Disturbance observer-based robust coordination control for unmanned autonomous helicopter slung-load system via coupling analysis method

This work studies the robust coordination control for a strong coupled and under-actuated unmanned autonomous helicopter (UAH) slung-load system subject to external disturbances. Firstly, disturbance observers are designed to obtain the disturbance estimations, and a dynamic coupling matrix is introduced to describe the coupling relationships between the UAH system and the slung-load system. Secondly, based on the proposed coupling matrix, a disturbance observer-based coordination control scheme is designed for the position system of the UAH and the slung-load one by using hierarchical sliding mode control. Thirdly, an improved controller is designed for the attitude system of the UAH by combining the backstepping control, disturbance observer, and dynamic surface control, in which the detrimental coupling is suppressed while the beneficial one is retained to improve control performance. Especially, the stability for the overall closed-loop system is guaranteed based on Lyapunov stability theory. Finally, some simulations are presented to show the effectiveness and advantage of the proposed control scheme.