  This paper proposes a fuzzy logic controller for design of autopilot of a
ship. Triangular membership functions have been use for fuzzification and the
centroid method for defuzzification. A nonlinear mathematical model of an oil
tanker has been considered whose parameters vary with the depth of water. The
performance of proposed controller has been tested under both course changing
and trajectory keeping mode of operations. It has been demonstrated that the
performance is robust in shallow as well as deep waters.
