Topological navigation and qualitative localization for indoor environment using multi-sensory perception

This article describes a navigation system for a mobile robot which must execute motions in a building; the robot is equipped with a belt of ultrasonic sensors and with a camera. The environment is represented by a topological model based on a Generalized Voronoi Graph (GVG) and by a set of visual landmarks. Typically, the topological graph describes the free space in which the robot must navigate; a node is associated to an intersection between corridors, or to a crossing towards another topological area (an open space: rooms, hallways, ...); an edge corresponds to a corridor or to a path in an open space. Landmarks correspond to static, rectangular and planar objects (e.g. doors, windows, posters, ...) located on the walls. The landmarks are only located with respect to the topological graph: some of them are associated to nodes, other to edges. The paper is focused on the preliminary exploration task, i.e. the incremental construction of the topological model. The navigation task is based on this model: the robot self-localization is only expressed with respect to the graph.