Rule-based traversability indices for multi-scale terrain assessment

This paper presents novel measures of terrain traversability at three different scales of resolution; namely local, regional, and global traversability indices. The local traversability index is related by a set of linguistic rules to local obstacles and surface softness, measured by on-board sensors mounted on the robot. The rule-based regional traversability index is computed from the terrain roughness and slope that are extracted from video images obtained by on-board cameras. The global traversability index is obtained from the terrain topographic map, and is based on the natural or man-made surface features such as mountains and craters. Each traversability index is represented by four fuzzy sets with the linguistic labels, corresponding to surfaces that are unsafe, moderately-unsafe, moderately-safe, or safe for traversal, respectively.