Rotating-unbalanced-mass devices and methods for scanning balloon-borne-experiments, free-flying spacecraft, and space shuttle/space station attached experiments

• US 5,129,600 A
• Filed: 05/23/1990
• Issued: 07/14/1992
• Est. Priority Date: 05/23/1990
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Polites, Michael E.
• Primary Examiner(s): BAREFOOT, GALEN L
• Application Number:
  US07/527,462
• Time in Patent Office: 783 Days
• Field of Search: 244/158 R-173, 244/1 R, 209/366.5, 209/367, 74/61, 74/87, 343/757-766, 404/500, 404/766
• US Class Current: 244/173.1
• CPC Class Codes: B64G 1/22 Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
• CPC Class Codes: B64G 1/66 Arrangements or adaptations of apparatus or instruments, not otherwise provided for
• CPC Class Codes: Y10T 74/18344 Unbalanced weights
• CPC Class Codes: Y10T 74/18552 Unbalanced weight

Abstract

A method and apparatus for scanning balloon-borne experiments, free-flying spacecraft, or gimballed experiments mounted on a space shuttle or space station, makes use of one or more rotating unbalanced mass devices for selectively generating circular, line, or raster scan patterns for the experiment line of sight. An auxiliary control system may also be used in combination with the rotating unbalanced mass device, for target acquisition, keeping the scan centered on the target, or for producing complementary motion for raster scanning. The rotating unbalanced mass makes use of a mass associated with a drive shaft, such mass having a center of gravity which is displaced from the drive shaft rotation axis. The drive shaft is driven with a substantially constant angular velocity, thereby resulting in relatively low power requirements since no acceleration or deceleration of the mass is generally involved during steady state operations. The resulting centrifugal force of the rotating unbalanced mass is used to generate desired reaction forces on the experiment or spacecraft to create a desired scan pattern for the experiment line of sight.

Claims

1. Apparatus for scanning experiments mounted on a support platform said apparatus including

drive means, supported on an experiment mounted on a support platform, and adapted for rotatably driving a shaft at a substantially constant angular velocity;

a drive shaft associated with said drive means for being rotatably driven thereby about a rotation axis of said shaft;

a mass supported on said drive shaft for rotation therewith, said mass having a center of gravity which is displaced from said drive shaft rotation axis so that a resulting rotating unbalanced mass is formed upon operation of said drive means; and

wherein said experiment is gimbally mounted on said support platform, said apparatus being capable of imparting one of a predetermined circular scan pattern and a predetermined line scan pattern to said experiment.

2. Apparatus as in claim 1, wherein said drive means comprises a servo drive system.

3. Apparatus as in claim 2, wherein said servo drive system includes a torque motor, a feedback tachometer for sensing rotation speed of said drive shaft, resolver, or encoder means for sensing angular position of said drive shaft, and feedback control means responsive to said rotation speed and angular position sensing for controlling operation of said torque motor so that a substantially constant drive shaft angular velocity is achieved.

4. Apparatus as in claim 1, wherein said mass includes a lever arm secured at one end thereof to said drive shaft at some angle thereto, and a mass member secured to an opposite end thereof.

5. Apparatus as in claim 4, wherein said angle of securement is preferably about 90 degrees.

6. Apparatus as in claim 4, further including means for adjusting the distance between said mass member and said drive shaft.

7. Apparatus as in claim 1, wherein said mass includes a generally solid circular member secured to said drive shaft for rotation therewith, said circular member defining an off-center opening therethrough so as to present an unbalanced mass to said drive shaft.

8. Apparatus as in claim 7, wherein said circular member is removably secured to said drive shaft so as to be interchangeable with another circular member having different unbalanced mass characteristics.

9. Apparatus as in claim 1, wherein the line of sight of said experiment is normal to the plane of rotation of said mass.

10. Apparatus as in claim 1, wherein the line of sight of said experiment is parallel to the plane of rotation of said mass.

11. Apparatus as in claim 1, further including auxiliary control system means for adjusting the position of said support platform relative a target of said experiment.

12. Apparatus for scanning experiments gimbal mounted on a support platform, said apparatus including:

a first drive means and a second drive means supported on an experiment gimbal mounted on a support platform,

a first drive shaft driven by the first drive means and a second drive shaft driven by the second drive means, said drive shafts each being rotatably driven at a substantially constant angular velocity; and

a first mass and a second mass supported on said first drive shaft and said second drive shaft respectively for rotation therewith, said masses each having a center of gravity which is displaced from said drive shaft rotation axis so that a resulting rotating unbalanced mass is formed upon operation of said first and second drive means.

13. Apparatus in claim 12, wherein the planes of rotation of said masses are parallel to each other, and the line of sight of said experiment is normal to said planes of rotation.

14. Apparatus as in claim 12, wherein the planes of rotation of said masses are parallel to each other, and the line of sight of said experiment is parallel to said planes of rotation.

15. Apparatus as in claim 12, further including synchronizing control means for operating said two drive means in synchronism.

16. Apparatus as in claim 12, further including auxiliary control system means associated with said gimbal mounted for adjusting the position of said experiment relative said experiment platform.

17. A device for controllably moving the line of sight of an experiment in a predetermined scan pattern, such experiment being supported on a given support platform, said device comprising:

a first rotatable unbalanced mass and a second rotatable unbalanced mass supported on respective drive shafts having a fixed axis of rotation relative to and associated with the experiment;

controllable drive means for rotating said first and second unbalanced masses about shafts with a constant angular velocity, so that predetermined reaction forces are brought on the experiment so as to move its line of sight in a predetermined, repeating scan pattern without requiring acceleration or deceleration of said mass, whereby the centrifugal force caused by rotation of said unbalanced mass creates a time-varying relatively large-amplitude/high frequency torque for producing the desired scan motion without relatively large power requirements;

wherein the experiment is gimbal mounted on the support platform;

auxiliary control system means for controllably positioning said gimbal mount for producing target acquisition and retention, and for producing complementary motion to the predetermined scan pattern generated with rotation of said unbalanced mass; and

wherein said axes of rotation for said drive shafts are parallel to the line of sight of the experiment and positioned on opposite sides of the center of gravity of such experiment for producing a predetermined circular scan pattern with the experiment line of sight.

18. A device for controllably moving the line of sight of an experiment in a predetermined scan pattern, such experiment being supported on a given support platform, said device comprising:

a first rotatable unbalanced mass and a second rotatable unbalanced mass supported on respective drive shafts having a fixed axis of rotation relative to and associated with the experiment;

controllable drive means for rotating said first and second unbalanced masses about said shafts with a constant angular velocity, so that predetermined reaction forces are brought on the experiment so as to move its line of sight in a predetermined, repeating scan pattern without requiring acceleration or deceleration of said mass, whereby the centrifugal force caused by rotation of said unbalanced mass creates a time-varying relatively large-amplitude/high frequency torque for producing the desired scan motion without relatively large power requirements;

wherein the experiment is gimbal mounted on the support platform;

auxiliary control system means for controllably positioning said gimbal mounted for producing target acquisition and retention, and for producing complementary motion to the predetermined scan pattern generated with rotation of said unbalanced mass; and

wherein said axes of rotation for said drive shafts are perpendicular to the line of sight of the experiment and positioned on opposite sides of the center of gravity of such experiment for producing a predetermined line scan pattern with the experiment line of sight.

19. A process for controllable moving the line of sight of an experiment in a predetermined scan pattern, such experiment being supported on a given support platform, such process including:

providing at least one rotatable unbalanced mass supported on a drive shaft having a fixed axis of rotation relative to and associated with the experiment;

controllably rotating said unbalanced mass about said shaft with a constant angular velocity, so that predetermined reaction forces are brought on the experiment so as to move its line of sight in one of a predetermined, repeating line scan pattern and circular scan pattern, without requiring acceleration or deceleration of said mass, whereby the centrifugal force caused by rotation of said unbalanced mass creates a time-varying relatively large amplitude/high-frequency torque for producing the desired scan motion without relatively large power requirements; and

mounting the experiment on the platform with one of a gimbal mount and a fixed mount.

20. A process as in claim 19, wherein the given support platform comprises a free-flying spacecraft, and wherein said drive shaft is supported relative to the experiment such that said drive shaft fixed axis of rotation is parallel with the line of sight of the experiment so as to generate a predetermined circular scan pattern for such line of sight.

21. A process as in claim 19, wherein the given support platform comprises a free-flying spacecraft, and wherein said drive shaft is supported relative to the experiment such that said drive shaft fixed axis of rotation is perpendicular with the line of sight of the experiment so as to generate a predetermined line scan pattern for such line of sight.

22. A process as in claim 19, further including generating a resulting raster scan pattern by selectively stepping the line scan pattern produced with said rotation of said unbalanced mass.

23. A process as in claim 19, further including gimbal mounting the experiment on the given support platform and controllably positioning said gimbal mount for producing target acquisition and retention, and for producing complementary motion to the predetermined scan pattern generated with rotation of said unbalanced mass.

24. A process as in claim 23, further including gimbal mounting the experiment on a space platform like a space shuttle or space station, with the fixed axis of rotation of said drive shaft in a plane parallel with the experiment line of sight, and in a line perpendicular with such line of sight, so that a resulting predetermined line scan pattern of such line of sight is produced by rotation of said unbalanced mass.

25. A process as in claim 24, further including selectively stepping the position of said experiment relative said space platform like a space shuttle or space station so as to form a raster scan pattern from said line scan pattern.

26. A process as in claim 23, wherein said gimbal mount includes two mutually perpendicular and intersecting axes of rotation for angular movement in two directions, and said process includes controlling the position of said gimbal mount in such two directions.

27. A process as in claim 19, wherein said rotatable unbalanced mass comprises a mass member connected with said drive shaft through a lever arm substantially perpendicular thereto, and said process further includes adjusting said lever arm for relative movement of said mass member towards or away from said drive shaft during rotation thereof, so that a spiral scan pattern may be generated.

28. A process as in claim 19, further including varying the position of the center of mass of said rotatable unbalanced mass relative said drive shaft axis of rotation, so that the radius of circular scan patterns and the amplitude of line scan patterns is correspondingly varied.

29. A process as in claim 28, wherein said rotatable unbalanced mass includes a mass member supported on the end of a lever arm, and said process includes repositioning said lever arm relative said drive shaft.

30. A process as in claim 19, further including controlling said drive shaft speed of rotation, wherein the period of rotation for said rotatable unbalanced mass directly determines the period of said repeating scan pattern.

31. A process as in claim 19, further including:

providing a second rotatable unbalanced mass supported on a drive shaft having a fixed axis of rotation relative to and associated with the experiment, and controllably rotating said second unbalanced mass; and

controlling rotation of said respective drive shafts so they are driven at the same constant angular velocity while their relative angular positions are maintained such that a predetermined angular separation is established between the respective centers of mass of said rotatable unbalanced masses.

32. A process as in claim 31, wherein said predetermined angular separation is 180 degrees.

33. A process as in claim 31, wherein said predetermined angular separation is 0 degrees.

34. A process for controllable moving the line of sight of an experiment in a predetermined scan pattern, such experiment being supported on a given support platform, such process including:

providing a first rotatable unbalanced mass supported on a drive shaft having a fixed axis of rotation relative to and associated with the experiment;

controllably rotating said unbalanced mass about said shaft with a constant angular velocity, so that predetermined reaction forces are brought on the experiment so as to move its line of sight in a predetermined, repeating scan pattern, without requiring acceleration or deceleration of said mass, whereby the centrifugal force caused by rotation of said unbalanced mass creates a time-varying relatively large amplitude/high-frequency torque for producing the desired scan motion without relatively large power requirements;

gimbal mounting the experiment on the support platform in two mutually perpendicular and intersecting axes of rotation for angular movement in two directions, and controllably positioning said gimbal mount for producing target acquisition and retention, and for producing complementary motion to the predetermined scan pattern generated with rotation of said unbalanced mass, and

providing a second rotatable unbalanced mass supported on a drive shaft, and controllably rotating same with a constant angular velocity, with the axes of rotation for said drive shafts parallel to the line of sight of the experiment and positioned on opposite sides of the center of gravity of such experiment, to produce a predetermined circular scan pattern with the experiment line of sight.

35. A process for controllable moving the line of sight of an experiment in a predetermined scan pattern, such experiment being supported on a given support platform, such process including:

providing a first rotatable unbalanced mass supported on a drive shaft having a fixed axis of rotation to and associated with the experiment;

controllably rotating said unbalanced mass about said shaft with a constant angular velocity, so that predetermined reaction forces are brought on the experiment so as to move its line of sight in a predetermined, repeating scan pattern, without requiring acceleration or deceleration of said mass, whereby the centrifugal force caused by rotation of said unbalanced mass creates a time-varying relatively large amplitude/high-frequency torque for producing the desired scan motion without relatively large power requirements;

gimbal mounting the experiment on a balloon in two mutually perpendicular and intersecting axes of rotation for angular movement in two direction, and controllably positioning said gimbal mount for producing target acquisition and retention, and for producing complementary motion to the predetermined scan pattern generated with rotation of said unbalanced mass, and

providing a second rotatable unbalanced mass supported on a drive shaft, and controllably rotating same with a constant angular velocity, with the axes of rotation for said drive shafts perpendicular to the line of sight of the experiment and positioned on opposite sides of the center of gravity of such experiment, to produce a predetermined line scan pattern with the experiment line of sight.

36. A process as in claim 35, further including selectively stepping the position of said experiment relative said balloon so as to form a raster scan pattern from said line scan pattern.