A quadcopter can use its inflatable body to land on a wide variety of objects. The collision-resistant drone could help search-and-rescue missions

An inflatable drone can perch on many different objects by colliding with them – taking advantage of its soft-body floppiness to increase the time spent in contact with the landing target and to avoid bouncing off.

This approach loosely mimics the physics of how birds land on branches and other objects. Although the drone itself resembles a traditional quadcopter with four arms and rotors, its fully inflatable body can be adjusted to have either a stiff or soft airframe based on the amount of air inside.

“The drone’s soft body is, of course, able to generate a lot of collision resilience,” says Wenlong Zhang at Arizona State University. “But the soft body itself is also what enables the perching to be successful.”

The drone perches on objects by using a lightweight gripper made of spring steel that can either lay flat or curl up. When the drone performs a “controlled collision” with any desired perch, the energy from that impact activates the flat spring steel so that it curls around the target object.

“We purely rely on the material properties such that it can always grasp without consuming any energy,” says Zhang.

When the drone is ready to release its grip and take off again, an inflatable component of the gripper fills with air to form a stiff beam, straightening the spring steel once more and opening the grip. This release process requires just a bit of energy to inflate the gripper component.

Zhang and his colleagues tested the drone on many possible perches, including a helmet, the edge of a ladder, a rock, a tree branch, a robot arm and a sanitiser stand. The drone’s straightened gripper can also act as a landing skid on flat surfaces.

“A tree branch or rock surface is effortlessly accommodated by this soft body design, while a rigid set of legs would have to overcome several other challenges, even with actuated legs,” says Robert Stuart-Smith at the University of Pennsylvania, who wasn’t involved in the study.

One downside is that the lack of a rigid airframe in the drone design creates “variations in the location and pitch of each propeller that would negatively impact flight efficiency and accuracy”, says Stuart-Smith. The main research team also acknowledged this as a tradeoff when deploying a soft-body drone.

Zhang and his colleagues aim to add more sensors to the drone so that it can better detect its environment and possible landing spots, along with developing a software algorithm that allows the drone to autonomously decide on where to land and when to take off.

The perching capability could help the drone conserve energy and extend its battery life by not having to hover constantly during longer observation missions. Its collision-resistant airframe could prove especially useful for search-and-rescue missions in obstacle-filled environments, such as ruined buildings in the aftermath of an earthquake.

“A lot of these disaster relief scenarios involve flying drones to collect data for the first responders, but the environment there is highly cluttered and then it’s very difficult to completely avoid collisions,” says Zhang.

Journal reference: Soft RoboticsDOI: 10.1089/soro.2022.0010