Adaptive Sliding Mode Control for Ship Path Following with Velocity Observer

This paper presents the design of an adaptive sliding mode controller to address the challenges posed by uncertain internal parameters and external time-varying environmental disturbances in underactuated ships. Initially, a reference heading angle is designed using the backstepping algorithm. An adaptive law is then introduced to compensate for both internal and external uncertainties, building upon the sliding mode controller framework. To overcome the issue of difficult velocity measurement, a state observer is developed to estimate the forward velocity and transverse drift velocity, which are typically hard to measure during ship navigation. Subsequently, Lyapunov stability analysis is employed to demonstrate that all error signals in the closed-loop system for ship path following are uniformly and ultimately bounded. Finally, MATLAB/Simulink simulations are conducted, and the results confirm the effectiveness of the proposed controller.