Control of Dynamic Positioning Ship Using Internal Model Control

Abstract

Dynamic Positioning Ship System (DP) is an automated system, which is used to keep the ship maintain its position and heading at a fixed location or navigate along a predetermined track exclusively by mean of its own actives propulsions systems without using such fixing device as the anchor. DP system’s task is to control the ship moving at a fixed position or moves following the route for previous with low speed to execute a task. This paper presents a novel stability robustness controller for a dynamic positioning ship with uncertainties and unknown external disturbances. For the development and testing of the controller we present shematic diagram of DP systems, the mathematical modeling of the ship and the bias forces as slowly-varying environmental disturbances. The proposed controller has two loops. The inner loop uses an internal model control (IMC) technique to control the speed of the ship. The outer loop uses a propotional (P) control ler to control the position of the ship. The stability robustness of the control system is analysed. One of the key aspects of the prposed controller is that the robustness of the closed loop system can tuned via a single tuning parameter. The simulation results demonstrate that the proposed control system has high performance and robustness in the present of environment disturbance and uncertainty. The proposed control system was compared with PID control.The control algorithm of ship dynamic positioning is generally based on the classic PID, PID control has many advantages and has a strong robustness. However, the parameters of the PID control depend on the test will cost a lot of time and energy. Simulation results are provided to illustrate the effectiveness of the proposed controller. The problem of guidance and control of thruster actuators is out of scope of the paper.