SATELLITE ATTITUDE CONTROL SYSTEM USING EIGEN VECTOR, NON-LINEAR DYNAMIC INVERSION, AND FEEDFORWARD CONTROL

• US 20200130869A1
• Filed: 10/25/2018
• Published: 04/30/2020
• Est. Priority Date: 10/25/2018
• Status: Active Grant

• Current Assignee: General Atomics, Inc.
• Original Assignee: General Atomics, Inc.
• Inventors: DERRICK, II, JOHN BENTON
• Granted Patent: US 11,279,501 B2
• Time in Patent Office: Days
• CPC Class Codes: B64G 1/244 Spacecraft control systems
• CPC Class Codes: B64G 1/245 Attitude control algorithms for spacecraft attitude control
• CPC Class Codes: B64G 1/283 using reaction wheels

Abstract

Systems and methods are described for a satellite control system that exhibits improved stability and increased efficiency by implementing a non-linear dynamic inversion inner-loop control algorithm coupled with an eigen vector outer-loop control algorithm. Thus, the attitude determination and control system (ADACS) may operate using commands to rotate directly about an eigen vector. Additionally, the outer-loop control system includes a feed-forward control element to enhance pointing accuracy when tracking moving targets.

Claims

1. A method of satellite orientation control, the method comprising:

applying with a processing device a satellite orientation control system, the satellite orientation control system comprising a double feedback loop system, wherein;

a first loop executes to determine an eigen vector to rotate the satellite from one orientation to another, and

a second loop that receives the eigen vector of the first loop as an input and executes a non-linear dynamic inversion algorithm to output a signal to at least one reaction wheel of the satellite;

rotating the at least one reaction wheel in response to the output signal; and

orienting the satellite based upon the rotation of the at least one reaction wheel.

2. The method of claim 1, wherein:

the first loop further comprises receiving a desired orientation of the satellite and an estimated orientation of the satellite as inputs.

3. The method of claim 2, wherein:

the first loop further comprises executing a satellite orientation error command based on the estimated orientation of the satellite and the desired orientation of the satellite.

4. The method of claim 3, wherein:

the eigen vector command executes to decompose the satellite orientation error command into a scalar component and a vector component.

5. The method of claim 2, wherein:

the first loop further comprises a feed-forward control system.

6. The method of claim 5, wherein:

the feed-forward control system controls for timing errors between rotation of the at least one reaction wheel and pointing at a target.

7. The method of claim 5, wherein:

the feed-forward control system accounts for motion of tracking dishes, antennae, cameras, robotic arms, and solar arrays associated with the satellite.

8. The method of claim 5, wherein:

the feed-forward control system further comprises receiving the desired orientation as an input.

9. The method of claim 1, wherein:

the second loop further comprises receiving the eigen vector determined from the first loop as an input.

10. The method of claim 9, wherein:

the second loop further comprises receiving measured satellite rotation rates from a navigation system associated with the satellite.

11. The method of claim 9, wherein:

the second loop further comprises receiving a measured reaction wheel speed of the at least one reaction wheel from a rotation wheel tachometer associated with the satellite.

12. The method of claim 9, wherein:

the second loop further comprises determining a desired rotational acceleration for the at least one reaction wheel.

13. The method of claim 9, wherein:

the second loop further comprises receiving a mass moment of inertia tensor of at least one reaction wheel, a rotation axis vector of at least one reaction wheel, and a mass moment of inertia tensor of the satellite.

14. An apparatus for satellite orientation control, comprising:

a memory;

a processor device in communication with the memory and configured to;

apply a satellite orientation control system, the satellite control system comprising;

a double feedback loop system, wherein a first loop executes to determine an eigen vector to rotate the satellite from one orientation to another, and a second loop that receives the eigen vector of the first loop as an input and executes a non-linear dynamic inversion algorithm to output a signal to at least one reaction wheel of the satellite; and

rotate the at least one reaction wheel in response to the output signal; and

orient the satellite based upon the rotation of the at least one reaction wheel.

15. The apparatus of claim 14, wherein:

the first loop further comprises receiving a desired orientation of the satellite and an estimated orientation of the satellite as inputs.

16. The apparatus of claim 15, wherein:

the first loop further comprises executing a satellite orientation error command based on the estimated orientation of the satellite and the desired orientation of the satellite.

17. The apparatus of claim 16, wherein:

the eigen vector command executes to decompose the satellite orientation error command into a scalar component and a vector component.

18. The apparatus of claim 15, wherein:

the first loop further comprises a feed-forward control system.

19. The apparatus of claim 18, wherein:

the feed-forward control system controls for timing errors between rotation of the at least one reaction wheel and pointing at a target.

20. The apparatus of claim 18, wherein:

the feed-forward control system accounts for motion of tracking dishes, antennae, cameras, robotic arms, and solar arrays associated with the satellite.

21. The apparatus of claim 18, wherein:

the feed-forward control system further comprises receiving the desired orientation as an input.

22. The apparatus of claim 14, wherein:

the second loop further comprises receiving the eigen vector determined from the first loop as an input.

23. The apparatus of claim 22, wherein:

the second loop further comprises receiving measured satellite rotation rates from a navigation system associated with the satellite.

24. The apparatus of claim 22, wherein:

the second loop further comprises receiving a measured reaction wheel speed of the at least one reaction wheel from a rotation wheel tachometer associated with the satellite.

25. The apparatus of claim 22, wherein:

the second loop further comprises determining a desired rotational acceleration for the at least one reaction wheel.

26. The apparatus of claim 22, wherein:

the second loop further comprises receiving a mass moment of inertia tensor of at least one reaction wheel, a rotation axis vector of at least one reaction wheel, and a mass moment of inertia tensor of the satellite.

27. A non-transitory computer readable medium storing code for satellite orientation control, the code comprising instructions executable by a processor to control a satellite to:

determine, at a first loop of a control system, an eigen vector to rotate the satellite from one orientation to another;

execute, at a second loop of a control system, a non-linear dynamic inversion algorithm to output a signal to at least one reaction wheel of the satellite;

rotate the at least one reaction wheel in response to the output signal; and

orient the satellite based upon the rotation of the at least one reaction wheel.

28. The non-transitory computer-readable medium of claim 27, wherein:

the first loop further comprises receiving a desired orientation of the satellite and an estimated orientation of the satellite as inputs.

29. The non-transitory computer-readable medium of claim 28, wherein:

the first loop further comprises executing a satellite orientation error command based on the estimated orientation of the satellite and the desired orientation of the satellite.

30. The non-transitory computer-readable medium of claim 29, wherein:

the eigen vector command executes to decompose the satellite orientation error command into a scalar component and a vector component.

31. The non-transitory computer-readable medium of claim 28, wherein:

the first loop further comprises a feed-forward control system.

32. The non-transitory computer-readable medium of claim 31, wherein:

the feed-forward control system controls for timing errors between rotation of the at least one reaction wheel and pointing at a target.

33. The non-transitory computer-readable medium of claim 31, wherein:

the feed-forward control system accounts for motion of tracking dishes, antennae, cameras, robotic arms, and solar arrays associated with the satellite.

34. The non-transitory computer-readable medium of claim 31, wherein:

the feed-forward control system further comprises receiving the desired orientation as an input.

35. The non-transitory computer-readable medium of claim 27, wherein:

the second loop further comprises receiving the eigen vector determined from the first loop as an input.

36. The non-transitory computer-readable medium of claim 35, wherein:

the second loop further comprises receiving measured satellite rotation rates from a navigation system associated with the satellite.

37. The non-transitory computer-readable medium of claim 35, wherein:

the second loop further comprises receiving a measured reaction wheel speed of the at least one reaction wheel from a rotation wheel tachometer associated with the satellite.

38. The non-transitory computer-readable medium of claim 35, wherein:

the second loop further comprises determining a desired rotational acceleration for the at least one reaction wheel.

39. The non-transitory computer-readable medium of claim 35, wherein:

the second loop further comprises receiving a mass moment of inertia tensor of at least one reaction wheel, a rotation axis vector of at least one reaction wheel, and a mass moment of inertia tensor of the satellite.