Large-scale multi-robot assembly planning for autonomous manufacturing

Abstract

Mobile autonomous robots have the potential to revolutionize manufacturing processes. However, effective employment of large robot fleets in manufacturing requires addressing numerous challenges including the collision-free movement of multiple agents in a shared workspace, effective multi-robot collaboration to manipulate and transport large payloads, complex task allocation due to coupled manufacturing processes, and spatial planning for parallel assembly and transportation of nested subassemblies. In this work, we propose a full algorithmic stack for large-scale multi-robot assembly planning that addresses these challenges and can synthesize construction plans for complex assemblies with thousands of parts in a matter of minutes. Our approach takes in a CAD-like product specification and automatically plans a full-stack assembly procedure for a group of robots to manufacture the product. We propose an algorithmic stack that comprises: (i) an iterative radial layout optimization procedure to define a global staging layout for the manufacturing facility, (ii) a ‘graph-repair’ mixed-integer program formulation and a modified greedy task allocation algorithm to optimally allocate robots and robot sub-teams to assembly and transport tasks, (iii) a geometric heuristic and a hill-climbing algorithm to plan collaborative carrying configurations of robot sub-teams, and (iv) a distributed control policy that enables robots to execute the assembly motion plan without colliding with each other. We also present an open-source multi-robot manufacturing simulator implemented in Julia as a resource to the research community, to test our algorithmic stack and to facilitate multi-robot manufacturing research more broadly: https://github.com/sisl/ConstructionBots.jl. Our empirical results demonstrate the scalability and effectiveness of our approach by generating plans to manufacture a LEGO® model of a Saturn V launch vehicle with 1845 parts, 306 subassemblies, and 250 robots in under three minutes on a standard laptop computer.