Fuzzy rule-based adaptive control method applied to ship steering

Fuzzy modelling and control is a technique to handling qualitative information in a formal, rigorous and efficient way if such information are properly used. In this paper it is presented an alternative method to control processes where fuzzy logic are to be applied. The developed algorithm for decision on the control variable (by some defuzzification strategies) is particularly emphasized, being the goal of these papers. Such algorithms exploits the knowledge of a rule-base created under fuzzy ideas of the system dynamics to be defuzzified by means of the proposed three methods: linearisation procedure by the small perturbation theory of a polynomial function achieved by a multidimensional least-squares method, single-dimensional least-squares, or optionally, online Lagrange interpolation