Objective   In the fields of marine oil exploitation and lake water quality monitoring, in order to realize the self-positioning and self-navigation of ships, it is necessary to realize the velocity control for dynamic positioning ship.

  Methods   Ship motion model of 3 Degree of Freedom (3-DOF) is established, and constant-velocity navigation control algorithm based on fuzzy decoupling control is proposed. Fuzzy controllers are designed separately for surge, sway and yaw loop to solve the modeling error of controlled object. In order to solve the coupling problem between sway loop and yaw loop variables, feed-forward compensated decoupling scheme is designed to eliminate mutual effect between controlled variables.

  Results   The experimental results of the constant-velocity navigation control simulation platform show that the fuzzy decoupling control algorithm has good dynamic performance, high steady-state accuracy and certain robustness.

  Conclusion   The study results provide references for the precise velocity control for dynamic positioning ship.