Coupled Dynamic Modeling and Analysis of Unmanned Aerial Vehicle Loaded Towed Antenna

Airborne towed-antenna systems have significant application potential in scenarios such as very-low-frequency communications, owing to their flexible deployment and high survivability. The system considered herein consists of an unmanned aerial vehicle (UAV) and a flexible towed antenna and exhibits pronounced nonlinearity and strong bidirectional coupling. To address the difficulty of providing a unified description of the two-way interactions between the UAV and the towed body, a coupling-oriented dynamic modeling approach for a UAV sling-loaded towed-antenna system is proposed. First, the towed antenna is discretized into multiple elements, and its flexible dynamics are formulated using the absolute nodal coordinate formulation. Subsequently, a six-degree-of-freedom rigid-body dynamic model of a quadrotor UAV is established. A bidirectional coupling mechanism incorporating kinematic constraints and force feedback is then constructed: the UAV center of mass is equivalently mapped to the top-end node of the antenna to transmit the UAV pose to the flexible body, while the equivalent towing load acting on the UAV is obtained by synthesizing the nodal external forces and inertial terms of the antenna. In this manner, a closed-loop force/pose coupling model at the UAV/antenna connection point is achieved. Finally, based on the developed coupled model, a model predictive control trajectory-tracking controller is designed, and comparative simulations against a proportional/integral/derivative controller are conducted.