Sliding into Balance: Benefits of a Sliding Payload for Load Distribution and Disturbance Rejection in Dual-UAV Transportation

This paper analyzes the cooperative transportation of a payload suspended from two drones in which, instead of being attached to two independent ropes, the payload is allowed to slide along a single rope connecting both UAVs. First, a planar nondimensional dynamical model of the sliding motion with viscous friction is presented. Then, considering stationary drones, this configuration is compared with a fixed payload with the same total rope length, both at equilibrium and under disturbances. The analytical results show that the sliding payload equalizes the tension in both rope segments for any relative position of the drones, so that no rope loses tension at equilibrium; it doubles the region reachable by the payload and, except for low friction combined with a large drone separation, it enlarges the set of admissible disturbances. Finally, a dynamic simulation also shows that under realistic gusty wind profiles, the average tension imbalance between the drones is reduced with respect to the fixed-payload solution.