基于非线性干扰观测器的UUV反演滑模深度控制

针对水下无人航行器（UUV）在浅水海洋环境下的悬停作业需求，提出一种基于非线性干扰观测器的 UUV 反演滑模深度控制算法。首先，根据全驱动 UUV 的悬停运动特性，建立五自由度及解耦的垂荡通道动力学模型。然后，采用非线性干扰观测器（NDO）对时变海浪扰动与模型的不确定进行有效估计，并证明了 NDO 的指数收敛特性。根据 UUV 的标称模型及 NDO 对扰动状态的估计，采用反演思路，设计了反演滑模控制器。通过引入双曲正切函数取代不连续切换函数，改进滑模趋近律，进而降低滑模的抖振效应。根据 Lyapunov 理论证明了系统的稳定性。最后，通过仿真实验验证了该控制算法的有效性与优越性。

Nonlinear Disturbance Observer Based Backstepping Sliding Mode Depth Control for UUVs

A nonlinear disturbance observer based backstepping sliding mode depth control algorithm is proposed for hovering operation of unmanned underwater vehicles（UUVs）in shallow marine environment. Firstly， based on the hovering characteristics of a fully actuated UUV，a five-degree-of-freedom decoupled heave channel dynamic model is established. Then，a nonlinear disturbance observer（NDO）is used to effectively estimate the time-varying wave disturbance and model uncertainty，and the exponential convergence property of the NDO is proved. Based on the UUV nominal model and the estimated disturbance state by the NDO，a backstepping sliding mode controller is designed using the backstepping method. By introducing a hyperbolic tangent function instead of a discontinuous switching function，the sliding mode approach law is improved and the chattering effect of the sliding mode is reduced. The stability of the system is proved using Lyapunov theory. Finally，the effectiveness and superiority of the control algorithm is verified through simulation experiments.