Incremental online topological map building with a mobile robot

We present a behavior-based technique for incremental on-line mapping and autonomous navigation for mobile robots, specifically geared for time-critical indoor exploration tasks. The experimental platform used is a Pioneer AT mobile robot endowed with seven sonar transducers, a drift-stabilized gyro, a compass and a pan-tilt color camera. While the thrust of our work is the autonomous generation of real-time topological maps of the environment, both metric and topological descriptions of the environment are created in real time, each preserving its unique representational power and ease-of-use. We also present initial results on multi-robot cooperative topological mapping. The building blocks of the topological map are corridors, junctions and open/closed doors, augmented with absolute heading and metric information. Since the robot does not begin with an a priori map, all environmental features have to be evaluated at run-time to ensure safe navigation and efficient exploration. Our enhanced dead-reckoning algorithm is backed up by the cyclic nature of indoor environments that provides additional hints for self-localization corrections. In addition, domain knowledge (such as perpendicular hallways) is used to actively correct maps as they are built on-line. All navigation, exploration, map building and self-localization capabilities are implemented as tightly-coupled behaviors, run by the onboard CPU.