Globally adaptive path tracking control of underactuated ships

In this paper, a nonlinear adaptive control strategy is developed to force an underactuated ship to follow a predefined path, despite the presence of unknown system parameters and environmental disturbances induced by wave, wind and ocean current. The techniques involved in the design and analysis include using the backstepping, parameter projection techniques and a traverse function. It is shown that with our proposed controller, the reference path can be tracked globally with an arbitrarily small tracking error. Simulation results demonstrate the effectiveness of our proposed controllers.