大槻 真嗣

For touchdown mission on rough but interesting terrain where no space probe has gone before, like "crater central hill" and edge of lunar lava tube hole, an actively controllable landing system is required. This paper proposes an of actively controlled landing leg system by using a variable coefficient damper. Further, to show the effectiveness of the actively controlled landing leg system, we simulate touchdown based on mathematical models. Further, show the effectiveness of the actively controlled landing leg system based on the proposed controller. Simulation model is virtually-fixed in two-dimensional plane, and investigates robustness of lander to touchdown to slope terrain and the case where the lander has initial horizontal velocity and initial attitude angle error.

This paper discusses landing response control methods of planetary exploration spacecraft on the basis of momentum exchange principles. For example, cantilever designs that incorporate honeycomb materials to dissipate shock energy through plastic deformation have been used as the landing gear systems; however, once tested on Earth, the system cannot be used in a real mission. The sky crane used in the Mars Science Laboratory by NASA provides safe and precise landings, but the costs are high. This paper introduces a momentum exchange impact damper (MEID) that absorbs the controlled object's momentum with extra masses called damper masses. The MEID is reusable, which reduces the mission cost. Until now, some types of MEIDs have been introduced; for example, in an upper-MEID (U-MEID), the damper mass is launched upward. A single-axis (SA) model has already been used to verify the effectiveness of MEIDs through simulations and experiments in terms of the rebound height of the spacecraft. However, the SA model cannot address the rotational motion and tipping of the spacecraft. This paper presents a two-landing-gear-system (TLGS) model that equips plural U-MEIDs for two-dimensional analysis. In contrast to the authors' previous studies, each MEID is launched when each landing gear lands. This mechanism can realize advanced control specifications compared with the previous mechanism that all of the MEIDs are launched simultaneously. For example, if each MEID works when each gear lands, the rebound height of each gear can be minimized, and tipping can be prevented. The results verified that the proposed mechanism can prevent tipping and rebounding of spacecraft. Copyright© (2013) by the International Astronautical Federation.

This paper presents the control method for vibration due to rotational motion of a casting manipulator. The casting accuracy of an end-effector, which is attached to the odd end of a wire rotated by the casting manipulator, significantly depends on the attitude at the release time. Further, the attitude of the casting manipulator is horizontally and vertically vibrated by the rotational motion if the rotational axis does not coincide with the position of the gravitational center of the rotated arm; consequently, the considerable casting error occurs. Hence, this paper mentions the vibration problem of the casting manipulator; first, we confirm the vibration experimentally; second, the casting error due to attitude shift is numerically analyzed; finally, the active vibration control method using an actuator is proposed. The vibration reduction due to the shift in yaw angle is particularly verified through the numerical calculation and the effectiveness of the active control is shown.

Moon holes were first discovered in the world by JAXA in 2009. It is believed that moon hole is helpful to know the formation of the moon because bedding plane is exposed. In addition, because inner hole is sealed from solar wind, it is also important as a candidate site for base camp in the future. However, exploration of the moon hole is difficult with the conventional robots. A new robot is required for going down and explore moon hole. In this study, a system to throw a small robot into a moon hole with wire is proposed. The author describes modeling and attitude control in a state where the robot is hanging by a wire, and evaluates the effectiveness of the system.

The development of highly accurate landing technology is required for the next generation lunar-planetary exploration lander to touch down on rough but interesting area. For the safe landing, the development of landing leg is required to prevent overturning and reduce landing impact of the lander in the final phase of landing sequence. However, it is difficult to design a landing leg which is applicable to a wide variety of terrain. The active landing leg is proposed as a solution of solving this problem. This paper presents the simulation of the lander with active landing leg and development of experimental system using Magneto-Rheological damper, and examines the landing shock response and penetration of the lander leg to the sand terrain.

This paper presents a technique for driving a wheel to control the sinkage of a planetary rover on loose soil. Dynamic sinkage of the wheels of the rover always occurs when it travels on loose soil in the planetary surface; sinkage is then caused by the soil deformation due to a compressive force generated by the wheel and the soil conveyance due to slippage in the wheel. When the wheel is driven in an acceleration profile with a trapezoidal shape, it is experimentally confirmed that the depth of sinkage changes during both acceleration and deceleration. Further, it is also confirmed that the terminal sinkage is proportional to the magnitude of the maximum rotational acceleration and deceleration of the wheel; consequently, we propose the method of controlling the sinkage by adjusting their magnitude. The proposed control is verified through the experiments using the single wheel test bed and the full body rover with 4 wheels; thus, it is confirmed that twofold increase of sinkage is caused and the terminal sinkage is controlled, especially suppressed.

We propose the method to control landing position and speed of an end-effecter in the air by multidirectional tension of wires. The end-effecter is connected with both dummy weights and reel system via the wires. After launching the end-effecter and dummy weights, its trajectory is changed by each tension of the wires when their motion is geometrically constrained. We develop the motion planner which makes the end-effecter reach the target at a suitable speed, and control algorithm for it. The proposed method is applied to the soft landing of the end-effecter. The effectiveness of the proposed method is verified through the experiment.

In 2009, the Selenological and Engineering Explorer (SELENE, nicknamed Kaguya) discovered a vertical hole of 〜60 m diameter and 〜50 m depth in the Marius Hills region on the Moon. After the discovery of the Marius Hills Hole (MHH), two other more gigantic holes were discovered by a global survey executed by the SENENE team. The vertical holes were likely formed by volcanic activities or tectonic processes such as skylight formation on lava tubes, from the terrestrial analogues. The indicative evidence of the existence of subsurface void spaces associating with the holes was indeed acquired by the US LRO later. Similar vertical holes have been discovered on the Mars. Various important knowledge of science on the Moon, the solar system, and extra-terrestrial life will be obtained by direct in-situ explorations into the lunar holes and their associating subsurface void space. However, the exploration of the holes and underlying subsurface voids require a system with the state of art which can overcome difficulties, such as the descent into the floors of the holes studded with boulders and the travel into the dark void spaces hidden from the lunar surface. We have studied on the exploration system by applying space robotics technology. We report the exploration system design, operational scenario in this paper.

The JAXA lunar orbiter spacecraft "SELENE (Kaguya)" found a vertical cave on the surface of the moon. For underground exploration of the moon, we propose the method to launch the probe vehicle into the cave by casting manipulator system. For the first step, we develop the launcher system which can generate kinetic energy of the end-effecter by rotating the boom and throw it to the target. We then verified that the system can throw the end-effector more than 17 meters and its positioning accuracy is less than 3.4% through experiments.

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 discuss 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 through experiment.

Estimating the position of a robot is an essential requirement for autonomous mobile robots. Visual Odometry is a promising localization method in slippery natural terrain, which drastically degrades the accuracy of Wheel Odometry, while relying neither on other infrastructure nor any prior knowledge. Visual Odometry, however, suffers from the instability of feature extraction from the untextured natural terrain. To date, a number of feature detectors have been proposed for stable feature detection. This paper compares commonly used detectors in terms of robustness, localization accuracy and computational efficiency, and points out their trade-off problems among those criteria. To solve the problem, a hybrid algorithm is proposed which dynamically switches between multiple detectors according to the texture of terrain. Validity of the algorithm is proved by the simulation using dataset at volcanic areas in Japan. © 2013 Springer-Verlag.

JAXA is planning moon exploration missions following Kaguya (SELENE), whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. SELENE-2 is the first Japanese moon lander. Its phase-A study started in the summer of 2007. It will demonstrate precision landing, hazard avoidance, surface mobility, and night survival technologies. In-situ geological and geophysical observations will contribute to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment and possible in-situ resource will be useful for future human exploration. In this paper, recent progress of research and development for SELENE-2 is presented. Key Words: Lunar exploration. Precision landing. Rover, Night survival. Copyright © (2012) by the International Astronautical Federation.

When a spacecraft lands, a large shock load can lead to undesirable responses such as rebound and tripping. The authors previously discussed the problem of controlling these shock responses using momentum exchange impact dampers (MEIDs). An active/passive- Hybrid-MEID (HMEID), which included an active actuator, was proposed, and stiffness control was applied. The stiffness control method controls spring coefficient between the damper mass and the body mass. The MEIDs' performances are evaluated by the maximum rebound height, which is proportional to mechanical energy of the spacecraft. However, the time responses of the energies have not been explained. In addition, the effectiveness of MEIDs was evaluated only in a one-dimensional motion simulation. This paper includes theoretical analyses, simulation studies, and experiments. The time responses of the energies of MEIDs are discussed. This paper proposes a robust landing gear system for spacecrafts using HMEID and evaluates its robustness against ground stiffness variation. In this paper, MEIDs are applied to a mass-damper-spring-model, which takes ground viscosity into account. Effectiveness of the proposed model is verified by simulations and some experimental results. © 2012 by Yohei Kushida, Susumu Hara, Masatsugu Otsuki, Yoji Yamada, Tatsuaki Hashimoto, and Takashi Kubota.

This paper addresses a method of releasing a penetrator during a boom's rotation to improve the precision of the position when its landing First, we point out the disadvantage of using the electromagnetic release device from a viewpoint of response variation We then propose a mechanical release device which is activated by collision between a release-lever equipped on the boom and a stopper set at the pillar of the system A gripping device based on the toggle mechanism is also proposed to hold the penetrator tightly against an excessive centrifugal force when the boom rotates at a high speed Developing these proposed devices, we finally conducted experiments of releasing the penetrator and analyzed a position error of its landing point We verified the effectiveness of the proposed method by showing that the error is less than 3% of the distance to the launching point through the experiments

Estimating a robot's own position is an essential requirement for autonomous mobile robots. Visual Odometry (VO) can play a key role in navigation tasks in slippery natural terrain, which highly degrade the accuracy of Wheel Odometry, without relying on other infrastructures nor any prior knowledge. A challenge of VO system lies in how to increase the number of features tracked between continuous frames in untextured terrain. Although there has been many feature selection algorithms proposed, none of them are sufficient in terms of calculation speed and robustness. Hence, this paper propose an algorithm that dynamically switches between high-speed/low-accuracy and low-speed/high-accuracy algorithm according to the texture of terrain. Validity of this algorithm was proved by the simulation using datasets taken at Izu-Oshima, Japan.

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 this paper new procedures for the measurement of mobility parameters, such as contact pressure, and an analysis of a low-pressure wheel model on deformable terrain, are presented. Because the lunar surface is covered by regolith which implies an irregular and rough terrain, the rover has difficulty in moving. 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. The presented measurement is achieved by a new measurement instrument on the wheel, and we presented analysis model is conducted through analysis of terramechanics mobility dynamics of a low-pressure wheel with normal stress. These procedures are valuable for evaluating the longitudinal velocity of the low-pressure wheel on deformable terrain.

JAXA is planning moon exploration missions following Kaguya (SELENE), whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. SELENE-2 is the first Japanese moon lander and its phase-A study started in the summer of 2007. SELENE-2 will demonstrate precision landing, hazard avoidance, surface mobility, and night survival technologies. In-situ geological and geophysical observations will contribute to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment and possible in-situ resource will be useful for future human exploration. In this paper, recent progress of research and development for SELENE-2 is presented.

We present the synthesis procedure of the target profile for a motion control system to simultaneously control the sinkage and vibration of a planetary rover. The experimental result, using a single-wheel testbed on lunar regolith simulants, indicates that the sinkage is proportional to the magnitude of the maximum acceleration of the driving mechanism. Hence, we propose a method of suppressing the sinkage by designing an asymmetric acceleration profile as a target for a motion control system. Moreover, it was confirmed that the vibration due to the flexibility of the wheel is induced by self-motion, and we experimentally verified the reduction of vibration using the general command-shaping method. © 2011 SICE.

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.