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A solar power sail demonstrator “IKAROS” demonstrated solar sailing technology in 2010. The membrane of the spinning solar sail IKAROS is estimated to be deformed toward the Sun. The deformation was kept even under low spin-rate. Previous studies suggest that curvature of thin-film solar cells on the membrane increases the out-of-plane stiffness by finite element analysis. Shape, out-of-plane stiffness, and natural frequency of membranes have to be predicted for solar sails with thin-film devices, such as thin-film solar cells, dust counters, and reflectivity control devices in order to reduce the margins of sail size and propellant mass against disturbance solar pressure torque acting on the membrane. In this paper, the effect of a curved thin-film device on the natural frequency of a rectangle membrane under uniaxial tension was investigated. Three types of membranes were evaluated: a membrane with a curved thin-film device, a membrane with a flat thin-film device, and a plane membrane. Geometric nonlinear finite element analysis and eigenvalue analysis were conducted to investigate the natural frequencies under varying tension. The simulations were verified by vibration experiments. It was found that under low tension, the natural frequency of the membrane with the curved thin-film device is significantly higher than that of the others and that under high tension, the natural frequency of the membrane with the thin-film device is slightly lower than that of the plane membrane. In addition, parametric analysis on the curvature of the thin-film device shows that natural frequency at low tension is sensitive to the curvature. The eigenvalue analysis of a whole solar sail with the curved thin-film devices also suggests that the curvature remarkably affects the vibration modes. In conclusion, curved thin-film devices have a significant impact on the out-of-plane stiffness of a membrane under low tension.

Since observation tasks of micro-satellite require rapid multi-target acquisition and high pointing accuracy, the single-gimbal control moment gyro (CMG) is considered as an ideal torque-generating actuator due to its practical performance for the satellite. This paper compares two useful robust attitude control algorithms (sliding mode control method and high order sliding mode control method). These control methods have improved the system's robustness and accuracy. The pseudo-inverse steering logic based on mixed two-norm and least-squares minimisation is chosen in this paper which can deal with both the internal singularity problem and momentum saturation singularities. This attitude control system is verified through numerical simulation. The results demonstrate the validity and feasibility of the proposed approach.

When a space robot performs tasks, disturbances caused by payload motion downgrade attitude control performance of the main body. Thus, the payload should be controlled not to generate large disturbances, and the attitude controller should have high robustness to these disturbances. In this paper, a payload motion planing method based on angular momentum constraints (AMC) is proposed, where the disturbance torque caused by the payload rigid motion is reduced. An attitude control method based on Lac/Hac is also proposed, where the disturbance torque caused by the payload flexible motion is compensated. The usefulness of this approach is verified through numerical simulation results.

This paper discusses a method for damping the angular momentum of an uncontrolled target satellite in order to make it easy to capture using a chaser-satellite-mounted manipulator. During the capture operation of an uncontrolled floating target, it may be difficult for a manipulator to grapple it directly because of target nutation or tumbling. In this paper, the authors propose using a cushion type damper in order to absorb the rotational motion. The scenario is as follows: 1) a cushion type damper is attached to the end-effector of the manipulator, 2) the manipulator softly pushes the damper on a selected point on the target, and 3) the contact force between the damper and the target causes the angular momentum of the target to decrease. The validity and feasibility of the proposed method are verified through numerical simulations.

Rapid attitude orientation and stable pointing accuracy are critical characteristics for observation missions of nano-satellite nowadays. This paper focuses on analysis of attitude control law for nano-satellite TSUBAME which is developed by Laboratory of Space System at Tokyo Institute of Technology. In recent years, the higher order sliding mode control (HOSMC) is considered, which is more useful in handling the chattering effect against external disturbance and unknown friction effects. Furthermore, HOSMC can remove the chattering effect if appropriate relative degree was chosen. To overcome the singularity problem inherent in the control moment gyros, a modified steering law for single gimbal control moment gyros (SGCMG), which aims at precisely exporting commanded torque is discussed based on the optimal output torque capability principle. This paper includes a comparison between two different control algorithms in the attitude controlling system which used control moment gyro (CMG) as the actuator for TSUBAME. The numerical simulation results demonstrate the efficiency and feasibility of the proposed HOSMC algorithm.

Tokyo Institute of Technology, Laboratory for Space Systems had developed a 1 kg pico-satellite CubeSat, CUTE-I, and it was successfully launched on June 30 2003 by a Eurockot's rocket. CUTE-I is one of the first launched CubeSats and also the smallest civilian satellites in the world, which are able to make dual-directional communications with the ground stations. In this paper, the total design of CUTE-I flight model and operation results focused on its attitude analyses are explained.

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To suppress the low frequency vibration of Large Space Structures, the possibility of using a proof-mass based actuator is discussed. In order to avoid instabilities caused by the effect of the actuator's own natural frequency on the low frequency components of the structural vibration, it is proposed that the only control force be the electromagnetic force generated by the actuator and that there be no mechanical spring between the moving and the fixed parts of the actuator. In this configuration, it is easy for the moving mass of the actuator to exceed the stroke limit, so the actuator must be controlled to avoid these limits. Using the proposed actuator, three kinds of intelligent control methods are considered in order to achieve reliable control of the low frequency vibrations: fuzzy control, dithered fuzzy control, and rule based crisp control. Simulation results show the effectiveness of the proposed control algorithms.