49 Crazyflie 2.1 Brushless lifting off their charging docks, flying formations, and landing back to recharge, all driven from a single Crazyradio 2.0. That’s what we have been flying lately, and it’s a great showcase of what the Crazyflie ecosystem can do with a big swarm.
If 49 Crazyflies sounds familiar, you might remember 49 Crazyflies, 1 Crazyradio, and cflib2. This time the formations are a lot more dynamic. They come from a collaboration with the Institute for Data Science in Mechanical Engineering (DSME) at RWTH Aachen University, and we recorded some videos we’re really happy with.
Where the formations come from
The choreographies were generated with SWAN, a pipeline developed at DSME that turns text promt into drone trajectories. In short:
- A generative video model turns the prompt into a reference video.
- A point tracker converts the motion in that video into trajectories for the swarm.
- A planner assigns them to individual drones, and a safety filter makes sure they are collision-free.
What makes these formations fun for us is that they are not static shapes: they move in ways that would be hard to animate by hand. That also makes them a demanding test for the swarm.
Taking it to the real world
The generated SWAN trajectories are turned into splines and deployed on a dense swarm of 49 Crazyflie 2.1 Brushless, flying under the Lighthouse positioning system and lit up by bottom-mounted Color LED decks. We won’t go through the whole setup again (covered by the earlier post), but two parts of the Crazyflie ecosystem made this kind of work practical:
- Built on cflib2. All communication with the swarm goes through cflib2 over a single Crazyradio 2.0. Before takeoff, we use cflib2 to upload each drone’s trajectory to its memory, and during the show, the High-Level Commander executes it onboard. While they are flying, we log every drone’s position every 50ms, giving us a record of how closely the swarm followed the choreography.
- No battery swapping. Each Crazyflie takes off and lands on its charging dock. When you want to fly the swarm many times back to back, not having to handle 49 batteries makes a huge difference.
The result is a setup where any idea can go from the computer to a real swarm without having to build the infrastructure yourself.
The videos
Enough talking, here is what it looks like. The video below shows the formations we flew: a ballerina (49 drones), a karate fighter (29 drones), and a hand making an “I love you” (ILY) sign (49 drones).
Wrapping up
Flying 49 Crazyflies through dynamic formations, with one radio, full position logging and drones that recharge themselves between flights shows how far the Crazyflie ecosystem has come for large swarms.
A big thank you to Pascal Reinhold, Alexander Gräfe and Sebastian Trimpe at DSME for their awesome work, and an extra special thanks to Alexander, who coordinated the whole project during his internship with us at Bitcraze. If you want to learn more about SWAN, check out their paper, Generative AI for Safe and Photorealistic Drone Light Shows. And if you want to fly your own swarm, cflib2 is ready to try.
