Nonlinear Robust Control for Dual-UAV Collaborative Aerial Transportation System

Quadrotor UAVs have the advantages of high flexibility and mobility, and the use of UAVs for transportation tasks can avoid the restrictions of complex terrain while improving transportation efficiency and reducing transportation costs. However, as the load capacity of a single UAV is very limited, multiple UAVs are introduced for coordinated transport to increase the system’s capacity. Aiming at transporting bar-shaped cargos, this paper studies the dual-UAV cooperative transportation system. However, compared with the single UAV transportation system, the dual-UAV cooperative transportation system has higher degrees of freedom, stronger nonlinearity, and more complex state coupling. Besides, considering the uncertainty and complexity of the actual environment, the system may encounter external disturbances during actual flight. Thus, to overcome the aforementioned challenges, an effective control scheme is urgently needed to ensure precise UAV positioning and cargo swing suppression for smooth cargo transportation. Therefore, this paper proposes a nonlinear robust control scheme based on the finite-time disturbance observer for the dual-UAV collaborative aerial transportation system. Subsequently, the convergence of the equilibrium point is proved by Lyapunov techniques and LaSalle’s Invariance Theorem. Finally, the excellent performance and robustness of the proposed control scheme are verified by groups of simulations.