Research drone uses touch to perch on branches and preserve battery

A drone hanging from a branch is doing something unusual: it is no longer flying. Developed by researchers at Delft University of Technology in the Netherlands, the drone uses nine soft touch sensors in a humanlike hand to find a branch, grip it and shut off its motors. The payoff is quieter monitoring and less time spent hovering, which can preserve battery life.

The drone begins with only a rough estimate of where the branch might be. It flies a figure-eight search pattern while opening and closing its three-fingered hand. The first contact reveals where the branch is and how it is oriented; the drone then rotates and repositions until sensors on all three fingers confirm a stable grasp. If the attempt fails, it retreats to a safe hover and tries again.

That matters because cameras lose their advantage at the final moment of landing. The approaching branch and the drone’s own gripper can block the view, making a precise visual model difficult to use. Here, each sensor gives only a simple yes-or-no contact signal, but the drone knows the shape and position of its own fingers, allowing it to turn those contacts into a location and direction for its next move.

The hand is designed to keep holding without spending motor power. Torsional springs naturally close the fingers, while one tendon per finger opens them; soft silicone pads add friction and allow the hand to adapt to different surfaces and textures. In flight experiments, the researchers found the tactile strategy stayed reliable when the target’s position, orientation and size had been estimated incorrectly, while a conventional vision-based strategy quickly failed.

Concretely, this could let drones monitor rainforest canopies, cluttered industrial structures or other places where cameras alone are unreliable, and perch instead of hovering continuously. The study, published in npj Robotics, demonstrates the capability in experiments.