Multi-range traversability indices for terrain-based navigation

This paper presents novel measures of terrain traversability at three different ranges; 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 within a local perception range, measured by onboard 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 of the terrain within a regional perception range 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 within a global perception range. Each traversability index is represented by four fuzzy,sets with the linguistic labels {POOR, LOW, MODERATE, HIGH}, corresponding to surfaces that are unsafe, moderately-unsafe, moderately-safe, or safe for traversal, respectively. These indices are used. to develop a behavior-based navigation strategy for 6 mobile robot traversing a challenging terrain. The traversability indices form the basis of three navigation behaviors; namely, Traverse-Local, Traverse-Regional, and Traverse-Global-behaviors. These behaviors are integrated with the Seek-Goal behavior to ensure that the mobile robot reaches, the goal safely while avoiding obstacles and impassable terrain segments. The paper is concluded by an illustrative graphical simulation study (1).