Tracking Control of Underactuated Ships with Input Saturation

This chapter addresses tracking control of underactuated ships in the presence of input saturation. By dividing the tracking error dynamic system into a cascade of two subsystems, i.e., (ϕ_e, r_e) subsystem and (x_e , y_e, v_e, u_e), the torques in surge and yaw axis are designed separately using the backstepping technique. The chapter solves the global tracking control problem by proposing a state-feedback control scheme. Firstly the tracking error dynamic system is divided into a cascade of two subsystems so that the torques in surge and yaw axis can be designed separately based on the two subsystems. A new finite-time control scheme is proposed to design the torque in yaw which enables the two subsystems to be de-coupled within finite time. After decoupling, a new backstepping scheme is proposed for the surge subsystem.