REPRESENTING GLOBAL WORLD OF A MOBILE ROBOT WITH RELATIONAL LOCAL-MAPS

Many mobile robot systems adopt a two-dimensional (2-D) map, a top view of the space, represented with a Cartesian coordinate system fixed to an object in the scene, and plan the route to the destination on it. These approaches tend to be brittle, accumulate error and utilize little or no qualitative information. Instead of numerical integration of local maps into a global map, a method for representing a global map consisting of local map representations and relations between them has been developed. Sensor maps (maps of which origins are fixed to the moving sensor) viewed at locations close to each other are integrated into a local map representation in a Cartesian coordinate system fixed to an object. First, three-dimensional (3-D) information of the edges on the floor is obtained at each sensor map by assuming the camera model and the flatness of the floor. A reliable feature is selected as a reference in a sensor map, which has important roles in finding the correspondence between the current sensor map and the following ones and in building a local map with these sensor maps. During the motion of the robot, the local map is updated by the motion stereo method unless the current reference point disappears from the sensor map. Farther edges should be represented in other local maps when the robot approaches to them since the precise estimation of their locations in the current local map is difficult. Finally, the relation between local maps that represents the relative orientation and the approximate distance from the previous local map to the current one is included in the global map. The method is tested in an indoor environment and experimental results are shown. © 1990 IEEE