Map based navigation is a crucial task for any mobile robot. On many platforms this problem is addressed by applying Simultaneous Localization and Mapping (SLAM) based on metric grid-maps. Such solutions work well on robots with adequate resources and limited workspaces. Platforms with limited payload which operate in unbounded workspaces, do often have insufficient resources to keep a metric world representation. Nevertheless, many applications demand that the robot can autonomously navigate between different operation areas. In this work the Landmark-Tree map (LT-map), a resource efficient topological map concept, is for the first time applied to a mobile robotic platform equipped with an omnidirectional camera. It enables the robot to efficiently adapt the acquired map online to the available memory. During map acquisition and navigation the motion is estimated by the Z∞-algorithm. Both methods are based on similar concepts, which results in a mutual benefit. An efficient navigation strategy based on the LT-map allows the robot to reliably follow previously recorded paths. The presented approach is evaluated on a mobile robot in indoor and outdoor scenarios. The experiments prove its feasibility and show that pruning the map just smooths the trajectories, which is the expected and desired behaviour.
I. MOTIVATIONAutonomous navigation is a highly complex task, which often requires most resources on mobile robots. In general, robotic platforms build metric maps during exploration and localize themselves within these maps. A large variety of approaches for this so called Simultaneous Localization and Mapping (SLAM) concept exist in literature [1]. They differ in the way the map is organized and the localization is performed, but they, in general, have in common to rely on a metric representation of the environment. While such a metric map eases many computation steps, e.g. accurate planning of new trajectories, it requires a significant amount of memory to represent the environment.Many applications require resource limited robots to cover long distances, which connect different workspaces: a Micro Aerial Vehicle (MAV), which starts at the rescue team and flies in a specific direction to detect people who require help, or a rover on a foreign planet which has to find back to the base station after some time for analysing the collected probes. Such applications do not require a complete metric representation of the environment, but rather local metric maps at the locations of operation and resource efficient This work was supported by the Institute of Robotics and Mechatronics of the German Aerospace Center (DLR).