For the spacecraft attitude control, several sensors such as Earth sensor, star sensor, Sun sensor and gyroscope are used. However, each sensor has its own features. For example, star sensors can measure the attitude accurately, while its sampling rate is slow. On the other hand, gyros can measure only the attitude rate with drift, while its sampling rate is high. In this report, we consider combining gyros and star sensors, and study some types of controllers of direct measurement feedback so that their advantages and drawbacks are covered with each other.

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This paper proposes a design method of optimal H_∞-PD controller for attitude control of flexible spacecraft model. In the spacecraft industry, PD controller is widely used for attitude control of spacecraft. However, there is no systematic optimal design method of PD controller. In this study, we propose a design method of optimal PD gain satisfied mixed sensitivity problem's condition in the H_∞ control framework.

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In this paper, research and development of folding and deployment mechanisms is introduced for a deployment wing type autonomous air vehicle. We propose two type mechanisms. One is a hard wing type that can be stored by folding wing segments connected with spring hinges and can be deployed by the springs. The other one is a soft wing type made from EPP that can be stored by bending the wing and can be deployed by its own bending restitutive force. These two autonomous air vehicles are developed and flight experiments including an opportunity to launch them to an altitude of 4,000m are conducted. This paper shows the design details and the results of these experiments.

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The Laboratory for Space Systems (LSS) of the Tokyo Institute of Technology has proposed a tether-controlled spinning solar sail. By controlling its tether length, the offset between the C.P. (Center of Pressure) on the membrane due to solar radiation and the C.M. (Center of Mass) of the system can be generated. In this paper, tether length control methods are introduced and an application of input shaping as vibration suppression method is studied by using numerical simulations. Then, an attitude maneuver by using C.M.-C.P. offset torque is examined and nutation damping method is investigated.

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Controlling of a space robot without actuators on the main body is an underactuated control problem. As stabilization methods, time-varying feedback controllers, discontinuous feedback controllers, centre manifold methods, zero-dynamics methods, and sliding mode controllers have been proposed. Mukherjee et at have established an almost smooth and time-invariant feedback control method with respect to a planer two-link space robot, by introducing a concept of a "radially isometric orientation," which is the attitude variation of the main body caused by the link motions, based on the angular momentum conservative law, and can be interpreted as an invariant manifold, from any states on which the goal state can be achieved. However, their method suffers from slow rate of convergence. In addition, modeling errors and delay time have not been considered in the past control methods. In order to obtain more fast convergence time and compensate modeling errors and delay time, adaptive invariant manifold based switching control method is proposed. Firstly the link angles are controlled to reach the invariant manifold by constant periodic motion and the modeling error is estimated by a discrete adaptive method. Secondly the angular velocity rate of the two links is controlled to constant for the state to slide on the invariant manifold and reach the goal state. In the first stage, the delay time is detected by measuring the difference between the predicted response and the actual one. In order to evaluate the performance of the switching control method, numerical simulations are conducted not only for the case with modeling error, but also with delay time.

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This report describe a thickness distribution finding problem and an initial shape finding problem for a gas-inflatable reflector. The problems are formulated as the problems to find the thickness distribution and the initial membrane shape whose deformed shape under prescribed pressure becomes a paraboloid of revolution. The deflection analysis is performed by the finite element method. In the optimization, the objective function is the surface profile error between the paraboloid and the inflated shape of membrane. The discrete distribution of optimum thickness is obtained in the former case and the initial shape is obtained in the later case.

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The Solar Observations Satellite SOLAR-B("Hinode") was successfully launched in 2006. It carries three telescopes covering different wavelength. The telescopes required the tightest pointing accuracy/stability in Japanese satellites ever developed, ranging from absolute accuracy, long-term and short-term stability to co-alignment among three telescopes. In order to realize the requirements, many new technologies and challenges were needed. In particular, for the achievement of short-term pointing stability, the internal disturbance that is generated by the mechanical movements of many moving components and causes the microvibration was the biggest problem. In this paper, technologies relating to internal disturbance control, that were developed for Hinode, are introduced.

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The authors have developed a new thermal control device called Smart Radiation Device (SRD) for space use. SRD regulates amount of heat radiation to space without mechanism unlike conventional thermal louvers. Its variable emittance function is based on the metal-insulator transition of the ceramic material, La_<1-x-y>Sr_xCa_yMnO_3. The authors have developed two types of SRD, bulk-type and the thick film type and conducted flight demonstration of them on MUSES-C "HAYABUSA" and INDEX "REIMEI" respectively. Flight temperature data proved that bulk-type and thick film type SRD saved heater power and suppressed temperature drop as expected. We have been developing third type of SRD, which is with multi-layer solar reflecting coating. We have achieved drastic reduction of solar absorptance from 0.81 to 0.2. The Multi-layer type SRD is now subjected to atomic oxygen (AO) simulation test as the final step of qualification. Moreover, we expect that SRD is also effective for energy conservation of terrestrial products such as house, window glass and so on.

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A performance of ball bearing used in reaction wheel toward retainer instability was investigated by numerical simulation. The dynamic simulation of ball bearing showed that the retainer instability occured easily when the friction coefficient at retainer-ball was higher than 0.3. Meanwhile, the mixed lubrication analysis clarified the friction coefficient at retainer-ball kept lower than 0.2 even if oil amount increased under reaction wheel 6000 rpm operation. Combining these results the reaction wheel bearing countered the retainer instability was demonstrated.

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A solar-array paddle has a high probability of a space-debris impact because it has a large area. The space-debris impact on the solar array causes not only mechanical damage but also electrical damage such as solar-array arcing through the local high-density plasma created by hypervelocity impact. In the worst case, Joule heating of the arcing carbonizes an insulation layer, and a permanent short-circuit path is created. This is permanent sustained arc (PSA). However, no PSA caused by space-debris impact in orbit has been reported. This paper evaluates the possibility of PSA caused by debris impact. Hypervelocity-impact tests on solar-array coupons in the condition of pseudo power generation were conducted. We ascertained that a space-debris impact could lead to PSA on the solar array.

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This paper describes the effect of analytical model error on predicting the dynamic characteristics of large structures with component modal tests. We consider a large structure consisting several components and perform modal tests of components with an additional mass and stiffness. Additional mass and stiffness are derived from analytical model of untested component. Therefore, analytical model error affects additional mass and stiffness. We reduce model error by using the system identification for each component. A numerical example shows that proposed method gives highly accurate test results identical with the dynamic characteristics of structures.

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JAXA is carrying out research and development of a mobile robot (rover) aimed at base construction and searching for rocks and soils on the lunar surface. The target areas for base construction and lunar exploration are mainly in mountainous zones, and the moon's surface is covered by regolith. Achieving a steady run on such irregular terrain is the big technical problem for rovers. A newly developed lightweight crawler mechanism is good for driving on such irregular terrain because of its low contact force with the ground. This was determined considering the mass and expected payload of the rover. This paper describes the composition of the mobility system of the lunar exploration rover, and presents the results of dynamics testing.

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JAXA is examining research and development of an autonomous system, such as mobile rover required for searching ground and constructing basement on the lunar surface in succession of KAGUYA (SELENE) project. Because the lunar surface covered by irregular terrain and muddy soil called regolith, rover has a difficulty in running on such harsh environment. Therefore rover is required of taking a sustainable running mechanism that does not become cautions of fatal functional and mission stop. Then some functions are needed for rover running system on lunar surface, for example certain acting on brake and drive, removing adhered soil and tightens muddy soil. Newly flexible wheel is required to achieve running with high reliability by changing the wheel contact shape itself and being lower contact force on the ground. This paper describes the static measuring test results of flexible wheel contact and distributed pressure, and analysis results of flexible wheel dynamics model.

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This paper presents a new guidance law for a lunar exploration rover. Information of terrain is not always satisfied for the guidance system in exploration. Although a rover has to avoid rocks or holes on the way, the existence of small objects cannot be known prior to the path planning. Such objects are recognized through the visual information, thus quick motion is necessary to avoid the object when there is a visual obstacle. In order to avoid hard maneuver, the new guidance law uses the information amount of visual sensor. The rover is guided to the position where the visual information amount satisfies the requirement of safety. The numerical results show that the guidance law provides moderate avoidance maneuver even if an object exists behind a large visual obstacle.

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