Posted September 25, 2015

Drones can build your rope bridge

At the Swiss Federal Institute of Technology (ETH) in Zürich a team of drones has woven a 7 meter long rope bridge autonomously. No human steered a drone or directed the team as a whole. Afterwards, the bridge could easily carry persons crossing all the way to the other side.

That's a world's first, and a major step forward for drone technology as well as autonomous building. Four years ago the guys at ETHZ had a team of drones build a brick wall of a very particular shape, automatically and autonomously.

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To achieve this feat the drones were directed by a computer system that also had cameras attached to it, monitoring the whereabouts of each drone all the time. So the drones themselves had no knowledge of who was where. In a way they were the unattached limbs of a weird beast that also had eyes outside of its body.

About two years ago the Zürich school started using drones to make 'tensile structures.' As you can see in the next video, lines were attached to poles simply by winding the line around the pole many times. Then the ropes were used as new support points for a very crude weaving pattern. Toward the end of the video you can also see two drones working together, but it's not clear what their objective is.

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In today's video you can see how much smarter they operate now. They attach the lines in a purposeful and complicated way, actually tying knots. The drones stay out of the way of the scaffolding structure, the lines, and each other (although it's unclear how many failures have been edited out). The connections between the first lines are tied in a particular way too, by two drones flying around one another and around the lines, to make sure these connections can't move in an undesired way. Then students test the strength of the bridge, after which further stabilizing connections are made.

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This bridge spans 7.4 m and consists of 120 m of 4 mm Dyneema, a very light and strong fiber developed at DSM in The Netherlands in the 1970s. One string of 4 mm Dyneema can sustain a load of 1300 kgs and a meter of it weighs only 7 grams. It ought to be relatively easy to build such a bridge outside, although some adaptations could be necessary. Using a tree instead of scaffolding complicates matters a bit, and longer lines mean a bigger load for the drones, shortening flight times or even requiring different drone types.

This can be solution to a real world problem: how do you attach your bridge to a tree on the other side without crossing the rapids first? But it's also a stepping stone to even more complicated building processes. The researchers expect  their work 'will foster new forms of architecture and construction methods.'


About Herbert Blankesteijn

Herbert Blankesteijn is a technology journalist from the Netherlands who has written for many prominent Dutch newspapers. He presented and directed television and radio programmes and has 10 books to his name. Herbert is interested in nascent fields such as 3D printing, drones, robotics and the private space business.