3D printing is becoming increasingly important in the construction industry. Both on the construction site and in the factory, stationary and mobile robots print materials for use in construction projects such as steel or concrete structures. However, this requires either very large machines or mobile robots – which, however, have limited range and mobility.
Like a wasp
Ketao Zhang from Imperial College London and colleagues therefore propose using swarms of autonomous drones that deposit material in flight – inspired by wasps, bees or swallows. In the current issue of the specialist magazine Nature, they present hardware and software that can at least in principle master this feat.
For “Aerial Additive Manufacturing”, as the researchers call their process, they modified two multicopters: The “Build Drone” deposits a self-hardening foam. Zhang had already shown the principle in an earlier work: The material consists of two components that hang in separate containers on the drone and are mixed in a nozzle when deposited, so that they then quickly harden in air. In order to position the nozzle more precisely in flight, the team also developed a delta gripper that can position the nozzle with an accuracy of up to five millimeters in flight.
The second drone, the “Scan Drone”, constantly checks the position of the working drone and the workpiece and sends the data to the control computer. He compares the geometry of the built structure with the internal construction plan and steers the drones if necessary. In addition, the researchers presented a software framework that is based on the ROS robot operating system and allows the operation of several drones in a cooperative swarm.
More complex structures with more drones
In order to show what their system can do, the researchers had their drones build an approximately two meter high cylinder made of polyurethane-based foam and an 18 centimeter high cylinder made of a specially developed cement-like structural material. In simulations, they also showed the construction of more complex structures with several coordinated drones.
Contrary to what spectacular demonstrations of drone swarms suggest – like this one, in which drones build a kind of wall – the coordination of the swarm is usually not self-organized like in insects or birds. In the present work, too, there is a central authority that takes over the planning and coordination.
Nevertheless, lead author Mirko Kovac from the Imperial Department of Aeronautics and Empa’s Materials and Technology Center of Robotics is convinced: “We have proven that drones can work autonomously and in tandem to construct and repair buildings, at least in the laboratory.” Um In order to be able to use the technology outside of the laboratory, the researchers are now working on an algorithm for joint localization and mapping in the swarm.They also want to explore how durable the 3D-printed structures are, or which structures lend themselves to this type of construction particularly well suited.
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