This Glider Is a Real Tree Hugger

Drones, such as quadcopters, have proven themselves to be invaluable for tasks like aerial photography, search and rescue operations, and infrastructure inspections. And where greater distances need to be covered than a multi-rotor vehicle can handle, winged unmanned aerial vehicles (UAVs) have been found to be more than capable of filling in. But what these winged UAVs lack is the ability to safely land without a large stretch of flat land that is free from obstructions. Accordingly, when a job calls for a long-distance drone to keep a fixed target in its sights for an extended period of time, there are not a lot of good options.

Researchers at the Swiss Federal Institute of Technology Lausanne noticed that this is a solved problem in the natural world. Consider bats, for example. They can fly long distances, then land just about anywhere — including on tree limbs and vertical poles — by wrapping their wings around the object they are landing on to grip it tightly. It would be pretty hard to beat that solution, so the researchers decided to emulate it instead. They designed and built a gliding drone called PercHug that, on contact with a surface, can wrap its wings around it to hang on.

Calling what PercHug does a landing might be a little bit too generous. It is definitely more in the neighborhood of what would typically be called a crash-landing, with the glider slamming nose first into the landing area. This is by design, however, as it eliminates the need for complex maneuvering. When the glider comes into contact with a surface, an upturned nose element reorients the vehicle from a horizontal position to a vertical one.

PercHug also has foldable, segmented wings that are loaded with tension springs. On impact, a latch system allows the wings to collapse, which in turn enables the springs to contract and tightly wrap the wings around the landing area. As you might expect, making a habit of crashing can wreak havoc on an airframe, so the team also designed a reinforced tail and body to take the stress without going to pieces.

This may be a simple design, but that should not count against it. As is so often the case in engineering, the more simple a design is, the more reliable it is. And that is what the researchers discovered in their experiments. PercHug was shown to be able to adapt to many different scenarios as it grabbed onto several different types and sizes of trees, and from varying orientations.

It does take a bit of skill to learn the right throwing technique to get consistently good landings, however, so a more formal landing process might need to be worked out in the future. It is also worth noting that the glider is not equipped with motors, sensors, control units, or much of anything else, so some additional considerations are likely to pop up when trying to build the technology into a practical UAV. But if the researchers can work through those issues successfully, PercHug might prove to be a good option for long-distance drones that need to land on a dime.