Research On Motion Control System Of Remote Operated Vehicle

Remote Underwater Vehicles are often used in marine science and engineering.However,the diversities of working task and the complicated subsea environments present great challenges to ROV control system.This paper designs the motion control system for an open-frame ROV working for jacket platform cleaning.The thrusters configuration is determined after hydrodynamics computation,and the control system is designed based on the propeller performance and its positioning system.The motion control system design is closely linked to the structure,electric devices and thrusters configuration of the ROV.Therefore,the model of the open-frame ROV is built using Solidworks and simplified in order to finish the CFD procedure.AQWA is used to obtain the added mass of the ROV.Fluent is used to model straight movements and different inflow angles as well as constant rotation,which is a traditional CFD method for calculating viscous hydrodynamic coefficients.Besides,Spatial Captive Motion Simulation is used to compare the results.Least square fitting,neural network fitting and genetic programming is used to figure out the hydrodynamic properties of the ROV.According to the resistance of different directions,propellers configuration of the ROV is accomplished.Taking into account of the propeller dynamics and thrust saturation,the control design of the ROV is augmented to the control problem of a third-order cascade system.In the existence of modeling uncertainties and ocean current,an adaptive super-twisting disturbance observer is introduced to estimate and eliminate the lumped disturbance without any prior knowledge.The “explosion of complexity” problem of backstepping method in high order system is solved by command filter based method.The effecting boundary error of the command filter and the thrust saturation is fixed by two auxiliary systems.Control simulation is conducted in Simulink,and the designed control scheme is compared with an NDO-based adaptive control method.Considering the limitation of sonar device onboard,the designed ROV only measures its position and attitudes with USBL sonar and compass in the cabin.High order sliding mode extended state observer is used to tracking the ROV velocity and estimate the lumped disturbance,and a robust stable control scheme is designed for the ROV only with the position and attitude measurement and the thrusters system feedback.Simulations are carried out to check the performation of the newly designed control method.