| Offshore cage is an important strategic direction of marine facility aquaculture because of its large volume,strong wind and wave resistance,high degree of automation.The existing rigid cages have fixed structures after assembly,and it is difficult to adaptively adjust the breeding areas and transport,which hinders their applications in deep-sea aquaculture.In view of the development status of offshore cages,this article introduces the deployable mechanism into the design of offshore cages,and proposes a novel primary and secondary embedded deployable offshore cage.It can effectively adjust the cage volume through the deployment of the frame mechanism,and the primary and secondary structures can realize diversified ecological aquaculture.This design provides a new idea for the design of offshore cage.The main contents of this paper are as follows:(1)In view of the large volume and inability to adjust the size of the breeding area of the existing rigid cages,the deployable mechanism is introduced into the design of offshore cage and a novel primary and secondary embedded deployable offshore cage is proposed.The evolution of the dimension constraint types of the threefold-symmetric Bricard mechanism which forms the primary frame mechanism is investigated.The geometric invariance of the symmetry planes during the deployable process is revealed,then the cage driven mechanism is designed.(2)In order to study the deployable performance of cage,the kinematics of cage frame is analyzed.Based on the geometric projection of the symmetry plane,the mapping relationship between slope angle of the rotation axis and the twist angle of the threefold-symmetric Bricard mechanism is determined.Then,the new input-output equation of the threefold-symmetric Bricard mechanism is obtained.Furthermore,the relationship between the rotation angle of the driving link and the displacement of the rotation axis is established in the symmetrical plane,so the relationship between the driving angle and corresponding open state of the cage can be derived from geometric projection on the symmetric planes.Based on the ABAQUS software,the secondary flexible frame is investigated and the driving mode is determined.Then a closed-loop cable driving scheme is proposed,and the calculation formula of the envelope area is established,and the deployable ratio of the secondary frame is analyzed.(3)In order to meet the requirements of aquaculture and ensure the stability of the aquaculture environment inside the cage,the seakeeping performance of the cage in the marine environment was analyzed.Based on the ANSYS AQWA hydrodynamic analysis software,the numerical simulation of the hydrodynamic response characteristics of the cage under regular waves is carried out.The amplitude frequency response operator RAO curves of the cage and the motion track of the cage under wave forces are drawn,and the hydrodynamic performance of the cage is analyzed.(4)In order to improve the design of cage mooring,and realize the functions of cage lifting and self-cleaning through mooring cable,the cage system is abstracted into six degrees of freedom cable-driving parallel mechanism,and the kinematics and dynamics model of the parallel mechanism is established.This paper analyzes the change of the cable length and tension of the mooring system under the influence of regular waves,which provides a reference for the design of the mooring system.At the same time,the corresponding relationship between the rope length and the tension during the cage lifting,rotating cleaning and swinging cleaning is studied,which provides the basis for the mooring system to control the cage position and posture. |
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