Autonomous Recovery System of Aerial Child-Mother Unmanned Systems Based on Visual Positioning

The aerial child and mother UAV systems can effectively improve the operational range and task flexibility of UAV systems, and their recovery method is of great significance for the cooperative operation between the child and mother UAVs. In this paper, a separated lift and thrust vertical takeoff and landing mother UAV and a multi-rotor child UAV are proposed for the child-mother UAV systems. The solutions are proposed for the navigation and control problem of the recovery mission. The recovery mission is divided into an approaching stage, and a landing stage, using GPS and visual positioning to provide navigation information for the child UAV, respectively. In addition, the proposed multi-level visual marker effectively avoids the loss of navigation information during the landing process. Moreover, the recovery control problem of the child UAV is transformed into a position tracking problem, and the designed controller effectively ensures the accurate recovery of the child UAV. Finally, the proposed child-mother UAV systems are tested in a simulated environment (Gazebo) and verified that the proposed navigation and control method can effectively perform the recovery mission of the child UAV in static and moving states of the mother UAV.