Loop exploration for SLAM with fusion of advanced sonar features and laser polar scan matching

SLAM is a well studied technique for robots to build a map of environments while at the same time keeping track of their pose (position and orientation). However SLAM does not provide control approaches for how the robot moves around the environment. This paper presents an integrated approach to create a fully autonomous exploring and mapping robot. An EKF-SLAM approach is used to fuse Advanced Sonar and Laser Scan-Matching. This also tackles the problem of map-drifts in some types of environment where lasers do not supply sufficient information in some directions such as along a corridor. In addition, the proposed exploration algorithm takes advantage of the characteristic of the Voronoi Graph to enable the robot to strategically explore the environments in a loop-closing fashion and safe manner. By revisiting areas to close loops as early as possible, the robot can build a more stable map incrementally while still reliably tracking its pose. Experimental results of the integrated approach are shown to demonstrate the algorithm provides real-time exploration of a mobile robot in an initially unknown real environment. Experimental comparisons of exploration strategies with and without early local loop closing demonstrate the benefits of the approach in the map quality.