| Dynamic Positioning System(DPS) is a closed-cycle control system that realizingship positioning without anchorage system. It can keep the ship steadily in the givenposition by using all kinds of sensors to get the deviation between the real and theobjective position, then calculate the required propulsive force and moment whichmaintain the objective position by combining the outer turbulent motion forces, andallocate the thrust and give directions to every propeller installed in a ship, thus it cancorrect the deviation continuously in order to maintain the objective position. DPcapability analysis system is an important part of DPS. It can ensure the reliability ofthe system when DPS is running, and check the executive ability of the system in realtime.This article is based on a development project named Z-DP of Shanghai ZhenHua Heavy Industries (ZPMC) to research the algorithm and software actualization ofDP capability analysis system. The paper has explicit engineering applicationbackground and practical significance. The main jobs are as follows:1. The preciseness of the DP Capability and Motion Prediction Analysis functionslargely depends on the rationality of environment load estimation. For the ship DPS,the main loads to the ship in the deepwater including the wind, current and wave driftloads. As per the environment load calculation requirements of several shipclassification societies, the article establishes the environment load calculation modelfrom the aspect of DP capability evaluation. 2. The principle of the ship DP system is making the correct environment loadsprediction according to the outer environmental factors (wind, wave drift and current)and calculate the thrust force required to maintain the objective position and bowdirection, then give direction to each thruster as per the thrust allocate rules. Thethrust optimum allocation rules are realizing the optimization of the thrust strengthand direction of each thruster by controller, so it can increase the efficiency andprecision of positioning. Meanwhile, it can also reduce the energy lose. It plays animportant role in the DPS. It's the connection belt of the positioning control algorithmand implements mechanism. The article analyses and researches the thrust allocationalgorithm to the target ship model based on the optimum algorithm.3. A dynamic positioning capability analysis system can evaluate the positioningcapability at specific system status (fault mode) and environmental conditions. It canalso evaluate the positioning capability online at present system status andenvironmental conditions. The analysis results must be output in intuitive graphicalforms to guide and facilitate the practical vessel operation. Dynamic positioningcontrol capability analysis software is designed and realized using VC++programming language based on the overall architecture of the Z-DP control system.The effectiveness and application of the system was verified based on the simulationand the real ship experiment.In last chapter, a comprehensive conclusion is summarized. |
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