Influence Of Random Structural Parameters On The Electronic Performance And Optimization Of Space-borne Cable-net Reflector Antennas

Influence of structural errors in the faceted surface and cable-net structure on the antenna performance is investigated for space-borne deployable cable-net antennas, and based on which, surface configuration design, cable tension and lofting length design as well as worst-case design of the cable-net considering the random errors in the cable lengths and supporting nodal positions are performed. The main work can be described as follows.1. The geometric approximation error of the faceted surface are periodically distributed on the surface, and can result in strong grating lobes. For the preliminary design, the grating lobe level is degraded by disturbing the periodicity of the geometric approximation errors. First, periodicity of the geometric approximation error and its effects on the electrical performance is studied. Second, three approaches are proposed to disturb the periodic geometric approximation error. The first approach is to introduce radial direction disturbance parameters, the second one is to change the shape of the outlines and the last one is to use Penrose-tiling-like configurations. Finally, in combination with optimization technique, the surface configurations that can obviously reduce the grating lobes level are obtained, without either decreasing the gain or increasing the total cable number of the cable-network reflectors.2. Since the surface configuration that meets the electrical performance requirements should be formed by the tension-only cable-net, integrated surface configuration design method is presented considering both the electrical performance and the cable tension distribution. The topology of the cable-net for the three surface configuration design approaches mentioned above is given, and combining with form-finding of the antenna structure, the reflector with good electrical performance and appropriate cable tensions can be achieved.3. The supporting structure of a space-borne cable-net reflector consists of the cable-net and the deployable rim truss of which the displacements and stresses are coupled. For the influence of the rim truss, the predesigned cable tensions of the cable-net will be redistributed and the surface precision will decrease. Therefore, it is of great importance to perform form-finding for the whole supporting structure. An optimal model for form-finding is proposed with the lofting cable lengths as design variables. To simplify the solution of the model, the objective and constraint functions are expressed as the second-order and first-order Taylor expansions. This method is integrated into the form-finding module of Multidisciplinary Integrated Design Platform for Space-borne Cable-net Reflectors, developed by Mechanical and Electrical Technology Research Institute of Xidian University. Once the primary parameters of a reflector is imported, the finite element model can be established quickly, and then the form-finding process will be carried out using the self-developed algorithm.4. The surface precision of a cable-net reflector is determined not only by its geometry approximation error but also by the manufacturing accuracy. As the reflector surface is supported by the cable-net, the manufacturing errors of the cables and the supporting node positions of the cable-net can affect the reflector’s precision strongly. Analytical sensitivities are derived to evaluate the effects of the manufacturing errors on the surface precision and cable tensions. The sensitivity analysis can identify sensitive factors and provide important information for the follow-up work, such as optimal design, manufacturing and assembling of the antenna structure.5. To decrease the effects of the parameters carrying random errors on the surface precision and cable tensions, robust design model considering the worst-case is presented. In this model, the parameter that carry random errors are taken as bounded parameters, and the worst-case surface precision and variations of the cable tensions are formulated in terms of the tolerance of the parameters with random errors and the derived sensitivities. By optimizing the tolerance of the parameters and nonlinearity of the antenna structure, the effect can be degraded.