Cable-network Antenna Research Articles

Global sensitivity analysis for cable-network antennas by Kriging models with a sensitivity-based accuracy indicator

Global sensitivity analysis for cable-network antennas by Kriging models with a sensitivity-based accuracy indicator

Low Grating Lobe Cable-Network Reflector Antenna Design Using Integrated Structural-Electromagnetic Optimization Method

Geometric approximation errors of periodically distributed surface facets of cable-network reflector antennas can result in grating lobes undesired in some space missions. As the surface is shaped by the tensioned flexible cable-network structure, the electromagnetic (EM) and structural parameters are highly correlated, and the well-designed surface obtained only concerning the EM performance may not be shaped by the tension-only cable network with specified cable-tension constraints. To address the problem, this study proposes an integrated structural-EM optimization method to enable low grating lobe cable-network antenna design. In this method, force densities of the cables, which can determine both the cable tensions and surface node positions that decide the boundary conditions of the EM field, are selected as the design variables. An adaptive objective/constraint function is proposed, which enables the grating lobe level (GLL) to be minimized with constrained cable tensions, antenna gain, and first sidelobe level (SLL) in a simultaneous, feasible and relatively fast way. To demonstrate the feasibility and effectiveness of the proposed method, it was implemented on a 12 m-diameter cable-network antenna. The results indicate that the grating lobes are greatly degraded and the achieved surface can be formed by well tensioned cables.

Pretension modeling and form-finding for cable-network antennas with varying topologies and parameters

Cable-network antenna is regarded as one of the most ideal satellite antennas. In previous configuration design methods, some basic information including the node connectivity is usually not considered, which affects the subsequent analyses. Meanwhile, the existing form-finding methods mainly adapt to specific cable-network antennas with fixed configurations. Only the antenna accuracy or tension distribution is optimized, which usually cannot guarantee an optimal result. Here an integrated method both for the cable-network antenna's configuration and pretension design with varying topologies and parameters is proposed. Firstly, a parameterized configuration design approach is presented. The node coordinates are calculated by the design requirements, and the antenna topology is described by graph theory. Secondly, a pretension modeling approach is proposed. The parameterized equilibrium equation for the cable-network antenna with a flexible supporting truss is established. Thirdly, the original length approach for form-finding is proposed. Using this approach, a bi-objective optimization model is established to optimize both the antenna accuracy and tension distribution. Lastly, numerical examples are provided to verify the effectiveness of the proposed method, and the form-finding results are compared with the previous method.

Design optimization of mesh antennas for on-orbit thermal effects

Cable network antennas are widely used in space missions, and high requirements on the reflector surface accuracy should be met to achieve reasonable electromagnetic performance. As the form of the cable network is dependent on forces and vice versa, the optimization design for the antenna's cable forces is extremely important. The current optimization methods are usually conducted under ambient temperature, ignoring the shape errors caused by the on-orbit thermal effects in space. Besides, the application of the active shape adjustment method is also limited by the on-orbit measurement and on-orbit control techniques at present. To reduce the on-orbit thermal disturbances and relieve the burden of shape pre-adjustment before launch, we proposed an optimization design method focusing on the on-orbit performances. The antenna's uneven temperature filed at typical orbital positions was calculated based on the heat radiation and conduction theories. The thermal-structural model considering the cable network's and the truss's thermal deformation and elastic deformation was established. For the optimization, the cable force densities were chosen to be the optimization variables, the antenna's shape errors at typical orbital positions were taken as the objectives, and the tension distributions at these orbital positions were considered as the constraint conditions. Numerical examples demonstrated that the proposed method improved the antenna's on-orbit surface accuracy effectively. This work provided ideas and solutions for the cable network's optimization design considering the on-orbit performances in the space environment.

Pretension design of cable-network antennas considering the deformation of the supporting truss: A double-loop iterative approach

Cable-network structures are usually adopted as an ideal form of satellite antennas. The performance of cable-network antennas crucially depends on the surface accuracy and the tension distribution. In some cases, conventional algorithms, such as the equal tension algorithm and the equal force density algorithm, may lead to the decrease of the effective region. Thus the equal length algorithm based on the force density method is proposed in this paper. In this algorithm, the free nodes are restricted as close as possible to their desired positions, which ensures the area of the effective region and the high surface accuracy. The cable tensions are restricted by the maximum tension ratios, which ensures the uniform tension distribution. Furthermore, the elastic deformation of the supporting truss seriously affects the antenna’s performance. Therefore, a double-loop iterative form-finding approach for the cable-network antenna with flexible supporting truss is proposed to find a pre-tensioned configuration that meets the requirements of the surface accuracy and the tension distribution. Firstly, an inner loop based on the equal length algorithm is established for the form-finding of the cable-network. Through this inner loop, the high surface accuracy and the uniform tension distribution can be achieved. Secondly, a compatible strategy between the cable-network and the flexible supporting truss is proposed. Through this strategy, a nonlinear finite element (FE) model of the cable-network antenna is established to capture the compatible deformation. Thirdly, an outer loop combining the equal length algorithm and the compatible strategy is established, in which the node coordinates and the cable tensions are iteratively fed to the force density model and the FE model in steps 1 and 2. Through this outer loop, the compatible deformation is fully considered. The whole loop will stop and converge to a reasonable solution of the surface accuracy and the tension distribution within given criterions. Numerical examples of an offset cable-network antenna are provided, and the results are compared with previous literature.

A FEM Based on the Parametric Variational Principle for the Cable-network Antenna's Form-finding Design

According to the form-finding of the flexible cable-network antenna, a new form-finding analysis approach based on FEM is presented. A parametric variable and Co-rotational formulation are used to model antenna’s constitutive nonlinearity and geometrical nonlinearity, and then the FEM governing equation is established. In order to improve the convergence ability, the Lemke algorithm combined with the improved Newton method is employed to solve the governing equation. The method is applied for nonlinear form-finding analysis of cable-network antenna and an ideal configuration is obtained. The research shows that the method can also be applied for studying other similar antennas.

Modification of cable-network antenna for grating lobe mitigation

Modification of cable-network antenna for grating lobe mitigation

Shape Control of Cable-Network Antennas Considering the RF Performance

Manufacturing errors can result in variation of the cable tensions and degradation of the RF performance of cable-network antennas. To compensate the effects of the manufacturing errors, a novel shape control procedure, which takes the RF performance into consideration, is presented. Both the boundary cables and the tension ties are selected as adjustable cables. Sensitivity analysis is adopted to evaluate the influence of the unstrained cable lengths on the RF performance and cable tensions. The antenna performance is finally expressed as the incremental form of the adjustable cable lengths on the basis of the sensitivity analysis. A mathematical model of the shape control procedure is established and solved using optimization strategy. The proposed shape control method is applied to a 10-m diameter cable-network antenna. Numerical results show that the directivity of the antenna is more sensitive to the boundary cable lengths, while the tension in a cable is much more sensitive to the length changes of itself, the cables connected to it, and the boundary cables. Comparisons of the directivities and tensions before and after shape control demonstrate the feasibility of the proposed shape control method and recommend the antenna RF performance as the shape control objective.

Manufacturing error sensitivity analysis and optimal design method of cable-network antenna structures

Inevitable manufacturing errors and inconsistency between assumed and actual boundary conditions can affect the shape precision and cable tensions of a cable-network antenna, and even result in failure of the structure in service. In this paper, an analytical sensitivity analysis method of the shape precision and cable tensions with respect to the parameters carrying uncertainty was studied. Based on the sensitivity analysis, an optimal design procedure was proposed to alleviate the effects of the parameters that carry uncertainty. The validity of the calculated sensitivities is examined by those computed by a finite difference method. Comparison with a traditional design method shows that the presented design procedure can remarkably reduce the influence of the uncertainties on the antenna performance. Moreover, the results suggest that especially slender front net cables, thick tension ties, relatively slender boundary cables and high tension level can improve the ability of cable-network antenna structures to resist the effects of the uncertainties on the antenna performance.

Robust Design of Cable-Network Antennas with Imperfect Cable Lengths

AbstractUncertainties can be introduced into the structural performance of cable-network antennas by inevitable manufacturing errors, which may result in failure in service. In this paper, robust optimization is first adopted to address the design of cable-network antenna structures with imperfect cable lengths. First, an analytical sensitivity analysis method is proposed to evaluate the effects of the uncertainties on the shape precision and cable tensions. Second, based on the sensitivities, the mathematical model of the robust design is established. At last, the proposed method is applied to a 3-m-diameter cable-network antenna structure. The analytical sensitivities are validated by comparing with the sensitivities computed by finite-difference method, and the feasibility of the presented robust design model is demonstrated by Monte Carlo simulations. The numerical experiments show that the robustness is greatly increased by the application of the robust design method. The results recommend that highe...

Exact mesh shape design of large cable-network antenna reflectors with flexible ring truss supports

An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consideration, and searched for the desired mesh shapes that can satisfy the requirement that all the free nodes are exactly located on the objective paraboloid. Compared with the conventional design method, a remarkable improvement of surface accuracy in the obtained mesh shapes had been demonstrated by numerical examples. The present work would provide a helpful technical reference for the mesh shape design of such cable-network antenna reflector in engineering practice.

Placement Optimization of Smart Piezoelectric Rods for Shape Control of Large Cable-Network Antenna Structures

Large cable-network antennas are typical flexible space structures, which will inevitably generate deformations under various disturbances from out space. To avoid the degradation of shape accuracy due to deformations, it is imperative to find effective approaches to implement shape control for such antennas. In this paper, a novel application of smart piezoelectric rods that are mounted in the ring truss supporting structure of the antenna is presented to solve the shape control problem. The control mechanism is to generate displacements in opposite direction to resist primal deformations by using the direct piezoelectric effect of piezoceramic materials. Based on the genetic algorithm, optimal locations of the smart piezoelectric rods used for shape control is analyzed in the study. Numerical results demonstrate that the present shape control approach with appropriate placement of smart piezoelectric rods is feasible and effective.

Mesh topological form design and geometrical configuration generation for cable-network antenna reflector structures

A well-designed mesh shape of the cable net is of essential significance to achieve high performance of cable-network antenna reflectors. This paper is concerned with the mesh design problem for such antenna reflector structure. Two new methods for creating the topological forms of the cable net are first presented. Among those, the cyclosymmetry method is useful to generate different polygon-faceted meshes, while the topological mapping method is suitable for acquiring triangle-faceted meshes with different mesh grid densities. Then, the desired spatial paraboloidal mesh geometrical configuration in the state of static equilibrium is formed by applying a simple mesh generation approach based on the force density method. The main contribution of this study is that a general technical guide for how to create the connectivities between the nodes and members in the cable net is provided from the topological point of view. With the new idea presented in this paper, multitudes of mesh configurations with different net patterns can be sought by a certain rule rather than by empiricism, which consequently gives a valuable technical reference for the mesh design of this type of cable-network structures in the engineering.

General Mesh Configuration Design Approach for Large Cable-Network Antenna Reflectors

AbstractA well-designed mesh configuration is of great importance to the performance of large cable-network antenna reflectors. The motivation of this study is to find a general approach for designing appropriate mesh configurations of such reflector structure. By synthetically considering the shape-forming criteria, boundary connection conditions, and surface dividing ways, a versatile approach with the ability to generate desired spatial parabolic mesh configurations with specific engineering significance is proposed. In this paper, three shape-forming criteria based on the force-density method are developed. By introducing various boundary connection conditions, mesh configurations with different surface accuracies are achieved. Furthermore, by employing different polygonal elements to divide the surface, arbitrary polygon-faceted mesh configurations are acquired. The work presented in this paper will provide a valuable technical reference for the mesh design of large cable-network antenna reflectors a...

P02 ケーブルネットワークアンテナにおけるグレーティングローブ低減(ALSSポスターセッション/アピールタイム(1))

P02 ケーブルネットワークアンテナにおけるグレーティングローブ低減(ALSSポスターセッション/アピールタイム(1))