Attitude determination by pulse beacon and low cost inertial measuring unit

Patent metadata

Field	Value
Publication number	US-10962990-B2
Application number	US-201916534040-A
Country	US
Kind code	B2
Filing date	Aug 7, 2019
Priority date	Aug 7, 2019
Publication date	Mar 30, 2021
Grant date	Mar 30, 2021

Abstract

The system and method of attitude determination by pulse beacon and extremely low cost inertial measuring unit. A pulse beacon is used to generate a plurality of pulses detected by a detector or receiver located on the rear of a projectile such that direction of arrival can be determined. A synchronized clock proved for velocity and range information. Altitude can also be determined and may use an altimeter or the like. The use of a low cost IMU is possible with internal calibration by the system. Real-time attitude information provides for correction for crosswind and other drift enabling the system to have less down range dispersion.

First claim

What is claimed:

1. A system for attitude determination of an airborne object, comprising:
a pulse beacon located on a fire control system, the beacon being configured to deliver a sequence of timed pulses;
a rearward facing sensor configured to detect the sequence of timed pulses;
a clock located and synchronized with the pulse beacon, the clock being configured to initiate a time stamp upon detection of the timed pulses by the rearward facing sensor;
an inertial measurement unit (IMU), the IMU configured to determine attitude of the airborne object;
a barometer or altitude sensor configured to detect changes in altitude of the airborne object; and
a processor configured to integrate data from at least the sensor, the clock, and the IMU and compare it to a pre-flight script of range, position, and altitude for the airborne object to determine a direction of arrival for the sequence of timed pulses, a range and a velocity for the airborne object based on an increasing time differential between pulses, and attitude of the airborne object.

2. The system according to claim 1 , wherein the airborne object is a munition round.

3. The system according to claim 1 , wherein the pulse beacon operates in the RF or IR spectrum.

4. The system according to claim 1 , wherein the sensor is a detector array or an antenna.

5. The system according to claim 1 , further comprising an up finding device configured to decompose the direction of arrival for the sequence of timed pulses detected by the sensor into pitch and yaw with an earth reference.

6. The system according to claim 5 , wherein the up finding device is a magnetometer, an onboard imager, or a polarized pulse beacon.

7. The system according to claim 1 , wherein the processor is further configured to calculate pitch and yaw in earth's reference to calibrate the IMU.

8. The system according to claim 1 , wherein the IMU has an angle random walk (ARW)<0.1° SQRT(Hz) or tactical grade accuracy.

9. A method of attitude determination, comprising:
detecting a sequence of timed pulses from a pulse beacon via a rearward facing sensor located on an airborne object;
synchronizing a precision clock located on the airborne object with the pulse beacon;
initiating a time stamp upon detection of a timed pulse by the rearward facing sensor;
determining an attitude of the airborne object via an inertial measurement unit (IMU) located on the airborne object;
detecting changes in altitude of the airborne object via a barometer located on the airborne object;
integrating data from at least the sensor, the clock, and the IMU via a processor located on the airborne object;
comparing the data from at least the sensor, the clock, and the IMU to a pre-flight script of range, position, and altitude for the airborne object; and
determining a direction of arrival for the sequence of timed pulses, a range and a velocity for the airborne object based on an increasing time differential between pulses, and the attitude of the airborne object.

10. The method according to claim 9 , further comprising computing adjustments to account for crosswind and variations in the velocity of the airborne object.

11. The method according to claim 10 , wherein the down range dispersion for a 100 Km projectile is improved to 10 to 100 meters versus 2-3 Km for a conventional system.

12. The method according to claim 9 , wherein time intervals of pulses sent from the pulse beacon result in an increasing time lag that is directly proportional to the velocity of the airborne object thus generating a down range dispersion referred to as a miss distance or circular error probable.

13. The method according to claim 9 , wherein the airborne object is a round.

14. The method according to claim 9 , wherein the pulse beacon operates in the RF or IR spectrum.

15. The method according to claim 9 , wherein the sensor is a detector array or an antenna.

16. The method according to claim 9 , further comprising an up finding device configured to decompose the direction of arrival for the sequence of timed pulses detected by the sensor into pitch and yaw with an earth reference.

17. The method according to claim 16 , wherein the up finding device is a magnetometer, an onboard imager, or a polarized pulse beacon.

18. The method according to claim 9 , wherein the processor is further configured to calculate pitch and yaw in earth's reference to calibrate the IMU.

19. The method according to claim 9 , wherein the IMU has an angle random walk (ARW)<0.1° SQRT(Hz) or tactical grade accuracy.

20. A method of attitude determination of a projectile, comprising:
pulsing infrared (IR) or radio frequency (RF) energy based on a predetermine pulse timing sequence;
receiving the pulsed energy at a rearward facing sensor located on the projectile;
determining a direction of arrival (DOA) for the pulsed energy;
initiating a time stamp using a precision clock when the pulsed energy is received by the sensor;
determining range and velocity of the projectile from an increasing differential due to an increased range along a flight path;
calculating changes in altitude of the airborne object with respect to a fire control system;
decomposing measured sensor angles into pitch and yaw in earth's reference;
calculating pitch and yaw in earth's reference and calibrating an inertial measurement unit (IMU); and
computing adjustments to account for crosswind and variations in the velocity of the projectile.

Assignees

• Bae Sys Inf & Elect Sys Integ

Inventors

• Choiniere Michael J
• Batchelder Jason H
• Chrobak Matthew F

Classifications

• G05D2109/20

  Aircraft, e.g. drones · CPC title

• G05D1/49

  Control of attitude, i.e. control of roll, pitch or yaw · CPC title

• G01S5/163

  Determination of attitude (using inertial means G01C9/00; control of attitude G05D1/49) · CPC title

• G01S5/0247

  Determining attitude · CPC title

• G01S3/782

  Systems for determining direction or deviation from predetermined direction · CPC title