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Effects of surface modifications of a cable-network antenna on reduction of grating lobe level are investigated. Some systematic or random modifications of the node positions of the cable-network antenna are introduced and the reductions of grating lobe level are investigated through numerical simulations. The results show that the grating lobe levels are reduced by these surface modifications and the appropriate systematic modifications achieve the reduction of grating lobe level and the improvement of antenna gain, simultaneously..

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Today, there are many satellites which are not in operation in orbit. Failure causes of these satellites are various, and we do not understand about them well enough. Therefore, in situ inspection of the failure cause of the satellite is very important for the future satellite development. A satellite which explores failure satellites and removes them from orbit has been proposed. The method of docking with failure satellite is simple: Firing a metal anchor to satellite structure and docking with this satellite structure. However, the impact of lodging an anchor may cause other failure of the satellite. So, in this research, we conducted experiment and the impact was evaluated through SRS analysis.

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Composite material has been used in aircraft structure since decades ago. The main disadvantage of this material is weakness of its lamination strength. Damage, for example delamination causes stiffness degradation of structure. There are many traditional non-destructive inspection ways to inspect such damages i.e. eddy current inspection, magnetic particle inspection as well as X-Ray etc. However, those ways are not only costly but also requiring much time. Thus, cheaper and more convenient inspection method is needed. This paper presents an identification of CFRP's damage using MFC Sensor. Damage is identified by measuring the transmission of pulse wave. The experiments are performed on two CFRP plates which are undamaged or damaged plate. The latter has artificial delamination by inserting a thin Teflon into CFRP plate during its manufacture. The experiment's results show that there is a degradation of natural frequency's transmission in damaged CFRP plate comparing to undamaged one when we perform the experiment using low frequency pulse wave.

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In order to perform planetary exploration experiments utilizing the commercial systems which would realize short term and low cost development, we designed and developed a small simulated satellite called CANSAT, as well as assessed its usefulness. This CANSAT, as commercial product, has Smart Phone (SP) for bus system for wide area survey and tiny Quad Rotor (QR) for narrow area exploration. We also aim to show versatility of SP by publishing and sharing APPs we developed. This paper describes the system, developing and experiments of our CANSAT and show the result of experiments of ARLISS.

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This paper experimentally evaluates the shape-control performance of the prototype of smart reconfigurable reflectors, and proposes an updated design that will ameliorate the problems identified in the experiments. The prototype is a preliminary model of a secondary mirror for future radio astronomy satellites. The prototype can control the shape of a 300mm-diameter CFRP mirror, using six piezoelectric actuators integrated with displacement-magnification mechanisms.

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In usual, when using tensioned members such as cables to stiffen structures, the elastic stiffness of tensioned members plays an important role, and tension force in tensioned members can also affect the stiffness of whole structures. In this paper, authors propose a new concept that the elastic stiffness of tensioned members can be ignored and then the tension force mainly contribute to stiffening structures. In this kind of stiffening method, tensioned members is in a mechanism state, such as curved shapes of cables. Authors firstly use a column with cables to deduce a so-called stiffness of pseudo-spring, and the buckling control formula in 2D space. Nonlinear FEM method is used to prove the validity of this control buckling formula and the 1^<st> order buckling modes of column are obtained. Finally, stiffening effect of curved cables in arch structure is investigated.

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This paper proposes an innovative concept of deployable membrane structure for small satellites.

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[in Japanese]

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「皺」は物性の劣化を招き,美観を損なうものとして消極的に捉えられ,皺を避ける研究は多くみられるものの,客観的に皺そのものを考察した研究はほとんどない.しかし,力学的な観点から見ると,一度丸めて広げた紙の方が平な紙よりも面外剛性が高いように,皺が生じることにより材料が塑性化しているにも関わらず,面外剛性が上がることは経験的に知られている.本研究では,軽量で剛性が高く,意匠的に優れた部材の作成を目指し,皺の生成により面外剛性・耐力が上がる理由について定量的に考察する.また,薄板の座屈によって簡易な皺モデルを生成し,その力学特性を定量的に把握することを目指す.

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[in Japanese]

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[in Japanese]

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This paper provides a new method for robust spacecraft attitude estimation in the presence of constant and but unknown measurement biases. The proposed method is developed based on the separate-bias or two-state Kalman filter which was first introduced by Friedland. The separate-bias Kalman filter consists of two stages: the nrst stage, the "bias-free" filter, is based on the assumption that the bias is nonexistent; the second stage, the "bias" filter, produces an estimate of the bias vector. The output of the first filter is then corrected with the output of the second filter. In this research, the authors propose an adaptive calculation of the Kalman gain inside the "bias" filter in order to improve the convergence speed, robustness when the estimator works with larger initial errors. Moreover, the research also provides analysis and comparison between proposed method with original separate-bias filter, unscented Kalman filter and extended Kalman filter based on the results of several numerical simulation scenarios about spacecraft attitude estimation.

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In recent years, the demand of the on-orbit inspection has been rising because of the increasing in size of spacecrafts which require deployment of themselves on-orbit, dramatic increase in the number of space debris and so on. In this paper, an on-orbit inspection system of a separable inspection device (a deputy satellite) controlled with Coulomb force is presented. Coulomb force can be controlled with some charge control devices mounted on the main satellite. A sequential guidance, navigation and control method is proposed for the deputy satellite to be guided to a specified position and kept the direction of the inspection device to point toward the main satellite. Control of all degree-of-freedom of movement can be achieved with only the main satellite utilizing electrostatic induction on the deputy satellite. The feasibility of proposed method is evaluated with a numerical simulation in terms of position control accuracy, attitude one and electricity consumption.

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Influences of jitter caused by disturbance sources located inside of a spacecraft on its mission feasibility tend to be an important issue. Solar Array Drive Mechanisms (SADMs) are typical disturbance sources, and the micro-vibration caused by them is estimated from test results using hardware without Solar Array Panets (SAPs). This study validates traditional assumption that the SAPs are not needed to estimate response of micro-vibration in the middle frequency range.

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[in Japanese]

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[in Japanese]

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The purpose of this study is to propose an optimized design methodology to construct a ultra-light-weight cable mesh antenna reflector structure whose aperture is required to be more than 30 m for the future mobile satellites communication system, it is required to reduce the areal density(mass/area) to be less than 0.2 kg/m^2. The surface error of less than 2 mmRMS is required for the future mobile communication satellite system using the S-band frequency (2-4 GHz). Therefore, the antenna reflector is required to be both light weight and high surface accuracy. We proposed a design methodology that is considered as a whole antenna renector structure. In this paper, we optimized supporting structure of our proposed antenna structure and confirmed that structural stability of cable network affects reduction of the weight of the supporting structure. We also conducted topological optimization including interface member and modified the weight of cable connect point. We achieved the cable mesh antenna renector that areal density is less than 0.2kg/m^2 by the proposed design methodology.

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The purpose of this study is to derive the formulation for buckling analysis of mechanical linkages. Flexible multibody structures are constructed by structural elements (such as beams and cables) and mechanical linkages. Numerical analysis for flexible multibody structures is required to solve geometric non-linearity in large displacements and/or rotations caused by a deployment motion. For this purpose, a flexible multibody dynamics formula based on the corotational formulated finite element method and the direct coordinate partitioning (DCP) has been proposed. However, buckling analysis for flexible multibody structures has not been accomplished because the DCP's geometric stiffness has not been defined. In this paper, we formulate the DCP's geometric stiffness and show the numerical examination of joint buckling. The buckling load calculated by numerical examination shows good agreement with theoretical one.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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One of the most important issues in space structure designs is to reduce total weight of the structure. Structural size of a solar cell paddle for spacecraft becomes large corresponding to increasing electric power requirements for future advanced missions. Lightweight structures can be adopted for many space applications considering growing requirements of future missions. In the design of solar array paddles deployable structure has a large percentage of the total weight. In the deployment mechanism, using components with low rigidity and lightweight may reduce the total weight. Then we should consider influence of the deployment mechanism on structural characteristics. We performed structural analysis and experiment to clarify the dependence of the dimension and the configuration of deployment mechanism. As a result, we found that the influence on the vibration characteristics of the deployment mechanism like a hinge disposed between the panels against large structure is small and in particular the influence of the bending stiffness in the vertical direction of the panel surface is large. We found that it becomes possible to lightweight by obtaining optimum design parameters such as the Young's modulus and the cross-sectional area of deployment mechanism corresponding to the scale of structure.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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The restoring moment of a cylindrical boom is examined numerically and theoretically to evaluate the deployability of a boom-membrane structure for small satellites. The results of the finite element analyses show that the restoring moment becomes large when the boom radius decreases and when the center hub radius increases. The dominant parameter of the restoring moment is determined by the theoretical analyses, which is the ratio between the boom radius and the center hub radius. As the results of the theory are in agreement with the results of the finite element analyses, the theoretical analyses are verified.

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[in Japanese]

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[in Japanese]

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ITF-1 "YUI" is the 1U size CubeSAT (100mm cube size satellite) developed by University of Tsukuba as the first challenge. It will be launched as a piggyback satellite of GPM mission (planned in early 2014). Even small satellites require self-controlling ability and fail-safe concept in order to work properly in the outer space severe environment. Learning from failure reports of other CubeSATs, we include various idea to gain more robustness toward the successful mission achievement. In this paper, among many design efforts, the mutual computer watching architecture against the failure due to cosmic-lay irradiation, and the newly developed antenna system for secure communication are reported. In addition, the design method of YUI's battery box is also reported.

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[in Japanese]

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This report deals with a derivation of heat conduction equation for plate bending analysis and an application of the thermal buckling problem of a thin plate. In the plate, temperature distribution of the direction perpendicular to the plate surface is assumed to be linear function. A finite element formulation of a thermal buckling problem of plate is also performed. As an application of our formulation, a thermal buckling problem of the plate subjected to local heating on the plate surface is analyzed. We can obtain buckling temperature from the finite element analysis. Also, under the transient analysis of temperature, we can estimate when the buckling occurs.

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An efficient scheme for steady-state thermal temperature prediction in vacuum tests is presented. First, heat balance equations of spacecraft thermal mathematical models are analytically solved without nonlinear radiation terms. Then, perturbation solutions with radiation terms are deduced. Observation equations based on both linear and nonlinear solutions are presented, which are applied for the least square estimations of steady-state thermal temperature prediction with transient temperature data. A simple experimental result shows the effectiveness of presented scheme.

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A three-dimensional shape measurement based on the Direct Linear Transformation (DLT) method was performed to clarify the modal characteristics of the measurement errors. A spherical mirror model whose surface shape was processed with high accuracy was measured. Comparing the measurement results with the ideal spherical surface features, the effects of the model characteristics of the measurement error was discussed.

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[in Japanese]

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