Imperfect Premise Matching fuzzy control for nonlinear stochastic ship steering systems

This paper deals with the control problem of nonlinear stochastic ship steering system. The system exhibits nonlinear interaction on three degrees of freedom (surge, sway and yaw) by means of main propellers aft of the ship. For guaranteeing the global stability, the Takagi-Sugeno (T-S) fuzzy model is employed to represent nonlinear ship steering system. Using the technique of Imperfect Premise Matching (IPM), the fuzzy controller is designed without limitation of sharing the same membership function of the fuzzy model. In other words, the IPM technique provides a generalization in designing the fuzzy controller. Besides, the fuzzy controller design can be enhanced more flexibility and robustness than one applies Parallel Distributed Compensation (PDC) approach. Based on the Lyapunov theory, the stability conditions are derived into Linear Matrix Inequality (LMI) problems for applying the convex optimal algorithm. At last, simulation results are given to show the effectiveness of the proposed design method.