Automated Fabrication of double curved reinforcement structures for unique concrete buildings

In this paper we present research and development results that have lead to a fully automated fabrication cell with two robots, that in one integrated step can produce unique double curved steel reinforcement structures with sizes up to 2 times 2 meters. Input is a computer-aided design description of the reinforcement bar layout. The reinforcement bars are bent and transported to the structure by one robot and assembled (bound together) with the other. The paper encompasses a presentation of the design of the bending tool and the associated optimal bending strategy. Moreover, we present a method to automatically plan collision free robot motions that account for deflections of the bars, and finally a sensor based robot control method that binds the bars together while accounting for unexpected positional deviations. The paper is concluded with a set of experimental validations where we show that the bent bars accurately follow the specified shapes.