Taking cues from geckos, EPFL researchers have developed an unmanned aerial vehicle with an upturned nose that crashes into vertical poles, and then wraps its wings around to perch. The PercHug could find use in inspection and surveillance tasks.
The team from the Laboratory of Intelligent Systems at the Swiss Federal Institute of Technology (EPFL) notes that a number of nature-inspired perching methods for drones have been developed over the years – including the use of claws, spines and grippers. But the focus for the PercHug project was to come up with a passive method for landing on vertical poles in the built and natural environments, again using nature as a jumping off point.
"Geckos in their natural habitat exhibit a remarkable landing strategy on tree trunks," states a recently published paper on the project. "They crash head-first onto the trunk followed by a full body rotation, which is halted by the landing of their hind limbs and tail."
Inspired by this crash-landing technique, the team developed a winged UAV with a rigid tail, which is made using expanded polypropylene for an overall weight of 550 g (19 oz) and wingspan measuring 96 cm (37.7 in). This intrepid flyer happily glides along until it hits a pole or tree with its shapely nose.
The upturned curvature of its front end helps the drone to reorient itself from horizontal flight to a vertical position needed for perching, and pushes the fuselage flat against the surface of the pole. On impact, a latch system passively releases a tension wire that keeps the segmented wings open during flight. Torsion springs then pull the wings around the pole and secure the UAV in place.
"Our solution avoids dedicated perching feet structures that increase body mass and complexity, opting instead for a dual-use strategy leveraging existing UAV elements," the paper explains. "This includes employing front limbs (wings) to tightly hug poles and maintain the center of mass close to the pole to minimize the pitch-back effect. The use of a long tail is also found to be effective in nature for both landing and resting."
In experiments designed to test the design, the unmotorized PercHug was launched by hand and aimed at trees. The team found that even with wings wrapped around the trunk, the bot would often slip down rather than remain where it landed. Installing removable hooks helped mitigate the issue and resulted in more successful perching.
The researchers say that their project lays the foundation for "advancing perching technologies and paves the way for the development of highly versatile robotic systems tailored to diverse applications." Examples of potential uses include inspection of complex or tall buildings without risk to human workers, assessment of challenging infrastructure such as cell towers, on-demand surveillance operations or environmental monitoring, and remote study of wildlife behavior to support conservation efforts.
As for next step for the project, team member Mohammad Askari told us that "the current platform is fully passive and thus limited in capabilities. Our goal is to develop a follow-up motorized platform based on PercHug to demonstrate climbing and relocation at the perched location for inspection purposes, followed by detachment and continued flight to complete its mission."
A paper on the PercHug project has been published in the journal Communications Engineering.
Source: Nature via Interesting Engineering
