Large Mesh Antenna Research Articles

Research and Application on High Precision Measurement Method of Large Mesh Antenna Surface

Abstract The development process of large mesh antennas requires a significant investment of time and resources for iterative measurements and adjustments to achieve high precision in the large mesh reflector. In this paper, a novel measurement method for the precision of large mesh antenna surfaces is proposed to reduce the development process. Multiple measurement cameras have been utilized to set up a network system, enabling data integration for comprehensive analysis and computational calculations. In this approach, the implementation of a one-click and the rapid measurement function represent substantial advancements. The single measurement time has been successfully reduced from 40 minutes to 2 minutes, which addresses the challenge of high efficiency and precision measurement application on the complex mesh antenna surface. Then the optimization of calibration is accomplished through the meticulous measurement of network patterns, marker points, and reference bars to improve the precision accuracy on the foundation of rapid measurements, combined with the simulation analysis. The final results have been practically verified and successfully applied to model development, which provides a crucial reference for subsequent endeavors involving the rapid and automated measurement of similar antennas.

Electrical Property of 3D Printed Continuous Fiber Reinforced Thermoplastic Composite Mesh Reflecting Surfaces

Continuous fiber reinforced thermoplastic composites have been widely used in modern aerospace and other high-end manufacturing fields because of their light weight, high strength, fatigue resistance, and corrosion resistance properties. Due to the reinforcement of carbon fiber strands, continuous fiber reinforced thermoplastic composites have good conductivity which makes it a potential material for the preparation of space-borne antennas reflecting surfaces. The reflecting surfaces of common mesh antennas are usually prepared by gold-plated molybdenum wire which is expensive and hard to produce. In this study, the continuous fiber reinforced thermoplastic composites mesh reflecting surfaces are prepared by 3D printing technology. The effect of different mesh shape and mesh size on the electrical properties are investigated systematically. The electrical property of the reflecting surface were tested by waveguide method at the S band with the frequency of 1.9 ~ 2.3GHz. The results show that the reflection loss of the 3D printed continuous fiber reinforced thermoplastic composite mesh reflecting surfaces are lower than 0.25 dB, which can well meet the requirement of space-borne antennas in the S waveband. The reflection loss of the 3D printed continuous fiber reinforced thermoplastic composite mesh reflecting surfaces increases with the increase of mesh size accordingly for both the quadrangular and the triangular mesh reflecting surface. The reflecting property of the mesh reflecting surface tends to be better with a higher surface mass density. The results foresee that the continuous fiber reinforced thermoplastic composites can be used to develop the reflector of large mesh antenna in the future work.

Structural design, dynamic analysis, and verification test of a novel double-ring deployable truss for mesh antennas

This study proposes a novel deployable antenna consisting of a double-ring deployable truss and a cable net reflector, intended for large mesh antennas. The structural design of deployable antennas is presented, and the geometric relationship is formulated. Compared with the same type of antennas, the storage ratio of the double-ring deployable antenna is significantly improved, especially the storage ratio in the height direction. Meanwhile, the stiffness is also improved. Considering the influence of the cable net structure, a dynamic model is established using Lagrange's equation and the driving force for deployment is analyzed from the perspective of work. Finally, a 5-m prototype is fabricated to demonstrate the feasibility of the proposed structure and carry out the experiments. The deployment tests show that the antenna can be driven by driving cable to deploy successfully, the surface accuracy is also tested and the results show good repeatability of the double-ring deployable antenna.

Wind resistance calculation of large rotary mesh antenna and its influence on dynamic balance precision

Due to the wind resistance which acts on the main reflector of large rotary mesh antenna, the correct balancing result of satellite antenna is difficult to be gotten in the ground dynamic balancing test. In order to solve this problem, the dynamic balance method of large rotary mesh antenna which is under the influence of wind resistance in both low pressure environment and standard atmospheric pressure environment on the ground is studied. Based on the theoretical analysis and the experimental data of two-dimensional flow around circular cylinder, a new method of the large rotary mesh antenna wind resistance calculation is proposed, according to the CFD analysis of the three dimensional flow field. Through the dynamic equivalent method, the distributed wind resistance acted on the main reflector of the mesh antenna in the rotating state is equivalent to the principal vector and principal moment of the action point in each quadrant, and then transformed into the eccentric mass on the distribution plane. It provides a feasible and innovative way to estimate the influence of wind resistance on the dynamic balance accuracy of large mesh antenna, so as to compensate the wind resistance effect. Combined with the ground dynamic balancing requirements of a certain type of satellite mesh antenna, the whole finite element model of the mesh antenna is established, the simulation of ground dynamic balancing test is carried out, and the influence of wind resistance on the ground dynamic balancing results of the antenna is analyzed in this study, which provides important data for compensating the influence of wind resistance and ensuring the on-orbit balancing accuracy of the antenna.

From multiscale modeling to design of synchronization mechanisms in mesh antennas

Flexible multibody simulation is supposed to be a promising method for studying the deployment dynamics of large mesh antennas and assisting the design of the related crucial mechanisms. However, fulfilling a full-scale deployment simulation of a mesh antenna is so challenging that it can be rarely found in the literature. In our opinion, the bottleneck of modeling some mesh antennas is dealing with the multiscale physics mainly sourced from the cable-pulley systems that are frequently used to transfer forces for long distance range. A traditional model of a cable-pulley is based on contact method, which involves fine cable mesh, a large amount of contact detection, and small time step for numerical integration, resulting in low calculation efficiency. To cope with this difficulty, we proposed a novel and efficient multiscale method to handle the cable-pulley systems. The basic idea is avoiding the contact detection by separating a cable into two segments: non-contact and contact segments, according to which part of the cable is in contact with the pulley. The non-contact segment is meshed with variable-length elements based on the arbitrary Lagrangian–Eulerian (ALE) formulation. The contact segment is considered an invisible segment to constrain the variable-length cable element on the pulley; its border is dynamically located by the relative configuration between the pulley and the cable. The accuracy and efficiency of the proposed method were confirmed by a numerical example. Then, it was used to evaluate, compare and design the synchronization mechanism in a kind of mesh antenna. The obtained results can directly guide the actual design of mesh antennas, and the proposed multiscale method can be applied to simulating other similar mechanical systems.

Thermal Response Analysis of Flexible Connecting Structure of Large Mesh Antenna

The thermal uniformity of large mesh antennas in orbit is influenced by the thermal encironment, which results in thermal deformation and affects the performance of the antenna.Therefore, it is the basis of improving antenna performance to accuratey predict the temperature and analyze the influence facors of the thermal stability of the antenna.In this paper, a large mesh antenna model is constructed by using the FEM analysis software to simulate the thermal response of the flexible connecting structure of the metal mesh reflector, tension cable and rib component.The analysis results show that the temperature of antenna metal mesh and rib components are sensitive to the connection of the two, and their connection to tension rope is not sensitive. The tension cable is sensitive to the connection of the metal mesh and is insensitive to the connection of the rib components. The above analysis can provide an important reference for the design of large mesh antenna connection structure.

Structural design and static analysis of a double-ring deployable truss for mesh antennas

This paper addresses the structural design, the deployment control design, the static analysis and the model testing of a new double-ring deployable truss that is intended for large mesh antennas. This deployable truss is a multi-DOF (degree-of-freedom), over-constrained mechanism. Two kinds of deployable basic elements were introduced, as well as a process to synthesise the structure of the deployable truss. The geometric equations were formulated to determine the length of each strut, including the effects of the joint size. A DOF evaluation showed that the mechanism requires two active cables and requires deployment control. An open-loop control system was designed to control the rotational velocities of two motors. The structural stiffness of the truss was assessed by static analysis that considered the effects of the constraint condition and the pre-stress of the passive cables. A 4.2-metre demonstration model of an antenna was designed and fabricated. The geometry and the deployment behaviour of the double-ring truss were validated by the experiments using this model.

ケーブルネットワーク構造の特性を考慮したメッシュアンテナの高精度化

This paper addressed cable network configurations to improve surface accuracies for large mesh antennas. In this study, we focused on manufacturing error, assembling error, and sensitivity to displacements of support points. To facilitate accuracy management by the lengths of cables, high stiffness cables were used in surface cable network. Then, low stiffness cables were used in other cables. The effect of the lengths of errors was estimated by analysis and experiments for a test model. Micro-gravity test was also executed to estimate the accuracy of shape adjustment on ground. The sensitivity is calculated under some variations of cable stiffness. From the results, it is clarified that the proposed configuration can reduce the surface distortion and keep high surface accuracy.

メッシュアンテナのケーブルネットワーク構造設計手法の提案

This paper addressed a design method for cable network systems that primarily define characteristics of large mesh antenna reflectors. In the design process of the cable network systems, many parameters and conditions are required to be determined such as network topologies, geometries and cable maximum tensions. However, these parameters are defined by trial and error against the design constraints and there is no established methodology. In this paper, the requirements of the mesh antenna reflectors were clarified and a design methodology of the cable network systems was presented. By using of proposed method, a desirable cable network system, which is content with the requirements and constraints for an antenna reflector, is obtained.

Key technologies for high-accuracy large mesh antenna reflectors

Nippon Telephone and Telegram Corporation (NTT) continues to develop the modular mesh-type deployable antenna. Antenna diameter can be changed from 5 m to about 20 m by changing the number of modules used with surface accuracy better than 2.4 mm RMS (including all error factors) with sufficient deployment reliability. Key technologies are the antenna's structural design, the deployment mechanism, the design tool, the analysis tool, and modularized testing/evaluation methods. This paper describes our beam steering mechanism. Tests show that it yields a beam pointing accuracy of better than 0.1°. Based on the S-band modular mesh antenna reflector, the surface accuracy degradation factors that must be considered in designing the new antenna are partially identified. The influence of modular connection errors on surface accuracy is quantitatively estimated. Our analysis tool SPADE is extended to include the addition of joint gaps. The addition of gaps allows non-linear vibration characteristics due to gapping in deployment hinges to be calculated. We intend to design a new type of mesh antenna reflector. Our new goal is an antenna for Ku or Ka band satellite communication. For this mission, the surface shape must be 5 times more accurate than is required for an S-band antenna.

Active Damping of Structures with Guy Cables

HE current design of the space station is largely based on trusses, but it is quite likely that the future large space structures (LSS) will use large trusses connected by tension cables, to increase their global stiffness, in a way similar to that used to stiffen the airplanes in the early days of aeronautics. This concept of tension trussstructure has already beenused for large mesh antennas (a 10-m deployable mesh antenna was e own by the Russians in 1979 ); it has the advantages of being deployable and easily recone gurable by changing the static tension in the cables and of lending itself naturally to shape control. 1;2 The active damping of LSS has long been recognized as a major issueforvariousreasonssuchastheinteractionofthee exiblemodes with the attitude control system, the pointing requirements of various instruments mounted on the station, or simply preservation of the microgravity environment. The active damping of truss structures has received considerable attention for the past 10 years or so, and effective solutions have been proposed 3;4 ; active struts including piezoelectric actuators have been developed, and control laws with guaranteed stability have been tested successfully. 5 The active damping of cable structures is more dife cult because cables and strings behave in a nonlinear manner and are prone to parametricexcitationwhenthefrequencyofthesupportingstructure is close to twice the natural frequency of the cable. Chen 6 showed thatthevibrationofastringcanbecontrolledby apositiveuseofthe parametric excitation resulting from the longitudinal motion of the support at afrequencyequal to twice the frequency of the transverse vibration of the string (stiffness control ). The damping of cable structures has also become a major issue in civil engineering because the ever-increasing span of the cable-stayed bridges 7 makes them more sensitive to wind and trafe c induced vibrations as well as to e utter instability. The distinctive feature here is the presence of some sag in the vertical plane, resulting from the gravity loads (typical value of the sag to length ratio is 0.5%). The active damping of cable-stayed bridges with an active

On‐board large mesh antenna reflector with high surface accuracy

AbstractAn increase in the size of on‐board antenna reflectors is a key technology in providing economical services by miniaturized portable equipment in future mobile satellite communication systems. In practice, a mesh antenna can be used as the on‐board antenna. However, since the reflector surface of this antenna is supported by the cable and the mesh, and its size is larger, the surface is subject to larger thermal deformation in orbit than is the solid antenna reflector. Conventional compensation methods such as passive thermal control or rotation of the antenna reflector cannot maintain the required antenna performances. Various methods have been reported to compensate for the deterioration of antenna performance by thermal deformation.This paper describes a static shape control system for a 10‐m diameter antenna which actively compensates for the deformation by using a shape‐measuring sensor and shape‐compensation actuator. The configuration of the sensor and the experimental results by a functional model are described to confirm the design validity. The shape‐compensation method by the actuator was confirmed to be useful in achieving a required surface accuracy.

衛星搭載用大形メッシュアンテナ鏡面の形状制御

This paper describes an on-board shape control technique for large mesh antenna reflectors that compensates the surface errors caused by thermal deformation. Shape control is carried out by displacing the stand-offs to which the cable network is attached. The displacement values are calculated so as to regain the designed parabolic surface. The experimental system consists of a 4m∅ mesh antenna reflector, two theodolites for position measurements and actuators for displacing the stand-offs. The surface error caused by thermal deformation in orbit is assumed and the proposed surface control is applied to compensate this error. The validity of the control method is confirmed by the good agreement of calculated and experimental results. Finally, the antenna patterns are calculated by using experimental data. The effectiveness of the proposed method is confirmed by the restoration of antenna gain.