This paper presents a self-contained system for the robust utilization of aerial robots in the autonomous exploration of cave environments to help human explorers, first responders, and speleologists. The proposed system is generally applicable to an arbitrary exploration task within an unknown and unstructured subterranean environment and interconnects crucial robotic subsystems to provide full autonomy of the robots. Such subsystems primarily include mapping, path and trajectory planning, localization, control, and decision making. Due to the diversity, complexity, and structural uncertainty of natural cave environments, the proposed system allows for the possible use of any arbitrary exploration strategy for a single robot, as well as for a cooperating team. A multi-robot cooperation strategy that maximizes the limited flight time of each aerial robot is proposed for exploration and search & rescue scenarios where the homing of all deployed robots back to an initial location is not required The entire system is validated in a comprehensive experimental analysis comprising of hours of flight time in a real-world cave environment, as well as by hundreds of hours within a state-of-the-art virtual testbed that was developed for the DARPA Subterranean Challenge robotic competition. Among others, experimental results include multiple real-world exploration flights traveling over 470 meters on a single battery in a demanding unknown cave environment.

翻译：本文提出了一套自包含系统，用于实现空中机器人在洞穴环境自主探索中的稳健应用，以协助人类探险者、应急救援人员和洞穴学家。所提出的系统普遍适用于未知非结构化地下环境中的任意探索任务，通过连接关键机器人子系统为机器人提供完全自主能力。这些子系统主要包括建图、路径与轨迹规划、定位、控制及决策制定。鉴于天然洞穴环境的多样性、复杂性与结构不确定性，该系统支持单机器人及协作机器人团队采用任意探索策略。针对探索与搜救场景（无需所有部署机器人返回初始位置），提出了一种最大化每架空中机器人有限飞行时间的多机器人协作策略。通过包含真实洞穴环境中累计数小时飞行时间的实验分析，以及为DARPA地下挑战赛机器人竞赛开发的最先进虚拟测试平台中数百小时的验证，完成了整个系统的评估。实验结果表明，在具有挑战的未知洞穴环境中，单次电池续航可支撑多次真实探索飞行，飞行距离超过470米。