Safe and Efficient Navigation in Extreme Environments Using Semantic Belief Graphs

To achieve autonomy in unknown and unstruc- tured environments, we propose a method for semantic-based planning under perceptual uncertainty. This capability is cru- cial for safe and efficient robot navigation in environment with mobility-stressing elements that require terrain-specific locomotion policies. We propose the Semantic Belief Graph (SBG), a geometric- and semantic-based representation of a robot’s probabilistic roadmap in the environment. The SBG nodes comprise of the robot geometric state and the semantic- knowledge of the terrains in the environment. The SBG edges represent local semantic-based controllers that drive the robot between the nodes or invoke an information gathering action to reduce semantic belief uncertainty. We formulate a semantic- based planning problem on SBG that produces a policy for the robot to safely navigate to the target location with min- imal traversal time. We analyze our method in simulation and present real-world results with a legged robotic platform navigating multi-level outdoor environments.