Swiss researchers develop perching drones with a hugging-wing design

Researchers have devised an innovative advancement in drone technology that uses passive wing morphing to achieve crash-landing on trees and vertical poles.

Inspired by animal limbs, these drones have dual-purpose wings for both aerial gliding and secure perching, simplifying control and design complexity.

According to the team at the Swiss Federal Institute of Technology Lausanne (EPFL), when the robot collides with a pole head-on, its raised nose allows it to passively reorient from horizontal flight to vertical flight and then hug its wings to perch.

The team believes that such drones will enable close inspections in industrial settings and tall buildings, avoiding scaffolding and risky human interventions.

The details of the team’s research were published in the journal Nature.

Gecko-inspired design

Due to their high endurance, unmanned aerial vehicles (UAVs) excel in long-distance missions such as delivery, mapping, and search and rescue.

However, unlike winged animals, the drones struggle to land or perch on complex structures for tasks such as inspection and battery recharging.

Various control and mechanical systems have been developed to address this. Control-oriented methods focus on pitch-up maneuvers and post-stall control, often using micro spines or hooks for vertical surfaces.

Mechanical solutions include claws, wrapping arms, and adhesive pads. Despite these advancements, options for winged UAVs remain limited, with existing methods facing challenges like surface dependency and scalability issues.

To address drone perching challenges, the team developed PercHug, a 550 g winged UAV inspired by geckos, for passive perching on vertical poles like scaffolding, towers, and trees.

Using an “upturned nose” for reorientation and foldable wings for wrapping, PercHug avoids additional structures, reducing complexity. It features an unlatching mechanism, a bistable trigger, foldable wings with hooks, and a reinforced tail for stability and resting.

Innovative perching by drone

In the experiments, PercHug was hand-launched against six trees, both with and without an extended elastic nose. Successful perching involves four steps: gliding, reorienting, wrapping wings, and maintaining perch.

Hooks were essential to decreasing slippage and increasing perching success. The primary impact wing release’s superior effectiveness over the secondary impact resulted in faster and more dependable perching.

According to the team, precise approach angles that minimize angular and lateral errors were necessary for optimal perching. The tail was necessary to stop the reorientation at ninety degrees.

All trees successfully perched at impact speeds of 3–5 m/s and angles greater than 15°; the standard nose outperformed the elastic nose, with a success rate of 73 percent compared to 42 percent.

The elastic nose, while improving reorientation, hindered surface attachment by creating a gap and releasing stored kinetic energy .

According to researchers, the experiments highlighted the importance of nose design and precise timing in the perching mechanism. Wider trees generally led to lower success rates, emphasizing the significance of tree diameter and static friction in dynamic perching success.

“We firmly believe that our study lays a foundation for advancing perching technologies and paves the way for the development of highly versatile robotic systems tailored to diverse applications,” said the team in the study .

Such robots enable access to challenging locations like towers for infrastructure inspection, enhance surveillance on lamp posts in urban areas, and monitor biodiversity and wildlife behavior in environmental conservation efforts.