| When a ship with dynamic positioning device or mooring system is working at sea,it will be affected by wind,waves and surges,and the ship will have rolling,pitching and heave motion with three degrees of freedom.Such three-dimensional rocking motion will bring security risks to the staff on board the ship when they transfer to the offshore platform.In this dissertation,aiming at the problems of heavy and partial load,large driving force,complex mechanism and large area of land for existing products at home and abroad under the condition of large compensation range,an R+2RPR/RP+RP hybrid wave compensation mechanism is proposed for personnel transfer and cargo barge.The main research contents are as follows:According to the technical problems existing in Marine personnel transfer products,combined with the characteristics of ship rocking and the requirements of the subject,the characteristics of freedom required by tandem hybrid bridge are analyzed,and two different tandem hybrid wave compensation mechanisms are compared,and a configuration scheme of R+2RPR/RP+RP tandem hybrid wave compensation mechanism is analyzed and determined.And according to the configuration of the mechanical structure design,reference to the relevant national standards to check the key components.The R+2RPR/RP+RP hybrid wave compensation mechanism is equivalent to RRPRPR six-degree-of freedom series mechanism.The position,velocity and acceleration mappings of working space and joint space are analyzed in non-inertial system,and the Jacobian matrix and Hessian matrix of equivalent series mechanism are derived.The displacement,velocity and acceleration maps of joint space and drive space are established by analyzing 2RPR/RP parallel mechanism and four-bar mechanism.The velocity and acceleration mapping relationship between inertial and non-inertial systems is derived.Based on the position inverse solution,the influence of different installation positions on the working space of the series-parallel wave compensation mechanism on the ship is analyzed,which provides a theoretical basis for the installation and use of the prototype.Through MATLAB programming and the mechanical model established in Simulink,the kinematics was verified.Based on the recursive formula of velocity and acceleration,Newton-Euler method,combined with D ’Alembert principle and virtual work principle,the dynamics model of the equivalent series mechanism was established,and the mapping relationship between the joint space driving force and the driving space driving force was further derived.The dynamics modeling was verified by MATLAB programming and the mechanical model established in Simulink.Based on the mechanical structure characteristics of the tandem hybrid mechanism,the overall scheme of the hydraulic system is designed and analyzed,and the key hydraulic components are selected and calculated.Based on the parameters of the designed hydraulic system,the corresponding hydraulic system model is built in Amesim.The trajectory tracking of the hydraulic actuator is realized by using the PID controller of the position loop and the speed loop.The relevant performance of the hydraulic system under different parameters is analyzed,which provides theoretical support for the prototype development.Based on the inverse solution of equivalent series mechanism with dummy rotation pair,the control flow of wave compensation mechanism is established,and the trajectory planning of the docking process is carried out.Based on the potential f low theory and applied AQWA simulation software,the ship’s hydrodynamic simulation was analyzed.Based on the motion law,the Stewart platform was used to simulate the ship’s motion,and the wave compensation control algorithm was verified. |
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