Combining metric and topological navigation of simulated robots

Mobile robotics and robot navigation is a growing area of scientific research. Robot simulators are useful designing and analizing tools of this domain. Webots ([1]) is a well-known representant of these programs, a three-dimensional mobile robot simulator. Various guidance principles can be developed in C/C++ or Java programming language with the use of Webots controller programs. In this paper a short overview is given about the problems arising in the process of the navigation, and a short taxonomy is presented about the possible problem solving methods ([2]). A brief introduction to the probabilistic navigation techniques concerning Kalman filter and expectation maximization is included with a special focus on occupancy grid. Formerly I presented a metric navigation method based on occupancy grid working in the Webots simulation environment ([3]). As a continuation of that research I created an enhancement of the former processes, a hybrid metric-topological navigation mechanism. A topologic layer is introduced in the environment exploration phase replacing the older value iteration ([4]). The implementation of a topologic graph of the explorable places using the metric map enables the robot to navigate in a more efficient manner. A comparison of the pure metric and the new hybrid methods is also given.