Multi-robot exploration for the CADRE mission

We present the design, implementation and testing of a multi-robot exploration algorithm for NASA’s upcoming Cooperative Autonomous Distributed Robotic Exploration (CADRE) lunar technology demonstration mission. The CADRE mission, among its various objectives, entails utilizing a trio of autonomous mobile robots to collaboratively explore and construct a map of a designated area of the lunar surface. Given the mission’s inherent constraints, including limited mission duration, constrained power resources, and restricted communication capabilities, we formulate an exploration algorithm to improve exploration efficiency, facilitate equitable workload distribution among individual agents, and minimize inter-robot communication. To achieve these requirements, we employ a semi-centralized exploration algorithm that partitions the unexplored area, regardless of its shape and size, into a series of non-overlapping partitions, assigning each partition to a specific robot for exploration. Each robot autonomously explores its designated region without intervention from other robots. We explore the design space of the proposed algorithm and evaluate its performance under diverse conditions in simulations. Finally, we validate the algorithm’s functionality through two sets of hardware experiments: the first utilizes prototype rovers using a ROS-based navigation software stack for feasibility testing, while the second employs high-fidelity development model rovers running CADRE’s custom flight-software stack for flight-like performance validation. Both sets of experiments are conducted in the Jet Propulsion Laboratory’s lunar-simulated rover testing facilities, demonstrating the algorithm’s robustness and readiness for lunar deployment.