Application of Fuzzy Sliding Mode Control in Nonlinear Ship Autopilot System

A method of designing integral sliding mode controller combining fuzzy self-adaptation and sliding mode control for a category of nonlinear uncertain systems is proposed.The nonlinear functions are approximated with fuzzy logic and an integral term is introduced into the sliding mode control in order to eliminate the limitation of conventional sliding mode control where tracked signals and their derivatives must be known.The on-line-switching gain adaptation algorithm deducted with Lypunov method eliminates effectively the dithering inherent in sliding mode control.The closed loop system is theoretically proved to be globally stable in the sense that all signals involved are bounded,with tracking errors converging to a neighborhood of zero.Simulation results of the ship course tracking control show that this control approach has strong robustness and good tracking performance.