How to Swoop and Grasp Like a Bird With a Passive Claw for a High-Speed Grasping

There is a growing interest in unmanned aerial vehicles (UAVs) grasping, perching, and interacting with their surroundings by means of claws, arms, hooks, and other appendages. While multirotor vehicles can slowly lower onto a target object and grasp it, winged UAVs require a minimum speed to remain airborne and cannot hover. In this article, we describe a novel avian-inspired grasping mechanism that allows winged UAVs to grasp an object while flying over it. We have developed a high-speed, passively triggered claw that can close in under half a second. We characterize the loads encountered by the vehicle during the grasp event and find that grasping an object of about 30 g produces a maximum load of less than 12 N. Numerical experiments indicate that these loads cause a change in pitch of less than 1 deg and a decrease in speed of about 0.3 m/s for a fixed-wing vehicle of about 1 kg, and are thus negligible. We demonstrate outdoor in-flight grasping at 8 m/s, the fastest recorded grasping by a flying robot to date to best of our knowledge.