Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
2000-01-06
2001-09-04
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C244S165000
Reexamination Certificate
active
06285928
ABSTRACT:
BACKGROUND OF THE INVENTION
The system of this application is designed to control the attitude of a satellite. Satellites must be maintained in a predetermined orbit and attitude in order to accomplish the assigned mission which can be surveillance, photography, detection and many others. The orbit and attitude of the satellite must be periodically adjusted to compensate for disturbances which occur in space or for the purpose of changing the mission.
In general, spacecraft attitude is adjusted by activating actuators, such as, momentum wheels, magnetic torguers, or thrusters in response to an attitude correction signal. The attitude error may be sensed by reference to sensors monitoring the position of the sun, stars and earth relative to the satellite or by onboard inertial sensors such as gyroscopes. The attitude is adjusted to its mission orientation in which the system is pointed at its predetermined target and is maintained in this orientation during orbital flight. During flight the satellite is subject to motions induced by external forces, on board mechanisms or other sources and the attitude control system must continuously monitor and adjust attitude. Attitude control is therefore of primary importance in order to point the satellite to accomplish its mission and to maintain that position with the required accuracy.
It is a purpose of this invention to use fuel efficient reaction wheels to achieve attitude corrections wherever possible. This is accomplished while obtaining a tighter pointing capability with increased spacecraft autonomy. It is a purpose of this invention to utilize four reaction wheels preferably arranged in a trihedral configuration to provide better performance and enhanced redundancy.
SUMMARY OF THE INVENTION
The control system of this invention employs a configuration of four reaction wheels preferably arranged in a trihedral relation as the primary attitude adjustment mechanism. The primary attitude sensors consist of a three axis gyroscope system. The control module includes stored orbital and related sun ephemeris data and appropriate estimating algorithms. The attitude is estimated with reference to the output of the three axis gyroscope system. Compensation for errors relating to gyroscope drift are provided by reference to data from on board earth and star sensors. Utilizing this data, the control module provides an estimate of the actual attitude of the satellite. The estimated attitude is compared to the desired attitude to obtain an attitude adjustment in terms of the three axis reference system. Each of the components of the adjustment is transformed to obtain the four wheel torque rates required to accomplish the adjustment. In order to further refine the estimated adjustment, the predicted three axis torque adjustments are fed back to the control module.
REFERENCES:
patent: 3999729 (1976-12-01), Muhlfelder et al.
patent: 4071211 (1978-01-01), Muhlfelder et al.
patent: 5020745 (1991-06-01), Stetson, Jr.
patent: 5054719 (1991-10-01), Maute
patent: 5058835 (1991-10-01), Goodzeit et al.
patent: 5098041 (1992-03-01), Uetrecht
patent: 5130931 (1992-07-01), Paluszek et al.
patent: 5201833 (1993-04-01), Goodzeit et al.
patent: 5205518 (1993-04-01), Stetson, Jr.
patent: 5279483 (1994-01-01), Blancke et al.
patent: 5308024 (1994-05-01), Stetson, Jr.
patent: 5452869 (1995-09-01), Basuthakur et al.
patent: 5556058 (1996-09-01), Bender
patent: 5826829 (1998-10-01), Holmes
patent: 5931421 (1999-08-01), Surauer et al.
patent: 6145790 (2000-11-01), Didinsky et al.
Holmes Thomas J.
Reckdahl Keith J.
Tilley Scott W.
Gibson Eric M
Perman & Green LLP
Space Systems Loral, Inc.
Zanelli Michael J.
LandOfFree
Onboard attitude control using reaction wheels does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Onboard attitude control using reaction wheels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Onboard attitude control using reaction wheels will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2486650