Although quadcopter drones show promise as a means of exploring hazardous environments such as disaster sites, they do have one drawback – they're wide, limiting their ability to squeeze through tight spaces. An experimental new drone addresses that problem, by folding into different shapes while in flight.

The one-of-a-kind quadcopter was developed via a collaboration between the University of Zurich and Swiss research group EPFL.

In regular flight, its four propeller arms sit in the traditional X-shaped configuration (when viewed from above). Once it's time to go through a narrow vertical opening, however, the two front arms fold forward while the two rear ones fold back, making the aircraft considerably narrower. And the fun doesn't stop there.

If the drone needs to hover up or down through a horizontal opening, all of its arms can fold over to one side, minimizing its circumference (see photo below). It can also fold its front arms straight out to the sides, allowing its front-mounted camera to get closer to items that the operator wishes to inspect. Those two front arms can likewise fold forward and inward, clasping objects that the drone then carries through the air.

All four arms are independently moved by individual servo motors, which are in turn remotely-controlled through an onboard microprocessor. Additionally, the thrust of each propeller is automatically adjusted to compensate for the different configurations, allowing the quadcopter to maintain stable flight.

The researchers who developed the prototype are now hoping to make the drone even more autonomous. Among other things, this would allow it to perform inspections of dangerous sites such as collapsed buildings, automatically changing its shape to fit through tight passages as needed, then finding its way back out when done. There are also plans to allow its arms to move vertically, making more flight configurations possible.

This isn't the first time we've seen a quadcopter that's able to get narrow. Earlier this year, France's Étienne Jules Marey Institute of Movement Sciences unveiled its Quad-Morphing drone, which can halve its wingspan by aligning all four of its propellers in a row.

The U Zurich/EPFL drone can be seen in action, in the video below. A paper on the research was recently published in the journal IEEE Robotics and Automation Letters.

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