Flying "tug" drones anchor to objects to pull 40 times their weight

Inspired by wasps, tug drones are all about doing real work in the sky.

Researchers from Stanford University and the Ecole Polytechnique Fédérale de Lausanne (EPFL) have developed a small but super powerful drone that can anchor to objects in order to haul heavy loads. While most drones passively monitor the world as flying sensor stations, the new drone actively manipulates the environment around it by either hoisting, pushing, or dragging objects, depending on the masses involved.

There's increasing need for drones that can grapple and move heavy objects as drone delivery begins in earnest around the world. Drones capable of moving debris and opening doors would also be well-suited to disaster relief and search and rescue work.

Called FlyCroTugs, short for "flying, micro, tugging robots," the drones anchor to objects using gecko-inspired adhesives and microspines. Once anchored they can drag objects that would otherwise be immovable for a small robot via a cable and winch.

Top payload capacity for most drones today is about 2X the drone's weight. The FlyCroTugs, developed in the labs of Dario Floreano at EPFL's School of Engineering and Mark Cutkosky in the School of Engineering at Stanford University, can haul about 40X their weight. The breakthrough behind that carrying capacity comes from nature, and in particular wasps.

"Wasps fly quickly to a piece of food, and if it's too heavy to carry off, they drag it along the ground. This observation was the genesis of our approach," said Cutkosky, a co-author of the paper.

The researchers turned to entomological studies to figure out how wasps decided whether to lift or drag an object. Through their analysis, they were able to pinpoint the thresholds of flight-related muscle to total object mass that determine how a wasp chooses to move its cumbersome prey.

Wasps are particularly adept at anchoring to surfaces of differing textures. However, the researchers turned to different corners of the animal kingdom to come up with their grasping mechanisms. Geckos famously use intermolecular forces between their non-sticky adhesive toes and the surfaces of objects to scale vertical walls. The researchers equipped their flying tug robots with non-sticky adhesive pads to anchor to smooth surfaces.

For rough surfaces, the researchers deployed a series of tiny fish-hook metal spikes that latch onto small pits in the surface of an object. When the drone lands on carpet, for example, the hooks grasp the fibers like velcro.

"People tend to think of drones as machines that fly and observe the world. But flying insects do many other things, such as walking, climbing, grasping and building. Social insects can even work together and combine their strength," says Floreano, the study's lead senior author. "Through our research, we show that small drones are capable of anchoring themselves to surfaces around them and cooperating with fellow drones. This enables them to perform tasks typically assigned to humanoid robots or much larger machines."