Three-dimensional Path Following Control for an Underactuated UUV Based on Nonlinear Iterative Sliding Mode

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.