大槻 真嗣

我々のグループは,将来の月惑星表面探査をめざして,移動型探査ロボットの研究開発を進めている.開発したロボットは,宇宙のみならず,火山地域などの不整地においても自由自在に探査を行うことができる.現在,屋内および屋外において基本性能の評価を行っており, 2011年秋に,伊豆大島にて探査実験を行った.実験では,観測地点への誘導制御,観測行動の運用試験を行い,火山地形における探査の課題を明確にした.提案するロボットは,太陽電池による発電を行い長時間の自立運用が可能なため,人間が入ることのできない場所・状況での観測に適している.本稿では,探査ロボットの概要および試験結果について報告する.

月惑星探査において岩石試料を自動で分析するユニットでは，試料表面を平滑化する装置が必要となる．ソレノイドを駆動源に用いた小型破砕装置に格子状に突起を配置した工具を取り付けて，岩石が加工可能であることが明らかになっている．しかし，1方向に送るだけでは，深い溝となり，平滑化が困難であった．そこで，被加工物を平面内でランダムに送ることで平滑化した．

月惑星探査において岩石試料を自動で分析するユニットでは，試料表面を平滑化する装置が必要となる．本報では，ソレノイドを駆動源に用いた小型破砕装置を真空中で動作させ，加工特性を実験的に調べた．加工中に発生する静電気により，工具に岩石の加工くずが付着しやすかった．そのため，加工量は真空中の方が小さかった．構造部材を通じた熱伝導により，工具温度はほとんど上昇しなかった．

In future lunar, planetary or asteroid explorations, in-situ analysis of rock samples are strongly demanded to obtain many data from various aspects. For precise composition analysis, a sample surface should be smoothed. In this report, a surface shaver with a piezoelectric actuator is proposed and its machining performance in air is investigated. Shaving teeth are mounted at the ends of a lever mechanism. The device is pressed through four springs onto the specimen with a linear actuator. When a sinusoidal voltage of 50 Vp-p and an offset voltage of 25 V ware applied, the natural frequency was 556 Hz and the unloaded amplitude of shaving teeth were 0.77 mmp-p. Basalt samples were machined for 10 minutes in air. The surface roughness was small with an increase of the pressing force. However, the removal amount was smaller with an increase of the pressing force further. The surface roughness varied widely not only due to removal amount but also due to pores.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the measurement of shear modulus for low-pressure wheel on the deformable terrain is presented. This procedure is valuable for rover turning analyzing with a low-pressure wheel on the deformable terrain.

Supposing a space mission of setting monitoring devices at suitable positions on the moon, we discuss how to apply a casting manipulation to the mission. This paper addresses a control method to launch a penetrator to the desired position. First, we focus on a method by using rotation of a boom, and then introduce the mechanism that keeps a posture of the penetrator equipped at the tip of the boom constant for the absolute coordinate system during its rotation. This mechanism prevents the wire which connects the penetrator and the robot's base from winding the boom. Analyzing a position error of landing point caused by delay of releasing the penetrator and control error of the boom, we propose the motion control of the boom to reduce the error. Finally, we verify the effectiveness of the proposed method through experiments.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption with a less complex mechanism. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the procedure for the measurement of mobility parameters like contact pressure on the deformable terrain, and a contact mobility model for low-pressure wheels are presented. This measurement is valuable for analyzing the interaction between a low-pressure wheel and the deformable terrain.

Supposing a space mission of setting monitoring devices at suitable positions on the moon, we discuss how to apply a casting manipulation to the mission. This paper addresses a mechanism of a casting manipulator system and control method to launch a penetrator to the desired position. First, we classify launching methods, and focus on a method by using rotation of a boom. We then propose the mechanism that keeps a posture of the penetrator equipped at the tip of the boom constant for the absolute coordinate system during its rotation. This mechanism prevents the wire which connects the penetrator and the robot's base from winding the boom. Analyzing a position error of landing point caused by delay of releasing the penetrator, we propose the motion control of the boom to reduce the error. Finally, we develop the system and verify the effectiveness of the proposed method.

On the landing of a spacecraft, a large shock load leads to undesirable responses, such as rebound and trip. The authors have discussed the control problem of these shock responses by momentum exchange impact dampers (MEIDs). The optimal design parameters of MEIDs for the landing of a spacecraft are investigated. The parameters are crucial for applications of MEIDs. This paper discusses the parameters of MEIDs with single-axis falling type problem, which is the most fundamental problem. It is found that the rebound height is proportional to the mechanical energy of the spacecraft. Thus, the optimal design parameters of the MEIDs correspond to the parameters that minimize the mechanical energy. Then, in order to improve the performance of the MEIDs, a novel MEID - HMEID (Active/Passive-Hybrid-MEID) has been proposed. The HMEID combines actuators with passive elements such as contact springs. Based on the optimal design result of the MEIDs, a stiffness control is applied to the HMEID in order to suppress the mechanical energy further. Simulation studies reveal that the HMEID can effectively reduce the influence of shock responses. The robustness of the HMEID against the stiffness of the landing ground is shown. The feasibility of the HMEID is also discussed. The effectiveness of the HMEID is superior to that of PMEID, even if the actuator has a dynamics with a large electric time constant or force constraint.

JAXA is developing a mobile rover to lunar surface exploration or base construction as a follow-on KAGUYA. Because the lunar surface is covered by regolith, implying an irregular and rough terrain, the rover has difficulty in mobility. Therefore a new low-pressure wheel is recommended for high mobility performance and low power consumption. A low-pressure wheel can change its contact shape and pressure distribution to account for terrain. In this paper, the procedure for the evaluation of drawbar pull calculated by shear stress on the deformable terrain is presented. This procedure is valuable for analyzing the interaction between a low-pressure wheel and the deformable terrain.

In this paper, a comprehensive wheel model for both flexible/rigid wheels driving on deformable terrain is developed. The wheel model exploits a terramechanics-based approach with taking account of pressures generated by wheel elasticity as well as terrain stiffness. Deflection of a (semi-) flexible wheel depends on a relative pressure between the wheel and terrain: the wheel will be significantly deformed on rigid terrain whereas it will be hardly/slightly deformed on soft terrain. The wheel-terrain interaction in the proposed model is divided into three contact sections: wheel front section, wheel deflected (flat) section, and wheel rear section. The stress distribution at each contact section is formulated, and then, the traction force of the wheel is obtained as an integral of normal and shear stresses generated at each section. Simulation studies with varied wheel pressures, such as flexible, semi-flexible, and rigid wheels, are conducted to validate the proposed model. Also, traction performances of flexible/rigid wheels are compared based on a metric called tractive efficiency. The simulation results provide an important finding in terms of an optimal wheel pressure of flexible wheel for better traction.

This paper presents the synthesis procedure of an input profile for a motion control system to simultaneously reduce sinkage and vibration in a planetary rover. The sinkage of the rover changes depending on the degree of a contact force against loose soils in surface of a planet. Through the experiments using the lunar regolith simulant, it is confirmed that the sinkage is largely concerned with acceleration and deceleration in a driving mechanism. Hence, we proposes the method to suppress the sinkage by appropriately designing the acceleration profile with an asymmetric shape. Moreover, the vibration due to flexibility of the wheel is induced by self-motion and we verify the vibration reduction using the command shaping method through the experiment. Consequently, this paper presents the easy design procedure of the acceleration profile and the valuable experimental results.

In the lunar-planetary exploration, most of landers made a landing on flat areas of surface, because there are a lot of rocks craters and hills on lunar-planetary surface. For the next generation lunar-planetary exploration, the development of a highly accurate landing technology is demanded to land on the complex terrain. The navigation-guidance technology and hazard avoidance have been studied for the safe landing. Moreover the development of landing leg is required for the safe landing in the final phase of landing sequence. This paper presents the development of experimental system of active landing leg, and examine the landing shock response. In addition, we consider the effectiveness of active landing leg and the application to the control method of lander's overturn prevention.

This paper proposes the synthesis procedure for the motion control system to reduce slippage in a planetary rover. The slippage in the rover is mainly due to degree of contact force against the loose soil on the planetary surface. In this paper, particularly, it is confirmed that the slippage generating in early phase of the rover motion is involved with acceleration and deceleration in the driving mechanism through the experiment. Hence, we propose the command shaping method of the target acceleration to prevent the increase of the slippage and the acceleration profile is then derived only by solving a regulator problem with an initial velocity and taking account of the maximum value in acceleration.

This paper describes an application of conventional terramechanic contribution to mobile robots or vehicles in rough terrain. Terramechanics, addressing the interactive mechanics between a vehicle and a terrain, has mainly affected machines for agriculture, construction or planetary exploration. However, it is not clear that wheeled locomotion is able to cope with a critical situation getting stuck into soil. So, the authors elaborate the application of established wheel models in terramechanics to discuss an avoidance capability of such situation. Further to this, different characteristics of a single wheel and a multi-wheeled robot are presented. In this paper the interpretation of the conventional studies and experimental remarks is noted based on simulation analyses.

本論文では月や火星といった惑星を探査するローバの砂上における走行効率を上げるための方法論を提案している．加減速履歴に応じて沈下量が増加することを実験で確認し，数値計算にて加減速履歴修正方法の有効性を確認する．

遠隔地で機能する自律システムに共通で必要となりうる、ミッション実行のためのコマンド計画、実行、およびシステムの状態監視の仕組みについて提案する。宇宙機の自律コマンド実装モデルとして一般的なDeliberation, Execution, Driverという３層構造を基礎として、機能が一意に定義されている通常のコマンド発行だけでなく、「状態によって判断や分岐を伴う論理処理」をもコマンドとして認めるスプリプトエンジンを準備し、それを用いて状態監視をも行う方法である。さらに、この提案を具体的に検証すために試作したAUV（Autonomous Underwater Vehicle）の実験結果を示し、自律システムのための計画表現方法について議論する。

JAXA is examining research and development of a mobile rover required for searching or constructing basement on the lunar surface in succession of KAGUYA. Because the lunar surface is covered by regolith which is an irregular terrain and muddy soil, the rover has a difficulty in running. Therefore newly low contact force mechanism to achieve running with high reliability by changing the contact shape itself. In this research, the stiffness properties on experimental flexible wheel were determined to use flat elongated rectangle sensor made in scattered material pressed against the wheel longitudinal direction. This paper described the longitudinal contact pressure and distribution of flexible wheel by dynamic measurement.

Mobile rovers for lunar or planetary exploration are expected to break a new ground in the field of space science. The realization of adequate locomotion mechanisms for traveling on the surfaces of extraterrestrial bodies is principally a technical challenge. In particular, a reliable mobility on loose soil such as the lunar soil is required for successful rover missions on the Moon. So, the authors propose the novel concept of a micro-rover with an old and new locomotive component, screw unit, and such innovative rover is called Screw Rover. The screw units basically enable the rover to move in various directions by the simple combination of driving modes. Furthermore, Screw Rover can possess a robust and insensitive structure to the serious situation which is a stuck phenomenon caused by slippage and sinkage. In this paper, the fundamental considerations which include the design overview of Screw Rover and the theoretical discussion are presented as the primary study on Screw Rover.

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.