An introduction to the use of fuzzy sets in the implementation of control algorithms

The purpose of this paper is to present to the reader who is unfamiliar with fuzzy set theory the basic concepts in a straightforward manner. Thus a tutorial approach is adopted in the explanation of these concepts. After describing fuzzy sets, it is shown how fuzzy logic can be used to develop a fuzzy control algorithm by means of the fuzzy conditional statement. In order to unify the ideas that are presented, a detailed description of the development of a fuzzy controller is discussed. Computer simulation results are shown of the fuzzy controller with heading error and yaw rate as input and rudder demand as output activating the non-linear yaw dynamics of a ship during course-changing manoeuvres. For the simulation ship study, the model was derived from full-scale sea trials on a Royal Navy frigate.