Topological exploration of unknown and partially known environments

We present the mathematical framework and algorithms for multi-robot topological exploration of unknown environments in which the main goal is to identify the different topological classes of trajectories and thus efficiently distribute the task of exploration among different groups of robots. We consider two-dimensional configuration spaces. At any point in time, the robots' map consists of known, partially-mapped obstacles. The unknown, yet-to-be-explored area is mapped to a single point, thus giving us a quotient space. The topological classes on the quotient space allows us to define topological classes of trajectories connecting a robot pose to the unknown region in the original configuration space. Robots explore this configuration space choosing different homology classes when confronted by obstacles or walls. We illustrate the basic idea with simulations of small teams of robots. Experiments with a single robot illustrate the applicability of the method to robots that have small sensor footprints and limited computational resources. We also provide comparisons with a standard frontier-based algorithm.