Form-finding For Loop Antenna With Flexible Truss

Loop antenna, which is composed of ring truss, cable net structure consisting of front/rear cable net and vertical cable, and metal reflector attached to the front cable net, has become the ideal form of the antenna structure because of its large diameter, light weight, high storage characteristics. Surface accuracy is an important indicator of loop antenna electrical properties, affecting the quality of communication signals. As support structure of metal reflector net, forming state of cable net structure, which can not be divided with pretension distribution of cable segment, will determine the shape of the reflecting surface. Optimized design of cable net shape is to configure pretension in the cable segments with meeting the surface precision requirements. This process is also called form-finding, which is affected by truss deformation, hinge stiffness. The main works in this paper are summarized as follows:Firstly, Form-finding result evaluation of cable net structure is analyzed, and the surface precision and uniformity of tension cable segment is treated as the main design goals. Optimization model is built based on the force density method, with cable segment force density as design variables, net surface root mean square error as objective function, cable segments tension ratio and limit of pretension as constraints. Form-finding study case shows that higher accuracy and more uniform cable net pretension can be achieved.Secondly, a new form-finding method is proposed taking deformation of the flexible truss and stiffness of hinge into account, combined force density method and finite element method. This method mainly include three steps. Boundary rope residual pretension and truss nodal displacements is obtained by finite element method, then update truss coordinates, and a new mathematical optimization model based on force density method is established with the boundary rope segment as a known quantity. Pretension of the rest of the cable segment can be got through optimization.At last, to replace finite element modeling and analysis in the third chapter and to improve the efficiency of form-finding, the ring truss stiffness equation is established with the use of matrix displacement method. For boundary cable beam composite structure, optimal mathematical model is established with load on the truss in balance state as design variables, and the load difference between residual pretension in the boundary cable segments and variables as objective function, then cable beam coupling deformation is analyzed, which made integrated form-finding of flexible cable net structure possible, and laid the foundation for revealing coupled deformation mechanism of flexible truss, flexible hinge, flexible cable net...