Modeling And Simulation Of Hydraulic Cylinder Heave Compensation System

Crane ship is inevitably needed for offshore lifting engineering operations,however,floating crane in the high sea state will result in severe swing motion,which may cause the load cannot be accurately installed,or the cable easily be fractured due to the snap load.Among the swing motions,ship's heave has the greatest impact on the lifting operation,and is most dangerous,too.Therefore,it is necessary to carry out simulation research on the heave compensation system,emulating the parameters of the system during the offshore operations and provide theoretical and technical support for engineering design.On the basis of crane ship HYSY286,this paper calculate the hydrodynamic coefficients of the ship,and by considering the external environmental forces such as wind,wave and current and the influence of hydrostatic force(moment),the 6 DOF mathematics models are established.Then we simulate in MATLAB and get the ship's swing motion during time frequency.As the crane lifting load through the tip of boom,the paper derived its heave motion according to the relative position,and use it as the load's movement input which to make it closer to actual situation.The heave compensation system of HYSY286 can workes in the PHC(passive heave compensation)model and in the APHC(hybrid active-over-passive heave compensation)model:the passive heave compensation is mainly used to balance the external load of the system,while the active heave compensation is used to eliminate the deficiencies of passive heave compensation.As to the PHC model,an improved model is proposed by introducing the dynamic equation of the medium separator and considering the influence of the reduction of tension.For the lifting operation,the performance of the compensation system with the heave motion and the boom tip is discussed.The results show that the compensation efficiency is different,and the necessity of motion conversion is proved.Compared with other methods,the results show that the proposed method is effective,and the efficiency of motion compensation and tension compensation are about 64%and 79%,respectively.As to the APHC model,the paper setup the models of servo proportional control valve and auxiliary active cylinder on the basis of PHC model,and analyzes its working principle.Due to the complex of controller design,the paper only analyzes the dynamic characteristics of servo-controlled hydraulic cylinder system,and the result shows that the closed loop circuit system supplemented with feedback control mechanism is stable.