Robust approximation-based control of ocean surface vessels

Abstract

In this paper, we consider the problem of tracking a desired trajectory for fully actuated ocean vessels, in the presence of parametric/functional uncertainties, unmodelled dynamics, and/or disturbances from the environment. To compensate for the uncertainties and unknown time-varying disturbances, linearly parameterized adaptive feedforward approximators are used. Using backstepping and Lyapunov synthesis, the stable tracking controller is first designed for the full state feedback case. Subsequently, the output feedback problem is tackled by employing a high gain observer to estimate the unmeasurable states required by the stable tracking controller. It is shown that the designed controller guarantees semiglobal uniform boundedness for both the full state and output feedback cases, provided that the initial conditions are bounded, and that the design parameters satisfy some rather relaxed conditions. © 2005 SICE.