Watch a Swarm of Flying Robots Build a 6-Meter Brick Tower

Drones carry bricks to build a wall
Image: ETH Zurich

What happens when you put a bunch of roboticists and architects together in an empty art gallery?


This is the Flight Assembled Architecture, an installation that opened yesterday near Paris and is still going up as I write this. It's the result of a collaboration between ETH Zurich roboticist Raffaello D'Andrea and architects Fabio Gramazio and Matthias Kohler, also from ETH.

D'Andrea, an IEEE Fellow and IEEE Spectrum editorial board member, is known for his amazing robotic sculptures and flying robot stunts, and Gramazio and Kohler, who run their own design studio, are pioneers in bringing together robotics and architecture. But for an installation at the FRAC Centre, in Orléans, near Paris, they wanted to do something entirely new and bold.

How about using a fleet of quadcopters to build a 6 meter (20 feet) twisting tower out of 1500 foam bricks? Sure!

D'Andrea tells me they're using four flying robots at the same time. First, the robots grab foam bricks from a special brick dispenser on the ground. Next the quadcopters receive the exact coordinates of where the bricks should go based on a detailed digital blueprint of the tower. Then they fly off.

Drone carries brick to build wall

The robots fly autonomously, but they get help from the environment: The ceiling of the room where the assembly is taking place was equipped with a motion-capture system. A computer uses the vision data to keep track of the quadcopters and tell them where to go -- the same approach used at ETH's Flying Machine Arena. (More technical details here.)

When a robot's battery runs low, it automatically lands on a charger and a new quadrotor takes its place. The assembly is happening at a pace of 100 bricks per hour on average, D'Andrea says. Glue on the bottom of the bricks keeps them in place (the installation will become part of FRAC's permanent collection).

The foam tower is actually a 1:100 model of a "vertical village" conceived by Gramazio and Kohler. It would have a height of 600 meters and living space for 30,000 people, with each "brick" housing up to three floors of apartments as well as stores, cinemas, and gyms. A system of express and local elevators would allow efficient transportation, and traversing the entire building would take just 7 minutes. If you don't like the idea of having 29,999 other people living less than 7 minutes away, you may take some comfort in the fact that the village would be everything but densely packed: Looking out your window to the interior of the tower, the other side would be more than 300 meters away, and while shielding wind, the porous structure would allow for plenty of sunlight from all directions.

This week, after some test runs in Zurich, D'Andrea, Gramazio, and Kohler gathered their teams, packed their robots and bricks, and started the setup at the FRAC space. Last night, the museum opened its doors, and a crowd filled the room, letting off "lots of oohs and ahhs," reports Markus Waibel, a member of the D'Andrea team.

Below, more photos and captions, courtesy of Waibel:

844 bricks placed, 656 to go.
flying robots build tower raff d'andrea gramazio and kohler

Two of the 19 Vicon motion capture cameras used.
flying robots build tower raff d'andrea gramazio and kohler

Wall projection of the "freeway reservation system" that quadcopters use to navigate. Extra points if you can explain why the propellers look like rainbows.

Quadrotor at the brick pick-up station. The brick gripper, which uses servo-activated pins to puncture and hold the bricks, is a critical part of the system. Many designs were evaluated and tested to optimize, among other things, least interference with air flow, detachment reliability, and overall robustness.

A quadrotor just before a precision landing on a brick. After the landing and before take off, the off-board computer control system uses the Vicon cameras to calculate out the landing error. This error is then taken into account when placing the brick on the structure. Even with this correction, precise brick placement is extremely challenging due to the turbulent aerodynamics involved (ground effect, air cushions forming between bricks). The best way to do this is to hover quite high above the calculated placement position and then drop down rapidly (see video). 

Four quadrocopters perched on their recharging stations, high above the audience.

Bricks are glued together. It took three months of work to find the right glue and curing period (testing everything out there that wouldn't attack styrofoam). Glue is critical because it needs to settle so that it automatically corrects for minute differences in brick shape and size. At a total height of 60 bricks, even a tiny 0.5mm difference in brick height could translate into an error of 3cm - and a dangerously unstable (and very ugly) tower without the right glue.

A rendering of the final building, including two park floors allowing for a 1 km stroll (or jog) around the building. (Image: Gramazio & Kohler)

Rendering of the completed vertical village at the selected location: A rural area close to Gare de Meuse, 59 minutes from the center of Paris by high-speed TGV train. (Image: Gramazio & Kohler)

The happy team with the structure half-built at the end of the opening night.

The structure after lights were off under a Vicon-camera sky. :)

Video and photos: Markus Waibel/ETH Zurich



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