Robust Nonlinear Control for Quadrotor Slung Load System Subject to External Disturbances

Unmanned aerial vehicles serve as carriers for diverse payloads, emphasizing the importance of achieving load transportation with trajectory-smoothing capabilities to ensure safety. Addressing the challenge of payload transport in varying environments involves coping with external disturbances like wind and uncertainties linked to the payload. This paper introduces a control strategy consisting of two loops. The outer loop employs robust backstepping control to attain Euler angles and control laws. Meanwhile, the inner loop utilizes a controller combining backstepping and fast terminal sliding mode control to regulate the yaw angle and tilting angles. The research adopts a comprehensive modeling approach, using the Lagrange-Euler method for the translational subsystem of the quadrotor and dynamic modeling for the suspended load, alongside the Newton-Euler method for the rotational subsystem. The aim is to identify a suitable control strategy that ensures practical guidance and stability for the entire system. The proposed method exhibits robust performance in tracking desired trajectories and managing load perturbations within a finite time. Lastly, simulation results are presented, comparing the proposed control method with other approaches. The simulations demonstrate the superior performance of the proposed control method over other techniques