Sliding mode control for a quadrotor UAV transporting a cable-suspended payload

In this study, a second-order sliding mode control (2-SMC) strategy has been developed to control a small quadrotor UAV with a suspended payload. It is shown that the existence of a load will cause an oscillation on the system and its movement will remarkably change the dynamics of the quadrotor. In order to overcome this, an upgraded 2-SMC has been suggested to ensure the stability of the system. Firstly, the mathematical model of the quadrotor-suspended payload system is derived based on Lagrange approach, then the suggested controller is designed, and the stability of the system is proved by Lyapunov theory. Finally, numerical simulations are carried out to demonstrate the robustness of the proposed method.