Nonlinear Characteristic Model-Based Discrete-Time Sliding Mode Control for the Hovering Flight of an Aerial Manipulator

Stable and precise hovering flight control is essential for successful aerial manipulator (AM) operations, especially when a persistently moving onboard manipulator causes nonnegligible coupling disturbances. In this article, a novel discrete-time characteristic modeling and control method is proposed to improve the coupling disturbance suppressing ability of an AM. First, characteristic modeling of system dynamics is achieved by a newly designed identification method based on dual-source error, which greatly reduces model complexity compared to traditional dynamic modeling. Second, a novel output-feedback attitude controller is proposed using the characteristic model and a discrete-time sliding mode surface, which does not require accurate dynamic analysis and is thus easy to implement in practice. Then, the finite-time stability of the attitude control system and the boundedness of the attitude tracking error are proved by theoretical analysis. Finally, real flight experiments for validation and comparison with three state-of-the-art methods are conducted using a self-built AM platform. The results demonstrate that the proposed method has stronger robustness against coupling effects and achieves higher hovering precision when the onboard manipulator is persistently moving.