This paper presents the application of an adaptive sliding-mode controller for trajectory tracking of a surface vessel. Sliding-mode control is insensitive to parametric uncertainties and disturbances. However, the control signal amplitude is usually overestimated that may cause energy losses and undesirable chattering effects, usual in sliding-mode systems. An adaptive control signal scheme is developed to reduce the amplitude. Adaptation is based on the estimation of the disturbances, that include environmental effects and residuals of imperfections of the adopted feedback linearization scheme. The estimation of disturbances on the vessel will also allow their modeling. Experimental results obtained with a small vessel subject to disturbances generated in pool tests are also presented. The position and orientation of the vessel were measured by an accurate motion capture system.
