Takeoff and Landing Control of a Hybrid Aerial Underwater Vehicle on Disturbed Water’s Surface

This article proposes a disturbance observer-based nonlinear control strategy for the accurate takeoff and landing control of a novel hybrid aerial underwater vehicle, Nezha III, subjected to wave and wind. The approach consists of the dynamic surface controller (DSC) and the nonlinear disturbance observers (NDOs). The problem is first modeled with full consideration of diverse external forces, including the capsizing buoyant moment, the added mass effect, and wave and wind loads. The DSC forms the base of the controller and benefits the tracking behavior by handling the nonlinearity of the system. Meanwhile, the integrated NDOs enhance the robustness of the closed-loop system by estimating the unmeasurable external forces. The proposed method is proved theoretically to stabilize the vehicle when it tracks the reference trajectory across different media in the presence of environmental disturbances. Finally, the proposed controller is tested numerically by challenging it under the wind and wave disturbances. The results show the controller makes Nezha III achieve successful takeoff and landing on the disturbed water’s surface in spite of the hazardous environment, which strongly evidence the outstanding performance of the proposed method.