Robust Trajectory Tracking Control of a Multi-Rotor UAV Carrying a Cable Suspended Load

In this paper, the synthesis of a robust trajectory tracking controller for a UAV carrying a slung load is presented using hierarchical sliding mode and super-twisting methodologies. A second-order sliding mode disturbance observer is used in conjunction with the sliding mode controller. Since the slung load system is underactuated, the sliding mode closedloop dynamics is analyzed to derive conditions for the sliding surface parameters that guarantee stability. Lyapunov analysis is used to prove the stability of the system. A controllability analysis is also carried out. Simulation results are presented for different cases to demonstrate the performance of the proposed controller.