Research On Control Algorithm Of Dynamic Positioning Ships With Time-delay Of Actuator

As one of major resources, marine resource has attracted more and more attention. As a result, Dynamic Positioning (DP) gets more recognition too. It refers to a ship or other marine instruments using its own propulsion which was ordered by control system to resist environmental disturbances and keep station or tracking,these disturbances include wind, wave, and current. Control system based on the observed value of the sensor system generates control commands. Because of dead-zone and great inertia of thruster, there is time-delay problem on actuators which include thrusters and rudders in the position operation. This time-delay problem has negative effects on control performance, such as, large overshoot, long settling time, even worse , it may lead to oscillation, divergence, and instability. This thesis aims at to solve the time-delay problem of actuators.First, a mathematical model of three degrees of freedom (3DOF) motion of the DP ships in the horizontal plane was established. Time-delay of actuators is turned into control input time-delay, simultaneously the wind, wave and current models were established,The simulation experiments were implemented and proved that the model is legitimacy and correctness.Secondly, the ship motion is effected by superposition of low and high frequency disturbances from ocean circulation, controller depend on position and states to generate control commands after filtering high frequency component in order to avoid response them, waste energy and thruster wear, the actuators only counteract low frequency disturbances. This paper designs an adaptive sliding-mode observer and a nonlinear observer to filter high frequency component and estimate position and velocity. The consequence of simulation reveals that their performance is better than Kalman filters.At last, thesis design an robust sliding-mode control law by analysing sliding-mode control and backstepping , a proper Lyapunnov-Krasovskii function is designed to analysis its stability to prove system control error is convergence. The consequence of simulation reveals that its performance is better than PID and has robustness for the time-delay influence. Fuzzy control do not need accurate mathematical model,which combines with adaptive control law to form adaptive fuzzy controller. Adaptive fuzzy controller can overcome time delay to adaptive delay system .the results of Adaptive fuzzy controller has robustness and adaptability compare with PID in time-delay of actuators.