Dynamic Response And Heave Compensation Of ROV System Subjected To Waves And Currents In Deep-water Ocean

The pace of human moving to the ocean is accelerated by the abundant ocean resources and short land resources.Deep ocean missions,such as underwater detection,pipeline inspection,underwater observation and salvage,can be completed by Remote Operated Vehicle(ROV),which is important in area of ocaen exploration.The safety and the precision of ROV is influenced by the obvious heave motion of ship which is inevitablely subjected to the waves when the ROV is in operation.Because of this,heave compensation is applied to the ROV system to solve that problem.Based on large hydrodynamic software OrcaFlex,passive heave compensation model and active heave compensation model are built.Simulations are made to these two models.Passive compensation is suitable for large load with lower compensation accuracy,while active compensation is suitable for small load with higher compensation accuracy.Energy input is not needed for passive compensation but is needed for active compensation.As to active compensation,sensitivity analysis is made for the parameters such as length of line,weight of ROV,axial stiffness of line,unit mass of line and node.Large snap load of line appeared in the simulation of changing length,which is to be avoided.Compensation depth of ROV is set near the equilibrium position to solve the problem mentioned.The target depth has no impact on the compensation efficiency from the simulation of changing line unit mass but will give rise to snap load.Python is used in wire compensation to build heave compensation model.The depth and the current profile are set by the real condition.Dynamic simulation of ROV system in deep-water is conducted based on specific ocean area in South China Sea.Controller parameters are tuned by comparing responses to different control factors.The system is sensitive to the wave period,with little variation of wave period,amplitude of tension is higher and higher,the compensation function fails.Result shows,the passive comepensation system can decrease the noise of tension;active compensation system base on PID control can compensate effectively.