Aerial cooperative robotic manipulation of cable-suspended objects has been largely studied as it allows handling large and heavy objects, and cables offer multiple advantages, such as their low weight and cost efficiency. Multirotors have been typically considered, which, however, can be unsuitable for long-lasting manipulation tasks due to their scarce endurance. Hence, this work investigates whether non-stop flights are possible for maintaining constant the pose of cable-suspended objects. First, we show that one or two flying carriers alone cannot perform non-stop flights while maintaining a constant pose of the suspended object. Instead, we demonstrate that \emph{three} flying carriers can achieve this task provided that the orientation of the load at the equilibrium is such that the components of the cable forces that balance the external force (typically gravity) do not belong to the plane of the cable anchoring points on the load. Numerical tests are presented in support of the analytical results.

翻译：空中协同机器人操作悬吊物体已被广泛研究，因为该方法可处理大型重型物体，且缆绳具备重量轻、成本效益高等多重优势。通常采用多旋翼飞行器，但其续航能力有限，难以适用于持久性操控任务。为此，本文探究能否通过非停飞模式保持悬吊物体位姿恒定。首先证明：单个或两个运载体单独无法在维持悬吊物体位姿恒定的条件下实现非停飞。反之，我们论证了当平衡状态下负载朝向满足缆绳力分量（用于平衡外力，通常为重力）不属于负载缆绳锚点平面时，三个运载体可完成该任务。数值实验结果验证了理论分析结论。