Real-time “Sense-and-Act” operation for construction robots

A new concept of real-time “Sense-and-Act” operation is presented for mobile construction robots performing accurate and/or delicate tasks. The concept enables an indoor mobile robot to be positioned merely in the vicinity of its temporary workstation, with an approximate accuracy of about 10 cm. The robot then calibrates itself to the immediate environment relevant only to the current workstation. The movements made by the robotʹs end-tool, when bringing a building element to its target position, are directed in real-time by sensing the toolʹs immediate surroundings. The overall task cycle starts with a swift long-distance movement of the arm towards the target, followed by a series of fine, short-distance, iterative, “Sense-and-Act” cycles. This constant interaction with the immediate environment renders unimportant many errors that may occur in the broader environment. This concept was applied to tile setting on walls, one of the most challenging interior tasks for construction robots, which requires three-dimensional precision to the millimeter. A special device, based on a CCD camera and several laser projectors, combined with computer image processing, was developed for the delicate “Sense-and-Act” cycles. This device is also introduced and discussed in the paper, along with a presentation and analysis of full-scale tile setting experiments.