大槻 真嗣

Recently, a small size hopping rover is received attention for the moon and planetary exploration society. In a low gravity environment, a lightweight hopping rover might have high traversabilities: by jumping over long distance and obstacles. While a lot of hardware designs for hopping system are presented, few software designs for its system are presented. For the near future, software design for the rover is necessary to satisfy some requirements including sensing and navigation. A hopping rover has more uncertainties than conventional wheeled rover because a hopping movement is fundamentally different from a wheeled movement. Its uncertainties might be risks for the rover, in addition, it is difficult to reduce uncertainties because of its payload and hopping behavior. In this paper, we focus the navigation on hopping software system, and discuss about hopping movement with some uncertainties. Next, we propose the determination method of landing position using the geometric features of the triangle. The method is considered risks for the rover. We confirmed effectiveness of path planning with proposal method by simulation.

This paper discusses a 3D mapping technology using an active stereo sensor based on a surface sampling. In recent years, various sampling missions such as asteroids and satellites have been actively investigated. In these missions, a wide range of mapping is an essential aspect of obstacle detection and the best selection for the sampling from the unknown surface. In conventional methods, Flash LIDAR and stereo vision are widely used, however, Flash LIDAR only gets information about the distance and cannot determine the object. Furthermore, because this method is specialized for long distances, the accuracy tends to be low in the short distance such as within 1 m. The second way is stereo vision. In this way, it is necessary to extract several feature points. Therefore, because the entire surface is covered by the regolith, it is impossible to measure. In addition, the performance is also greatly dependent on sunlight conditions. For this reason, an auto regulatable active stereo is suggested, because it can adapt to any surface condition.In this the auto regulatable active stereo, two methods of a local binarization and a color modulation are proposed to keep a high mapping accuracy. First, the local binarization can correspond to the environment on which the shade and sunshine areas exist at the same time. Second, the color modulation can provide a stable measurement due to not depending on the surface color. These performances are evaluated by means of experiments conducted taking into consideration several sunlight and surface conditions. The experiment results confirmed that the accuracy is higher than other TOF( time of flight) sensors. Furthermore, the mapping can be made under strong sunlight and the environment of high gray scale of sand. Therefore, this 3D mapping method is expected to maintain high accuracy in an unknown environment such as the sampling mission.

For planetary exploration, small robots of just a few kilograms installed in the main spacecraft have a lot of advantages. Small robots can provide us with a wide range of exploration opportunities by using multi-robots, technical demonstrations, and science missions which require detailed data acquisition. There are not only mission advantages, but they can also be developed in a short period of time and at a low cost. MINERVA, MINERVA II, MASCOT are examples which are installed in the main spacecraft for surface exploration.In order to move on the surface of a "low gravity" object, like the Moon by a small robot, there are several options of locomotion, such as jumping, wheels, and legs. Wheel locomotion cannot step over obstacles where the size is bigger than the wheel radius, and the structure of leg locomotion is a very complicated piece of machinery and requires a lot of actuators. However, jumping locomotion is capable of moving a long distance by one action and the number of actuators required for jumping capability is very small. In addition, it can travel a longer distance on a planet or satellite which has a gravity lower than the Earth. For instance, it can jump 6 times longer on the Moon than on the Earth.To realize jumping locomotion for small robots in a low gravity environment, the mechanism has to meet the following functional requirements. (1) it can charge the required jumping energy, (2) it can release the energy instantly, (3) it can change the amount of the energy needed to control jumping distance, (4) it doesn't consume resources such as fuel and should be able to repeat the movement, (5) it has a ground contact part to apply power, (6) the size should be small and the weight should be small (7) it can move in a space environment (vacuum, high radiation). We studied some jumping mechanism concepts to meet these requirements. Our design of the mechanism uses springs to charge the energy and they are supported and connected to the shaft structure. A jumping pad is attached to the end of the structure and pushes the ground and robot so it can jump from the ground. For actuation, only one motor is used. In our mechanism, a one-way clutch is used to change from energy charge mode to release mode. This mode change is executed by changing the direction of motor rotation. After jumping, it can change the mode to energy charge mode again.The authors have developed a research model of the jumping rover which the jumping mechanism is mounted on. This model is developed for a lunar exploration mission. Science mission equipment mock-ups and wheels are also mounted on the model. The wheel is used to control the jumping direction.In this paper, our design of the jumping mechanism, development of a research model, and test results are presented in detail.

© 2017 by the International Astronautical Federation (IAF). All rights reserved. A 6U CubeSat "OMOTENASHI" will be the world's smallest moon lander which is launched by NASA SLS rocket in 2019. Because of its severe mass and size limitation, soft landing to the surface will be impossible. Hence, semi-hard landing scheme is adopted. That is, OMOTENASHI is decelerated to within around 30 m/s by a small solid rocket motor and shock absorption mechanism is developed for the high speed impact. Ultra small communication system (X-band and P-band) is also developed. It observes radiation environment of Earth and moon region with portable dose meters. This paper shows the latest design and development status of OMOTENASHI.

© Copyright 2017 by the International Astronautical Federation (IAF). All rights reserved. Martian Moons eXploration (MMX) is a mission under study in ISAS/JAXA to be launched in 2020s. This paper introduces the concept of MMX mission. "How was water delivered to rocky planets and enabled the habitability of the solar system?" This is the key question to which MMX is going to answer. Solar system formation theories suggest that rocky planets must have been born dry. Delivery of water, volatiles, organic compounds etc. from outside the snow line entitles the rocky planet region to be habitable. Small bodies as comets and asteroids play the role of delivery capsules. Then, dynamics of small bodies around the snow line in the early solar system is the issue that needs to be understood. Mars was at the gateway position to witness the process, which naturally leads us to explore two Martian moons, Phobos and Deimos, to answer to the key question. The goal of MMX is to reveal the origin of the Martian moons, and then to make a progress in our understanding of planetary system formation and of primordial material transport around the border between the inner- and the outer-part of the early solar system. On the origin of Martian moons, there are two leading hypotheses, "Captured primordial asteroid" and "Giant Impact". We decide to collect samples from a Martian moon to conclude this discussion, and on the conclusion, to investigate further to improve our understanding of material distributions and transports at the edge of the inner part of the early solar system as well as of planetary formations. Moreover, circum-Martian environment will be measured and Martian atmosphere will be observed to improve our views of evolutions of Martian moons as well as Mars surface environmental transition. In the conceptual design phase, the goals and objectives of the mission are defined, and the feasibility of the mission is evaluated. Fundamental engineering options are listed up, and trade-off studies are conducted to define baseline plan. Key technology issues are identified and their technology readiness is evaluated. The results will be shown in the paper.

<p>This paper describes the design of the hopping rover for the moon or Mars surface exploration. Hopping rover is one of solution for locomotion on loose and rocky terrain on the moon and planetary surface. The hopping rover can jump over an obstacles. Since the height of hopping is equal to the height which the rover can get over, the traversability of rover becomes higher than that of the small wheeled rover. In this paper, we describe the whole design of the hopping rover, design of hopping mechanism, simulator with the estimation of terrain force, action strategy, and the scientific missions.</p>

<p>Planetary surface mobility is one of the key technologies for future deep space missions. However conventional rovers are so big and expensive. To enhance robotic surface exploration missions, small, light-weight explorers are required. Therefore this paper proposes a new hopping locomotion system for small planetary rover using shape-memory-alloy(SMA) actuator. The proposed mechanism is analysed based on SMA constitutive mathematical model. Simulation results show that proposed mechanism has the capability of horizontally 2.5 m jump under the 1/6 gravity environment.</p>

This study discusses an airbag system as a landing gear of a spacecraft for a planetary exploration. The inflated airbag has the capability to attenuate impact acceleration at the instant of landing and submergence into regolith that covers a planetary surface. Crash tests in this paper verify the attenuation performance of the airbag and specify an issue.

For planetary exploration, small robots of just a few kilograms installed in the main spacecraft have a lot of advantages. In order to move on the surface of a &ldquo;low gravity&rdquo; object, like the Moon by a small robot, there are several options of locomotion, such as jumping, wheels, and legs. Jumping locomotion has capable of moving a long distance by one action and the number of actuators required for jumping capability is very small. In addition, it can travel a longer distance on a planet or satellite which has a gravity lower than the Earth. For instance, it can jump 6 times longer on the Moon than on the Earth. To realize jumping locomotion for small robots in a low gravity environment, authors proposed a new jumping locomotion method which consists of one jumping mechanism and one wheel for attitude and direction change, as well as they are now studying the mechanism which moves in a space environment (vacuum, high radiation). In this paper, the jumping mechanism is mainly described. The design of the jumping mechanism, test results on granular media are presented.

The authors have installed a tiny rover payload &ldquo;MINERVA-II&rdquo; into Hayabusa2 spacecraft which was launched in 2014. The payload consisted of three rovers installed in two containers. Two of them packed together in one container were the responsibilities of the authors. The other one in the secondary container came from the domestic university members. We developed a new rover deployment mechanism ejected from the containers. The rovers and the cover of the container were released by one action. But the cover headed for different direction of the one from rovers, so as to prevent the combination of them. The deployment mechanism was evaluated under the microgravity environment using a drop tower. This paper describes the deployment mechanism as well as the results of the microgravity experiments.

NASAのロケットシステムSLSに相乗りするCubeSatの一つとして，超小型月面技術実証機OMOTENASHIの開発が進められている．OMOTENASHIではソフトランディングが行えないため，月面との衝突緩和を目的としてエアバッグの使用が提案されている．本発表では，エアバッグへの使用を検討しているポリイミドフィルム製空気室の構造と基礎特性について述べる．

大気球シンポジウム 平成28年度（2016年11月1-2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: 17名資料番号: SA6000057014レポート番号: isas16-sbs-014

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). MEIDs are classified by momentum exchange directions as follows: Upper-MEID (U-MEID) that launches the damper mass upward, Lower-MEID (L-MEID) that drops the damper mass downward, and Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID, and G-MEID-A (G-MEID-Advanced) that has both upward and downward launching effect on single damper mass, by introducing initial tension to the MEID spring. However, studies of these MEIDs are mainly based on one-dimensional motion. Two-dimensional motion analyses have been done for only U-MEID. This research aims to derive the generalized MEID design methodology for two-dimensional motions. G-MEID-A, that is the most effective one for shock response control in previous MEIDs in the one-dimensional motion, are applied to multi-legged landing gear system. There are two damper masses, one is released to control spacecraft attitude, and the other is released to reduce landing shock. Their parameter design and optimal release timing are discussed in this paper. The effectiveness and robustness against landing slope angle variation of the proposed design methodology are verified by simulations.

© 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. The development of highly accurate and safe landing technology is required for the next generation lunar and planetary exploration landers in order to achieve touch down on rough but interesting areas. Especially, the explorations inside craters, highland regions, and the moon holes are demanded to achieve an unprecedented result that is pivotal in investigating the origin of the Earth and the Solar System. These areas, however, are rough terrain. Hence, they are considered to be unsuitable areas for landing. Therefore, for the next generation lunar and planetary landing explorations, the robust touch down technology will become more and more important. For the safe landing to such rough and steep terrain, the landing gear is required to prevent the lander from overturning and reduce the impact of landing in the final phase of landing sequence. In this paper, we propose a new landing gear system that uses a shock absorber with actively-variable damping coefficient and present its advantages for attitude stabilization during touch down.

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. Most of lunar or planetary landers have landing legs to reduce shock at the touchdown. They are usually made by passive elements that use aluminum honeycomb structure. When the spacecraft has horizontal velocity or lands on inclined surface, however, reaction force from legs causes rotational moment and the spacecraft might tumble down. The spacecraft should be designed to have lower center of gravity in order to prevent turnover. To avoid turn over and optimize elasticity and damping parameter of landing legs, we had proposed actively controlled landing legs. Since full-actively controlled legs which use high speed and high torque motors require large mass, large power and complexity, semi-actively controlled landing legs are considered. That is, only damping coefficient is controlled following states of the spacecraft. As a result of our study, damping coefficient should be switched to low or high depending on the sign of angular velocity of the spacecraft and shrinking speed of each landing leg. In the presentation, summary of our study is shown. The control scheme of the landing legs are introduced from theoretical consideration. Effectiveness of the proposed scheme is validated with numerical simulations and scale model experiments.

<p>In recent years, the eyes of the world has been upon a space exploitation mission with a micro robotic science probe such as MINERVA, MINERVA2 and son on, which mostly have been used under micro gravity environment. However we can find enough room in a launching vehicle and have many chances launching micro robots for large gravity environment, and they are expected for a lot of scientific results. In this paper, we discuss a micro rover for heavenly bodies, and propose some designs of one wheeled hopping rovers under a severe conditions for launching size and weight. Its basic behavior flow is also discussed with some technical subjects, and finally we focus on direction recognition with illuminance dependence of the sun light. According to this estimation of sun direction, the rover will be able to navigate to a goal point or area by itself. Here, we discuss a method to estimate the direction of the sun with some photo diodes, and also mention about arrangements and minimum number of diodes.</p>

<p>This paper presents a novel method of monocular visual odometry for a hopping robot, or a hopper. Firstly, a monocular scheme of visual odometry is applied to estimate the relative poses between three frames up to a scale factor. The scale ambiguity is resolved with the parabolic motion constraints of hopping robots. The whole trajectory can be recovered by estimating motion parameters including the initial velocity and angle. The proposed method is validated with synthetic data, and proved that it can accurately estimate the hopping motion with the absolute scale using only a single monocular camera.</p>

<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>