A Fault-Tolerant Cooperative Positioning Approach for Multiple UAVs

Due to the increasing potentials and benefits of unmanned aerial vehicles (UAVs) in civil and surveillance applications, the cooperative flight using multiple UAVs has attracted more and more attention. However, fault-tolerant cooperative positioning for malfunctions in global positioning system (GPS) is one of the challenges that need to be addressed in various practical applications of UAVs. Motivated by solving this issue, this paper presents a reliable cooperative positioning approach for multiple UAVs cooperative flight by using the geometric azimuth angle and the inclination angle relative to the reference UAVs. In this proposed cooperative positioning system (COPS), these relative angles are measured through radio direction finding equipped on UAVs. With the horizontal dilution of precision of the various reference UAVs carefully analyzed, the optimal reference UAVs set can be first selected. Based on a constant acceleration kinematic model, an extended Kalman filter is then employed to improve the positioning accuracy. A COPS/GPS fault-tolerant navigation algorithm is finally developed to accommodate GPS fault. Simulation results are further presented to verify that the proposed algorithm can guarantee satisfactory navigation of the UAVs even when their GPS cannot work.