mode control for a parachutist navigation system

• US 10,378,903 B2
• Filed: 01/27/2017
• Issued: 08/13/2019
• Est. Priority Date: 01/27/2017
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Mansur, Sabrina M., Savage, Trevor C.
• Primary Examiner(s): Heinle, Courtney D
• Application Number:
  US15/417,798
• Publication Number:
  US 20180216939A1
• Time in Patent Office: 928 Days
• CPC Class Codes: B64D 17/00 Parachutes non canopied parachutes B64D19/00
• CPC Class Codes: B64D 23/00 Training of parachutists
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 23/00 Combined instruments indicating more than one navigational value, e.g. for aircraft; Combined measuring devices for measuring two or more variables of movement, e.g. distance, speed or acceleration
• CPC Class Codes: G01S 19/19 Sporting applications
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/393 Trajectory determination or predictive tracking, e.g. Kalman filtering
• CPC Class Codes: G01S 19/396 Determining accuracy or reliability of position or pseudorange measurements

Abstract

A method of identifying operational modes experienced by a user during a jump from an aircraft may comprise estimating a user altitude and a user descent rate, based on a set of navigation state data vectors. The method may further comprise determining that the user is ready to transition from a flight mode to a descent mode when the user altitude is above a jump altitude threshold, and a variation of the user altitude is below a predetermined altitude variation threshold. After determining that the user is ready to transition from the flight mode to the descent mode, the method further comprises determining that the user has transitioned from a flight mode to a descent mode when a user ground speed is below a ground speed threshold, and one or both of (i) a GNSS position error estimate, and (ii) the user descent rate estimate, indicates a jump signature.

Claims

1. A method of identifying operational modes experienced by a user during a jump from an aircraft, comprising:

estimating, by a navigator device, a user altitude and a user descent rate, based on a set of navigation state data vectors sampled according to a sampling interval;

determining, by a computer-based jump determination module, that the user is ready to transition from a flight mode to a descent mode, but not yet in decent mode, when;

the user altitude is above a jump altitude threshold, the jump altitude threshold being an altitude below which a jump should not be attempted; and

a variation of the user altitude is below a predetermined altitude variation threshold;

after determining that the user is ready to transition from the flight mode to the descent mode, determining, by the computer-based jump determination module, that the user has transitioned from a flight mode to a descent mode when;

a user ground speed is below a ground speed threshold; and

one or both of (i) a GNSS position error estimate, and (ii) the user descent rate estimate, indicates a jump signature; and

receiving, by a multipurpose navigation system, information transmitted from the computer-based jump determination module about the transition from the flight mode to the descent mode, and changing a display presented by a display device associated with the multipurpose navigation system based on the information.

2. The method of claim 1, wherein the set of samples of navigation data comprises one or more of current raw altitude, ground speed measurements and GNSS position error estimate.

3. The method of claim 2, wherein estimating a user altitude comprises applying a Kalman filter to a set of samples of the current raw altitude.

4. The method of claim 2, wherein estimating a user descent rate comprises applying a Kalman filter to a set of user altitude changes, wherein each user altitude change is a change measured between consecutive raw altitude samples.

5. The method of claim 1, wherein determining the variation of the user altitude comprises determining a difference between (i) a current filtered altitude, and (ii) a minimum filtered altitude observed during a leveling test duration.

6. The method of claim 1, wherein determining the variation of the user altitude comprises first determining that the user altitude is above the jump altitude threshold, then determining that an absolute value of a difference between (i) a current filtered altitude and (ii) a greatest filtered altitude measured during a leveling test duration.

7. The method of claim 1, wherein determining the user ground speed comprises calculating a ground distance D_g between consecutive position measurements from the set of navigational state data, and calculating a ratio of (D_g)/(sampling interval).

8. The method of claim 1, wherein the GNSS position error estimate indicates the jump signature when a first set of samples of the GNSS position error estimate exhibits a higher GNSS position error than a second set of samples of the GNSS position error estimate, the first set of samples occurring later in time than the second set of samples.

9. The method of claim 1, wherein the GNSS position error estimate indicates the jump signature when one or more samples of a first set of samples of the GNSS position error estimate exceeds a threshold value.

10. The method of claim 9, further including calculating the threshold value as a function of a second set of samples, the first set of samples occurring later in time than the second set of samples.

11. The method of claim 1, wherein the user descent rate estimate indicates the jump signature when each of a set of consecutive user descent rate estimate samples exceeds a descent rate threshold.

12. The method of claim 1, further including indicating that the user has transitioned from a descent mode to a landed mode when:

the user altitude is below a landed mode altitude threshold;

a user ground speed is below a landed ground speed threshold; and

one or both of (i) a GNSS position error estimate, and (ii) the user descent rate, indicates the landed mode signature.