Research On Hydrodynamic Performance And Motion Simulation For Open-frame ROV

As an underwater vehicle,ROV(Remotely Operated Vehicle)has been widely used in many areas,such as observation and sampling,detection,installation as well as maintenance and repair in deep sea environment,because of its advantages of low cost,high efficiency and long operation in complex deep-sea environment.However,because of the complex operation environment at sea,it is of great significance to develop the ROV operation simulation training system to train the operaters,rehearse the underwater operation scheme,reduce the risk of operation and improve the safety.This paper is based on the sub project of national science and technology projects "marine deepwater engineering major equipment and supporting engineering technology","ROV operations training equipment and technology research”.In view of the demand for accuracy and real time of the ROV underwater operation simulation training system,a new type of openframe ROV hydrodynamic model is established based on its geometic unsymmetry and the motion characteristics.Through the model experiment,the influence degree of the geometric asymmetry of open-frame ROV on the different hydrodynamic force components is studied.The influence of geometric asymmetry of ROV on hydrodynamic coefficients is obtained,and the coupling characteristics of open-frame ROV hydrodynamics are studied in detail as well.Using the lumped mass method and consider the effect of cable,the mathematical model of the open-frame ROV real-time motion simulation is builded to meet the requirements of the realtime simulation,so as to realize the prediction and simulation of the hydrodynamic performance and the motion performance of the open-frame ROV.The main contents of this paper are as follows:Based on the vectorization modeling method,the construction of ROV kinematics and dynamics mathematical model is carried out.As to the construction of hydrodynamic model,by summarizing the working experience and shortcomings,we abandoned the hydrodynamic modeling method of Taylor expansion,which is based on small disturbance and made longitudinal motion as benchmark.Considering its working characteristics and geometric asymmetry,an innovative hydrodynamic model is pressented,which is completely suitable for ROV.The hydrodynamic performance of ROV is studied by model test which is carried out based on the operation characteristics and geometric asymmetry.And the hydrodynamic coefficients for building ROV hydrodynamic model are obtained as well.Especially,the influence of geometric asymmetry of ROV on the asymmetric hydrodynamic performance of ROV is studied quantitatively.And the experiment results also can be applied to improve the ROV hydrodynamic model,and obtain the hydrodynamic model which is finally used in the simulation of ROV motion,and the accuracy of the hydrodynamic model is verified.The ROV hydrodynamic model constructed in this paper is applied to simulate the ROV motion by using Runge Kutta numerical algorithm.By comparing and discussing the asymmetric motion properties,the cognition of asymmetric hydrodynamic as well as motion caused by the asymmetry geometry of ROV is further deepened.Based on the lumped mass method to analyze cable forces and calculate its motion,a mathematical model suitable for real-time calculation of the dynamic motion of the ROV coupled motion system is proposed.The mathematical model is verified according to relevant literatures.And in order to satisfy the reliability of numerical calculation as well as the realtime requirement of ROV simulator,the dividing schemes with different cable length and time step are studied and discussed to provid the theoretical and data support.The simulation experiments are carried out by using the ROV coupled motion system mathematical model.The influence of ROV hydrodynamic performance,ocean current and cable on ROV motion is analyzed and studied.At the same time,the motion response of the mother ship movement to ROV is also studied and discussed.According to the simulation results,the generality and regularity are summarized,and the understanding of ROV hydrodynamic performance and coupling system motion characteristics is deepened,and the reference for actual operation is provided as well.