A center-less quadrotor design with a soft enveloping grasper for aerial grasping and delivery tasks

Abstract

Unmanned aerial vehicles (UAVs) are a fast and effective platform that can be used for item delivery. However, the use of a conventional multirotor structure often require the payload to be manually loaded and unloaded, increasing the turnaround times and reducing efficiency of such systems. While adding a conventional gripper can enable grasping and releasing of payload, the typical solution of attaching such grippers in an underslung manner below the UAV leads to undesirable flight dynamics when payload is carried. In this paper, we aim to unify the goal of effective aerial delivery with direct grasping capabilities, improving the flight dynamics of load-carrying UAVs while enabling loading and unloading of payload without human presence or external receiving stations. To do so, we propose a design that optimizes the structure of UAVs for payload transportation by hollowing out the center of the UAV for the payload bay. This positioning of the payload prevents large changes in the center of mass and moment of inertia of the UAV between loaded and unloaded states, hence improving the control authority of the vehicle. Combined with a soft enveloping grasper, the proposed UAV successfully demonstrated the full mission profile of approach, capture, grasp, carry, and release. In addition, grasping an object from below as well as controlled perching were also performed with the same grasper, demonstrating its multifunctionality. The proposed UAV configuration in this work provides a compact, adaptable, and dynamically stable aerial grasping platform and strategy for delivery and pick-and-place tasks.