Design And Simulation Of An Offshore Transfer Gangway With Wave Compensation Function

With the development of China's offshore industry,the demand for offshore transfer is also increasing.The traditional offshore transfer technology can only transfer people in a stable sea state,and the new offshore transfer technology,offshore transfer gangway,usually requires the end of the gangway to be fixed.Therefore,the scope of application is limited.In order to solve the above problems,this paper designs an offshore transfer gangway for vessels applied to high sea states,and the end of the gangway doesn't need to be fixed.It compensates the vessel motion of sway,surge and heave direction by active wave compensation function,so that the end of the gangway is still relative to the offshore structure,so the safety transfer of personnel between vessel and offshore structure is realized.It mainly includes the following four design aspects:(1)Based on the comprehensive analysis of the existing offshore transfer gangway,the design requirements and the overall scheme of the offshore transfer gangway are proposed.On the basis of analysis the working states,the structure of the offshore transfer gangway is designed,and the gangway of the truss structure is designed,and the truss structure is checked by using the finite element anlysis method.The moving mechanisms of the offshore transfer gangway are designed: the telescopic mechanism,the pitch mechanism and the slew mechanism.They are used to move the gangway and automatically complete wave compensation in the direction of sway,surge,heave and yaw.(2)The movement of the offshore transfer gangway caused by the wave motion is analyzed,and the gangway movement in 4-level sea state is obtained.By modeling stochastic wave,the response motion of vessel to wave is obtained,then the position of the end point of the gangway and the displacement to be actively compensated by each moving mechanism are obtained by the coordinate transformation method.(3)The hydraulic system of the offshore transfer gangway is designed.The hydraulic system scheme is analyzed,and the servo-directional valve position control system is used to compensate wave motion.The hydraulic power unit is designed,and the hydraulic system of the moving mechanisms are designed,and the mathematical modeling is carried out.The control strategy of active wave compensation is designed: The control strategy of telescopic mechanism is feed forward + PID correction,and the control strategy of pitch mechanism is cross-coupled synchronous control,the control strategy of slew mechanism is feed forward + fuzzy self-adaptive PID correction.(4)The offshore transfer gangway under 4-level sea state is simulated and analyzed.The master-slave synchronous control and cross-coupled synchronous control of the pitch mechanism are comparison and analyzed.The feed forward+PID correction and feed forward + fuzzy self-adaptive PID correction of the slew mechanism are compared and analyzed.Through these comparative,the rationality of the selected control strategy is verified.The active wave compensation function of the offshore transfer gangway is simulated to verify the effect of the offshore transfer gangway on the wave compensation.