| Dynamic positioning system is a positioning system that relies on the ship's own propulsion to generate thrust to resist the environmental load such as the external wind,waves and current.It can guarantee the normal operation of the marine engineering structure in the complicated and volatile marine environment.The frequency domain analysis and time domain analysis of dynamic positioning capability were studied in the paper.A multi-function tugboat was used as an example to analyze the control capability,and complete the development of dynamic positioning capability frequency domain analysis software which based on the frequency domain analysis method and adapting hybrid programming(Matlab and C++).The main work of the thesis includes the following aspects:(1)Research on mathematical model of ship dynamic positioning systemMathematical models of ship motion were established,including low frequency motion model,high frequency motion model,propeller thrust model and environmental load model.Simulation calculations and verification were performed on the models,which provide model support for the design of ship dynamic positioning system and positioning capability evaluation software.(2)Dynamic positioning frequency domain analysis methodFrequency domain analysis process of dynamic positioning capability was established.Optimization algorithm of thrust distribution and calculation process for thrust utilization and extreme wind speed were studied.The extreme wind speed curve of the multi-purpose tug was drawn,and then its positioning ability was analyzed.(3)Dynamic positioning time domain analysis methodAccording to the kinematic characteristics of the dynamic positioning system and the corresponding mathematical model,the filter is designed based on the Kalman filter principle,and the filtering effect was verified by simulation.PID controller,fuzzy PID controller and DMC-PID controller were designed according to characteristics of the dynamic positioning control system.The control effect of controllers was verified by simulation.The result shows that all controllers can meet the dynamic positioning control system's request,but fuzzy PID is better.Time domain analysis process of dynamic positioning on multi-purpose tug,and its positioning capability was analyzed.(4)Design and implementation of frequency domain analysis software for dynamic positioning capabilityAccording to the process of frequency domain analysis,using Microsoft Visual Studio 2008 as the development tool,adapting hybrid programming(Matlab and C++),the ship dynamic positioning system positioning capability evaluation software was designed and application software programming was completed. |
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