Exploration of unknown environments with a tethered mobile robot

This paper presents a tangle-free frontier based exploration algorithm for planar mobile robots equipped with limited length and anchored tethers. After planning a path to the closest point in the frontier between free and unknown space, the robot computes an estimate of the future length of its tether and decides, by comparing the anticipated length with the minimum possible tether length, whether the path should be followed or not. If the anticipated tether is longer than the minimum tether by a function of the expected radius of the obstacles, a path planner with homotopic constraints is used to plan a path that brings the robot tether to the same homotopy class of the shortest tether. This behavior will not only limit the tether length but also will prevent tether entangling on the obstacles of the environment. We evaluate our method in different simulated environments and illustrate the approach with an actual tethered robot.