Design Of An Active Heave Compensation Gangway Based On A Novel 3-SPR Parallel Platform

In marine engineering operations,personnel transfer between ships and offshore structures are frequent.Unlike land transfer operations,the wind,waves and currents at sea can seriously affect the safety of traditional transfer methods.In this paper,a personnel transfer gangway with active wave compensation function(wave compensation gangway)for engineering ships with power positioning system is designed.It can compensate the heave,roll and pitch movement of a vessel,and complete the construction of personnel transfer channel between ships and offshore buildings under high sea state safely and quickly.It can effectively reduce the requirements of the marine environment and extend the transfer time window.The main contents of this paper include the following four aspects.(1)The overall scheme and workflow of the wave compensation gangway are designed.The wave compensation gangway is divided into two parts: the compensation platform and the manned ladder,and the forward kinematic equations of the compensation platform are solved using the least squares method;the kinematic calculation of the compensation platform are simplified by using the "inverse solution method";the compensation performance of different types of compensation platforms is analyzed by comparing their position and attitude workspaces.Finally,the 3-SPR parallel structure is selected as the compensation platform;the structure of the compensation platform is optimized to reduce its working height and shorten the drive chain elongation without changing the compensation capacity of the platform.(2)A wave compensated gangway non-inertial system dynamic response analysis was performed.The inverse kinematic model of the compensation platform was established using the D-H matrix;the motion relationship between the gangway connection point and the manned ladder drive support chain was calculated;the relationship between the ship motion in the inertial system and the non-inertial system and the motion of the drive support chain of the compensation platform was derived.On this basis,the dynamics model of the wave compensated gangway is established using the Newton Euler method,and the relationship between the driving force and the gangway motion is constructed.(3)The control system design and simulation of the wave compensation gangway are completed.In view of the differences in the performance requirements of the control system for different components of the wave compensation gangway,the PID control and sliding mode control are adopted to design and simulate the control system for the manned gangway and the compensation platform respectively;The control strategy of large closed-loop of the position attitude is adopted to better solve the problem of non-coordination of the motion of each branch chain of the compensation platform;A fuzzy controller is designed to adjust the gain of the switching function of the sliding mode control,which effectively suppresses the chattering of the sliding mode control.(4)Experiment of wave compensation gangway scaling prototype.The design and processing of the scaled-down prototype of wave compensation gangway,the construction of electronic control system and measurement unit,the writing of control program and the design of control interface were completed;the experiments of given-position motion of compensation platform,motion following experiment and simulation of wave compensation gangway were conducted;the movement of the compensation platform was smoothed by using the speed foresight method.The feasibility and practicality of the new platform solution are verified.