Using Local Force Measurements to Guide Construction by Distributed Climbing Robots

Construction automation has historically been driven by top-down implementations of specific tasks, which are neither responsive nor resilient to dynamic situations, and often require centralized control or human supervision. Previous work on robotic assembly has generally neglected to consider forces acting on the structure, whether in the completed structure alone or throughout the building process. In this paper, we investigate the utility of local force measurements in guiding construction by a distributed team of strut-climbing robots, focusing on a scenario involving building an unsupported span out across a gap in a two-dimensional vertical plane, as a step towards building a bridge. We show that such measurements enable robots to build structures that cantilever significantly further than those built by robots without access to such information, while maintaining stability throughout the building sequence. We consider both structures securely anchored to the ground and those resting unanchored atop it, using a counterbalancing approach in the latter case to permit cantilevering. The principles explored in simulation are also demonstrated in hardware, including a prototype strut-climbing robot and truss components, incorporating a cost-effective sensor implementation that reports the requisite force information.