Tracking control of underactuated ship based on partial state feedback scheme

For underactuated ship without side-propeller equipment, a new global partial state feedback control scheme is proposed which is applied to the curve tracking problem including straight line case. The proposed controller does not need forward speed and by-pass speed as the state feedback variable. By global nonlinear state transformation, the ship dynamic model is converted into affine form, as a result, an exponential convergent speed of state observer is constructed to estimate the unmeasurable velocity item. The design of controller is dependent on the Lyapunov direct method and backstepping technique, and passivity of ship dynamic systems and connection structure as well. Simulation shows the proposed control law is effective.