To achieve high-dexterity motion planning on floating-base systems, the base dynamics induced by arm motions must be treated carefully. In general, it is a significant challenge to establish a fixed-base frame during tasking due to forces and torques on the base that arise directly from arm motions (e.g. arm drag in low Reynolds environments and arm momentum in high Reynolds environments). While thrusters can in theory be used to regulate the vehicle pose, it is often insufficient to establish a stable pose for precise tasking, whether the cause be due to underactuation, modeling inaccuracy, suboptimal control parameters, or insufficient power. We propose a solution that asks the thrusters to do less high bandwidth perturbation correction by planning arm motions that induce zero perturbation on the base. We are able to cast our motion planner as a nonholonomic rapidly-exploring random tree (RRT) by representing the floating-base dynamics as pfaffian constraints on joint velocity. These constraints guide the manipulators to move on zero-perturbation manifolds (which inhabit a subspace of the tangent space of the internal configuration space). To invoke this representation (termed a \textit{perturbation map}) we assume the body velocity (perturbation) of the base to be a joint-defined linear mapping of joint velocity and describe situations where this assumption is realistic (including underwater, aerial, and orbital environments). The core insight of this work is that when perturbation of the floating-base has affine structure with respect to joint velocity, it provides the system a class of kinematic reduction that permits the use of sample-based motion planners (specifically a nonholonomic RRT). We show that this allows rapid, exploration-geared motion planning for high degree of freedom systems in obstacle rich environments, even on floating-base systems with nontrivial dynamics.

翻译：为实现浮基系统的高灵巧运动规划，需谨慎处理由机械臂运动引起的基座动力学效应。通常，由于机械臂运动直接作用于基座的力与力矩（例如低雷诺数环境下的臂拖曳力及高雷诺数环境下的臂动量），在任务执行过程中建立固定基座坐标系具有显著挑战性。虽然理论上可借助推进器调节航行器位姿，但受制于欠驱动、建模误差、控制参数次优或功率不足等因素，往往难以建立用于精密操作的稳定位姿。我们提出一种解决方案，通过规划对基座产生零扰动的机械臂运动，降低推进器的高带宽扰动修正需求。通过将浮基动力学表征为关节速度的Pfaffian约束，我们将运动规划器构建为非完整快速探索随机树（RRT）。这些约束引导机械臂在零扰动流形（位于内部构型空间切空间的子空间中）上运动。为调用该表征（称为"扰动映射"），我们假设基座体速度（扰动）是关节速度的关节定义线性映射，并描述了该假设切实可行的场景（包括水下、空中及轨道环境）。本工作的核心洞见在于：当浮基扰动与关节速度具有仿射结构时，系统可获得一类运动学降阶特性，从而允许使用基于采样的运动规划器（特指非完整RRT）。研究表明，这种方法能够为高自由度系统在复杂障碍环境中实现快速探索导向的运动规划，即便在具有非平凡动力学的浮基系统上同样有效。