Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
1999-10-14
2001-04-24
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S004000, C701S215000, C244S15500A, C244S171000, C244S164000, C342S062000
Reexamination Certificate
active
06223105
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to navigation and attitude determination systems, and more particularly to the determination of the attitude of a moving body relative to the earth where the solution includes knowledge of the specific force of a point on the moving body.
2. DESCRIPTION OF THE PRIOR ART
The attitude of a moving body through space can be described by the three components of heading, pitch, and roll. In an airplane, the heading is the compass direction, the pitch is a measure of how far the nose is up or down, and the roll relates the angle of the wings to the horizon.
Bubble levels allow for a very crude measurement of the pitch and roll of a moving vehicle. But if the vehicle is turning or accelerating, then the vehicle's acceleration will disturb the bubble level. Magnetic compasses allow for heading determinations, but these too suffer from gross inaccuracies, and many common items and activities can disturb a compass measurement too.
The prior art includes the measurement of two or more vectors in each of two frames to determine the attitude between the frames. For example, star trackers that are common in orbiting satellites allow the taking of two vectors in the vehicle frame, e.g., to each of two different particular stars. The knowledge of earth-frame vectors to these same two stars allows for the solution of the attitude of the vehicle frame relative to the earth frame.
LaMar Timothy, et al., in U.S. Pat. No. 5,406,489, issued Apr. 11, 1995, describes the determination of the attitude of a moving aircraft from a measurement of the specific force in two frames. Three accelerometers, a global positioning system (GPS) receiver, an electronic estimating module, and an electronic output module are used. The accelerometers indicate the vehicle accelerations, including the gravity acceleration field, in the three principle aircraft body axes. A composite “specific force vector” is measured with the accelerometers at successive time intervals. Each interval provides one of the multiple vector measurements needed, and this imposes a solution time delay while all the measurements are gathered. Such multiple measurements are required to fully resolve attitude. A series of aircraft position changes along the three aircraft body axes caused by the measured accelerations, times a vector, approximately match a corresponding series of position changes along the earth-fixed axis as indicated by the GPS receiver. Trigonometry is used on the vector to indicate the pitch, roll, and heading of the aircraft.
Two-baseline GPS attitude determination systems use three antennas. The differential position of each antenna is computed from differential carrier-phase measurements. A prior art example of this is described by LaMar Timothy, et al., in U.S. Pat. No. 5,101,356, issued Mar. 31, 1992.
Roger Hayward, et al., all of Stanford University, published an article titled “Two Antenna GPS Attitude and Integer Ambiguity Resolution for Aircraft Applications,” Proceedings of the 1999 Institute of Navigation (ION) Technical Meeting, January 1999, San Diego, Calif. Such article describes the attitude determination of a moving aircraft, starting with a priori attitude information, and then using the measurement of specific force in two frames. Roll and pitch are determined by incorporating the a priori information with the specific force measured in two reference frames.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an attitude determination system that uses the specific force vector as one of two or more vectors collected to resolve the attitude of a moving vehicle.
It is a further object of the present invention to provide an attitude determination system that measures the specific force vector in the earth-fixed frame with a navigation satellite receiver.
Briefly, an attitude determination system embodiment of the present invention uses navigation satellite receiver measurements of the acceleration of a point on moving vehicle to derive valuable attitude information about the vehicle. This acceleration is added to the known gravity vector to form the specific force in the earth-fixed frame. Three-dimensional accelerometer measurements aboard the vehicle are used to determine the specific force vector in the body-fixed frame. Such specific force vector is simply combined with measurements of one or more additional vectors, e.g., antenna baselines, magnetic fields, etc. The attitude of the moving vehicle can then be determined with a conventional optimization algorithm.
An advantage of the present invention is that an attitude determination system is provided that provides accurate estimates of an aircraft's pitch, roll, and heading.
Another advantage of the present invention is that an attitude determination system is provided that uses standard GPS receiver output solutions.
A further advantage of the present invention is that an attitude determination system is provided that simultaneously solves for pitch, roll, and heading.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.
REFERENCES:
patent: 4930085 (1990-05-01), Kleinschmidt
patent: 5101356 (1992-03-01), Timothy et al.
patent: 5406489 (1995-04-01), Timothy et al.
patent: 5856802 (1999-01-01), Ura et al.
patent: 5884214 (1999-03-01), Krasner
patent: 5944770 (1999-08-01), Enge et al.
patent: 5974359 (1999-10-01), Ohkubo
patent: 5999880 (1999-12-01), Okada et al.
patent: 5999890 (1999-12-01), Kihara
patent: 6064336 (2000-05-01), Krasner
Roger Hayward, et al., “Two Antenna GPS Attitude and Integer Ambiguity Resolution for Aircraft Applications”, pp. 1-6, Stanford University, CA. Jan. 1999.
Cuchlinski Jr. William A.
Hernandez Olga
Law Offices of Thomas E. Schatzel A Prof. Corp.
Schatzel Thomas E.
Seagull Technology, Inc.
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