Payload grasping and transportation with quadcopters is an active research area that has rapidly developed over the last decade. To grasp a payload without human interaction, most state-of-the-art approaches apply robotic arms that are attached to the quadcopter body. However, due to the large weight and power consumption of these aerial manipulators, their agility and flight time are limited. This paper proposes a motion control and planning method for transportation with a lightweight, passive manipulator structure that consists of a hook attached to a quadrotor using a 1 DoF revolute joint. To perform payload grasping, transportation, and release, first, time-optimal reference trajectories are designed through specific waypoints to ensure the fast and reliable execution of the tasks. Then, a two-stage motion control approach is developed based on a robust geometric controller for precise and reliable reference tracking and a linear--quadratic payload regulator for rapid setpoint stabilization of the payload swing. Furthermore, stability of the closed-loop system is mathematically proven to give safety guarantee for its operation. The proposed control architecture and design are evaluated in a high-fidelity physical simulator, and also in real flight experiments, using a custom-made quadrotor--hook manipulator platform.

翻译：四旋翼无人机的载荷抓取与运输是近十年来快速发展的活跃研究领域。为在不借助人工交互的情况下抓取载荷，现有主流方法多采用附着于四旋翼机身的机械臂。然而，此类空中机械臂因质量大、功耗高，会显著限制无人机的机动性与续航时间。本文提出一种基于轻量化被动操纵结构的运动控制与规划方法，该结构通过1自由度旋转关节将钩爪连接至四旋翼机体。为实现载荷抓取、运输与释放，首先通过特定航点设计时间最优参考轨迹，确保任务快速可靠执行；继而开发两阶段运动控制方法：基于鲁棒几何控制器实现精准可靠的参考轨迹跟踪，并采用线性二次型载荷调节器快速实现载荷摆动的定点稳定。此外，从数学上证明了闭环系统的稳定性，为其运行提供安全保障。在自行搭建的四旋翼-钩爪操纵平台中，通过高保真物理仿真与真实飞行实验对所提控制架构与设计方案进行了评估。