Method and apparatus for stabilizing payloads, including airborne cameras

• US 20040173726A1
• Filed: 12/18/2003
• Published: 09/09/2004
• Est. Priority Date: 01/17/2003
• Status: Active Grant

• Current Assignee: Insitu Incorporated (The Boeing Co.)
• Original Assignee: Insitu Incorporated (The Boeing Co.)
• Inventors: von Flotow, Andreas H., Mercadal, Mathieu
• Granted Patent: US 7,000,883 B2
• Time in Patent Office: Days
• US Class Current: 248/660
• CPC Class Codes: F16M 11/10 around a horizontal axis F16M11/12 takes precedence
• CPC Class Codes: F16M 11/12 in more than one direction
• CPC Class Codes: F16M 11/18 with mechanism for moving the apparatus relatively to the stand
• CPC Class Codes: F16M 11/2014 around a vertical axis F16M11/2035 takes precedence
• CPC Class Codes: F16M 13/027 Ceiling supports
• CPC Class Codes: G01C 21/18 Stabilised platforms, e.g. by gyroscope
• CPC Class Codes: G02B 27/644 compensating for large deviations, e.g. maintaining a fixed line of sight while a vehicle on which the system is mounted changes course
• CPC Class Codes: G03B 15/006 Apparatus mounted on flying objects
• CPC Class Codes: G03B 37/00 Panoramic or wide-screen photography; Photographing extended surfaces, e.g. for surveying; Photographing internal surfaces, e.g. of pipe

Abstract

Methods and apparatuses for stabilizing payloads, including airborne cameras, are disclosed. In one embodiment, the apparatus employs a gimbal system in which the camera is mounted, together with suitable motors for pointing the camera by actuating this gimbal system and suitable sensors for deriving a signal to drive these gimbal motors. The gimbal axes can be arranged in a sequence that can provide for camera stabilization while reducing complexity, avoiding gimbal lock, increasing redundancy and enhancing performance.

Claims

1. An gimbal apparatus, comprising:

a first support;

a first actuator coupled to the first support to rotate the first support about a first axis;

a second support rotatably carried by the first support and configured to carry a tracking payload;

a second actuator coupled to the second support to rotate the second support about a second axis transverse to the first axis; and

a third actuator carried by the second support to rotate about a third axis, the third actuator being operatively coupleable to the tracking payload to rotate the tracking payload relative to the second support, the third axis being generally parallel to the first axis when the second support is in a first angular position relative to the second axis, the third axis being non-parallel to the first axis when the second support is in a second angular position relative to the second axis.

2. The apparatus of claim 1, further comprising:

the tracking payload, and wherein the tracking payload includes a camera having a line of sight and an image field, the image field having a first image axis and a second image axis transverse to the first image axis; and

a controller operatively coupled to the first, second and third actuators and being configured to direct movement of the actuators such that;

when the second support is in the first angular position, the first actuator moves the line of sight along the first image axis and the second actuator moves the line of sight along the second image axis; and

when the second support is in the second angular position, the third actuator moves the line of sight along the first image axis and the second actuator moves the line of sight along the second image axis.

3. The apparatus of claim 1 wherein the first actuator is positioned to move the first support through a first angular range, the second actuator is positioned to move the second support through a second angular range, and the third actuator is positioned to move the tracking payload through a third angular range, the third angular range being less than both the first and second angular ranges.

4. The apparatus of claim 1 wherein the first actuator is positioned to move the first support through a total angular range of about 360 degress, the second actuator is positioned to move the second support through a total angular range of about 180 degrees, and the third actuator is positioned to move the tracking payload through a total angular range of about 20 degrees.

5. The apparatus of claim 1, further comprising a controller operatively coupled to the first, second and third actuators to direct motion of the actuators.

6. The apparatus of claim 1, further comprising a controller operatively coupled to the first, second and third actuators to direct motion of the actuators, the controller being configured to direct the first actuator to rotate the first support by 180 degrees when the second actuator rotates the tracking payload to face downwardly.

7. The apparatus of claim 1, further comprising the tracking payload, and wherein the tracking payload includes a camera.

8. The apparatus of claim 1 wherein the first actuator has a first actuation rate and the third actuator has a third actuation rate higher than the first actuation rate.

9. The apparatus of claim 1, further comprising a housing coupled to the first support to move with the first support.

10. The apparatus of claim 1 wherein the first axis includes a pan axis, the second axis includes a tilt axis and the third axis includes a scan axis.

11. The apparatus of claim 1 wherein the first actuator is configured to operate at a first maximum frequency, the second actuator is configured to operate at a second maximum frequency and the third actuator is configured to operate at a third maximum frequency, with the first maximum frequency being less than the second and third maximum frequencies.

12. The apparatus of claim 1 wherein the second and third actuators are configured to stabilize the tracking payload against vibrations.

13. The apparatus of claim 1, further comprising a controller operatively coupled to the first and third actuators, the controller being configured to automatically:

receive a signal corresponding to a position of the third actuator relative to a range of motion for the third actuator when the first support has a first orientation;

direct a signal to the first actuator to rotate the first support to a second orientation; and

direct a signal to the third actuator to move toward a center of the range of motion for the third actuator while moving the first support to have a third orientation at least approximately the same as the first orientation.

14. The apparatus of claim 1 wherein at least one of the second and third actuators includes a stepper motor.

15. An airborne surveillance apparatus, comprising:

a camera having a camera aperture configured to receive radiation along a line of sight, the camera further having an image field with a first image axis and a second image axis generally transverse to the first image axis;

a gimbal system supporting the camera, the gimbal system including;

a first support coupled to a first actuator to rotate about a first axis, the first actuator having a first actuation rate capability;

a second support carried by the first support and coupled to a second actuator to rotate about a second axis transverse to the first axis, the second support carrying the camera, the second actuator having a second actuation rate capability;

a third actuator carried by the second support to rotate about a third axis, the third actuator being operatively coupled to the camera to rotate the camera relative to the second support, the third axis being generally parallel to the first axis when the second support is in a first angular position relative to the second axis, the third axis being non-parallel to the first axis when the second support is in a second angular position relative to the second axis, the third actuator having a third actuator rate capability greater than the first actuator rate capability; and

a controller operatively coupled to the first, second and third actuators and being configured to direct movement of the actuators such that;

when the second support is in the first angular position, the first actuator moves the line of sight along the first image axis and the second actuator moves the line of sight along the second image axis; and

when the second support is in the second angular position, the third actuator moves the line of sight along the first image axis and the second actuator moves the line of sight along the second image axis.

16. The apparatus of claim 15, further comprising a housing carried by the first support to rotate with the first support, the housing having a generally strip-shaped portion aligned with the camera aperture, the generally strip-shaped portion being at least approximately transparent to the radiation.

17. An apparatus for tracking a target from the air, comprising:

first support means;

first actuation means for rotating the first support means about a first axis;

second support means carried by the first support means and configured to carry a tracking payload;

second actuation means for rotating the second support means relative to the first support means about a second axis transverse to the first axis; and

third actuation means for rotating the tracking payload about a third axis, with the third axis being generally parallel to the first axis when the second support means is in a first angular position relative to the second axis, the third axis being generally inclined relative to the first axis when the second support means is in a second angular position relative to the second axis.

18. The apparatus of claim 17, further comprising:

the tracking payload, and wherein the tracking payload includes a camera having a line of sight and an image filed, the image field having a first image axis and a second image axis generally transverse to the first image axis; and

control means for directing motion of the first, second and third actuation means such that;

when the second support means is in the first angular position, the first actuation means moves the line of sight along the first image axis and the second actuation means moves the line of sight along the second image axis; and

when the second support is in the second angular position, the third actuator means moves the line of sight along the first image axis and the second actuator means moves the line of sight along the second image axis.

19. The apparatus of claim 17, further comprising a control means for controlling the first and third actuation means, the control means being configured to automatically:

receive a signal corresponding to a position of the third actuation means relative to a range of motion for the third actuation means when the first support means has a first orientation;

direct a signal to the first actuation means to rotate the first support means to a second orientation; and

direct a signal to the third actuation means to move toward a center of the range of motion for the third actuation means while moving the first support to have a third orientation at least approximately the same as the first orientation.

20. The apparatus of claim 17 wherein the second and third actuators are configured to stabilize the tracking payload against vibrations.

21. A gimbal apparatus, comprising:

a first support;

a first actuator coupled to the first support to rotate the first support about a first axis;

a second support rotatably carried by the first support and configured to carry a tracking payload;

a second actuator coupled to the second support to rotate the second support about a second axis transverse to the first axis; and

a housing carried by the first support, the housing having a generally strip-shaped window curved about single axis, the window being positioned to pass radiation to the tracking payload.

22. The apparatus of claim 21 wherein the housing includes a curved, dome-shaped portion disposed outwardly from the window, and wherein the dome-shaped portion includes a first material and the window includes a second material different than the first material.

23. The apparatus of claim 21 wherein the window has a single radius of curvature extending outwardly from the second axis.

24. The apparatus of claim 21, further comprising the tracking payload, and wherein the tracking payload includes a camera.

25. The apparatus of claim 21, further comprising a third actuator carried by the second support to rotate about a third axis, the third actuator being operatively coupleable to the tracking payload to rotate the tracking payload relative to the second support, the third axis being generally parallel to the first axis when the second support is in a first angular position relative to the second axis, the third axis being generally inclined relative to the first axis when the second support is in a second angular position relative to the second axis.

26. A method for tracking a target from the air, comprising:

rotating a first support about a first axis by activating a first actuator;

rotating a second support relative to the first support about a second axis transverse to the first axis by activating a second actuator, the second support carrying a tracking payload; and

rotating the tracking payload about a third axis by activating a third actuator, with the third axis being generally parallel to the first axis when the second support is in a first angular position relative to the second axis, the third axis being generally inclined relative to the first axis when the second support is in a second angular position relative to the second axis.

27. The method of claim 26 wherein the tracking payload includes a camera having a line of sight and an image field, the image field having a first image axis and a second image axis transverse to the first image axis, and wherein the method further comprises:

when the second support is in the first angular position, activating the first actuator to move the line of sight along the first image axis and activating the second actuator to move the line of sight along the second image axis; and

when the second support is in the second angular position, activating the third actuator to move the line of sight along the first image axis and activating the second actuator to move the line of sight along the second image axis.

28. The method of claim 26 wherein rotating the tracking payload includes rotating a camera.

29. The method of claim 26 wherein rotating the tracking payload about a first axis includes rotating the tracking payload with a first actuator having a first actuation frequency response, and wherein rotating the tracking payload about a third axis includes rotating the tracking payload with a third actuator having a third actuation frequency response greater than the first actuation frequency response.

30. The method of claim 26 wherein rotating the tracking payload about the first axis includes rotating the tracking payload at a first frequency to track a target, and wherein rotating the tracking payload about the third axis includes rotating the tracking payload at a second frequency higher than the first frequency to at least partially correct for vibration of the tracking payload.

31. The method of claim 26 wherein rotating the tracking payload about the second and third axes includes stabilizing the tracking payload against vibrations.

32. The method of claim 26, further comprising rotating the tracking payload 180 degrees about the first axis with the first actuator when the second actuator tilts the payload to face downwardly.

33. The method of claim 26, further comprising:

receiving a signal corresponding to a position of the third actuator relative to a range of motion for the third actuator when the first support has a first orientation;

directing a signal to the first actuator to rotate the first support to a second orientation; and

directing a signal to the third actuator to move toward a center of the range of motion for the third actuator while moving the first support to have a third orientation at least approximately the same as the first orientation.

34. A computer-implemented method for tracking a target from the air, comprising:

directing a first actuator to rotate a first support about a first axis;

directing a second actuator to rotate a second support relative to the first support about a second axis transverse to the first axis, the second support carrying a tracking payload; and

directing a third actuator to rotate the tracking payload about a third axis, with the third axis being generally parallel to the first axis when the second support is in a first angular position relative to the second axis, the third axis being non-parallel to the first axis when the second support is in a second angular position relative to the second axis.

35. The computer-implemented method of claim 34 wherein the tracking payload includes a camera having a line of sight and an image field, the image field having a first image axis and a second image axis transverse to the first image axis, and wherein the method further comprises:

when the second support is in the first angular position, directing the first actuator to move the line of sight along the first image axis and directing the second actuator to move the line of sight along the second image axis; and

when the second support is in the second angular position, directing the third actuator to move the line of sight along the first image axis and directing the second actuator to move the line of sight along the second image axis.

36. The computer-implemented method of claim 34, further comprising directing the first actuator to rotate the tracking payload 180 degrees about the first axis when the second actuator tilts the payload to face downwardly.

37. A method for operating an airborne camera, comprising:

launching an aircraft carrying an airborne camera;

selecting a target;

directing a viewing line of sight of the camera toward the target; and

moving the camera to maintain the viewing line of sight directed to the target as the aircraft moves relative to the target by;

activating a first actuator to pan the camera about a pan axis;

activating a second actuator to tilt the camera about a tilt axis transverse to the pan axis; and

activating a third actuator to rotate the camera about a scan axis and stabilize the camera against vibration, with the scan axis being generally parallel to the pan axis when the camera is in a first angular position relative to the tilt axis, the scan axis being generally inclined relative to the pan axis when the camera is in a second angular position relative to the tilt axis.

38. The method of claim 37 wherein the camera has an image field, the image field having a first image axis and a second image axis transverse to the first image axis, and wherein the method further comprises:

when the camera is in the first angular position, activating the first actuator to move the line of sight along the first image axis and activating the second actuator to move the line of sight along the second image axis; and

when the camera is in the second angular position, activating the third actuator to move the line of sight along the first image axis and activating the second actuator to move the line of sight along the second image axis.

39. The method of claim 37, further comprising rotating the camera 180 degrees about the pan axis as the viewing line of sight tilts through a vertical line.

40. The method of claim 37, further comprising:

receiving a signal corresponding to a position of the third actuator relative to a range of motion for the third actuator when the first support has a first orientation;

directing a signal to the first actuator to rotate the first support to a second orientation; and

directing a signal to the third actuator to move toward a center of the range of motion for the third actuator while moving the first support to have a third orientation at least approximately the same as the first orientation.