Relative Navigation System for Manned and Unmanned Vehicles

S. Moafipoor, L. Bock, J.A. Fayman

Abstract:	Future generations of unmanned vehicles (UAV - Air, UGV - Ground, USV - Sea or UXV's), will require precise relative navigation information to enable autonomous behavior in demanding situations including formation operations, aerial refueling, docking, collision avoidance, swarming, landing etc. What is common to all of these applications is the interaction between two or more vehicles. For example, in aerial refueling, the two vehicles are the fueling tanker and the vehicle being refueled. We refer to these vehicles as the leader and follower respectively. In these applications the absolute navigation information of the leader and follower is less important than the relative navigation information between them. We call this information Relative Time Space Positioning Information or Relative TSPI. Traditionally, algorithms employing application specific approximations were developed to provide Relative TSPI. For aerial refueling it was assumed that the vehicles will be flying in close formation and it was further assumed that there is a similarity between the dynamic motions of each aircraft. For autonomous landings the assumptions were based on a reduced-order model of the relative inertial error process. In this paper we present the theoretical foundation and experimental results for a generic approach to relative navigation developed at Geodetics Inc. The approach is capable of meeting the full range of relative assisted manned and unmanned UXV operations. We present a Relative Kalman Filter (RKF) that integrates line-of-sight relative observations, including Global Positioning System (GPS) and on-board sensors measuring relative bearing and relative distance. The system provides 100 Hz Relative TSPI with an accuracy of ±1º for attitude and ±0.5m for position. We analyze the performance of the approach on real-world data collected on two vehicles, each equipped with an Inertial Navigation System (INS) consisting of GPS and IMU (Inertial Measurement Unit) sensors. The performance analysis of the RKF shows accurate relative prediction using relative distance measurements. The system also tolerates temporary GPS-denied conditions due to GPS signal loss.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	3512 - 3522
Cite this article:	Moafipoor, S., Bock, L., Fayman, J.A., "Relative Navigation System for Manned and Unmanned Vehicles," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 3512-3522.
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