Towards In-Flight Transfer of Payloads Between Multirotors

Multirotor unmanned aerial systems (UASs) are often used to transport a variety of payloads. However, the maximum time that the cargo can remain airborne is limited by the flight endurance of the UAS. In this letter, we present a novel approach for two multirotors to transfer a payload between them in-air, while keeping the payload aloft and stationary. Our framework is built on a visual-feedback and grasping pipeline that enables one UAS to grasp the payload held by another, thereby allowing the UASs to act as swappable carriers. By connecting the payload outwards along a single rigid link, and allowing the UASs to maneuver about it, we let the payload remain online while it is transferred to a different carrier. Furthermore, building entirely on monocular vision, the approach does not rely on precise extrinsic localization systems. We demonstrate our proposed strategy in a variety of indoor and GPS-free outdoor experiments, and explore the range of operating limits for our system.