Adaptive sliding mode output feedback control for dynamic positioning ships with input saturation

In this paper, a finite-time observer-based adaptive sliding mode output feedback controller is developed for dynamic positioning ship while the Coriolis matrix, hydrodynamic nonlinear damping matrix, input saturation, unmeasured states, unknown time-varying environment disturbances and transient performance are considered simultaneously. A continue finite-time state observer is proposed to estimate the unmeasured states of dynamic positioning ship in finite time and an auxiliary system is constructed to handle with the control saturation. A terminal sliding mode surface with the signal generated by the auxiliary system is designed while the good transient performance is achieved under multiple constraints and the nominal output feedback controller proposed in this paper is chatter-free guaranteeing the steady performance. In additional, an adaptive update law is introduced that the prior knowledge of disturbance is no need and the finite-time convergence of loop-system is proved strictly. Finally, simulations are given to illustrate the effectiveness and advantages of the proposed control scheme.