| In recent years,it has become a research hot topic of space deployable antenna for modular parabolic cylindrical antenna because of its advantages of strong expandability,high folding ratio,strong directivity,high gain,and easy scanning.In this paper,the modular parabolic cylindrical antenna is taken as the research object to study the connecting configuration,the degree of freedom and singularity of the space closed-loop coupling mechanism,and the pretension design of the mesh reflecting surface considering truss deformation.(1)A parabolic cylindrical antenna configuration based on the connecting of hexagonal prism modules is studied.Firstly,the cylindrical surface is fitted by the least square method to determine space coordinates of the key points.According to the geometric characteristics of the module connecting,using the mechanism disassembly method and the drawing method,two basic dimensions of the unfolding rib mechanism are designed to achieve the smallest volume of the antenna.Finally,the connecting configuration is verified by ADAMS multi-rigid body simulation and the prototype of the experimental principle.The results show that the connecting configuration is feasible.(2)The degree of freedom and singularity of the spatial closed-loop coupling mechanism are studied.Firstly,according to the calculation formula of the degree of freedom for planar linkage mechanism,the calculation formula for the degree of freedom of spatial closed-loop coupling mechanism established under the specific application conditions is given.According to the property of the coupling between the planes,six geometric constraint equations of the spatial closed-loop coupling mechanism are established.Based on the constraint equations,the geometric constraint conditions for two types of spatial closed-loop coupling mechanisms with one degree of freedom are revealed.The correlation between the equations and the singularity of the Jacobian matrix are analyzed,and degree of freedom of the two types of spatial closed-loop coupling mechanisms is proved,and the spatial singularity is given.(3)The geometric design and pretension design of the cable net structure for the parabolic cylindrical antenna are studied.First,the geometric topology of the reflector is designed by using a triangular and quadrilateral grid respectively.Calculating and comparing the principle errors of the triangular and quadrilateral grids under different segment numbers,the appropriate number of segment is selected to design quadrilateral geometry of cable net structure for the parabolic cylindrical antenna.Based on the force density and singular value decomposition theory,the genetic algorithm is used to solve the optimal pretension of the front mesh surface,and the coupling design of the coordinate of the back mesh surface and the pretension is carried out.Finally,an optimization model of the shape accuracy considering the deformation of the truss is established,through the force density method and the finite element software ANSYS,the pretension under the optimal shape accuracy is obtained.The results of numerical examples prove the effectiveness of the method. |
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