Two novel robust nonlinear finite time control schemes for unmanned ship course system

This paper investigates the finite time trajectory tracking problem for the nonlinear dynamics of ship heading system in the presence of external disturbances and model uncertainties. In fact, based on the second order nonsingular terminal sliding mode control, two novel classes of robust nonlinear controllers (rudder angles) are designed to precisely reach the ship course to the desired trajectory in the specified finite times. Moreover, two new formulas (in the form of two nonlinear inequalities) are derived to estimate these convergence finite times. Furthermore, two theorems and their proofs are presented to demonstrate the global finite time stability of the uncertain closed-loop ship heading system forced by each class of proposed controllers. Finally, two computer based numerical simulations are provided to depict the applicability and the good performance of two suggested controllers.