| In the 21 st century,the ocean has once again become the focus of world attention,and the national strategic position of the ocean has never been higher.And marine lifting equipment is inseparable whether it is the transshipment of goods in the ocean transportation industry or the loading and transportation of coastal defense equipment.While changing rapidly the sea environment is,the crane vessels will produce a large pitch,roll,and yaw motion under the effect of wind and waves during the operations,which will not only bring great difficulties to the operators of the hoisting system,but also imposes more stringent requirements on the stability of the offshore hoisting system.Compared with the rigid drive parallel mechanism,the cable drive parallel mechanism(CDPMs)has the characteristics of convenient assembly and disassembly,high qualityload ratio,and is very suitable for lifting operation.And thus,a cable-driven 6-DOF motion system for offshore lifting operations was proposed in this paper.The system proposed not only can compensate the movement caused by the sea wave disturbance,realizes the automatic compensation and control of the error,and has better environmental adaptability,which can effectively reduce the difficulty of lifting operation and improve the efficiency of lifting operation.Considering the application background of the cable-driven 6-DOF motion system,under which both the upper and lower platforms will produce movement,this paper established the kinematics model and dynamics model firstly,calculated the Jacobian matrix and the cable tension subsequently,and then verified the correctness of the models based on Adams software.Subsequently,the relationship between the singularity of the incompletely restrained cable parallel mechanism(IRPMs)and its working space was analyzed in this paper,and the static working space and dynamic working space of the system were solved.Afterwards,this paper studied the capability of vector force output,and based on this,the concept of the anti-interference workspace is proposed.The antiinterference workspace is more practical in structural parameter design.On the basis of completing the workspace of the cable-driven 6-DOF motion system,this paper studied the influence of the choosing structural parameters on the specific shape and size of the workspace quantitatively.And then analyzed the influence of the choosing structural parameters on the system performance from the points of both the condition number of the Jacobian matrix and the natural frequency of the system.And a dimensional synthesis method for the Optimized design of cable-driven 6-DOF motion system was proposed finally,which can give an optimized design of the structural parameters while given the movement request of the load.Finally,This paper studies the control problem of the IRPMs.And on the basis of considering the elasticity of the cable,the dynamics model of AC servo lifting system was established,and on the basis of this,the Control characteristics of the IRPMS was analyzed.For the nonlinear,lower stiffness,lower damping and incompletely constrained features the IRPMs performed in the control system,a hinge space control strategy based on calculated tension feedforward was proposed in this paper.Combined with the application background of the subject,the step response and sinusoidal response of the system under the control strategy proposed was studied on the basis of co-simulation between the Simulink software and the Adams software.And finally,the effectiveness of the control strategy proposed was verified by a simulation of a motion compensation conducted by the cable-driven 6-DOF motion system. |
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