We propose and experimentally demonstrate a reactive planning system for bipedal robots on unexplored, challenging terrains. The system consists of a low-frequency planning thread (5 Hz) to find an asymptotically optimal path and a high-frequency reactive thread (300 Hz) to accommodate robot deviation. The planning thread includes: a multi-layer local map to compute traversability for the robot on the terrain; an anytime omnidirectional Control Lyapunov Function (CLF) for use with a Rapidly Exploring Random Tree Star (RRT*) that generates a vector field for specifying motion between nodes; a sub-goal finder when the final goal is outside of the current map; and a finite-state machine to handle high-level mission decisions. The system also includes a reactive thread to obviate the non-smooth motions that arise with traditional RRT* algorithms when performing path following. The reactive thread copes with robot deviation while eliminating non-smooth motions via a vector field (defined by a closed-loop feedback policy) that provides real-time control commands to the robot's gait controller as a function of instantaneous robot pose. The system is evaluated on various challenging outdoor terrains and cluttered indoor scenes in both simulation and experiment on Cassie Blue, a bipedal robot with 20 degrees of freedom. All implementations are coded in C++ with the Robot Operating System (ROS) and are available at https://github.com/UMich-BipedLab/CLF_reactive_planning_system.
翻译:我们提议并在实验中展示一个反应式规划系统,用于在未探索、具有挑战性地形上的双栖机器人。这个系统包括一个低频规划线(5 Hz),以寻找一个无干扰的最佳路径和高频反应线(300 Hz),以适应机器人偏差。这个规划线包括:一个多层本地地图,用以计算机器人在地形上的可穿行性。一个随时随机的全向控制 Lyapunov 函数(CLF),用于快速探索随机树星(RRRT*),生成一个矢量字段,用于指定节点之间的运动;当最终目标超出当前地图时,一个子目标查找器;以及一个处理高层任务决定的定时反应线(300 Hz)。这个系统还包括一个可避免传统 RRT* 计算路径运行过程中产生的非瞬间移动动作的本地地图;一个活性线与机器人偏移同时通过矢量场(由闭路反馈政策定义)消除非移动运动运动动作(由闭式反馈政策定义),为机器人的实时控制命令,在目前地图轨道/直径直径的轨道上,一个直径直径直径机机机机机机机机操作系统将自动操作系统进行。