Autonomous drone recovery system enables precise midair multirotor docking
Integrated Guidance and Control of a Mother-Child UAV-UGV System for Cooperative Missions
Robotics
Summary
Landing a small drone onto another hovering drone is tricky because the landing surface moves and uses its own thrust. The authors developed a system where a larger drone (the mothership) carries and launches a smaller drone (the child), which then returns and lands on the mothership autonomously. Their approach uses advanced control techniques and sensors to keep both drones aligned and safe during landing. They tested the system outdoors 20 times, achieving an 85% success rate in complete missions.
What this means in practice
- •For drone fleet operators: Implement autonomous deployment and midair recovery of small drones using a larger carrier drone to extend mission range and flexibility.
- •For search and rescue teams: Use coordinated aerial-ground drone systems for deploying rovers and retrieving them autonomously to improve operational efficiency in outdoor environments.
Authors
Aashish Sahu, R. Prasanth Kumar
Abstract
Autonomous recovery of a small multirotor onto a hovering multirotor carrier differs from recovery onto ground or shipborne platforms because the recovery surface is itself an actively controlled, thrust-limited aerial vehicle. This paper presents a field-validated autonomy framework for a heterogeneous rover-mothership-child system executing rover supervision, mothership transit, child deployment and sortie, autonomous return, aerial recovery, and synchronized descent. The recovery stack combines jerk-bounded reference generation, disturbance-observer-augmented planar tracking, feasibility-aware vertical control, a discrete-time barrier-based safety filter for relative vertical geometry, and communication-aware carrier-state prediction. The contribution is the coordinated system-level integration of these methods for recovery onto a hovering multirotor and its full-scale outdoor validation. The framework is implemented on a PX4-ROS 2 architecture using RTK-enabled GNSS, IMU, and barometric fusion, with mothership-side 1D lidar used only as an auxiliary near-contact cue. RTK-fixed positioning was maintained throughout testing. Across 20 outdoor cooperative missions, 17 successfully completed deployment, sortie, and recovery, giving an observed mission success rate of 85%. For successful recoveries, mean terminal-alignment time was 6.3 s, mean planar alignment error at acceptance was 0.18 m, maximum terminal planar deviation was 0.32 m within a 0.40 m capture radius, and minimum logged relative vertical separation during coupled descent was 0.41 m. Mothership planar station-keeping RMS error was 0.25 m. The three unsuccessful trials occurred at different mission stages and are analyzed separately. Results demonstrate practical autonomous aerial recovery within the tested outdoor operating envelope.