Dynamic Positioning Capability Analysis Of Deepwater Pipelay Crane Vessel Based On Fuzzy Control

With the increase of China's efforts to develop marine resources, more attention has been paid to the development of dynamic positioning technology. Because of the advantages, it's widely used in ships and offshore platforms. Traditional control techniques cannot perfectly work in deep water with the increasing exploited range in the oceans, and new control method is gradually applied to dynamic positioning systems. As an intelligent control method, fuzzy control has been applied in many fields. It does not depend on accurate mathematical models and has good robustness. So it's of great significant to apply fuzzy control in dynamic positioning.In this paper a deepwater pipelay&crane vessel is studied, from basic motion model and environmental loads to dynamic positioning (DP) system analysis and calculation based on fuzzy control. First, the mathematical model is established based on the study of DP vessel motion characteristics. To analyze the ship suffering a variety of environmental loads in the ocean, wind, wave and current loads are theoretically calculated. Then the basic principles of fuzzy control are studied. Fuzzy set theory and the theoretical basis of fuzzy control are discussed, and then each of the key aspects of fuzzy control is separately analyzed, including input fuzzification, fuzzy inference rulesand the output defuzzification process. Next, based on the above fuzzy control theory,combined with DP vessel motion characteristics, fuzzy controller of DP system is designed. Also, the thrust system is designed and analyzed. According to the specifications and engineering practices, combined with the thrust system and environmental loads, dynamic positioning capability plots are drawn in static analysis both in the intact mode and failure modes, verifying the ability to control and redundancy of the positioning system. Finally, according to the fuzzy control theory, a mathematical model is established for dynamic positioning system using MATLAB and dynamic simulation analysis is processed in time domain with the Simulink toolbox. The results show good controllability of fuzzy DP system, verifying the ship with an excellent positioning capability.With this research, the analysis method of the ship dynamic positioning system and fuzzy control theory can be mastered to provide a theoretical reference for future engineering practices, the development of novel intelligent control systems and the feasibility validation of development of the DP technology with proprietary intellectual property rights.