FLIR boresight alignment

• US 5,672,872 A
• Filed: 03/19/1996
• Issued: 09/30/1997
• Est. Priority Date: 03/19/1996
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Youhanaie, Mark, Hartman, David F., Wu, Yeong-Wei A.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/618,646
• Time in Patent Office: 560 Days
• Field of Search: 250/330
• US Class Current: 250/330
• CPC Class Codes: F41G 3/326 for checking the angle between the axis of the gun sighting device and an auxiliary measuring device F41G3/323 takes precedence

Abstract

A FLIR boresight alignment system (52) for aligning a sensor pod LOS associated with a weapons pod of a fighter aircraft to a navigation reference frame. A pod inertial navigation and global positioning system (62) provides position, velocity and attitude of a sensor (58) within the pod. An aircraft inertial navigation and/or global positioning system (68) provides position, velocity and attitude of the aircraft. The sensor position and velocity and the aircraft position and velocity are applied to a transfer alignment filter (64) that utilizes Kalman filtering. An output of the transfer alignment filter (64) is applied to a sensor inertial navigation system to correct the pod LOS relative to the navigation reference frame. Alternately, the transfer alignment filter (64) may operate directly upon the pseudo ranges and delta pseudo ranges to satellites being tracked by the GPS receiver.

Claims

1. A boresight alignment system for aligning an optical sensor boresight to a navigation reference frame associated with an aircraft, said system comprising:

a pod secured to the aircraft, said optical sensor being positioned within the pod;

a pod inertial navigation system positioned in the pod and providing signals of the position and velocity of the pod;

an aircraft inertial navigation system positioned on the aircraft and being separate from the pod, said aircraft inertial navigation system providing signals of the position and velocity of the aircraft; and

a transfer alignment filter, said transfer alignment filter being responsive to the position and velocity signals from both the pod inertial navigation system and the aircraft inertial navigation system and providing a signal to the pod of a difference in attitude between pod INS coordinates from the pod position and velocity signals and reference navigation coordinates from the aircraft position and velocity signals.

2. The system according to claim 1 wherein the transfer alignment filter includes a cascaded Kalman filter utilizing a plurality of cascaded Kalman filters to provide the difference in attitude between the pod INS coordinates and the reference navigation coordinates.

3. The system according to claim 1 wherein the pod includes an optics stabilizer, said optics stabilizer stabilizing the sensor and being responsive to the output of the transfer alignment filter.

4. The system according to claim 1 further comprising an inertial measurement unit, said inertial measurement unit including a plurality of accelerometers that generate position and velocity solutions and a plurality of gyroscopes that compute coordinate transformations from the pod coordinates to the navigation coordinates.

5. The system according to claim 1 further comprising a mission control computer, said mission control computer controlling the alignment between the sensor boresight and the navigation reference frame.

6. The system according to claim 1 wherein the sensor is an infrared sensor.

7. A boresight alignment system for aligning an optical sensor boresight to a set of navigation coordinates, said alignment system being associated with an aircraft, said system comprising:

a pod secured to the aircraft, said optical sensor being positioned within the pod;

a pod global positioning system (GPS) and inertial navigation system (INS), said pod GPS and INS providing a signal indicative of the position and velocity of the pod;

an aircraft GPS and INS positioned on the aircraft and being separate from the pod, said aircraft GPS and INS providing a signal indicative of the position and velocity of the aircraft; and

a transfer alignment filter, said transfer alignment filter being responsive to the signal of the position and velocity of the pod from the pod GPS and INS system and the signal of the position and velocity of the aircraft from the aircraft GPS and INS, said transfer alignment filter providing a signal of the difference between the position and velocity signals.

8. The system according to claim 7 wherein the transfer alignment filter includes a direct Kalman filter that utilizes pseudo range and delta-pseudo range GPS outputs.

9. The system according to claim 7 wherein the transfer alignment filter includes a cascaded Kalman filter utilizing a plurality of cascaded Kalman filters to provide the difference between the position and velocity signals.

10. The system according to claim 7 further comprising an optics stabilizer, said optics stabilizer stabilizing the sensor and being responsive to the output of the transfer alignment filter.

11. The system according to claim 7 further comprising an inertial measurement unit, said inertial measurement unit including a plurality of accelerometers that generate position and velocity solutions and a plurality of gyroscopes that compute coordinate transformations from pod coordinates to navigation coordinates.

12. The system according to claim 7 further comprising a single aircraft GPS antenna, said aircraft GPS antenna providing radio frequency GPS signals to the pod GPS and INS and the aircraft GPS and INS.

13. A boresight alignment system for aligning an optical sensor boresight to a reference frame, said system comprising:

a first structure, said first structure including the optical sensor, said first structure further including a first inertial navigation system positioned on the structure and providing signals of the position and velocity of the structure;

a second structure, said second structure including a second inertial navigation system positioned on the second structure and being separate from the first structure, said second inertial navigation system providing signals of the position and velocity of the second structure; and

a transfer alignment filter, said transfer alignment filter being responsive to the position and velocity signals from both the first inertial navigation system and the second inertial navigation system and providing a signal to the first structure of the difference in attitude between the first structure and the second structure.

14. The system according to claim 13 wherein the second structure is an aircraft and the first structure is a pod secured to the aircraft.

15. The system according to claim 13 wherein the transfer alignment filter includes a Kalman filter for providing Kalman filtering of the position and velocity signals from both the first inertial navigation system and the second inertial navigation system in order to generate an error signal between the signals.

16. The system according to claim 15 wherein the Kalman filter is a cascaded Kalman filter utilizing a plurality of cascaded Kalman filters to provide the difference in attitude between inertial navigation system coordinates and reference navigation coordinates.

17. The system according to claim 13 wherein the first structure includes a first global positioning system and the second structure includes a second global positioning system.

18. The system according to claim 17 wherein the transfer alignment filter includes a direct Kalman filter that utilizes pseudo range and delta-pseudo range global positioning system outputs from the pod global positioning system and the aircraft global positioning system.

19. A method of aligning an optical sensor boresight to a set of navigation coordinates for an aircraft, said method comprising the steps of:

providing a pod secured to the aircraft in which the optical sensor is positioned within the pod;

providing a pod global positioning system and inertial navigation system;

using the pod global positioning system and inertial navigation system to provide signals indicative of the position and velocity of the pod;

providing an aircraft global positioning system and inertial navigation system positioned on the aircraft and separate from the pod;

using the aircraft global positioning system and inertial navigation system to provide signals indicative of the position and velocity of the aircraft;

providing a transfer alignment filter that is responsive to the signals from the pod global positioning system and inertial navigation system and the aircraft global positioning system and the inertial navigation system; and

using the transfer alignment filter to provide a difference between the position and velocity signals.

20. The method according to claim 19 wherein the step of providing a transfer alignment filter includes providing a transfer alignment filter having a direct Kalman filter that utilizes pseudo range and delta-pseudo range global positioning system outputs.

21. The method according to claim 19 wherein the step of providing a transfer alignment filter includes providing a transfer alignment filter having a plurality of cascaded Kalman filters to provide the difference between the position and velocity signals.