Design and implementation of model test installation of heave compensation system of deepsea mining

In order to validate the simulation model and develop heave compensation control strategy,heave compensation model tests were performed.The model test installation includes themining ship motion simulator,the heave compensation system,the lifting pipe simulator,the buffer simulator and the water pool.The tests ofmining ship motion simulator show that it is able to perform under the predetermined attitude path smoothly and can meet the requirements of themining ship motions.The heave compensation effect is more than 60% under random wave and the goal is set to be 50%.The model test results indicate that this heave compensation system is effective and feasible.

Adaptive Robust Control for an Active Heave Compensation System

Active heave compensation systems are usually employed in offshore and deep-sea operations to reduce the adverse impact of unexpected vessel’s vertical motion on the response of underwater instruments.This paper presents a control strategy for an active heave compensation system consisting of an electro-hydraulic system driven by a double rod actuator,which is subjected to parametric uncertainties and unmeasured environmental disturbances.Adaptive observer and discontinuous projection type updating law with bounded adaption rate are presented firstly to estimate the uncertain system parameters.Then a similar estimation algorithm is designed by using a multiple delayed version of the system to enhance the performance of parameter observation.A reduced order observer is also introduced to estimate unknown wave disturbances.Using the obtained uncertainty information,the resulting control development and stability analysis are implemented based on the Lyapunov’s direct method and back-stepping technique.The proposed controller guarantees the heave compensation error convergent to a bounded neighborhood around the origin.Simulations illustrate the effectiveness of the proposed control system.

Wave Heave Compensation Based on An Optimized Backstepping Control Method

The vessel heave motion caused by wave action increases the difficulty of installing offshore wind equipment.On-board wave heave compensation devices have therefore become increasingly critical in ensuring the stability and safety of the gangway and working platform.This study accordingly improves the compensation effect of such devices by developing a wave heave compensation model and designing an optimized backstepping control method.First,a model of the compensation system including the servo motor and electric cylinder is established by using the mechanism method.Second,a backstepping control method is designed to track the vessel heave motion,and particle swarm optimization is applied to optimize the control parameters.Finally,MATLAB/Simulink is used to simulate the application of the optimized backstepping controller,then regular and irregular heave motions are applied as input to a Stewart platform to evaluate the effectiveness of the control method.The experimental results show that the compensation efficiency provided by the proposed optimized backstepping control method is larger than 75.0%.

Feasibility Study on Recovering Human-Occupied Vehicle with An Offshore Crane

Launching and recovering human-occupied vehicles(HOVs)has always been a challenging problem.The current recovery process requires staff to manually complete the tethering task,which is inefficient and endangers the lives of staff.This paper suggests moving the recovery position from the surface to underwater at approximately half the wavelength of the water depth(30−50 m underwater),where the HOV experiences less environmental disturbance.An ROV equipped with a ultra-short baseline beacon(USBL)and a manipulator was used to complete the tethering operation.Additionally,a shackle customized to the shape of the manipulator’s gripper is fitted to the end of the cable to simplify the tethering process.To investigate the dynamic response of recovering the HOV using this suggested method,a comprehensive numerical model is developed in this research.The effects of wind,surface waves,ocean currents,and nonlinear interaction between the installation vessel and the HOV are quantitatively examined.The results show that the proposed recovery method can reduce the motion amplitude of the HOV and that the wave has the greatest influence on the dynamic response of the HOV during the recovery process.This model provides better insight into the proposed HOV recovery method and confirms the effectiveness of the heave compensation system.The proposed approach aims to enhance safety and operational efficiency by reducing direct human involvement in the recovery process and mitigating potential dangers.This finding holds particular significance,especially in environmentally sensitive areas,where reducing the impact on the surrounding ecosystem is crucial.

Research on the Performance of Passive Heave Compensator for Tethered Remotely Operated Vehicle System

A passive heave compensator is designed to enhance the operation safety of a 4.5 km remotely operated vehicle (ROV).This paper proposes a novel idea of designing a compensator with relatively low natural period to optimize gas volume and while adding a special device to remove the problem of ineffectiveness and resonance in long seas.Numerical simulations are done based on serious dynamic model of the whole system,including the compensator,the umbilical tether and the vehicle,solved by the fourth-order Runge-Kutta scheme.The compensator provides great attenuation of motion and tension in most sea states.As the working depth increases,the system natural period decreases,resulting in the occurrence of risk of resonance.By regulating the system damping,the compensator can be effective in these situations.