Finite-time swing attenuation for differentially flat quadrotor slung-load systems via robust AFITSM-OSMC partitioned...

This paper addresses the swing attenuation problem in quadrotor slung-load systems, which is challenging due to nonlinearity, underactuation, and strong dynamic coupling. A robust partitioned control strategy is proposed to handle model uncertainties, external disturbances, and load variations. By establishing the differential flatness of the system with load position and quadrotor yaw angle as flat outputs, the dynamics are partitioned into a fully actuated subsystem (FAS) and an underactuated subsystem (UAS). For the FAS, a novel adaptive nonsingular fast integral terminal sliding mode (AFITSM) controller is developed. It ensures finite-time convergence and enhances robustness through online estimation of lumped uncertainties. For the UAS, an overall sliding mode control (OSMC) strategy is formulated to coordinate lateral motion for swing damping. Comprehensive validation studies demonstrate that the proposed AFITSM-OSMC reduces tracking RMSE by 89%-99% and swing angle by 87%-93% compared to benchmark methods, while guaranteeing finite-time convergence within 1.7s under various uncertainties and disturbances. Under dynamic load variations, it limits maximum swing to 7.2^∘ and achieves rapid stabilization, whereas benchmarks fail to settle. Moreover, control chattering is drastically suppressed, and peak torque rates are reduced by over 85%. The scheme offers superior tracking precision, rapid swing attenuation, robustness, and practical deployability.