Research On Key Techniques Of Cargo Handling Simulator For Liquefied Natural Gas Carrier

With the vigorous development of the liquefied natural gas(LNG)transportation industry,it is more urgent to conduct specialized training for professional operators for LNG carrier.With its advantages of safety,energy saving,economy and high efficiency,the simulator has become an alternative method for the training and assessment of the majority of crew members.This is recognized by international conventions.It is also an indispensable equipment of simulation for the construction of LNG ships.However,In China,the liquid cargo handling simulator for LNG carrier relies heavily on imports.In the face of fierce international market competition,it is imperative to break the technical barriers and realize the independent development of simulators for LNG carrier.Therefore,the thesis is based on the requirements of the key discipline construction project of traffic information engineering&control for Dalian maritime university.This requirements is the "Twelfth Five-Year Plan"of the ministry of transport national.This research is based on the existing research work and studies three key technical issues of the development of the simulator:the accurate acquisition of system model of the liquid cargo system for the simulator;system pressure control during the liquid cargo handling;the development of simulator system platform.The main research contents and methods are as follows:Firstly,this thesis established dynamic mechanism models for the liquid cargo handling system by taking the liquid cargo system of LNG carrier as the research object and basing on the established assumptions.It fully considered the thermal properties and migration properties of liquid cargo,and the influence of the material of the containment system.These models were established by the methods and the theory of engineering thermodynamics,energy heat transfer,and fluid dynamics ignoring the natural convection in the air interlayer and the tumbling stratification inside the tank.The verification results show that the models can reflect the law of changes for the internal fluid from the output characteristics of temperature and pressure.That is in line with the actual situation.Thus the models are verified to be correct.Secondly,the thesis proposed the control method for the liquid cargo tank pressure and insulation layer pressure difference.Based on the system dynamic mechanism models established above,the controller was based on closed-loop gain shaping algorithm by introducing advanced control technology such as the mirror mapping technique and the sinusoidal function driven nonlinear feedback technique.Specifically,the cargo tank pressure gas flow model and the tank insulation layer difference model were taken as the research object.The control models of cargo tank pressure and the tank insulation layer difference were established.The pressure difference controller was designed for the tank insulation layer based on closed-loop gain shaping algorithm by introducing the mirror mapping technique and the sinusoidal function driven nonlinear feedback technique.The pressure controller was designed for the cargo tank based on closed-loop gain shaping algorithm at closing slope of-20dB/dec.The cascade control method was proposed for the control of pressure and temperature during the liquid cargo handling for the simulator.The simulation results show that the controllers designed in this thesis have better control performance and can achieve better energy-saving effect with better control performance.The controller designed by this method is simple,robust and easy to be used in engineering.Finally,the system platform of the liquid cargo handling for LNG carrier simulator was established based on the models and control method above,The overall architecture of system platform for the simulator was established and the console of simulator was developed.The system modules are integrated into the platform.These modules are:loading and unloading operation module,stability calculation module,operation evaluation module,etc.The core functions of the console are realized including management of liquid cargo handling exercises,delivery of liquid cargo handling exercises,real-time monitoring of liquid cargo handling,graphical interface display of the process and results,data playback of operation results,remote control of the system.The testing results show that the system platform developed for LNG carrier liquid cargo handling simulator is suitable for the training task and can undertake scientific research tasks.The experiments of model verification and control simulation in this thesis are all implemented by MATLAB/Simulink programming.The simulator platform is developed by VB.The correctness and usability of the models are verified by the actual ship data.The effectiveness of the design method for controller is verified by comparative experiments.The designed controller has the characteristics of simple implementation,strong operability and easy engineering realization.It can meet the training requirements of manual adjustment control for the trainees.This paper has played a role in promoting the further development of the simulator,and has important practical significance for the realization of the nationalization of the simulator.