In order to realize the three-dimensional path following control for underactuated (Unmanned underwater vehicle, UUV) under unknown ocean current, a nonlinear iterative sliding mode controller based on engineering decoupling is presented. The path following error equations in three-dimensions are established based on the virtual guide method. Then, a nonlinear feedback controller is designed based on iterative sliding modes, without estimating uncertainties of UUV model and ocean current disturbances. The problem of chattering of the hydroplane is circumvented, and the static error and overshoot are decreased. The results of simulation experiments indicate that the controller is robust against the systemic variations and time-varying current disturbances. Moreover, the parameters are easy to adjust, and the tracking control with high tracking precision can be achieved by the proposed control method.%为实现欠驱动无人水下航行器(Unmanned underwater vehicle,UUV)在末知海流干扰作用下的二维航迹跟踪控制,提出一种基于工程解耦思想设计的非线性迭代滑模航迹跟踪控制器.基于虚拟向导的方法,建立UUV空间航迹跟踪误差方程；采用迭代方法设计非线性滑模控制器,无需对UUV模型参数不确定部分和海流干扰进行估计,避免了舵的抖振现象以及减小了稳态设差与超调问题.仿真实验表明,设计的控制器对欠驱动UUV系统的模型参数摄动及海流干扰变化不敏感、且设计参数易于调节,可以实现三维航迹的精确跟踪.
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