Autonomous repositioning and localization of an in situ fabricator

Despite the prevalent use of robotic technologies in industrial manufacturing, their use on building construction sites is still very limited. This is mainly due to the unstructured nature of construction sites and the fact that the structures built must be larger than the machines which build them. This paper addresses these difficulties by presenting a repositioning and localization system which, using purely on-board sensing, allows a mobile robot to maintain a high degree of end-effector positioning accuracy while moving among numerous building positions during a building task. We introduce a newly developed machine, called the In situ Fabricator (IF), whose goal is to bring digital fabrication to the construction site. The capabilities of the repositioning and localization system is demonstrated through the construction of a vertical stack of bricks, in which the IF repositions itself after placing each brick. With this experiment, we demonstrate that the IF can build with sub-centimeter accuracy over long building sequences.