A hierarchical decoupled approach for multi robot motion planning on trees

In this paper, the multi robot motion planning problem is solved through a decoupled approach, where a new algorithm for prioritizing the robots moves is developed. Assuming that the workspace is mapped into a tree graph and the initial and final configurations of robots are known, the robots' shortest start-to-goal paths on the tree are calculated independently. Then, a new rule-based prioritization scheme is applied in two phases: (a) Path Prioritization, which determines which robot can directly move along its shortest path and which robot should deviate from it, and (b) Motion Prioritization, which decides the order of robots' sequential moves. Furthermore, an algorithm is presented for minimizing the number of moves by adding extra vertices to the tree.