Nonlinear Disturbance Observer Based Adaptive Dynamic Surface Control for Full Actuated Ship Trajectory Tracking

For the trajectory tracking control problem of three degrees of freedom full actuated ships, a disturbance observer-baded robust adaptive dynamic surface control scheme is proposed. The disturbance observer is constructed to acquire the signal of the unknown external environmental disturbance for compensating with the form of feedforward. In addition, a adapive law with the leakage terms of a-modification is designed to estimate the bounds of observation errors. The dynamic surface control (DSC) technique is introduced to remove the need of the derivation operation for the virtual control vector, which makes the proposed control scheme is easy to implement in engineering practice. Under the proposed control scheme, all the signal of trajectory tracking close-loop control system are bounded. Simulation results and comparisons with standard DSC method illustrate the effectiveness and advantages of the proposed control scheme.