Deployable Reflector Research Articles

New design of precise deployable reflector. Technologies for manufacturing of physical model

The new design of petal space antenna is considered in the paper. Various versions of solid petal-type mirrors have been considered and investigated in a number of articles and space projects. The classical scheme of petal type deployable space reflector was proposed and developed by Dornier Corporation within FIRST space project and was used in the Radioastron project to create a 10-meter antenna of space radio telescope. However, the classical petal mirror design has two significant drawbacks. Firstly, in the open state, the petals are cantilevered on the central mirror, what leads to low rigidity of the structure in open state. Secondly, in the classical design, the accuracy of the reflecting surface of the open mirror strongly depends on small errors in the operation of the deployment system. To overcome these drawbacks a new design of petal type mirror and a new system for precise opening of the mirror were proposed and studied. To test a new technical solution, a physical model of a deployable reflector was developed. The model contains a central mirror, a set of petals, hinges, locks and actuators for opening the mirror. 3D printing technology, CNC (computer numerical control) milling, plastic injection molding and carbon fiber technologies have been tested for central mirror and petals of the model fabrication. The results of computer and physical simulation are presented in the paper.

Structural Dynamic Improvement for Petal-Type Deployable Solid-Surface Reflector Based on Numerical Parameter Study

Petal-type Deployable Solid-surface Reflector (PDSR) is a kind of important structure widely applied in deployable reflector antennas in aerospace engineering. The dynamic properties of this reflector structure in deployed state are significant to the reflector accuracy for antennas. However, the study of the dynamic evaluation of deployable structure with revolute joints is difficult and seldom concerned by researchers. In order to study dynamic properties of the PDSR, the Cable Replacement Method (CRM) was utilized to equivalently simulate the nonlinear structural stiffness of the revolute joint for numerical analyses. The Finite Element Model (FEM) of this reflector structure was established by commercial software ANSYS (ANSYS Inc., Canonsburg, PA, USA) and verified by the theoretical analysis and dynamic test of actual prototype model. The natural frequencies and mode shapes of deployed reflector were computed to study the influence of drag spring design parameters as stiffness, pre-tensioned force, and distance of two adjacent linkage butts. Finally, the analysis results were concluded that the drag springs between two adjacent petals can essentially improve the dynamic performance of reflector structure in deployed state. It can be a useful technical system for future engineering applications of PDSR antennas.

New design modifications of the supporting ring for a large deployable space reflector

Though theoretical and experimental studies of the design of large deployable antenna reflectors have already been carried out for quite a long time, the results obtained in this area of research still attract a lively interest and have good application prospects. In the present paper, two novel design modifications are described for the symmetric (i.e. with circular apertures) radio telescopes. The novelty consists in that improved stiffness and stability have been obtained by combining two conical pantograph systems and thus getting the whole hinged-bar structure consisting of cylindrical and sliding hinges only. Three FE models of the supporting ring structure are constructed and compared with one another using the NASTRAN FEA software. The degrees of freedom of hinges are simulated in local coordinate systems. A static, modal and buckling analysis had been done to investigate, strength and stiffness characteristics.

Multifrequency Spaceborne Deployable Radiometer Antenna Designs

As part of overall ocean dynamic satellite research, the atmospheric correction microwave radiometer (ACMR) used to correct atmospheric path delay in the radar altimeter has been developed recently. The ACMR, composed of an observing antenna (OA) and calibration antenna, operates at 18.7, 23.8, and 37 GHz for improving atmospheric retrieval accuracy. The dual-polarized OA is realized by an offset deployable dish and the common corrugated horn feeding subsystem, while the calibration antenna uses three corrugated horns. The deployable reflector is made of carbon fiber composite (CFRP) supported by a CFRP frame that connects to the satellite deck, and the deployment of the dish is implemented by two hinges. The feeding subsystem has a loaded-ring corrugated horn, an ultra-wideband orthomode transducer (OMT) that covers almost 2:1 bandwidth ratio and bandpass filters. Compromise is made to guarantee that the root-mean-square errors of the deviation of the phase center from the focal point are as small as possible for the three frequencies. Measured results of the OA showed that the voltage standing-wave ratios (VSWRs) are lower than 1.5 while the cross-polarization levels are below −20 dB throughout the all working bands. Furthermore, the radiation patterns have sidelobe levels below −20 dB, and the antenna main beam efficiencies are all above 90% for the tri-band. The calibration horn antennas have VSWR below 1.2 throughout the tri-band, too. Thermal and vibration tests confirm that the antenna is suitable for space use.

전개형 반사판 안테나의 패널 불완전 전개에 의한 편파특성 영향

In this study, we analyzed the effects of panel misalignment on the polarization performance of a deployable reflector antenna. If panel misalignment occurs in a parabola-type deployable reflector antenna, the antenna shape is distorted compared with the original parabola. The shape distortion causes the degradation of co- and/or cross-polarization performance. We investigated the difference in performance degradation for the cases of symmetric and asymmetric misalignments. The cross-polarization is small when the misalignment is symmetric, and approximately 68 dB higher for asymmetric misalignment than that in symmetric case. It was confirmed that the cross-polarization mainly arises from the asymmetry of the antenna.

Failure analysis of a high precision deployable reflector in TED test

This paper investigates phenomenon and potential reasons for failure in TED (thermal elastic distortion) test of a high precision deployable reflector which is designed for the second HTS in China, the ChinaSat-18. Firstly, configuration of the reflector is introduced to give a comprehensive understanding of the reflector design. Then, setup and results of the thermal elastic distortion test are presented, and the test results are evaluated from two aspects: arm depointing and shell distortion, failure phenomenon of the test is also described in detail. Moreover, failure mode analysis is presented, and the final root cause of the failure is illustrated which indicates that the failure is caused by the arm-backup structure interface sliding. Failure analysis of the arm-backup structure interface is conducted and the same failure phenomenon is reproduced by analysis. Finally, a feasible repair scheme for engineering application is proposed, then thermal elastic distortion test after repaired is conducted in thermal vacuum chamber and the test results validate the correctness and effectiveness of the proposed failure cause analysis and repair scheme.

Design of a Large Deployable Reflector Opening System

Large Deployable Reflectors (LDR) are receiving considerable attention from aerospace government companies and researchers. In this paper, the design of the opening system of a LDR is presented. Starting from an elementary cell, a first ideal kinematic model is discussed. Then, a more complex “design model” including feasible design solutions for joints and links is developed. The final design avoids collisions between links while maintaining the original kinematic features.

Optimal design and robust analysis of a net of active devices for micro-vibration control of an on-orbit large space antenna

Large deployable antennas are required for the advancement of space communications, Earth observation, radio astronomy and deep space exploration. Most contemporary space antennas have exceeded the size of launching vehicles, leading to the necessity of stowed concepts to overcome the limitation. Many structural models have been investigated by different organizations. Generally, mesh deployable reflectors are currently more mature compared to other foldable solutions. This will be the topic of this paper. Orbital disturbances, perturbations originated by on-board sources and thermal deformations affecting the deployed configuration can deteriorate the accuracy of the communications system. Undesired dynamic behaviour of structural components has to be predicted and counteracted. Therefore, vibration control is a key technology to correct the distortions altering the proper functioning of the system. An intelligent active structure is introduced as a structure configured with distributed actuators and sensors and guided by a controller to modify the dynamic response of the system. In this paper, the supporting structure of a very large mesh reflector is described. A FEM formulation is adopted to assemble the frame and it is validated by comparing it with commercial codes. According to the adopted model, the active elements can be embedded in the middle of the truss elements. Of course, active control of all the devices at the same time requires a control effort which could be not affordable in space applications. However, the effectiveness is not the same for all the actuators. In this study, two cascade optimization procedures are performed to assess the best positioning and velocity feedback gains of the actuators that must be controlled to damp vibrations. In particular, a gradient-based technique is used after both a Genetic Algorithm and a Reinforcement Learning methodology to find the best set of gains for the controller. The objective function is set as a weighted sum of power consumption of the actuators. As a study case, the spacecraft implements a velocity feedback strategy when performing a generic attitude manoeuvre to coordinate the simultaneous action of the devices to ensure the damping performance of the system is enhanced. In addition, the impact of damaged actuators and uncertainties on the mechanical properties of the passive structure has been discussed and analysed.

Shape Adjustment of Flexible Rib for Large Deployable Reflector

The surface of large deployable reflectors has to be carefully adjusted to achieve the required accuracy, which is an effective way to compensate for manufacturing and assembly errors or other imperfections. An accurate mechanical model is essential for all shape-adjustment methods. The shape adjustment of large deployable reflectors based on the reconstruction, finite, genetic, and tension (RFGT) method is addressed in the assembly phase. The RFGT method includes reverse reconstruction, finite element method, genetic algorithm, and tension adjustment. Combined with the method of subarea photography and splicing, a digital photogrammetry system is used to test the reflector surface. Interpolation is used for curve fitting, and the flexible rib is accurately modeled through reverse reconstruction. The finite element method is used to analyze the deformation regularity of the rib under the stress load of each rope. The relationship between the node shape accuracy for the rib lower edge and the rope stress loads is established. The optimal combination of rope stress loads is obtained using a genetic algorithm. The ropes apply extra tension loads to adjust the shape of the rib based on the original tension. The surface test data show that the rib lower edge is optimized after multiple adjustments in the assembly phase.

Form-Finding Design of Cable–Mesh Deployable Reflector Antennas Considering Wire Mesh Properties

The wire mesh is a key component of a cable–mesh deployable antenna; it is laid on the cable net to reflect electromagnetic waves. The knitting form, mesh size, and wire mesh ductility directly affect the accuracy of the reflector. In this paper, a form-finding design method that considers wire mesh properties is proposed for cable–mesh deployable reflector antennas. First, a three-dimensional geometric model of the wire mesh is established. Based on the augmented Lagrange multiplier method, the finite element method model of the wire mesh is derived, and its accuracy is verified by experimental data. Second, to simplify the computation for a large-scale flexible wire mesh structure, the mechanical model is made equivalent to an anisotropy membrane. Third, based on the nonlinear finite element method, the form-finding design method of the cable–membrane composite structure is proposed. The simulation and experimental results demonstrate the significant influence of the mechanical properties of wire mesh and the validity of the proposed design method.

Tie-System Calibration for the Experimental Setup of Large Deployable Reflectors

The trade-off between the design phase and the experimental setup is crucial in satisfying the accuracy requirements of large deployable reflectors. Manufacturing errors and tolerances change the root mean square (RMS) of the reflecting surface and require careful calibration of the tie-rod system to be able to fit into the initial design specifications. To give a possible solution to this problem, two calibration methods—for rigid and flexible ring truss supports, respectively—are described in this study. Starting from the acquired experimental data on the net nodal co-ordinates, the initial problem of satisfying the static equilibrium with the measured configuration is described. Then, two constrained optimization problems (for rigid or flexible ring truss supports) are defined to meet the desired RMS accuracy of the reflecting surface by modifying the tie lengths. Finally, a case study to demonstrate the validity of the proposed methods is presented.

A compact C-Band CP-SAR microsatellite antenna for Earth Observation

This work describes the development of a compact Circularly Polarized SAR C-band antenna system and the design considerations suitable to use on small spacecrafts. To reduce size and weight of the small spaceborne SAR, we utilize a lightweight deployable parabolic mesh reflector and operate at low Earth orbital altitudes. The antenna is a wrap-rib center-fed parabolic reflector with dedicated receiving and transmitting feeds. Antenna requirements are: center frequency of 5.3 GHz with bandwidth of 400 MHz and circular polarization with axial ratio better than 3 dB. Simulation of the parabolic reflector and effects of different structural elements to the main radiation pattern is analyzed, which include ribs, struts, feed blockage and mesh surface. A research model of the parabolic reflector was constructed. Surface verification was realized using two different approaches, one using a laser distance meter along ribs and the other using 3D scanning of the reflector surface, with respective surface accuracy of 1.92 mm and 3.86 mm RMS. Near-field antenna measurements of the deployable reflector mesh antenna was realized for final antenna validation, presenting good agreement with the simulation results. Future work comprises of prototyping and testing of the full polarimetric feed assembly.

Development of an L-Band SAR Microsatellite Antenna for Earth Observation

A compact synthetic aperture radar microsatellite antenna operating in the L-band is presented. To reduce size and weight of the small spaceborne SAR, we utilize a lightweight deployable parabolic mesh reflector and operate at low Earth orbital altitudes. The antenna is a wrap-rib center-fed parabolic reflector with dedicated receiving and transmitting feeds. Antenna requirements are: gain better than 30 dBic, center frequency of 1.275 GHz with bandwidth of 28 MHz and circular polarization with axial ratio better than 3 dB. This work describes the development of a compact Circularly Polarized SAR L-band antenna system and the design considerations suitable for small spacecrafts. Simulation of the parabolic reflector and effects of different structural elements to the main radiation pattern were analyzed, which include ribs, struts, feed blockage, and mesh surface. A research model of the parabolic reflector was constructed, and the reflector surface verification was realized using two different approaches, a laser distance meter along ribs and the other using 3D scanning of the reflector surface. RMS errors wree 1.92 mm and 3.86 mm, respectively, both below required 4.55 mm of surface accuracy. Near-field antenna measurements of the deployable reflector mesh antenna was realized for final antenna validation, presenting good agreement with the simulation results. Future work comprises prototyping and testing of the full polarimetric feed assembly.

An optimized form-finding method of an asymmetric large deployable reflector

Deployable mesh reflector antennas are widely used for space applications and the form-finding analysis plays an important role to reach the high surface accuracy. In this paper, an optimized algorithm extends the traditional force density method for the form-finding analysis of an asymmetric offset antenna. The optimization problem is solved by minimizing the RMS error with respect to the ideal paraboloid. First, the algorithm is implemented considering rigid ring truss support. Then, the effect of the elastic deformation of truss support is taken into account. The minimum distance between each free node of the front net and the ideal surface is used for the calculation of the RMS error. Finally, a numerical example is carried out to demonstrate the validity of the proposed method.

Synthesis and optimization of modular deployable truss antenna reflector

PurposeThis paper aims to synthesize a modular deployable truss antenna with the lower degree of freedom (DOF) and larger folding ratio. Because of the advantages of this kind of new truss antenna, the modules that make up the antenna can be deployed together by the synchronous motor drivers instead of twist springs to realize the controllable deployment.Design/methodology/approachThe closed-loop branch equivalence method is proposed to synthesize the single DOF module and the large deployable reflector. The complex mechanism can be equivalently replaced by a simpler mechanism based on screw theory. The motion pairs are synthesized and optimized to make the curved surface achieve to the maximum folding ratio when the modular parabolic truss antenna is folded.FindingsThe results show that the 3(3RR-3RRR)-3RRR-3RRR planar module is a single DOF mechanism. Additionally, the adjacent parts of every two modules are connected with universal joints to obtain the new truss antenna when the modules are networked.Practical implicationsThe configuration of this new modular deployable truss antenna can be synthesized to design the structure, and the proposed method can be applied to other space multi-loop coupling mechanism and other spacecraft.Originality/valueThis paper presents an approach to synthesizing the motion pairs, as well as the DOF analysis. The results lay a foundation for the further analysis of the deployable control and dynamics of this kind of antenna. And the new modular truss antenna has a practical application in aerospace engineering.

Malleability and optimization of tetrahedral metamorphic element for deployable truss antenna reflector

The tetrahedral elements that make up the large deployable reflector (LDR) are a kind of metamorphic element, which belongs to the multi-loop coupling mechanism. Firstly, the method of combining topology with screw theory is put forward. The parametric model and the constrained matrix are established to analyze the malleability of 3RR-3RRR tetrahedral element. Secondly, the kinematics expression of each motion pair is deduced by the relationship between the velocity and the motion spinor. Finally, the configuration of the metamorphic element is optimized to make the parabolic antenna fully folded, so that the antenna can meet the maximum folding ratio. The results show that the 3RR-3RRR element is a single-degree of freedom (DOF) mechanism. What’s more, three new configurations 3RS-3RRR, 3SR-3RRR and 3UU-3RRR are obtained on the basis of optimization. In particular, it proves to be that the LDR which consists of the 3RS-3RRR metamorphic element can achieve the maximum folding ratio. This paper provides a theoretical basis for the computer-aided design of the truss antennas, which has an excellent applicability in the field of aerospace and other multi-loop coupling mechanism.

可展开固体反射面机构设计及运动学分析

可展开固体反射面机构设计及运动学分析

Insensitivity Characteristics in the Dual Polarization of Deployable CFRP Reflector Antennas for SAR

A large deployable reflector antenna is considered and designed for the application of a synthetic aperture radar system requiring high gain for the high resolution of a detected image within a distance of a few hundred kilometers. For its lightweight and strong characteristics, carbon fiber reinforced polymer (CFRP) is introduced as a composite material and fabricated for conductivity evaluation. Effective electrical characteristics are obtained as a function of carbon fiber direction, using measured S-parameters in a rectangular waveguide. By taking into account the changes of the effective electrical characteristics that depend on the fiber direction of reflector antenna, the radiation pattern is investigated at X-band in terms of gain and polarization variation effects. The proposed reflector antenna made of quasi-isotropic CFRP panel can realize the insensitive characteristics depending on the incident polarization.

Strain measurements on compliant knitted mesh used in space antennas, by means of 2D Fourier analysis

AbstractThe paper presents a strain measurement technique to be applied on repetitive knitted nets. The application of the procedure is focused on large deployable reflectors used in space applications. Manufacturing of these structures involves knitting of thin metallic wires. Besides space antennas, the method herein developed is advantageous for many other types of knitted tissues such as elastic coatings, elastic bandages for medical applications, or any other woven fabric requiring a defined elastic behaviour. All of them display an almost regular repetitive pattern whose variations due to imposed loads are the core of the method. Deformation of such kind of structural elements must be analysed in two dimensions, because the knitting causes an accentuated orthotropic behaviour. Strain measurement is tricky and requires special computational techniques. Indeed, the application of standard experimental methods and indirect strain determination, through well‐established image analysis algorithm, can be totally unsuccessful or unsuitable because of the lack of continuity of these structures. The paper presents a method based on two‐dimensional Fourier analysis. Numerical examples, supported by some experimental evidences, confirm the feasibility of the technique. Furthermore, a newly proposed frequency zooming algorithm, based on fast Fourier transform, makes the computational costs of the indirect strain measurement affordable.

ETS-VIII搭載大型展開アンテナの開発 : 電気性能評価について

ETS-VIII搭載大型展開アンテナの開発 : 電気性能評価について