Structure Design And Profile Adjustement Of Laqrge Deployable Mesh Antenna For Statellite

Large deployable Astromesh antenna, which is attracting more and more attention of space navigation scholars all over the world, is an important type for deployable mesh antenna for satellites. Triangular cable-net structure is a main form of the cablenet structure of this type antenna. Based on some engineering projects, the methods of geometrical design, pretension design and profile adjustment of structure of Astromesh antenna are mainly discussed in this paper. The main research works are as follows:Firstly, aimed at minimizing the principle error of the large reflector, a geometric design method for Astromesh antenna is developed. To subdivide a paraboloid surface, the first step of the geometric scheme is to subdivide the inscribed regular hexagon of the optical aperture circle into small regular triangles. Then the points of intersection of these triangles are projected or mapped on the paraboloid surface using a suitable origin of coordinates to obtain the final nodal coordinates of the facets. Certain formulas are established to determine the side length of the triangles and the origin coordinates of the paraboloid when the mapping is done. With axial square mean error as the measure of reflector's precision, the validity of the proposed method has been proved theoretically. Furthermore, illustration is provided to compare the results designed with the method proposed and with other methods.Secondly, the pretension design of the structure of large mesh antenna is discussed, which falls into two steps. In the first step, based on the assumption that the ring truss is rigid enough or the cablenet structure has an ideal boundary condition, pretension optimization for the pure cablenet structure of mesh antenna is done. Then, with the designed pretension cable-net structure as input, and taking the truss's elasticity into account, the ring truss of the mesh antenna is redesigned.When we discuss the pretension design of the pure cable-net structure of mesh antenna, two approaches are developed. The first optimum design method is especially for the cable-net structures of axi-symmetric parabolic antenna with a triangular net form, based on the characteristic of such structures. The second, otherwise, is a method for the pretension design of most general cable-net structures of mesh antenna, the optimization model of which is deduced from the static force balance equations of the structure by the concept of minimum norm solution of linear equations. By a comparison of the design results in some illustrations with the two approaches, it is showed that the first method takes less computation and gives a little better results, but the second method is always more applicable when the application scope is taken into account.Then, with the pretension cable-net structure designed under an ideal boundary condition as input, the elasticity of the ring truss is fully taken into account. Based on the feature of the deformation of the truss structure induced by the cable-net structure's pretension, a reiteration method to redesign the pretensions of cable-net structure of the mesh antenna is proposed. In each iteration step, the tension of the cable net structure is firstly redesigned using the minimum norm method with the position of the deformed structure as initial conditions, and then with the redesigned cable net structure as a part of the whole antenna structure, form-finding analysis of the whole structure is done. The iteration procedure is repeatedly done until the maximum tension ratio of the cables on the mesh surface is stabled. An illustrative example is given to clarify the effectiveness of the reiteration method proposed.Finally, with the goal to improve the reflector's precision in its assembling and setting procedure, the problem of optimal adjustment of the profile of mesh antenna is discussed. Aimed at minimizing the total adjustment workload and improving the calculative efficiency while we decide which cables are to be adjusted and how much the according adjustment are to be made, a new method for the profile adjustment of mesh antenna is proposed. Base on the fact that the cable adjustment is always done one by one in the factory, the method chooses only one cable as the adjusting cable and designates its adjustment quantity as the design variable at each optimization process. In order to gain maximum efficiency while only one cable is to be adjusted every time, certain criterion is established for selecting the suitable cable among all the adjustable cables. Simulation results show that the method has a certain validity and feasibility.