Princeton robot uses projector and laser for precise masonry collaboration

Princeton University researchers Jutang Gao and Arash Adel have published a paper detailing an adaptive human‑robot collaborative workflow for masonry construction. The system addresses two major challenges: limited robot‑to‑human communication and the accumulation of tolerances from material and assembly uncertainties. In their brickwork case study, a robot handles brick placement while a human applies adhesive. The workflow is enabled by two complementary mechanisms: an end‑effector‑mounted projector that provides spatially registered, just‑in‑time projection guidance for manual adhesive application, and laser scanning that enables feedback‑driven grasping and placement pose correction. Together, these mechanisms allow both human and robot actions to adjust in response to material variability and accumulated assembly tolerances.

Full‑scale experiments were conducted using conventional running‑bond patterns and nonstandard configurations. Results demonstrated that projection guidance significantly improves adhesive application consistency and reduces application time. The laser‑based correction system maintained level courses and avoided collision‑prone failures that typically occur in open‑loop execution. The authors conclude that integrating spatial projection with feedback‑driven adaptation – enabled by material and as‑built sensing – can mitigate tolerance accumulation and improve both precision and robustness in human‑robot collaborative construction. The paper has been accepted for publication in the Proceedings of the 43rd International Symposium on Automation and Robotics in Construction (ISARC 2026).