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Polar Traversability Index: A Measure of terrain traversal property for mobile robot navigation in urban environments

This paper presents a terrain mapping system and a terrain traversability analysis method for mobile robot navigation in urban environments. The terrain mapping system employs a 2-D Laser Rangefinder (LRF). In order to generate a reliable elevation map for navigation, a filtering method based on robot motion constraint and the LRF's characteristics is used to remove range data. A so-called "Polar Traversability Index" measure is proposed to evaluate terrain traversal property. A PTI dictates the level of difficulty for a robot to move along the corresponding direction and it can be used to guide the robot in urban environments. For instance, it enables the robot to traverse wheelchair ramps and avoid curbs when negotiating sidewalks. The efficacy of the PTI has been verified by simulation and experiments in a complete navigation system.