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Mobile robots taught together to print concrete structures

CRI Group @ NTU / YouTube

Singapore engineers have created a building 3D printer on a mobile platform. Several such printers can independently move to the print station and work simultaneously, thereby creating a single large design. The article describing the development is published in the journal Automation in Construction .

Most 3D printers have a design with a strictly limited working area, within which you can create a printable object. When printing parts or other small objects, this limitation does not interfere with the work, but it makes such printers unsuitable for creating massive objects, including buildings. To solve this problem, engineers apply two approaches – create huge 3D printers, a working area that is sufficient for printing buildings, or install a printer on a mobile platform. Nevertheless, both approaches suffer from serious shortcomings. For example, if a mobile 3D printer works alone to construct a large structure, in some places it has to connect already frozen concrete with new layers, which can reduce the strength of a single structure.

Engineers led by Quang Cuong Pham of Nanyang University of Technology created a pair of mobile robots equipped with a 3D printer for printing with concrete. The robot consists of several main parts – a wheeled platform equipped with several types of displacement sensors, including laser, mounted on a manipulator platform, capable of reaching objects at a distance of 90 centimeters, and an extruder installed at the end of the manipulator for a building mix. To accurately track the position of the platform relative to the print location, engineers used external stereo cameras to be installed around robots.

The developers used a hybrid robot localization scheme, in which they first rely on the indications of their own sensors, and when approaching the print site, they switch to control from data from external stereoscopic cameras that track the position of special visual markers on mobile platforms. The system allows robots not only to independently print the object, but also to transfer their location to avoid collision with another robot.
Engineers demonstrated the work of 3D printers in the example of a concrete part, the length of which exceeds the diameter of the working area of ​​the robomanipulator, and therefore requires the use of two robots. Also, this problem can be solved by actively moving the robot during printing, but so far the developers have not realized this possibility.

Earlier, the Dutch company CyBe introduced another 3D construction printer, which also can move around the construction site due to the crawler chassis. In this case, before starting the work directly, the printer pushes the hydraulic stops and fixes its position.

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