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地球へ向けて帰還中の「はやぶさ(MUSES-C: Asteroid Sample-return Spacecraft)」は現在3台中2台のホイールが故障し、いわばバイアスモーメンタム方式で1軸姿勢制御を行っている。この方式ではシンプルな姿勢安定が実現されるはずだが、2007年3月にニューテーションが発散する傾向を示した。本稿では、この現象がホイール回転軸と探査機慣性主軸の不一致によることを解析と数値シミュレーションによって示し、防止策を提案する。, Since Hayabusa (MUSES-C: Asteroid Sample-return Spacecraft) has lost two of three wheels, its attitude is currently stabilized by one-axis bias-momentum wheel. This method should lead to simple attitude keeping, but the motion showed nutation divergence in March 2007. This paper shows that the cause of the instable motion lies in the difference between the axis of wheel and of inertia, and a way to avoid this instability is proposed., 資料番号: AA0063718021

近年、指向安定度劣化の主要因として検討が盛んな機械的振動擾乱について、OICETS (Optical Inter-orbit Communications Engineering Test Satellite:きらり)に搭載したMVE (Micro Vibration Equipment)の軌道上加速度データ出力をもとに、軌道上で実際に発生した振動擾乱についての評価を行う。軌道上データから構造伝達特性を評価し、この結果と地上試験データから得られる構造伝達特性との比較を行うことで、地上試験の結果が軌道上でどの程度再現しているかを確認し、地上試験の有効性について、考察を行う。, The microvibration generated by some instruments on orbit is considered as a key factor of pointing stability deterioration. Therefore it is important that the influence of the microvibration is estimated before the launch. In this paper the results of the ground tests by using of OICETS (Optical Inter-orbit Communications Engineering Test Satellite: KIRARI) MTM (Mechanical Test Model) and the on orbit measured result by the accelerometer (MVE: Micro Vibration Equipment) installed in OICETS are described. By using these results and an assumption, the transfer characteristics from main disturbance sources to MVE installed in OICETS are calculated. We compare these structural transfer characteristics and confirm the reproducibility of the ground test on orbit and the effectiveness of the ground test., 資料番号: AA0063481054

For the demonstration and verification of solar power satellite's functions, a small demonstration solar power satellite has been examined by USEF and ISAS/JAXA. Structural characteristics and attitude motion in steady operation have already been studied. In this paper, deployment sequence for the stable and fast deployment is investigated. The deployment sequence consists of two-stage truss extension and two-stage panel deployment. At first, attitude motion in the deployment is analyzed through numerical simulations. From the result, it is shown that nonlinear effect can not be negligible when pitch angle exceeds about 0.6 rad. In such a case, because independency of the pitch angle does not hold true for the nonlinearity, pitch motion leads to the large roll and yaw motions. Next, to realize stable and fast deployment, optimization of the deployment is carried out by changing each deployment time, interval and acceleration of the deployment. As an objective function, weighted sum of deployment times, maximum amplitudes of attitude angles and residual amplitudes of attitude angles is used. The optimization is carried out by Powell's method. From the result it is shown that maximum amplitudes of attitude angles are kept within 0.08 rad, and residual amplitudes of attitude angles are kept within 0.01 rad without any active control if about five orbital periods (about eight hours) can be spent for the total deployment., 資料番号: AA0049120010

In the tethered-type solar power satellite, a large panel structure for the power generation and transmission is adopted. A huge number of actuators are required to deploy the large panel in orbit. In our research, a deployment mechanism using coils of shape memory alloy (SMA) has been studied. When the SMA coil is heated by applying an electric current, it works to deploy the folded panels if the coil has a memory for rotation. This mechanism has several advantages as: (1) Simple and light-weight as compared with motor activation, (2) Deployment speed is well controlled to minimize the effect on the attitude of the system during deployment and to suppress the shock when the panel is fully deployed, (3) The shape of the unfolded panels can be controlled using two types of SMA coils (this function can be used to compensate the thermal deformation of the panels), and (4) The oscillation of the panels can be suppressed by heating the SMA coils to the super-elastic state. We have fabricated the hinges containing the SMA coils as shown in this report and integrated them to a test panel composed of 4 x 8 sub-panels. The size of the sub-panel is 12 x 24 cm. The test model is equipped with a latch mechanism using the permanent magnet. In the laboratory test, it is confirmed that the hinge with the SMA coils work well as expected, but it is found that the life of the SMA coils is unexpectedly limited by the metal fatigue. Further study is required to redesign the SMA coils to eliminate the fatigue effect., 資料番号: AA0049120012

A SPS (Solar Power Satellite) which is a part of the Space Solar System (SSPS) project has been studied at the USEF. Quasi-static analysis had been carried out for the practical SPS. The present purpose is to evaluate the attitude stability of the SPS under construction. During construction, it is assumed that the modules of 100 x 95 sq m are arranged in the shape of line. As the result of quasi-static analysis, it is shown that the roll and yaw angular frequencies of attitude motion are twice and once as large as orbital angular velocity in first step of the construction, respectively. Furthermore, as the result of dynamical analysis, amplitudes of the roll and yaw angles tend to divergence in first step. To avoid such a divergence, another model was proposed which is constructed keeping similar configuration. The construction way is called construction with similarity. From the result of simulations, it is shown that divergences in the roll and yaw angles can be avoided in the construction with similarity. However, the stability around the pitch and yaw axes are weak in first step for construction with similarity. In particular, maximum amplitude around the pitch axis is 5 deg. Therefore, both constructions need active attitude control because there are problems in first step of the constructions., 資料番号: AA0047275019

筆者らは、将来の大型柔軟構造衛星に必要となる姿勢および振動制御則を確立し、その有効性を軌道上で確認することを目的とする、新しい軌道上制御実験を計画中である。本稿では、計画中の実験に採用予定の制御則の1つである、ゲインスケジューリング制御則の新しい設計手法について論じ、大型柔軟構造衛星の姿勢制御系へ適用するための設計手順について述べる。提案する設計手法では、太陽電池パドルの回転角に応じてダイナミクスが変動する「LPV(Linear Parameter Varying)システム」として制御対象を扱うことができ、パドル角の変化と高次振動モードに対してロバストな制御則を構築することができる。導出される制御則は、従来のゲインスケジューリング制御則と比較して、必要とするメモリ量とスケジュールのための演算負荷が小さいため、搭載計算機能力に制約のある衛星での使用に適している。シミュレーションによって、PD(Proportional-Derivative)制御によるベースライン制御則との比較を行ない、その有効性を明らかにする。, A new on-orbit control experiment is being planned aimed at establishing attitude and vibration control methods for future large flexible satellites and demonstrating the effectiveness of the proposed control methods on orbit. In this paper, a new design method for a gain scheduling controller which will be employed in the experiment is described, and a design procedure for an attitude control system for a large flexible satellite is explained. Using this method, a robust control system that is resilient to changes in the paddle rotation angle and higher order vibration modes is designed as this method can treat the satellite system as a Linear Parameter Varying (LPV) system whose dynamics vary according to the paddle rotation angle. The derived gains can be easily scheduled since the scheduling law consists of small number of grid points and requires just linear interpolation calculation. Using this method, stability and performance are guaranteed at each parameter value (paddle angle in this case). Some simulation results are provided to show the effectiveness of our controller., 資料番号: AA0063455000, レポート番号: JAXA-RR-06-016

ソーラーセイルは惑星間飛行を実現する推進機関である。JAXA宇宙科学研究本部で開発中のスピン型ソーラーセイルはマストやチューブなどの部材を用いず、遠心力によってのみ形状を維持する。このような巨大膜面は微小振動を起こし、システムを不安定化する可能性を持つ。本研究の目的は、探査機本体のスピン安定性を損なうことのない膜面設計を容易に行うことである。設計のためには、安定性を判別するための指標の獲得が望まれる。一般にスピン剛体の安定性は慣性モーメント比の大小によって決定される。柔軟構造物を伴った剛体においても、振動がどのように安定性に寄与し、安定性が何により決定されるか示したい。これを踏まえ、本論文では、まず膜面を連続体として捉え、本体姿勢が安定となる指標を解析的に求める。次に膜面を質点とバネ・ダンパからなる多粒子モデルとみなし、数値シミュレーションによって姿勢安定性を確認する。計算結果と解析から求められた指標とを比較することで、妥当性を検証する。, Solar sails are the spacecraft that are propelled by sunlight. The Institute of Space and Astronautical Science (ISAS) of Japan Aerospace Exploration Agency (JAXA) has studied the solar sails which are spinning and deployed by centrifugal force. One of the technological difficulties to be realized is how to design the spanned spinning solar sails to maintain the stability while those huge membranes unfurl with deformation and oscillation. In this paper, an attention is focused on the out-of-plane oscillation and an analysis is presented about the dynamics so that the characteristic parameters are identified as for the stability of those spinning solar sails., 資料番号: AA0063480029