Check out this video, where nine palm-sized flying robots work together to play a keyboard, drums, maracas, a cymbal and a "couch guitar" made by stretching guitar strings over a wooden couch frame:

A computer program tells the robots where they need to be at certain moments in time, to hit all the right notes. Cameras set up around the ceiling talk wirelessly with each robot, telling it where it is and what obstacles are around it 100 times a second. The little bots take it from there, autonomously deciding their own flight paths and avoiding collisions with their neighbors. 

These robots—and the couch guitar—are the work of doctoral students Alex Kushleyev and Daniel Mellinger from the General Robots, Automation, Sensing and Perception (GRASP) Lab at the University of Pennsylvania. They debuted their first musical performance Feb. 29, at a TED conference talk by Kushleyev and Mellinger's advisor, Vijay Kumar, but this isn't the first time the robots been the subjects of a viral video. The GRASP Lab previously demonstrated that their mini-drones can turn, flip, fly in formation, zip through a hula hoop that's thrown in the air, and come zooming back to their human users when thrown off a balcony, like high-tech boomerangs: 

Such agile machines could help scope out dangerous buildings after disasters such as earthquakes or radiation leaks, Kumar said in his TED Talk. Each is small, but together, they can lift loads and help in construction. Perhaps they could lift collapsed material off of earthquake victims. They might present a slightly friendlier face to trapped victims than a rescue snake-bot (Though their droning buzz is still pretty unsettling).

The secrets to their smooth, graceful movement are their small size, four rotors and smart on-board processor. By moving each rotor at different speeds, the bots can tilt and turn. Their processors decide the swiftest, smoothest path from Point A to Point B, then send out commands to the rotors 600 times a second.

In a swarm, the robots can also monitor where they are compared to their neighbors. It's important that each robot does this by itself, as it would be too difficult to have one central computer controlling each robot as it flies. 

Kumar's Feb. 29 TED Talk also included one last independent flyer that hasn't yet gotten its own YouTube video. Unlike its musical, in-lab colleagues, the newest robot doesn't need a camera system to tell it where it is. Instead, it carries a camera and a laser scanner to map its surroundings on the fly. Send it into a building it has never seen before, and it can map the building and bring the map back to you. Start watching the mapping robot at work at 11:57 in Kumar's Ted Talk

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