The Feasible Transition Graph: Encoding Topology and Manipulation Constraints for Multirobot Push-Planning.

Planning for multirobot manipulation in dense clutter becomes particularly challenging as the motion of the manipulated object causes the connectivity of the robots' free space to change. This paper introduces a data structure, the Feasible Transition Graph (FTG), and algorithms that solve such complex motion planning problems. We define an equivalence relation over object configurations based on the robots' free space connectivity. Within an equivalence class, the homogeneous multirobot motion planning problem is straightforward, which allows us to decouple the problems of composing feasible object motions and planning paths for individual robots. The FTG captures transitions among the equivalence classes and encodes constraints that must be satisfied for the robots to manipulate the object. From this data structure, we readily derive a complete planner to coordinate such motion. Finally, we show how to construct the FTG in some sample environments and discuss future adaptations to general environments.