Construction robots are machines that do building work on site, and the kind most used in India today plasters and paints walls. They do this repetitive finishing work evenly and faster than a crew with trowels and rollers. Finishing is the last stage of building work: plastering, putty, painting and tiling, after the structure, pipes and wires are in place.
Why automate plastering? A large housing project may have several lakh square metres of wall to plaster and paint. The work is slow and tiring, and builders find it hard to hire enough skilled plasterers. Hand plastering is also uneven. A wall that is not flat needs more putty and paint later, and its defects show under light.
How does a plastering robot work? It stands on a wheeled base, which the operator moves to each wall. First, it scans the wall with a laser or a camera. It builds a map of the wall's surface and finds the openings for doors, windows and switch boxes, using computer vision. Next, it works out how thick the plaster must be at each point to make the wall flat. Then a nozzle on a vertical arm sprays the plaster in strips, and a blade on the arm levels it. Painting robots work in the same way, and spray the paint in even coats.
Imagine a mass-housing project in Navi Mumbai with 1,400 flats. The robot works with one operator and one helper, who loads the plaster. Its scan of one bedroom wall shows a bulge of 18 mm at the middle. So it sprays less plaster there and more towards the edges, and the finished wall is flat within a few millimetres from floor to ceiling. The site uses the robot on the long, plain walls of the flats. Plasterers still finish around pipes and in corners, where the robot cannot reach. The robot plasters several times as much wall in a day as a hand crew of the same size.
How is it different from an industrial robot in a factory? A factory robot is fixed to the floor, and the part comes to it, always in the same position. A construction robot must go to the work. Every wall is in a different place and is slightly different in shape. So the robot must measure each wall before it starts.
The progress of finishing work, flat by flat, is recorded in construction management software, so the developer knows which flats are ready for inspection. Machines that use AI to act in the physical world in this way are described in physical AI.