Sequential Manipulation Planning for Over-Actuated Unmanned Aerial Manipulators

We investigate the sequential manipulation planning problem for unmanned aerial manipulators (UAMs). Unlike prior work that primarily focuses on one-step manipulation tasks, sequential manipulations require coordinated motions of a UAM's floating base, the manipulator, and the object being manipulated, entailing a unified kinematics and dynamics model for motion planning under designated constraints. By leveraging a virtual kinematic chain (VKC)-based motion planning framework that consolidates components' kinematics into one chain, the sequential manipulation task of a UAM can be planned as a whole, yielding more coordinated motions. Integrating the kinematics and dynamics models with a hierarchical control framework, we demonstrate, for the first time, an over-actuated UAM achieves a series of new sequential manipulation capabilities in both simulation and experiment.

I. Introduction

Combining the agility of unmanned aerial vehicles (UAVs) and the flexibility of manipulators, UAMs can conduct manipulation tasks across rough terrains and in regions unreachable by ground robots [1]–[3]. Oftentimes, a fully-or even over-actuated UAV serves as the UAMs' flying vehicle [4]–[6]; this type of UAVs can track position and orientation independently to provide the UAM with more agile maneuver, achieve a larger reachable workspace, and obtain better dynamic properties compared with traditional multirotors. Existing UAMs leverage a bi-level schema by combining (i) a controller to stabilize the system and track the desired trajectory under forceful contacts with the environment and (ii) a motion planner to produce trajectories satisfying task-related constraints. Such a bi-level schema has succeeded in various aerial manipulation tasks, such as pick-and-place [3], [7], inspection [8], [9], valve operation [10], and door-like articulated object manipulation[11], [12].