Adaptive control for fully-actuated autonomous surface vehicle with uncertain model and unknown ocean currents

Abstract

This paper proposes a robust adaptive controller for the trajectory tracking of an autonomous surface vehicle (ASV) in the presence of model uncertainties, ocean currents, and time-varying environmental disturbances. First, a novel adaptive virtual velocity command is designed to estimate and compensate the unknown ocean currents acting on the ASV. Then, an improved torque controller is derived by applying filter operations and a set of auxiliary variables to avoid measuring the acceleration signals. To address the unknown dynamics parameters, a modified adaptive law with an alternative leakage term containing the parameter estimation error is developed. With this adaptive law, the convergence of both the estimated parameters and the tracking error can be achieved simultaneously. The whole closed-loop system's stability under environmental disturbances and parameter uncertainties is proved by the Lyapunov stability theory. Comparative simulations are carried out to validate the effectiveness of the proposed method.