ROS 2-based autonomous navigation strategy for a lunar rover featuring multiple locomotion modes

Autonomous navigation is essential for planetary rovers, supporting science, maintenance tasks, and reliable operation in environments with limited human oversight and communication. Its role becomes even more crucial in unstructured terrains like the lunar surface, where adaptability, safety, and efficiency are paramount. This paper proposes and validates an extension of the state-of-the-art ROS 2-based Nav2 navigation framework, aimed at enhancing rover maneuverability by integrating an additional degree of freedom provided by a variety of steering-based locomotion modes, enabling the rover to effectively tackle diverse environmental challenges. The autonomous navigation system is tailored for a non-holonomic, non-skid-steering lunar rover prototype equipped with four independently steerable wheels, drawing inspiration from cutting-edge designs employed in recent proposals, such as NASA's RP15, NASA's VIPER, and ESA's EMRS. The proposed architectural framework leverages a behavior-tree-based approach to integrate path planning, maneuver selection, and secure trajectory tracking, enabling the rover to dynamically adapt its locomotion mode to terrain conditions and operational needs, such as dead-end navigation, solar panel alignment, or terrain stability, while prioritizing safety and energy efficiency for reliable, sustainable operation. The performance of the autonomous maneuvering strategy is validated through extensive simulations and real-world field tests with the European Moon Rover System (EMRS) prototype at the TAS-I RoXY outdoor facility in Turin. Experimental results confirm the rover's ability to navigate autonomously, adapt its strategies to diverse environmental conditions, and effectively achieve mission objectives, demonstrating the robustness, flexibility, and scalability of the proposed system for future lunar exploration missions.