Dynamic Modeling And Experimental Study Of Series-parallel Hybrid Offshore Gangway

The ship’s multi-dimensional swing motions are induced by the disturbances of the wind,waves,surges and other loads on her voyage,which poses a serious threat to the safe transit of the personnel and cargo on board.The offshore gangway mechanism can compensate for the ship’s swaying motion and keep the controlled object relatively stable under the inertia system.Improving the efficiency and safety of sea interchange plays an important role in China’s economic development and national defense construction.which plays an important role in China’s economic development and national defense construction.In view of the existing offshore personnel or to compensate for cargo transfer technology is difficult to achieve large travel,being a small deck area,large stiffness,and strong carrying capacity,This thesis has carried out a study on the six degrees of freedom of series-parallel hybrid offshore gangway with motion compensation capability.Firstly,the design indexes of the offshore gangway mechanism are formulated through the study of typical motion parameters of ships,and a new type of series-parallel hybrid offshore gangway mechanism is designed for the defects of existing maritime interchange technology,and a new type of ship motion compensation scheme is proposed to compensate the ship’s transverse and longitudinal rocking motion by using the parallel platform and compensate the ship’s vertical swing motion by using series gangway.The forward and inverse kinematics modeling analyses of both are carried out by using the D-H modeling method and Euler angular coordinate conversion method respectively.Secondly,the dynamics model of the 3-UPU/UP-RRP series-parallel hybrid offshore gangway is established by integrating the principle of virtual work and the Lagrangian method.The velocity and acceleration of each component of the mechanism are obtained by the vector method,the Jacobi matrix of each branch is solved,the mapping relationship between joint space and operation space is obtained by Jacobi analysis,and the dynamics model of the parallel platform is established by combining the virtual work principle.The dynamics model of the offshore gangway under dynamic load is further obtained by using the equivalent center of gravity method,and the dynamics of the system when performing personnel transfer operations are analyzed under this model.The accuracy of the kinematic and dynamical models is verified by joint simulation with Adams and Matlab,and the effect of motion compensation is analyzed by the simulation results,which show that the motion compensation scheme based on the offshore gangway structure can compensate 83% of the ship motion.The control strategy of the offshore gangway is studied.A fuzzy PID controller is designed for the mechanism of the offshore gangway,and the motion inverse solution module and control system is built by Simulink to realize the complete wave compensation system and simulate the motion compensation,and the simulation results show that the system can realize the safe transit at sea under four sea states.Finally,the test platform and the measurement and control system of the offshore gangway is completed,and the control program was written by Labview according to the compensation scheme and control strategy of this paper,and several sets of motion compensation experiments were conducted.The results show that the rocking reduction effect of the bridge is more than 60%.