Abstract: In this paper, a nonlinear control strategy is designed for a hybrid aerial underwater vehicle (HAUV) in the face of model-ing uncertainties and environmental interference. The controller consists of an adaptive backstepping controller (ABSC) and a nonlinear disturbance observer (NDO). Firstly, the cross-media mechanism of the coaxial water-air trans-domain flying buoy studied in this paper is analyzed and modeled, and some additional variables such as water resistance, buoy-ancy and its corresponding moment and wind wave load are fully considered. A continuous dynamic model is established by designing a smooth transition function. The backstepping controller forms the basis of the controller, and the integrated NDO enhances the robustness of the closed-loop system by estimating lumped uncertainties that are difficult to measure. At the same time, an adaptive algorithm is introduced to compensate the residual error of the observer. The adaptive al-gorithm and NDO work together to improve the robustness of the system. The closed-loop system stability is proved by Lyapunov method. Finally, through Simulink simulation of the proposed controller, the results show that even in the pres-ence of disturbance and uncertainty, the controller has a strong ability to suppress the unknown disturbance, which effec-tively demonstrates the superiority and robustness of the proposed method.

Key words: hybrid aerial underwater vehicle, air-water trans-medium, backstepping controller, nonlinear disturbance observer, robust control