Takao Maeda

Attitude Stabilization for Lunar and Planetary Lander with Variable Damper

This paper describes an attitude control method that has been designed to prevent the overturning of lunar and planetary landers, based on a variable-damping shock absorber for the landing gear. Conventionally, the landing gear of lunar and planetary landers has a fixed shock attenuation parameter that is not used proactively for attitude control of the lander during the touchdown sequence. The new method enables the suppression of any disturbance to the attitude of the lander by adjusting the damping coefficient of each landing leg independently, based on the angular velocity vector and displacement velocity of each leg of the lander. The results of a numerical simulation indicate that the control rule for a three-dimensional system is effective for preventing the overturning of the lander on inclined terrain. The results of the simulation and experiments show that the landing gear with the actively variable damping and the control rule play a major role in preventing the overturning of a lunar or planet...

Mechanism Design and Action Strategy for Small Hopping Rover

小型の月,惑星探査ローバ,特に質量数 kg 程度のローバは, 小型の着陸機にも搭載可能であり,様々なミッションでローバを 展開することが可能になる [1].小型ローバはその搭載性と引き 換えに,移動性能に制約を受ける [2].車輪の不整地走破性は,基 本的にその直径に依存する.そのため,小型ローバでは段差,岩 石などの障害物上の走破が困難になり,移動に制約を受けてしま うこの問題の解決策の一つに,跳躍移動の利用が考えられる.小 型であるが故のローバの軽量さを有効活用し,機体より大きな障 害物も飛び越えることで回避可能になる.跳躍はまたスタックを 回避することにも有効である.レゴリス上では車輪だけでなく優 秀な懸架機構を有していないと車輪がスタックする可能性が高い. 小型ローバでは複雑な懸架機構の搭載が難しく,車輪移動のみで はスタックし立往生する危険をはらむ.跳躍移動によりスタック 回避も可能になり,小型ローバの移動性向上に大きく寄与できる. 本論文では,小型跳躍ローバの要となる跳躍機構と,ローバ 全体の設計論,並びにこれらを用いた移動戦略について議論し, JAXAの次期月着陸探査機 SLIMへの搭載を目指す小型ローバ の設計に関する検討についてまとめる.

Protection against overturning of a lunar-planetary lander using a controlled landing gear

This paper describes an attitude control method to prevent the overturning of lunar and planetary landers. The proposed control method that is based on a variable-damping shock absorber for the landing gear is experimentally validated. Conventionally, the landing gear of lunar and planetary landers has a fixed shock attenuation parameter that is not used proactively for attitude control of the lander during the touchdown sequence. The proposed method suppresses any disturbance to the attitude of the lander by adjusting the damping coefficient of each landing leg independently, based on the angular velocity and displacement velocity of each landing leg. First, the control method for the variable damper is presented. Second, the result of a landing experiment conducted in a two-dimensional plane is shown. These results indicate that the proposed semi-active landing gear system is effective for preventing the overturning of the lander on inclined terrain.

Turbulent Flows inside Rotating Curved Channels for Different Aspect Ratios

Abstract Velocity and turbulence were measured inside rotating curved channels for different aspect ratios of the cross section. In a channel having a high aspect ratio, effects of the channel rotation and wall curvature on the turbulent motion are dominant and turbulence is stabilized or destabilized in the lower or higher pressure side of the section, respectively. With the decrease in the aspect ratio, however, secondary flows generated by pressure unbalance dominate the whole cross section and deform the velocity distributions at mid-height from those assumed in a two-dimensional flow.