大槻 真嗣

<p>In recent years, planetary surface exploration missions by rovers have been actively performed. Rovers are required to recognize the surrounding environment autonomously for an efficient and safe exploration. Above all, terrain slope estimation is one of the essential techniques, which is conventionally performed with stereo cameras or shape-from-shading techniques. However, those schemes have problems such as the degraded accuracy in low-textured terrain and the heavy computational cost. Therefore, this paper proposes a new method that uses the difference of surface temperatures between at and slanted surfaces. It is known that the difference of solar radiation generates the gap in surface temperatures, which can be remotely detected with an infrared camera. The proposed method estimates terrain tilt angles using the energy balance equation and a single thermal image from the infrared camera. The method is validated with a field experiment in Izu-Oshima island. The developed thermal-based technique potentially increases the applicability to various terrain types regardless of the terrain appearance.</p>

第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県著者人数: 11名資料番号: SA6000046252レポート番号: S5-004

大気球シンポジウム 平成27年度（2015年11月5-6日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県著者人数: 16名ほか資料番号: SA6000044002レポート番号: isas15-sbs-002

This paper describes the control method of the semi-active controlled landing gear system for the lunar and planetary lander. The purpose of this paper is to achieve touchdown on uneven terrain without overturning. Damping force control on each landing gear suppress attitude disturbance of lander main body and prevent from its overturning. The control rule of the landing gear damping coefficient of each landing gear for the three-dimensional lander model is shown and it validated in the three-dimensional numerical simulation model. Touchdown simulation executed on rough terrain which reproduced natural terrestrial surface. Especially, touchdown on the incline and touchdown with a lateral residual velocity are tested. The result of simulation indicates that the proposed control rule for the semi-active landing gear is effective to prevent overturning.

Surface mobility on planetary bodies has enabled nearly two decades of scientifically-rich exploration of the red planet, however not without its challenges. Future exploration will likely demand enhanced mobility to access more challenging terrain. In this paper, we apply resistive force theory (RFT) to a general grouser geometry model, and present simulation results that show the impact of several parameters on draw-bar pull. This work represents initial steps toward optimizing grouser geometry to maximize draw-bar pull, while maintaining ability to traverse rocks of certain geometries and minimizing energy usage per traverse distance. These criteria are of particular importance in power-constrained planetary rovers.

This paper presents that the skyline matching algorithm with considering camera tilt. Skyline matching is the method that estimating position and attitude by comparing two skylines. One skyline is simulated one from a digital elevation model (DEM). The other one is gotten from camera images taking around view. We conducted field experiments in Oshima Island. As a result, we conclude that considering camera tilt has a significant influence.

第15回宇宙科学シンポジウム (2015年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県資料番号: SA6000034342レポート番号: S5-008

大気球シンポジウム 平成26年度（2014年11月6-7日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)）, 相模原市, 神奈川県著者人数: 18名資料番号: SA6000021006レポート番号: isas14-sbs-006

2009年、JAXAの月探査機SELENE(かぐや)は、世界で初めて、月のマリウス丘群に直径60mの巨大な縦孔を発見した。さらに、SELENEデータを使用した全球サーベイにより、他に二つ、更に巨大な縦孔(直径、深さ共に数10m〜100m)が発見された。筆者らが"Haruyama Hole"と呼んでいるこれらの縦孔の下には、縦孔直径を超える地下空洞の存在が示唆されている。また、火星にも同様の縦孔が見つかっている。生命科学を含む様々な理学的意義に加え、将来の月・惑星探査技術の開発や月面基地開発の観点からも、月や火星の縦孔・地下空洞の直接探査が望まれており、筆者らは2020年頃を目標に、SELENEの発見した月の縦孔に、世界で初めて降下して直接探査するUZUME計画を検討している。このような深い縦孔や地下空洞を直接探査するためには、垂直に近い縦孔の壁を降り、岩体の転がる縦孔底に到達・観測した後、更に、未知の暗く拡がる空洞へと移動して調査を行える探査システムが必要である。筆者らは、ETS-VIIなどの宇宙ロボット技術の軌道上実証や地上実験による研究開発を行って来ており、これらの宇宙ロボット技術開発成果を活用した、縦孔・地下空洞の探査システムの研究を進めている。本講演では、宇宙ロボット技術を活用した縦孔・地下空洞の探査戦略と、探査システムの設計、運用シナリオおよび、その技術開発戦略と研究成果について述べる。

次期月惑星探査ミッションにおいては,遠隔からの観測だけでなく,地表面に降り立ち移動しながら詳細な探査を行うことが期待されている.その表面移動技術の要となる探査ローバにとって,安全で効率的なミッション遂行のために正しく現在位置を把握することが必要である.従来の車輪エンコーダや慣性観測装置を用いたデッドレコニング法では,月惑星表面の不整地においては誤差が蓄積し正確な推定を行うことができなかった.そこで本研究は,ステレオカメラと絶対方向センサを用いることにより,不整地においても自己位置を高精度に推定できる手法の構築を目指す.地球上の惑星類似環境である伊豆大島の裏砂漠における長距離走行試験によって,手法の有効性を示した.

Copyright © 2014 by the International Astronautical Federation. Lunar/planetary exploration requires soft landing methods so that a lander can land on any terrain. However, the existing landing methods have drawbacks such as high rebound and excessive resource consumption. To address these drawbacks, the authors propose a novel landing mechanism called BESM (Base-Extension Separation Mechanism). The BESM achieves a soft landing by energy conversion with springs and three separable units (lander, extension, and gear). The gear unit touches ground before the lander. The lander's energy is absorbed by the spring mounted on the gear, and the lander is then released from a small height with less energy. The rebound and acceleration suppression performance has been demonstrated in previous studies, and its reusability also contributes to resource savings. However, there are some issues associated with the BESM. The first issue is that soft landing performance is not ensured in landing on uneven ground, because the energy is not ideally absorbed by the spring with the gear inclined. The second issue is that the performance of the BESM is sensitive to spring parameter tuning. An improperly tuned BESM releases the lander from a greater height than it should. Accurate parameter tunings are required for proper performance. To address these issues, this paper proposes a fundamental solution using telescopic gear. The telescopic gear is composed of movable gear units and stopper units. The motions of the movable gear units are controllable by the stopper units. When it is mounted at appropriate positions with ideal stopper control, the telescopic gear can flexibly compensate for gear inclination and release height error caused by uneven ground and/or improper parameter tunings. To confirm the effectiveness of the telescopic gear analytically, the soft landing performance of the gear on uneven ground and/or with improperly tuned parameters was analyzed using simulation. The modeling of the BESM with the telescopic gear is presented, and the effective stopper control method is explained. The simulation results show that the issues mentioned with the BESM are addressed by the telescopic gear. The ideally controlled telescopic gear compensates for gear inclination and release height error, and the BESM performs as if it had landed at a flat location with properly tuned parameters. The telescopic gear improves the BESM's performance remarkably. It enables the BESM to land on more extreme terrain and contributes to ensuring proper performance. The telescopic gear is therefore concluded to be a promising device for future lunar/planetary explorations.

This paper presents an actively controlled landing gear system and its experimental validations. Active landing gear uses an variable coefficient damper as an shock absorber. We executed landing experiment with the two dimension lander model which introduced an magnetorheological damper as an shock absorber. Damping coefficient is controlled to reduce attitude disturbance during touchdown based on lander attitude and displacement of landing leg. The result of model experiment indicates that the active landing gear can reduce attitude disturbance which causes the lander overturning.

This paper presents a high-speed transportation of capsule by launch. One of the main issues for the transportation is how to decelerate the capsule during its flight to avoid a large landing impact. In order to stop the capsule temporally in the air just before its landing, we propose a flight control method by multidirectional tension of wires. Since the capsule is connected with both auxiliary weights and reel system via wires, it can be geometrically constrained not to move by multiple pull of the wires. We develop the motion planner which makes the capsule reach the target at the desired speed, and control algorithm for it. The proposed method is applied to the soft landing of the capsule. The effectiveness of the proposed method is verified through the experiment.

Lunar or planetary exploration is scientifically meaningful because they can give us the hint to throw a light on the origin and evolution of the solar system or the earth, the inner structure of planets, etc. In lunar or planetary exploration missions, it is important to save the weight of spacecraft. Light weight spacecraft leads to low cost and getting more chance to go to the space. Conventionally a lander carries a rover to the surface of the celestial body and the rover traverses the rough terrain to explore in wide region. If the lander and the rover are united, however, the total weight of the spacecraft could be reduced. The authors have already proposed a novel pulley suspension mechanism, which is called Load Equalization Pulley Suspension mechanism: LEPS mechanism, for rovers. The performance of the proposed mechanism as a suspension mechanism of rovers has been evaluated. In this paper, the application of LEPS mechanism to the landing gears of the lander is discussed. By applying the proposed mechanism to the landing gears, the lander can move around the wide region of the surface after landing. The landing dynamics model of the proposed "Movable lander" with LEPS mechanism is introduced. The landing performance is evaluated by 2-dimensional model. The simulation results show that LEPS mechanism has an advantage over normal landing gears.

The performance of an integrated navigation system is studied through the field experiments on a four-wheeled test-bed rover, AKI, operated in a terrestrial analogue. The AKI rover employs novel mobility and navigation systems which enable challenging long-range operations in natural terrain. AKI has a vision-based localization system aided by sun sensors and an inclinometer for absolute attitude estimation. The integration with absolute direction sensors improves accuracy in absolute positioning, as well as obtaining 5x run-time improvement of visual pose estimation. The paper reports the results of field experiment conducted in Izu-Oshima island in 2013, and discusses current challenges of the system.

In this paper, we firstly develop the system which connects an end-effector with wire just before launching the end-effector. We then conduct the experiment and verify the stable connection by six trials. We secondly propose the method to decelerate the flight speed of the end-effector after launching it. The spring is used for smooth deceleration and the ratchet is used for prevent the expanded spring from restoring. We develop the ratchet-reel system and confirm that it decelerates the translational speed of the end-effector as well as its rotational speed through experiments.

This paper presents that the method of position error correction for planetary rovers by using skyline matching azimuth estimation. Skyline matching is the method that estimating position and attitude by comparing two skylines. One skyline is simulated one from a digital elevation model (DEM). The other one is gotten from camera images taking around view. We focus on using azimuth attitude estimated by skyline matching to correct accumulation error of IMU. We modeled IMU angular velocity bias increases linearity. We conducted field experiments in Oshima Island and Chiba. As a result, estimated relative azimuth errors are lower than 1 degree. IMU azimuth errors decreased by 67% (6.25 deg to 2.15 deg ) and IMU position errors decreased by 70% (3.33m to 1.04m).

Next-generation lunar/planetary exploration spacecraft need to solve problems of conventional landing methods and mechanisms such as high rebound, impossibility of reuse and high cost. For this purpose, the authors discuss the landing method by means of Base-Extension Separation landing Mechanism (BESM) which uses energy conversion with springs and separable units. In the authors' conventional studies, its effectiveness was confirmed for a simple case based on single-axis restriction. However, the investigation of tumble prevention cannot be treated in the simple case. The purpose of this preliminary report is the response analysis of a slope landing case of BESM for more practical landing situations.

This paper presents the influence of shadow on the path planning of lunar rovers. To evaluate the influence of shadow, the terrain and shadow on the Moon are first modeled using the DEM derived from Kaguya data. Subsequently, on the basis of a path planning algorithm considering the shadow, numerical simulation is performed for the lunar terrain. In the simulation, a short path crossing shadow is compared with a long path avoiding shadow under various insolation conditions. The simulation results confirmed that although avoiding shadow adds a traveling distance and time, it doses not much affect the average power consumption but contributes to an increase in the average power generated.