Research On Underwater ROV Towing Operation And Active Heave Compensation Control Technology

Under the background of building a strong marine nation,the development of marine science has gradually entered the era of intelligent operation equipment,systematic ocean observation,integrated ocean technology and global ocean strategy.Marine engineering equipment such as Remotely Operated Vehicle,when encountering severe environment,the working vessel will generate six degrees of freedom motion,including heave,roll,sway,yaw,surge and pitch,connecting the repeater and robot motion through the armor cable.The resonance caused by wave impact will enlarge the heave amplitude and intensify the motion of underwater ROV,resulting in armor cable fracture and damage to ROV.In order to improve the safety performance of ROV operation,this paper focuses on the complex dynamic characteristics of ROV towing armor cable and the active heave compensation technology to increase the degree of decoupling.The specific contents are as follows:(1)Current situation at home and abroad.The development status of underwater towing system and heave compensation technology at home and abroad,and the development trend of heave compensation technology are introduced.(2)The dynamic load and state configuration distribution of underwater towing operation are studied.Aiming at the characteristics of multi-variables,strong nonlinearity,strong coupling,uncertainty,and the inability of some target point process parameters to be obtained directly,and the time-varying physical parameters and towing state in the process of ocean towing,a dynamic model of system ground armor cable was established.The control equation of the towing system is established based on the concentrated mass method.According to Newton 's second law,the cascading nodes are discretized to obtain the continuous dynamic characteristic partial differential equations.The time domain finite difference method is introduced to solve the partial differential equations of motion,and the simulation program is compiled to calculate the towing system.The tension variation and cable configuration under three different operating conditions of no current,coastal current and reverse current are given respectively,and the load tension and motion law of the towing system under multiple factors are considered,which is practical significance for improving marine safety and operating efficiency.(3)The active heave compensation system and its model are designed and analyzed in detail.Firstly,the classification and working principle of active heave compensator are introduced briefly,the relationship between the displacement of piston rod and the load heave of relay in passive compensation is expressed by using load formula,and the realization process of each compensation cycle is described from the angle of formula;the relative degree of system output and interference is determined by the derivation of Li derivative,which provides a certain theoretical basis for engineering application.(4)The electro-hydraulic position servo nonlinear control strategy of active heave compensation system is studied.In the process of active heave compensation electro-hydraulic position servo control,considering the continuous switching process of the system under complex working conditions,due to the discontinuity of the saturation function,there are occasions for derivation of s,and the performance of chattering elimination is significantly reduced.The curved tangent function can effectively reduce chatter in sliding mode control.Through the design of the winch lifting compensation system based on the hyperbolic tangent function desired compensation nonlinear cascade control(DCNC)strategy,a detailed nonlinear mathematical model is proposed.Aiming at the parameter uncertainty during the drag compensation process and the external load disturbance of the system,an extended state observer(ESO)is designed to predict and effectively suppress the estimated disturbance,avoiding the acceleration feedback of the pulley block,and combining with the expected compensation cascade control to form a DCNCESO controller,which effectively improves the robustness of the system.