An adaptive type-2 fuzzy logic controller for dynamic positioning

This paper presents an indirect adaptive type-2 fuzzy logic controller (FLC) for dynamic positioning (DP) vessels with attached thrusters under various time-varying hydrodynamic disturbances. Approximation-based adaptive control technique in combination with type-2 fuzzy logic system (FLS) is employed in the design of the control. The stability of the design is demonstrated through Lyapunov analysis where globally asymptotical convergence of the regulation error is guaranteed. Rigorous analysis shows the resultant closed-loop system is passive. The proposed adaptive type-2 FLC is able to reject the hydrodynamic disturbances without exact information on them. Comparative simulations with linear proportional derivative (PD) controller and adaptive type-1 FLC are carried out. The proposed technique is found to be effective, robust, and has better performance.