大槻 真嗣

JAXA-RR-16-008

The landing system which is adaptable to different kind of terrain condition is required to achieve touchdown on rough and inclined terrains. However, it is difficult to design a landing system which is applicable to a wide variety of terrains. In the conventional landing gear system, aluminium honeycomb crush and oil damper are used to mitigate landing impact. These classical mechanisms have advantages of simplicity and large shock absorption capability. However, those classical passive landing gears are ill suited for landing to the uneven and inclined areas and for landing with lateral velocity. To prevent from lander tip-over, it is necessary to make landing gear adaptable to wide condition of terrain. In order to solve this problem, we propose a new mechanism for safety landing on an inclination. In general, tipping-over of spacecraft is caused by the torque which is generated by the difference of the force acting on each leg. However, it is difficult to synchronize force acting on the all the landing legs. Here, we focused on the difference of the force acting on each leg. In case of touchdown on the inclination, the force acting on the upper leg is larger than any other legs. In case of touchdown with a lateral velocity, the force acting on the former leg is larger than any other legs. Therefore, if we can convert this force to torque which is acting to the direction against to the rotating of the spacecraft, it becomes possible to prevent tip-over of the spacecraft.

Spacecraft landing missions require a soft landing mechanism to prevent a large shock load and tipping over when landing on various types of terrain. The authors previously invented a novel landing mechanism called a telescopic-gear base-extension separation mechanism that operates by means of energy transfer and an adjustable structure. This mechanism passively adjusts the shape of the landing gear according to the landing terrain and transfers the energy of the lander to a spring as potential energy. The outstanding performance of this landing mechanism was demonstrated analytically in a previous study. However, its feasibility was not confirmed, and an effective parameter design method for various shapes of terrains was not presented. Therefore, in this study, two-dimensional experimental investigations are conducted using a small-scale prototype to assess the feasibility of the landing mechanism for several types of terrain. An effective parameter design approach based on a mathematical model derived from the experimental results is presented in this paper. To improve the robustness of the landing mechanism, the lengths of the telescopic gears should be as large as possible, and the spring stiffness should be tuned within a certain range. For sloped ground in particular, the width of the lander is an additional important design parameter; a smaller width is preferable in theory. A robustness study and several important notes on the practical design aspects of the landing mechanism are summarized in this paper.

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 planetary lander.

<p>We are planning to explore the caverns through the skylight holes on the Moon and Mars. The holes and their associated subsurface caverns are among the most important future exploration targets. The importance of the lunar and Martian holes and their associated caverns is categorized from two aspects: (1) fresh materials are easily observed and sampled there, and (2) the subsurface caverns provide a safe, quiet environment. The expectation of lunar and Martian hole and cavern exploration is increasing in Japan. We name the project as UZUME (Unprecedented Zipangu (Japan) Underworld of the Moon Exploration) whose name is after a Japanese mythology. The ultimate purpose of the UZUME project is to investigate how to expand human activity and survival in space and on extraterrestrial bodies. </p>

Lunar/planetary spacecraft should be able to land softly and conduct thorough explorations. Conventional landing methods suffer from various problems such as high rebound, the impossibility of reuse, and necessity of air. Therefore, a novel landing method that solves these problems is required for landing in severe environments. Toward this end, the authors have applied Momentum Exchange Impact Damper (MEID). MEID realizes landing by exchanging the momentum of the spacecraft with damper masses. However, flying damper masses may collide with and damage the spacecraft. Furthermore, they may pollute the lunar/planetary surface. Therefore, in this paper, the authors propose a Non-Flying-Type MEID (NFMEID) mechanism without flying damper masses. Unlike conventional landing methods and MEIDs, the NFMEID (i) reduces a spacecraft's rebound, (ii) can be reused, (iii) can be used in vacuum, and (iv) can protect a spacecraft and the surface pollution from launched masses. Furthermore, the NFMEID may extend the usefulness of MEID because it is considered effective for the shock response control of not only spacecraft but also general mechanical structures. This paper explains the NFMEID mechanism and evaluates its landing performance through some simulations. This study shows that the NFMEID is a promising landing method for further lunar/planetary exploration missions.

Future planetary exploration requires spacecraft to land softly on rough terrain and in severe environments. Since conventional landing methods have problems such as high rebounds and excessive resource consumption, the base-extension separation mechanism, which combines springs and separable units, is proposed as a novel landing mechanism. Although the mechanism performed good soft landings, the performance evaluation was limited. Therefore, this study evaluated its performance multilaterally. The proposed technology was analytically compared with two other landing technologies: a generalized-hybrid momentum exchange impact damper and an aluminum foam landing gear. The proposed technology suppressed rebound and acceleration better than the generalized momentum exchange impact damper. Once the components of the proposed technology had been lightened, its energy conversion efficiency matched that of the aluminum foam landing gear. In addition, experiments were conducted using small-scale models to confirm the feasibility. The experiments showed that the proposed technology has good soft landing performance, matching the results of the simulations. Finally, design optimization was discussed for further performance improvements. It was clarified that both the spring stroke and the pre-tension length of the spring should be large. Optimizing the design of the spring improved its performance and compensated for its disadvantages.

© 1994-2011 IEEE. This article presents a comprehensive path-planning method for lunar and planetary exploration rovers. In this method, two new elements are introduced as evaluation indices for path planning: 1) determined by the rover design and 2) derived from a target environment. These are defined as the rover's internal and external elements, respectively. In this article, the rover's locomotion mechanism and insolation (i.e., shadow) conditions were considered to be the two elements that ensure the rover's safety and energy, and the influences of these elements on path planning were described. To examine the influence of the locomotion mechanism on path planning, experiments were performed using track and wheel mechanisms, and the motion behaviors were modeled. The planned paths of the tracked and wheeled rovers were then simulated based on their motion behaviors. The influence of the insolation condition was considered through path plan simulations conducted using various lunar latitudes and times. The simulation results showed that the internal element can be used as an evaluation index to plan a safe path that corresponds to the traveling performance of the rover's locomotion mechanism. The path derived for the tracked rover was found to be straighter than that derived for the wheeled rover. The simulation results also showed that path planning using the external element as an additional index enhances the power generated by solar panels under various insolation conditions. This path-planning method was found to have a large impact on the amount of power generated in the morning/evening and at high-latitude regions relative to in the daytime and at low-latitude regions on the moon. These simulation results suggest the effectiveness of the proposed pathplanning method.

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 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 paper is the response analysis with a double-axis case and to discuss the robustness of BESM for more practical landing situations.

The safe and precise landing control method of planetary exploration spacecraft is indispensable to achieve its missions. However, the landing methods used in previous missions have some problems such as high complexity. To improve them, the authors' have focused on the momentum exchange principles and adopted momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum to extra masses close to the object. This extra mass is called damper mass. Some kinds of MEIDs have been introduced; for example, this paper shows 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. The authors' previous paper shows the effectiveness of G-MEID. The purpose of this paper is to introduce its improved version called G-MEID-A (G-MEID-Advanced). G-MEID-A can realize downsizing of the damper mass and more effective momentum exchange by tuning of momentum exchange timing. Simulation investigation verifies that the G-MEID-A has some advantages against the rebound reduction of the spacecraft and robustness against some variable conditions.

This paper describes a stereo visual odometry system for volcanic fields which lack visual features on the ground. There are several technical problems in untextured terrain including the diversity of terrain appearance, the lack of well-tracked features on surfaces, and the limited computational resources of onboard computers. This paper tries to address these problems and enable efficient and accurate visual localization independently of terrain appearance. Several key techniques are presented including a framework for terrain adaptive feature detection and a motion estimation method using fewer feature points. Field experiments have been conducted in volcanic fields for validation and evaluation of the system effectiveness and efficiency.

This paper discusses a landing response control system based on the momentum exchange principle for planetary exploration spacecraft. In the past, landing gear systems with cantilever designs that incorporate honeycomb materials to dissipate shock energy through plastic deformation have been used, but once tested before launch, the system cannot be used in a real mission. The sky crane system used for the Mars Science Laboratory by NASA can achieve a safe and precise landing, but it is highly complex. 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 makes it easy to ensure the landing gear's reliability. In this system, only passive elements such as springs are needed. A single-axis (SA) model has already been used to verify the effectiveness of MEIDs through simulations and experiments measuring 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 in which multiple MEIDs are equipped for two-dimensional analysis. Unlike in the authors' previous studies, in this study each MEID is launched when the corresponding landing gear lands and the MEIDs do not contain active actuators. This mechanism can be used to realize advanced control specifications, and it is simply compared with previous mechanisms including actuators, in which all of the MEIDs are launched simultaneously. If each MEID works when the corresponding gear lands, the rebound height of each gear can be minimized, and tipping can be prevented, as demonstrated by the results of our simulations. (C) 2014 IM. Published by Elsevier Ltd. All rights reserved.

© 2014 IAA. The Japan Aerospace Exploration Agency (JAXA) views the lunar lander SELENE-2 as the successor to the SELENE mission. In this presentation, the mission objectives of SELENE-2 are shown together with the present design status of the spacecraft. JAXA launched the Kaguya (SELENE) lunar orbiter in September 2007, and the spacecraft observed the Moon and a couple of small satellites using 15 instruments. As the next step in lunar exploration, the lunar lander SELENE-2 is being considered. SELENE-2 will land on the lunar surface and perform in-situ scientific observations, environmental investigations, and research for future lunar utilization including human activity. At the same time, it will demonstrate key technologies for lunar and planetary exploration such as precise and safe landing, surface mobility, and overnight survival. The lander will carry laser altimeters, image sensors, and landing radars for precise and safe landing. Landing legs and a precisely controlled propulsion system will also be developed. A rover is being designed to be able to travel over a wide area and observe featured terrain using scientific instruments. Since some of the instruments require long-term observation on the lunar surface, technology for night survival over more than 2 weeks needs to be considered. The SELENE-2 technologies are expected to be one of the stepping stones towards future Japanese human activities on the moon and to expand the possibilities for deep space science.

In future surveys, planetary exploration spacecraft will need to land on rock beds and slopes. Therefore, spacecraft should be equipped with landing methods to facilitate soft landings in these severe regions. However, conventional landing methods have problems such as high rebound, the impossibility of reuse, and excessive resource consumption. To overcome these problems, the authors previously invented several landing methods, but these have practical limitations. Thus, this paper proposes a novel landing mechanism called the base-extension separation mechanism (BESM), which focuses on energy conversion using springs and separable units, and discusses a single-axis falling-type small-scale model of a spacecraft with the BESM. Then, the rebound and acceleration suppression performance is evaluated through simulations. These reveal that the BESM realizes good performance under nominal conditions. The BESM is shown to have good robustness against variations in the ground stiffness, ground damping, spacecraft mass, and installed mass. The study findings reveal that the BESM is a promising method: it overcomes the drawbacks of the conventional methods and our previous inventions. In addition, the BESM generally performs better in soft landings than our previous inventions.

This paper describes the attitude control method for overturning prevention for a lunar planetary lander which uses a semi-active damper on the landing leg. In order to achieve safe landing on uneven terrain especially a sloped ground, a novel landing gear system is required. The landing leg with variable damping is one of the solutions for touchdown without overturning. Conventional landing gear for lunar and planetary lander has a fixed shock attenuation parameter and it is not used proactively for attitude control of the lander in the touchdown sequence. By controlling the damping coefficient of the each landing leg, it becomes possible to suppress the disturbance on the attitude of the lander, and it prevents overturning. First, the strategies for the overturn prevention for the lander by changing damping coefficient of landing legs are shown and the control rules based on the lander and landing leg state values are proposed. In the second place, the mathematical model of lander based on the differential algebraic equation in vertical two-dimensional plane is presented. Besides footpad-ground contact model is also described. Finally, touchdown simulations on a sloped terrain with the proposed landing gear control method are shown. Numerical simulations show that the proposed landing gear system works well during the touchdown on a sloped terrain.

Pose estimation is one of the important tasks for mobile robots exploring in outdoor environments. Recently, visual odometry has received a lot of attention since its localization is accurate even with low-cost sensors. Furthermore, the technique is not affected by wheel slips, and it can be performed without external infrastructures and preliminary maps. While existing techniques successfully provide good localization of outdoor vehicles, possible failures are not yet fully examined in untextured terrains where feature tracking occasionally fails. This paper proposes an approach to detect interest points from a wide variety of terrains by adaptively selecting algorithms. Experiments show that the approach provides robust and fast interest point detection even in untextured natural scenes.

This paper presents terrain mapping and path-planning techniques that are key issues for autonomous mobility of a planetary exploration rover. In this work, a LIDAR (light detection and ranging) sensor is used to obtain geometric information on the terrain. A point cloud of the terrain feature provided from the LIDAR sensor is usually converted to a digital elevation map. A sector-shaped reference grid for the conversion process is proposed in this paper, resulting in an elevation map with cylindrical coordinates termed as C2DEM. This conversion approach achieves a range-dependent resolution for the terrain mapping: a detailed terrain representation near the rover and a sparse representation far from the rover. The path planning utilizes a cost function composed of terrain inclination, terrain roughness, and path length indices, each of which is subject to a weighting factor. The multipath planning developed in this paper first explores possible sets of weighting factors and generates multiple candidate paths. The most feasible path is then determined by a comparative evaluation between the candidate paths. Field experiments with a rover prototype at a Lunar/Martian analog site were performed to confirm the feasibility of the proposed techniques, including the range-dependent terrain mapping with C2DEM and the multipath-planning method. (C) 2013 Wiley Periodicals, Inc.

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. An active/passive hybrid momentum exchange impact damper, which included an active actuator, was proposed. The momentum exchange impact dampers' performances are evaluated by the maximum rebound height, which is proportional to the mechanical energy of the spacecraft. However, the time responses of the energies have not been explained. In addition, the effectiveness of momentum exchange impact dampers 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 momentum exchange impact dampers are discussed. This paper proposes a robust landing gear system for spacecraft using a hybrid momentum exchange impact damper and evaluates its robustness against ground stiffness variation. First, momentum exchange impact dampers are applied to a mass-damper-spring model, which takes the ground viscosity into account. Next, the proposed model's effectiveness is verified by simulation studies and some experimental results. Finally, this paper studies two-dimensional motion analyses to address rotational motion.

JAXA is planning moon exploration missions following Kaguya (SELENE). The first Japanese moon lander is SELENE-2 whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. Its phase-A study started in the summer of 2007. SELENE-2 will land on the near side of moon and perform in-situ geological and geophysical observations to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment are important for future lunar exploration including human activity. It also demonstrates precise landing, hazard avoidance, surface mobility, and night survival technologies. In this paper, recent progress of technology development for SELENE-2 is presented.

In the past, landers have landed on flat areas of lunar/planetary surfaces in order to avoid terrains that are rocky, or that have craters or hills. For next-generation exploration, lunar/planetary landers will require sophisticated technology to land on these areas as well for furture exploration. In this paper, we propose predictive control for actively controlled landing gear with a ball screw linear actuator. The effectiveness of proposed method is shown through simulation and experimental results.

JAXA is planning moon exploration missions following Kaguya (SELENE). The first Japanese moon lander is SELENE-2 whose missions include technology demonstrations, scientific observations, investigations for future moon utilization, and social or political purposes. Its phase-A study started in the summer of 2007. SELENE-2 will land on the near side of moon and perform in-situ geological and geophysical observations to improve the knowledge on the origin and the evolution of the moon. Investigations of surface environment are important for future lunar exploration including human activity. It also demonstrates precise landing, hazard avoidance, surface mobility, and night survival technologies. In this paper, recent progress of technology development for SELENE-2 is presented.

© Springer International Publishing Switzerland 2014. Moon holes were first discovered by JAXA in 2009. It is believed that moon holes are useful for learning about the formation of the moon because the bedding plane is exposed. In addition, because the inner holes are sealed from solar wind, moon holes are also considered important candidate sites for base camp in the future. However, exploration of vertical hole is difficult with the conventional robots. A new type of robot is required to go down and explore a moon hole. In this study, a vertical hole exploration system with a small robot with wire is proposed. This paper describes a modeling and attitude control scheme in a state where the robot is hanging by a wire, and evaluates the effectiveness of the proposed system.

When a spacecraft lands, the large shock load can lead to undesirable responses, such as rebound and trip. The authors have previously discussed the problem of controlling these shock responses using momentum exchange impact dampers (MEIDs). However, the optimal design parameters of MEIDs for spacecraft landing have not yet been addressed. These parameters are crucial for MEID applications. This paper discusses the parameters of Passive-MEID (PMEID) for a 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 PMEID correspond to the parameters that minimize the mechanical energy. A PMEID with the optimal design parameters is called optimal PMEID in this paper. In order to improve the performance of the optimal PMEID, this paper proposes a novel MEID — HMEID (active/passive-hybrid-MEID). The HMEID combines actuators with passive elements such as contact springs. Based on the optimal design results for the MEIDs, this paper applies a stiffness control 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 landing ground is shown. The feasibility of the HMEID is also discussed. The HMEID is superior to a PMEID, even if the actuator has a dynamics with a large electric time constant.

This paper discusses landing response control methods of planetary exploration spacecrafts on the basis of momentum exchange principles. Concretely, the methods adopt momentum exchange impact dampers (MEIDs) that absorb the controlled object's momentum with extra masses close to the object (damper masses). For example, this paper shows Upper-MEID (U-MEID) that launches the damper mass upward and Lower-MEID (L-MEID) that drops the damper mass downward. Moreover, Generalized-MEID (G-MEID) consisting of U-MEID and L-MEID is introduced. The optimal design parameters of the G-MEID mechanism in a single-axis case for the landing of a spacecraft are investigated. Simulation investigation verifies that the G-MEID mechanism is superior than any other MEID mechanisms from the point of view of reduction of the maximum rebound of the spacecraft. Moreover, the effectiveness of the G-MEID whose U-MEID adopts an active actuator (G-Hybrid MEID) is verified in the view of the rebound reduction performance and the robustness against the landing ground stiffness and spacecraft's mass variations.

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.

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.

This chapter presents a path planning and navigation framework for a planetary exploration rover and its experimental tests at a Lunar/Martian analog site. The framework developed in this work employs a laser range finder (LRF) for terrain feature mapping. The path planning algorithm generates a feasible path based on a cost function consisting of terrain inclination, terrain roughness, and path length. A set of navigation commands for the rover is then computed from the generated path. The rover executes those navigation commands to reach a desired goal. In this paper, a terrain mapping technique that uses a LRF is described along with an introduction to a cylindrical coordinate digital elevation map (C2DEM). The gird-based path planning algorithm is also presented. Field experiments regarding the path planning and navigation that evaluate the feasibility of the framework developed in this work are reported. © Springer-Verlag Berlin Heidelberg 2014.

Upon landing of a spacecraft, a large shock load can lead to such undesirable responses as rebound, swing vibration, sideslip, and tripover of the spacecraft. This paper discusses the problem of controlling these shock responses by means of momentum exchange impact dampers, especially the active momentum exchange impact damper. The momentum exchange impact dampers are classified into two types: the passive momentum exchange impact damper composed of passive elements and the active momentum exchange impact damper that includes active actuators. The active momentum exchange impact damper can greatly reduce the effects of shock responses. First, landing systems consisting of momentum exchange impact dampers are designed to conduct simulations and model a two-legged system. The passive momentum exchange impact damper mechanism is a one-degree-of-freedom vibration system. The active momentum exchange impact damper mechanism employs electrical motors as actuators in addition to the passive momentum exchange impact damper components. To assess the effectiveness of the control system, three cases are simulated: without momentum exchange impact damper, with passive momentum exchange impact damper, and with active momentum exchange impact damper. The results of the simulations show that the active momentum exchange impact damper is most effective in controlling spacecraft landing responses.

JAXA is planning exploration missions to the moon, following upon the Kaguya (SELENE) mission., These missions aim to demonstrate some new technologies, observe the moon scientifically, investigate technical, social and political feasibility of utilizing the moon. For the first step of the missions, the phase A study of SELENE-2 has started from the summer of 2007. This mission will demonstrate the effectiveness of several technologies including precision landing, hazard avoidance, surface mobility, and night survival technologies. In situ geological and geophysical observations will be conducted to improve our knowledge on the origin and the evolution of the moon. Investigating the lunar surface conditions and its potential for in situ resource utilization will provide key information for future human exploration missions. This paper presents the current status of the SELENE-2 mission, its objectives, its design, and other important aspects of its development such as international cooperation. (C) 2010 Elsevier Ltd. All rights reserved.

This paper proposes a synthesis procedure for a robust control target to be utilized in the simultaneous control of position and vibration of a planetary rover with flexible structures. The target is designed as a type of feedforward control input and its profile is derived only by solving a regulator problem with an initial velocity. In the regulator problem, the non-stationary robust control method is employed to make the target profile be robust against parameter variation. Further, the design procedure for the target is independent of the positioning distance and time schedule. The robustness of the target against parameter variation is examined through numerical calculations and the results are compared with those obtained from conventional methods. As a result, the usefulness of the proposed command shaping procedure is demonstrated and the high robustness of the target is confirmed. (C) Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2010

Interest in robotic subsurface investigations has been growing internationally. So far, the development of devices for sampling and analyzing the Martian subsoil has particularly progressed. Currently, the detailed investigation regarding the interior of the Moon is notable. Hence, implementation of subsurface exploration technology is required. This paper presents a lunar subsurface explorer that can burrow by itself in order to bury a scientific instrument such as a long-period seismometer. For the development of this drilling and self-propelled robotic explorer, the authors first discuss qualitatively its locomotion strategies and then focuses on a conical screw drilling mechanism taking into account the lunar soil properties. More specifically, this paper presents a novel screw drilling mechanism, called the CSD (contra-rotor screw drill), which mainly consists of a front and a contra rear screw. The proposed mechanism also has a structure that exerts no reaction against the body and has the capability to agitate compacted soil. The performance of the CSD is evaluated by indexes based on kinematic states and dynamic inputs. The validity is confirmed by comparing the experimental results of the fundamental screw drill, called the SSD (single screw drill). The main contribution of this paper is to investigate the feasibility of screw drilling applied to the lunar subsurface explorer and to examine the possibility to realize an effective drilling condition of the CSD. (C) Koninklijke Brill NV, Leiden and The Robotics Society of Japan, 2010

The acquisition of scientific information with respect to the interior of the Moon is a considerably significant goal for the next lunar exploration missions. The purpose of this research is to develop a robotic subsurface explorer that can burrow into the lunar soils by itself in order to sample and analyze the subsoil or to bury scientific instruments. Firstly, this paper qualitatively describes the conceptual definitions of subsurface locomotive robots. In addition, as one of the essential components for the development of such a robotic explorer, an effective screw drilling mechanism, which can cancel the reaction forces to the main body and loosen fore-soils, is proposed. With respect to the proposed mechanism, the remarks of the validation analysis with some mechanical discussions and fundamental experiments are presented.

It is performed to suppress the transverse vibration of the elevator ropes on a high-rise building caused by resonance between building-sway and rope-sway. The elevator rope has the characteristics due to its flexibility and length-varying and some constraints for the active vibration control. Hence, for compensating the influence of the time-varying characteristics and spillover, the nonstationary robust controller which has the robustness against unstructured and structured uncertainties is employed for the active vibration suppression of the rope. The suppression and robust stabilizing performances of the controller are demonstrated through the numerical calculations for the case in which the building is subjected to the ground disturbance like an earthquake and the tension of the rope varies. Thereupon, the control input system actuated by an alternate current motor is located right below the traction sheave and then it moves the rope directly in the presence of gaps between the rope and actuator. Consequently, the nonstationary robust controller shows the advantages in terms of the robustness on the uncertainties and the performance as compared to the optimal controller; and then it can adequately suppress the transverse vibration of the rope.