An Adaptive, Reconfigurable, Tethered Aerial Grasping System for Reliable Caging and Transportation of Packages Shaoqian Lin, Joao Buzzatto, Junbang Liang, and Minas Liarokapis Abstract— Aerial robot development has gathered steam in recent years for applications such as package delivery and transportation of arbitrary payloads, both in academia and business. However, current solutions for Unmanned Aerial Vehicles (UAVs) based transportation of large objects and/or parcels rely on some form of standardization of packaging. This design constraint greatly limits the applicability of the autonomous package delivery drone concepts. In this paper, we propose a reconfigurable, tethered aerial gripping system that can allow for the execution of a more diverse range of package handling and transportation tasks, employing au- tonomous aerial robots. The system combines a reconfigurable, telescopic, rectangular frame that is used to conform to the parcel geometry and lift it, and a net system that is used to secure the parcel from the bottom, facilitating the execution of caging grasps. This combination provides reliable aerial grasping and transportation capabilities to the package delivery UAV. The grasping and transportation process used by the proposed concept system can be divided into three stages: i) the reconfigurable, telescopic frame conforms to the parcel geometry securing it, ii) the package is lifted or tilted by the frame’s lifting mechanism, exposing its bottom part, and iii) the net is closed, caging and securing the package for transportation. A series of airborne gripping and transportation trials have experimentally validated the system’s effectiveness, confirming the viability and usefulness of the proposed concept. Results demonstrate that the prototype can successfully secure and transport a package box. Furthermore, the complete system can be tethered to any type of aerial robotic vehicle. I. I NTRODUCTION Devices of various shapes, sizes, and designs have been utilised for both industrial applications and research follow- ing the creation of unmanned aerial vehicles (UAV). UAVs are capable of carrying out a range of jobs, including but not restricted to deliveries, surveillance, inspections, and search and rescue. UAVs can have one or more rotors, can have fixed wings like conventional aeroplanes or fixed wings and rotors combined on them (hybrid fixed-wing, multirotor drones), can be an airship, or take many other configurations [1], [2]. Package delivery with autonomous drones has attracted significant attention in both research and industry over the last decade [3]. In 2016, Domino’s Pizza and Flirtey Drones collaborated in New Zealand to complete the first autonomous drone food delivery in history [4]. Multi-rotor drone delivery services like Domino’s Pizza [5] and Ama- zon’s PrimeAir [6] have started to deliver goods and meals. Other examples include delivering crucial medical supplies Shaoqian Lin, Joao Buzzatto, Junbang Liang, and Minas Liarokapis are with the New Dexterity research group, Department of Mechanical and Mechatronics Engineering, The University of Auckland, New Zealand. E-mails: {slin188, jsan819, jlia904}@aucklanduni.ac.nz,minas.liarokapis@auckland.ac.nz Fig. 1: The prototype of the reconfigurable, tethered aerial grasping system is depicted attached to a co-axial octacopter. to far-flung hospitals for patients with urgent needs [7] and deploying lifeguard equipment to save swimmers [8]. These kinds of accomplishments keep making the news, but design limitations and stringent UAV flight rules are impeding progress in the drone-based delivery sector. Furthermore, current UAV-based solutions for the transportation of large objects and/or parcels are optimized for certain types of custom-made packaging. Thus, the usefulness of autonomous package delivery drones is severely limited as a result of these constraints and operation requirements. This article introduces a tethered aerial grasping mech- anism for UAVs that facilitates the execution of a wider range of package pickup, transportation, and delivery tasks. The proposed concept combines a telescopic, reconfigurable rectangular frame that can enclose a parcel, and a net system that can cage the parcel by supporting it from the bottom, trapping it geometrically. Such a combination equips the package delivery UAV with reliable aerial grasping and package transportation capabilities. The grasping process using the proposed mechanism is divided into three stages: i) the parcel is enclosed with the reconfigurable telescopic frame, ii) the package is lifted or tilted using the sliding lifting mechanism to expose its bottom surface, and iii) the net system gets actuated sliding underneath the package, caging it, and securing it. The sliding lifting mechanism con- sists of simple extendable leg that is attached directly onto reconfigurable frame to facilitate the execution of grasping tasks. When this leg pushes against the ground it is able to