Tie a knot: human–robot cooperative workflow for assembling wooden structures using rope joints

Abstract

In recent years, research in computational design and robotic fabrication in architecture, engineering, and construction (AEC) has made remarkable advances in automating construction processes, both in prefabrication and in-situ fabrication. However, little research has been done on how to leverage human-in-the-loop processes for large-scale robotic fabrication scenarios. In such processes, humans and robots support each other in fabrication operations that neither of them could handle alone, leading to new opportunities for the AEC domain. In this paper, we present Tie a knot, an experimental study that introduces a set of digital tools and workflows that enables a novel human–robot cooperative workflow for assembling a complex wooden structure with rope joints. The system is designed for a dually augmented human–robot team involving two mobile robots and two humans, facilitated by a shared digital-physical workspace. In this shared workspace, digital spatial data informs humans about the design space and fabrication-related boundary conditions for decision-making during assembly. As such, humans can manually place elements at locations of their choice, following a set of design rules that affect the gradual evolution of the structure. In direct response to such manually placed elements, the cooperating robots can continue the assembly cycle by precisely placing elements and stabilizing the overall structure. During robotic stabilization, the humans make rope connections, which require high dexterity. The concept and workflow were physically implemented and validated through the cooperative assembly of a complex timber structure over five days. As part of this experimental investigation, we demonstrated and evaluated the performance of two tracking methods that allowed the digitization of the manually placed elements. In closing, the paper discusses the technological challenges and how a hybrid human–robot team could open new avenues for digital fabrication in architecture, accelerating the adoption of robotic technology in AEC.