Partial-state and Output Feedback Trajectory-tracking Control of Underactuated Ships

Abstract

Global partial-state feedback and output feedback control schemes are discussed in this chapter for tracking control of an underactuated surface ship without sway force. For the case of partial-state feedback, we do not require measurements of the ship sway and surge velocities, while for the case of output feedback, none of the ship velocities are required for feedback. The reference trajectory to be tracked can be a curve including a straight line. Global nonlinear coordinate changes are introduced to transform the ship dynamics to a system affine in the ship velocities to design observers to globally exponentially estimate unmeasured velocities. These observers plus the techniques in the previous chapter facilitate the development of controllers in the following sections.