Improved extended disturbance observer-based integral backstepping sliding mode control for quadrotor slung-load system

Abstract

Quadrotor slung-load (QSL) systems are commonly employed in aerial transportation tasks, where precise trajectory tracking and effective load swing suppression are critical challenges. These objectives are challenged by model uncertainties and unknown environmental disturbances, such as wind, which can compromise system stability and control accuracy. This paper addresses these challenges by developing a novel control strategy for QSL systems, where the system dynamics are divided into the attitude, position, and swing angle of the slung-load. Wind disturbances, including turbulence and wind shear, are modeled to simulate realistic outdoor scenarios. The integration backstepping control method forms the basis of the controller design, the sliding mode control is added to enhance the control accuracy and robustness while reducing steady-state error. An improved extended disturbance observer (IEDO) is incorporated to estimate and compensate for unknown disturbances and model uncertainties. The stability of the proposed controller and the convergence of the disturbance observer are rigorously analyzed using Lyapunov theory. Simulation results demonstrate the effectiveness of the proposed approach, achieving significant reductions in trajectory tracking errors and slung-load swing, even under complex and varying disturbance conditions.