Small Fixed-wing Aerial Positioning Using Inter-vehicle Ranging Combined with Visual Odometry

Benjamin M. Fain and John Raquet

Peer Reviewed

Abstract:	There has been increasing interest in developing the ability for small unmanned aerial systems (SUAS) to be able to operate in environments where GPS is not available. Visual odometry (VO) approaches have been demonstrated which provide a form of dead reckoning, but do not determine absolute position. If we consider the scenario where a higher flying aircraft is providing range updates to a lower flying GPS-denied SUAS, and the higher flying aircraft knows its position, the higher flying aircraft can provide absolute position information to the lower flying SUAS. A single range however, is not sufficient for the SUAS to solve for its position as it does not provide full 3-D position information. This paper investigates the use of a combination of both ranging to a single aircraft and VO to determine an absolute navigation solution. It is demonstrated that a ranging update combined with an aircraft motion model and VO can greatly improve the accuracy of a SUASs estimated position in a denied GPS environment. Commercial-off-the-shelf (COTS) components and a simplified position estimation algorithm were used to estimate the SUASs position. A SUAS fitted with a non-GPS Pixhawk autopilot, a downward facing monocular camera, and a simulated RF ranging device were used to collect real-time flight data. A second simulated SUAS was used to provide RF ranging from a known loiter position. Attitude, body-axis rates, and airspeed data were fed into a simplified aircraft motion model using an Extended Kalman Filter (EKF) for estimation. Using the downward facing camera, VO provided velocity corrections to the aircraft motion model states. Ranging data from a simulated aircraft with a known trajectory was used to update the motion models position estimation resulting in greater position accuracy then the aircraft model and VO alone.
Published in:	Proceedings of the ION 2017 Pacific PNT Meeting May 1 - 4, 2017 Marriott Waikiki Beach Resort & Spa Honolulu, Hawaii
Pages:	1048 - 1064
Cite this article:	Fain, Benjamin M., Raquet, John, "Small Fixed-wing Aerial Positioning Using Inter-vehicle Ranging Combined with Visual Odometry," Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, Hawaii, May 2017, pp. 1048-1064. https://doi.org/10.33012/2017.15098
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