Adaptive Robust Control via a Nonlinear Disturbance Observer for Cable-driven Aerial Manipulators

This article proposes a novel robust control scheme for the trajectory tracking control of a cable-driven aerial manipulator in joint space, combining an adaptive fractional-order nonsingular terminal sliding mode (FONTSM) manifold and a nonlinear disturbance observer (NDOB). The proposed control scheme mainly consists of three aspects, i.e., an NDOB used to estimate the unmodeled dynamics and external disturbances, a FONTSM applied to guarantee the control accuracy of the tracking performance, and an adaptive reaching law applied to improve the robustness. The proposed scheme is based on the model-free idea that can reduce the difficulty of controller design without knowing the precise dynamics of the plant. The experimental results show that the proposed controller can ensure better transient performance and stronger robustness against lumped disturbances than two other existing controllers.