Tatsuaki Hashimoto

<p>In an earth observation satellite or a space observatory, micro vibration caused by a mechanical cryocooler is one of the problems that make the performance worse. In this article, we propose an active control method with feedforward signal for a cryocooler. The vibration of a cryocooler appears as a distinct spectrum. This algorithm identifies the transfer function of the control target and calculates the optimal control signal by giving feed-forward signals to this spectrum several times in advance. The effectiveness of the proposed method is confirmed by experiments using a cryocooler, and the effects of fluctuations in the spectrum of vibration and noise are discussed. </p>

<p>This paper describes a separation experiment conducted at extremely high spin rates for OMOTENASHI, being developed as the world's smallest Moon lander. The experiment validated the separation method used in the landing sequence and the tipoff impulse was estimated from the motion of the separated object. The study showed that the tipoff impulse increases superlinearly in the high spin rate region. This information is indispensable in determining the operational spin rate of OMOTENASHI in orbit. The method described in this paper can be applied widely to separation experiments for small spinning satellites and rocket stages.</p>

In this paper, direction control of balloon gondola with only untwisting motor is proposed. Typically a reaction wheel and another actuator for unloading the reaction wheel are in use to control the attitude (or direction) of the gondola. Although this method can get high accuracy control performance, two actuators spend many resources of the gondola. The proposed method uses only untwisting motor installed above the gondola to rotate. This method can not realize such high accuracy control performance but realize direction control with the most simple configuration. The proposed method is applied to prototype GAPS (General Anti-Particle Spectrometer) balloon experiment in 2012. This paper shows control design for this experiment and the results of the proposed method.

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This paper describes the attitude control method for overturning prevention for a lunar planetary lander which uses a semi-active damper on the landing leg. In order to achieve safe landing on uneven terrain especially a sloped ground, a novel landing gear system is required. The landing leg with variable damping is one of the solutions for touchdown without overturning. Conventional landing gear for lunar and planetary lander has a fixed shock attenuation parameter and it is not used proactively for attitude control of the lander in the touchdown sequence. By controlling the damping coefficient of the each landing leg, it becomes possible to suppress the disturbance on the attitude of the lander, and it prevents overturning. First, the strategies for the overturn prevention for the lander by changing damping coefficient of landing legs are shown and the control rules based on the lander and landing leg state values are proposed. In the second place, the mathematical model of lander based on the differential algebraic equation in vertical two-dimensional plane is presented. Besides footpad-ground contact model is also described. Finally, touchdown simulations on a sloped terrain with the proposed landing gear control method are shown. Numerical simulations show that the proposed landing gear system works well during the touchdown on a sloped terrain.