Full state sliding mode trajectory tracking control for general planar vessel models

A novel trajectory tracking sliding mode control law for general planar underactuated autonomous vessel models is presented where all six position and velocity states are asymptotically stabilized. The approach is based on defining a transitional trajectory vector function which can be used to reduce the sixth order system to a fourth order one with two control inputs. It is then shown that the stabilization of the reduced order system guarantees asymptotic stability of all six system states where the only restriction for reference trajectory is that it must satisfy the vessel´s nonholonomic constraint. The most important advantages of the approach are that it does not require any specific structure for the forcing functions such as hydrodynamic damping, it is robust to modeling uncertainties and disturbances, and it can be applied to models with diagonal and non-diagonal mass matrices. Simulation results are presented for an autonomous surface vessel.