Modeling And Simulation On Stopping Ability Of Azimuth Stern Drive Tug

Azimuth stern drive(ASD)tug is the main form of modern port tugs.Stopping test is one of the most typical maneuverability tests.Stopping motion mathematical model of ASD tug is important to improve the behavioural realism and complete the maneuvering functions of tug simulator.The development of tug simulator is significant to train tug crews and reduce accidents in port.In order to study the stopping performances of ASD tug with double ducted fixed pitch propellers(Ducted FPPs)and ducted controllable pitch propellers(Ducted CPPs),the main contributions of this thesis are summarized as follows:(1)A resistance calculation model applicable to all speed range is proposed.According to Froude method,hull total resistance is divided into friction and residual resistance.The later is estimated in terms of Target's chart.In order to meet the needs of tug's stopping process,Target's chart is reasonably extended to low speed range.(2)A four-quadrant thrust calculation model for Ducted FPP is provided.In the absence of the complete thrust chart,integrating Ducted FPP JD75 first quadrant chart with Nordstrom propeller four thrust quadrants chart,a new Ducted FPP four quadrants thrust chart is constructed.(3)A multi-task maneuvering thrust calculation model for Ducted CPP is provided.Integrating the amended JD7704 Ducted FPP first quadrant chart with CPP C4-40 multi-task maneuvering chart,a Ducted CPP multi-task maneuvering chart is constructed.The new chart not only includes the function of duct,but also reflects that pitch can be variable.(4)The simulation platform is established via Visual Studio.This paper takes"Delta Linda" and "Svitzer Mull" ASD tug as simulation objects,then carries out stopping tests,including rotating thruster stopping,engine stopping and varying pitch stopping.The simulation results are very similar to test data.The rationality and feasibility of thrust and resistance calculation models are verified.The stopping motion mathematical model of ASD tug is suitable and effective,and the simulation precision can meet the need of navigation simulator.