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The exploration of minor bodies, such as asteroids and comets using robotics is a necessary step for the study of the Solar System's evolutionary process. For such purpose, a multi-legged ground-gripping robot was proposed to perform precise locomotion towards specific places of interest. Moreover, stable locomotion is expected, since this robot has grippers capable of grasping the rocky and uneven terrain of the minor bodies, maintaining the attachment to the ground and preventing the flotation of the robot on the microgravity environment. Decreasing the forces induced on the grippers is essential to keep the stable locomotion in such environments and, in this paper, a gait control method is proposed to reduce accelerations and motion reactions on the robot, avoiding high reaction forces on the contact points with the ground. This method focuses on generating trajectories to be traveled by parts of the robot. A numerical simulation was developed to investigate the effectiveness of the proposed method in decreasing reactions on the robot during the motion of the robot on uneven terrains by comparing different trajectories' parameters., International Symposium on Space Technology and Science (32nd ISTS), June 15-21, 2019, Fukui, Japan

This paper presents an open-sourced MATLAB simulation and analysis platform dedicated to legged climbing robots. This simulator enables the design of any limbed robotic system as an articulated multi-body with a floating base and simulates it walking and climbing in an arbitrary environment. The main variable environmental parameters are inclination, gravity, and ground stiffness, and any point cloud can be installed as the terrain map. Furthermore, the simulator employs a rigid body dynamics engine. This paper first describes the simulator structure, and the computational flow and next presents the representative simulation examples where quadrupedal robots assumed gripping on the wall or climbing on the steep slope.

In an environment of increasing orbital debris and remote operation, visual data acquisition methods are becoming a core competency of the next generation of spacecraft. However, deep space missions often generate limited data and noisy images, necessitating complex data analysis methods. Here, a state-of-the-art convolutional neural network (CNN) pose estimation pipeline is applied to the Hayabusa2 Minerva-II2 rover deployment; a challenging case with noisy images and a symmetric target. To enable training of this CNN, a custom dataset is created. The deployment velocity is estimated as 0.1908 m/s using a projective geometry approach and 0.1934 m/s using a CNN landmark detector approach, as compared to the official JAXA estimation of 0.1924 m/s (relative to the spacecraft). Additionally, the attitude estimation results from the real deployment images are shared and the associated tumble estimation is discussed.

In this letter, we present a passive spine gripper that can hold rough rocky surfaces of boulders on cliff walls, and we discuss its application to a four-limbed robot for free-climbing in extreme terrain. The limbed robot has four degrees of freedom in each limb, where three are to drive joints of the limb and one for releasing the gripper. The fine spine of the proposed gripper also enables it to passively and adaptively latch on to microscopic asperities of the rough surface, and it is thus an efficient mechanism. In this letter, we present the fundamental design and mechanism of the proposed gripper, after which we introduce its static gripping model. We verify the gripping model by the experimental gripping performance of the prototype gripper. We show a lightweight four-limbed robot that is equipped with the grippers mounted on each limb. To evaluate the climbing capabilities of the robot, we use it to perform climbing experiments on a rugged and steep slope. The results show that the prototype can safely climb over such challenging terrain that is similar to a gravity offload system.

In the pursuit of a fully autonomous learning agent able to interact, move, and be useful in the real world, two fundamental problems are path planning and motion control, and user-agent interaction. We address these through reinforcement learning using our Path Planning and Motion Controller (PPMC) Training Algorithm, which uses a combination of observable goals and randomization of goals during training, with a customized reward function, to teach a simulated quadruped agent to respond to user commands and to travel to designated areas. In this regard, we identified two critical components of path planning and motion control: the first is region enabled travel, or the ability to travel towards any location within a prescribed area; the second is multi-point travel, or the ability to travel to multiple points in succession. An important open ended question is how many tasks should be handled by a single policy and if a single policy can even learn to manage several tasks. We demonstrate that it is possible to contain both a maples path planner and motion controller on a single neural network, which could prove promising in future work due to their interlinked and synergistic nature. Using control group policies and various test cases and using ACKTR and PPO, we empirically validate our algorithm teaches the agent to respond to user commands as well as path planning and motion control.

Much of robotics research aims to develop control solutions that exploit the machine’s dynamics in order to achieve an extraordinarily agile behaviour [1]. This, however, is limited by the use of traditional model-based control techniques such as model predictive control and quadratic programming. These solutions are often based on simplified mechanical models which result in mechanically constrained and inefficient behaviour, thereby limiting the agility of the robotic system in development [2]. Treating the control of robotic systems as a reinforcement learning (RL) problem enables the use of model-free algorithms that attempt to learn a policy which maximizes the expected future (discounted) reward without inferring the effects of an executed action on the environment.

Conventional wheeled or tracked robots are unable to traverse rough, uneven, or steep terrain. A multi-legged robot that has grippers at the tips of each leg is capable of grasping irregularities in the terrain, allowing for free climbing motion through a variety of challenging environments. To execute safe and reliable free-climbing locomotion, the motion of the robot should be planned in consideration of three aspects: optimal selection of gripping points along the path to the goal, tumble stability of the robot including the performance of the gripper, and feasibility of motion on the basis of kinematics. In this paper, we propose a method to satisfy these three conditions and verify the validity of the proposed method with a free-climbing robot walking simulation on inclined terrain with randomly distributed discrete grippable points.

This paper presents detumbling and capture of space debris by a dual-arm space robot for active space debris removal missions. Space debris, such as a malfunctioning satellite or a rocket upper stage, often has uncontrolled tumbling motion. It also has uncertainties in its parameters, such as inertial characteristics or surface frictional roughness. These factors make the debris capture missions difficult to accomplish. To cope with such challenging missions, we propose a detumbling and capture control method for a dual-arm robot based on repeated impact capable of suppressing the debris motion by repeatedly utilizing an effect of a passive damping factor in the contact characteristics. In this paper, as the initial step of a study on the repeated impact-based capture method, we assume that the capture target is a rocket upper stage that can be simply modeled as a cylindrical body and mainly has angular velocity motion in its principle axis of inertia. A motion tracking control law of an end-effector of the robot arm is introduced to maintain the repeated impact. The proposed control method enables the robot to accomplish the detumbling and capture without precise estimation of the inertial characteristics and surface frictional roughness of the debris. The validity of the proposed method is presented by numerical simulations and planar microgravity experiments using an air-floating system. In particular, the experimental evaluation shows the fundamental feasibility of the proposed method, and thus, the result contributes to a practical application.

A lunar rover requires an accurate localisation system in order to operate in an uninhabited environment. However, every additional piece of equipment mounted on it drastically increases the overall cost of the mission. This paper reports a possible solution for a micro-rover using a sole monocular omnidirectional camera. Our approach relies on a combination of feature tracking and template matching for Visual Odometry. The results are afterwards refined using a Graph-Based SLAM algorithm, which also provides a sparse reconstruction of the terrain. We tested the algorithm on a lunar rover prototype in a lunar analogue environment and the experiments show that the estimated trajectory is accurate and the combination with the template matching algorithm allows an otherwise poor detection of spot turns.

We report recent results from field experiments conducted with a team of ground and aerial robots engaged in the collaborative mapping of an earthquake-damaged building. The goal of the experimental exercise is the generation of three-dimensional maps that capture the layout of a multifloor environment. The experiments took place in the top three floors of a structurally compromised building at Tohoku University in Sendai, Japan that was damaged during the 2011 Tohoku earthquake. We provide details of the approach to the collaborative mapping and report results from the experiments in the form of maps generated by the individual robots and as a team. We conclude by discussing observations from the experiments and future research topics. © 2012 Wiley Periodicals, Inc. (This work builds upon the conference paper (Michael et al., 2012).)

Tracked vehicles are frequently used as search-and-rescue robots for exploring disaster areas. To enhance their ability to traverse rough terrain, some of these robots are equipped with swingable subtracks. However, manual control of such subtracks also increases the operator's workload, particularly in teleoperation with limited camera views. To eliminate this trade-off, we have developed a shared autonomy system using an autonomous controller for subtracks that is based on continuous three-dimensional terrain scanning. Using this system, the operator has only to specify the direction of travel to the robot, following which the robot traverses rough terrain using autonomously generated subtrack motions. In our system, real-time terrain slices near the robot are obtained using two or three LIDAR (laser imaging detection and ranging) sensors, and these terrain slices are integrated to generate three-dimensional terrain information. In this paper, we introduce an autonomous controller for subtracks and validate the reliability of a shared autonomy system on actual rough terrains through experimental results. © 2011 Wiley Periodicals, Inc.

In the future, mobile robots may be able to assist rescue crews in search and rescue missions that take place in the dangerous environments that result from natural or man-made disasters. In 2006, we launched a research project to develop mobile robots that can rapidly collect information in the initial stages of a disaster. One of our important objectives is three-dimensional (3D) mapping, which can be a very useful tool for assisting rescue crews in strategizing rescue missions. To realize this 3D mapping, we identified five issues that we needed to address: (1) autonomous traversal of uneven terrain, (2) development of a system for the continuous acquisition of 3D data of the environment, (3) coverage path planning, (4) centralization of map data obtained by multiple robots, and (5) fusion of map data obtained by multiple robots. We solved each problem through our joint research. Each research institute in our group took charge of solving one of the above issues according to its area of expertise. We integrated these solutions to perform 3D mapping using our tracked vehicle, Kenaf. To validate our integrated autonomous 3D mapping system, we participated in RoboCupRescue 2009 and demonstrated our system using multiple robots on the RoboCupRescue field. In this paper, we introduce our mapping system and report the mapping results obtained at the RoboCupRescue event. © 2011 Wiley Periodicals, Inc.

With the increasing challenges facing planetary exploration missions and the resultant increase in the performance requirements for planetary rovers, terramechanics (wheel---soil interaction mechanics) is playing an important role in the development of these rovers. As an extension of the conventional terramechanics theory for terrestrial vehicles, the terramechanics theory for planetary rovers, which is becoming a new research hotspot, is unique and puts forward many new challenging problems. This paper first discusses the significance of the study of wheel---soil interaction mechanics of planetary rovers and summarizes the differences between planetary rovers and terrestrial vehicles and the problems arising thereof. The application of terramechanics to the development of planetary rovers can be divided into two phases (the R&D phase and exploration phase for rovers) corresponding to the high-fidelity and simplified terramechanics models. This paper also describes the current research status by providing an introduction to classical terramechanics and the experimental, theoretical, and numerical researches on terramechanics for planetary rovers. The application status of the terramechanics for planetary rovers is analyzed from the aspects of rover design, performance evaluation, planetary soil parameter identification, dynamics simulation, mobility control, and path planning. Finally, the key issues for future research are discussed. The current planetary rovers are actually advanced wheeled mobile robots (WMRs), developed employing cutting-edge technologies from different fields. The terramechanics for planetary rovers is expected to present new challenges and applications for WMRs, making it possible to develop WMRs using the concepts of mechanics and dynamics.

In this paper, the development of a three-dimensional (3-D) odometry system for wheeled robots on loose soil in an application of planetary exploration is described. When a wheeled robot operates i...

Tracked vehicles are frequently used as search-andrescue robots for exploring areas affected by disasters. To enable good locomotion during search-and-rescue operations on rough terrain, some of those robots are equipped with active flippers. However, the manual control of such flippers requires a highly skilled operator, particularly when teleoperating with limited camera views. To eliminate this problem, we have developed a shared autonomy system that uses a manual controller for the main tracks and an autonomous controller for the active flippers. However, this system has a limitation in that the controller spreads out the flippers to maintain contact with the ground, and thus, the autonomous flipper motions hinder the turning motion of the robot. In this paper, we introduce a new autonomous controller for the flippers to support the turning motion of tracked vehicles. The new controller can be used instead of the previously developed controller, and it complements our shared autonomy system. We also validate the reliability of the new controller by performing experiments on an actual rough terrain.

This paper introduces a novel method for slip angle estimation based on visually observing the traces produced by the wheels of a robot on soft, deformable terrain. The proposed algorithm uses a robust Hough transform enhanced by fuzzy reasoning to estimate the angle of inclination of the wheel trace with respect to the vehicle reference frame. Any deviation of the wheel track from the planned path of the robot suggests occurrence of sideslip that can be detected and, more interestingly, measured. In turn, the knowledge of the slip angle allows encoder readings affected by wheel slip to be adjusted and the accuracy of the position estimation system to be improved, based on an integrated longitudinal and lateral wheel–terrain slip model. The description of the visual algorithm and the odometry correction method is presented, and a comprehensive set of experimental results is included to validate this approach.

Outer space is an ultimate field for the application of robotics technology. As outer space is a harsh environment with extreme temperatures, vacuum, radiation, gravity, and great distances, human access is very difficult and hazardous and is therefore limited. To assist human activities in space for constructing and maintaining space modules and structures, robotic manipulators have been playing essential roles in orbital operations. Moreover, expanding the horizons of exploration beyond the areas of human access, robots that land and travel on planetary surfaces have been greatly contributing to our knowledge of the solar system. New challenges are expected in the future. This article consists of three parts. In the first part, the achievements of orbital robotics technology in the last decade are reviewed, highlighting the Engineering Test Satellite (ETS-VII) and Orbital Express flight demonstrations. In the second part, some of the selected topics of planetary robotics from the field robotics research point of view are described. Recent achievements in the author's laboratory are added as an illustrative example. Finally, technological challenges to asteroid robotics are discussed. When designing a robot to explore the surface of an asteroid, microgravity raises an interesting problem of how to stick and move on the surface. Some ideas to address these questions are introduced.

For a mobile robot it is critical to detect and compensate for slippage, especially when driving in rough terrain environments. Due to its highly unpredictable nature, drift largely affects the accuracy of localization and control systems, even leading, in extreme cases, to the danger of vehicle entrapment with consequent mission failure. This paper presents a novel method for lateral slip estimation based on visually observing the trace produced by the wheels of the robot, during traverse of soft, deformable terrain, as that expected for lunar and planetary rovers. The proposed algorithm uses a robust Hough transform enhanced by fuzzy reasoning to estimate the angle of inclination of the wheel trace with respect to the vehicle reference frame. Any deviation of the wheel trace from the planned path of the robot suggests occurrence of sideslip that can be detected, and more interestingly, measured. This allows one to estimate the actual heading angle of the robot, usually referred to as the slip angle. The details of the various steps of the visual algorithm are presented and the results of experimental tests performed in the field with an all- terrain rover are shown, proving the method to be effective and robust.

In this paper, a novel crawler mechanism for sideways motion is presented. The crawler mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional crawler mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink. Motion experiments, with a test vehicle are also presented.

New tracking algorithm based on the nearest neighbor star search approach is proposed for fast star identification. In order to improve the performance of tracking, this algorithm is composed of two parts. One is a searching part of unknown stars in the field of view (FOV) using nearest neighbor star search approach. The feature of this method is that each star has connections with some adjacent stars. Unknown stars can be identified by tracing the nearest star from the previously recognized star with reference to the star catalog. Star neighborhood information is a list of neighbor stars in the order of closeness and included in the catalog. The other is a predicting part of position of stars on the current image frame. Star position can be predicted from satellite angular velocity and previous attitude information. In this technique, angular velocity is estimated by the last two captured images without gyroscope observation. Most of the stars in the FOV are tracked properly by matching star centroid position on the captured image with the predicted star position. Star trackers for micro-satellite developed by Tohoku University so far had only lost-in-space attitude determination algorithm, whose operation frequency was limited down to 1 Hz. It is expected that the above mentioned star identification method enables improvement both in reliability and operational frequency. This algorithm was evaluated in PC simulation. The results show that attitude determination can be carried out over twenty times faster compared to the conventional method. Hence, it is illustrated that the efficiency of star identification is improved by these approaches.

The Engineering Test Satellite VII (ETS-VII), an unmanned spacecraft equipped with a 2-m long, six-degree-of-freedom manipulator arm, was developed and launched by the National Space Development Agency of Japan (NASDA). ETS-VII has successfully carried out a variety of on-board experiments with its manipulator arm, and these key technologies are essential for an orbital free-flying robot. These results will provide a solid basis for future satellite servicing missions. This paper highlights manipulator control utilizing the concepts of the generalized Jacobian matrix and the reaction null-space. These concepts have been proposed and discussed for the past ten years using laboratory test beds, and their practical application has now been demonstrated in orbit.

An adaptive multifinger gripper system was developed for underwater ROV. The system, named The Artifact 'K' apture Operator (TAKO) gripper, provides soft and adaptive envelope grasp with three articulated fingers. Each finger comprises five segments and performs like an octopus tentacle. The gripper has 15 segments in total, yet they are coordinately driven by one single motor and tendon mechanisms. This design allows the gripper system compact, light weight, and less expensive. The TAKO gripper is mounted on an underwater ROV named Triton that is a research oriented test platform developed at Santa Clara University. The TAKO-Triton integrated test was carried out successfully for the artifact pick-up operation from the bottom of the water.

Many missions have been launched to explore the Moon, Mars, asteroids, and comets, and many researchers are studying and developing lunar and planetary rovers for unmanned planet exploration, and further cooperative missions targeting human lunar exploration are under discussion. A key technology in these missions and orbital services is space robotics, including Al and automation. Space robotics is expected to support external vehicular activities (EVA) and internal vehicular activities (IVA), which will include constructing, repairing, and maintaining orbiting satellites and space structures.This special issue presents the updated mission results and advanced research activities of space organizations, institutes, and universities, although it does not include all. We hope that this special issue will be useful to readers as an introduction to advanced space robotics in Japan, and that more robotics and Al researchers and engineers will become interested in space robotics and participate in space missions.We thank the authors for their fine contributions and the reviewers for their generous contributions of time and effort. In closing, we also thank the Editorial Board of the Journal of Robotics and Mechatronics for helping to make this issue possible.

During volcanic activity, people are restricted from coming within a certain distance to the volcano crater because of the danger posed. However, observing the restricted area is very important to reduce the risk to residents from eruptions such as pyroclastic and debris flows. Therefore, teleoperated mobile robots are being developed to observe conditions in such restricted areas, remotely. However, such volcanic environments include loose soil slopes of volcanic ash and lapillus, which may be impossible to traverse using current mobile robotics technology. Thus, we propose a contact angle control method for a multi-degrees of freedom (DOF) tracked vehicle. This controls the contact angle of the tracks and decreases the potential for the robot to sideslip on loose ground. To evaluate this method, we installed a contact load sensing system in each tracks. The effectiveness of the method was verified on an indoor simulated volcanic field and an outdoor field. In this paper, we explain the proposed method, introduce our developed robot and sensing system, and report the results of our evaluation experiments.

A collection of useful subroutines named the SpaceDyn is developed in order to offer an open, free tool of numerical simulations for researchers both in robotics and space engineering fields. The SpaceDyn is a MATLAB Toolbox for kinematic and dynamic analysis and simulation of articulated multibody systems with a moving base. Examples of such systems include a satellite with mechanical appendages, a free-flying space robot, a robotic system with structural flexibility, and a mobile robot, all of which makes motions in the environment with or without gravity.

FSR, the International Conference on Field and Service Robotics, is the leading single track conference of robotics for field and service applications. This book presents the results of FSR2012, the eighth conference of Field and Service Robotics, which was originally planned for 2011 with the venue of Matsushima in Tohoku region of Japan. However, on March 11, 2011, a magnitude M9.0 earthquake occurred off the Pacific coast of Tohoku, and a large-scale disaster was caused by the Tsunami which resulted, therefore the conference was postponed by one year to July, 2012. In fact, this earthquake raised issues concerning the contribution of field and service robotics technology to emergency scenarios. A number of precious lessons were learned from operation of robots in the resulting, very real and challenging, disaster environments. Up-to-date study on disaster response, relief and recovery was then featured in the conference. This book offers 43 papers on a broad range of topics including: Disaster Response, Service/Entertainment Robots, Inspection/Maintenance Robots, Mobile Robot Navigation, Agricultural Robots, Robots for Excavation, Planetary Exploration, Large Area Mapping, SLAM for Outdoor Robots, and Elemental Technology for Mobile Robots.

To efficiently evacuate an area threatened by volcanic disaster, onsite observation of active volcanoes by remotely controlled mobile robot systems is desired. Issues involved with developing such systems include planning a safe path for the robots. In this research, our objective was to realize a safe path planning method based on a digital elevation map (DEM) of volcanic mountain fields that considers the mobility of a mobile robot. We assumed that the DEM is obtained through airplane laser measurements beforehand. Because the target environment is vast, obtaining a DEM with sufficiently high resolution is difficult. Even if this is possible, path planning based on such a high-resolution DEM in vast environments significantly increases the computational load. Therefore, we propose a path planning method that can be applied to any DEM resolution; path planning is seamlessly performed roughly in a global scale and precisely in local scales. We extended the general DEM into 3-D space by adding an axis to denote the discrete heading direction of a mobile robot, which we call an extended elevation map (EEM). In the 3-D space EEM, the transition-cost from the start position is derived for each voxel by considering the mobility of the mobile robot. The transition-cost is sparsely propagated from the start position, and the sparsely valued field derives a single path with the lowest transition-cost to reach the goal position. The proposed method was implemented, and simulation experiments using DEMs of real volcanoes were performed to confirm its validity.

Point-to-point operation of a Flexible Structure mounted Manipulator Systems (FSMS) is discussed. Four operation strategies, i.e. (1) straight-line path in joint space, (2) high-coupling path and (3) low-coupling path derived from the Coupling Map concept, and (4) three-phase motion derived from the Reactionless Path concept, are examined and compared in terms of a minimum oscillation of the supporting flexible structure, using a FSMS testbed, TREP, developed at Tohoku University.

Tracked vehicles are frequently used as search-and-rescue robots for exploring disaster areas. To enhance their traversability on rough terrain, some are equipped with “active flippers.” However, manual control of such flippers also increases the operator's workload, particularly for teleoperation with limited camera views. To eliminate this tradeoff, we developed a shared autonomy system using an autonomous controller for flippers that is based on continuous three-dimensional terrain scanning. In our system, real-time terrain slices near the robot are obtained using three laser range sensors, and these are integrated to generate three-dimensional terrain information. In this paper, we introduce the autonomous controller for the flippers and validate the reliability of the shared autonomy system through experimental results on actual rough terrain.

During search missions in disaster environments, an important task for mobile robots is map building. An advantage of three-dimensional (3-D) mapping is that it can provide depictions of disaster environments that will support robotic teleoperations used in locating victims and aid rescue crews in strategizing. However, the 3-D scanning of an environment is timeconsuming because a 3-D scanning procedure itself takes a time and scan data must be matched at several locations. Therefore, in this paper, we propose a scan-point planning algorithm to obtain a large scale 3-D map, and we apply a scan-matching method to improve the accuracy of the map. We discuss the use of scan-point planning to maintain the resolution of sensor data and to minimize occlusion areas. The scan-matching method is based on a combination of the Iterative Closest Point (ICP) algorithm and the Normal Distribution Transform (NDT) algorithm.We performed several experiments to verify the validity of our approach.

In this paper, a tetrahedral mobile robot with central axis for transformation to the flat vehicle is presented. The throwable robot with the function of going into narrow spaces when its in the flat-vehicle mode is explained in detail. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: mode changing function and omnidirectional motion. Basic Motion experiments, with a test vehicle are also presented.

For tracked vehicles moving over rough terrain, it is important to avoid rollovers and rapid motion. To realize smooth locomotion on rough terrain, some tracked vehicles are equipped with “active flippers.” Such flippers increase the traversability and stability of tracked vehicles. However, their control increases the operator workload, especially in the case of teleoperation. To eliminate this problem, we have developed an autonomous controller for generating terrain-reflective motions of flippers. Terrain information is obtained using laser range sensors that are located at both sides of our tracked vehicle testbed. Using this system, operators only have to specify a direction to the robot, following which the robot traverses rough terrain using autonomous flipper motions. In this paper, we introduce a strategy and an algorithm for the controller for active flippers and validate the reliability of the system through experimental results on rough terrain.

In this paper, the basic running performance of the cylindrical tracked vehicle with sideways mobility is presented. The crawler mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional crawler mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype. Basic motion experiments with confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink.

In this paper, the authors present a path planing system for autonomous navigation of lunar/planetary rover. In the path planner, candidate paths are generated and evaluated by multiple criteria including occlusion index, terrain roughness/inclination indices. The proposed system considers the occlusion effect produced by obstacles present in the inspected environment and the features of the environment itself. An algorithm that computes the next sensing position within the map is introduced as part of the system presented. The different components of the system and their interactions are explained thoroughly. Simulation and experimental results where the proposed system is implemented are presented.

Localization and mapping are essential elements in the design of mobile robots used for search and rescue mission. Localization is a key-function of remote control and mapping in an unstructured environment. However, in general, odometry in tracked vehicles is ambiguous because of the track slippage. To solve this problem, we developed a three-dimensional gyro-based odometry that considers the compensation of slippage on the basis of an empirical model. The method was successfully implemented in a tracked vehicle, and its validity was confirmed by initial tests in real environments. Mapping is also very important in a searching task. A small three-dimensional laser range scanner provides operators and rescue crews with a wealth of information for understanding environments. However, to obtain this information, the operators must wait a few seconds and halt the robot's operation. To solve this problem, we propose the continuous acquisition of three-dimensional environment information for tracked vehicles using the three-dimensional gyro-based odometry reported above. In this paper, odometry and continuous acquisition methods are introduced for use by tracked vehicles operating in hostile environments.

Active flippers for tracked vehicles are very useful to improve traversability on uneven terrain. However it is widely known that control of flippers also increases the work-load for operators, particularly where the vehicle and the operator are far apart. To reduce the work-load, we aim to realize a sensor-based autonomous controller of flippers to enable a ldquosemi-autonomous operationrdquo of tracked vehicles. The ldquosemi-autonomous operationrdquo means that the only requirement for an operator is to indicate the robotpsilas direction. In this way, the robot is navigated autonomously through its sensors and actuators to surmount or avoid obstacles. In this research, two laser range sensors are used for terrain sensing, and gyro sensors are used for the measurement of the robotpsilas attitude. Based on such sensor system, we propose a strategy of simple sensor-based motion of active flippers for tracked vehicles to enable a semi-autonomous operation. In this paper, we introduce a strategy of motion of active flippers, and the stability analysis of tracked vehicles with active flippers. Finally, we report several experimental results to verify the validity of our approach.

In this paper, a novel crawler mechanism for sideways motion is presented. The crawler mechanism is of circular cross-section and has active rolling axes at the center of the circles. Conventional crawler mechanisms can support massive loads, but cannot produce sideways motion. Additionally, previous crawler edges sink undesirably on soft ground, particularly when the vehicle body is subject to a sideways tilt. The proposed design solves these drawbacks by adopting a circular cross-section crawler. A prototype has been developed to illustrate the concept. Motion experiments confirm the novel properties of this mechanism: sideways motion and robustness against edge-sink. Motion experiments, with a test vehicle are also presented.

Active flippers for tracked vehicles are very useful to improve traversability on uneven terrain. However it is widely known that control of flippers also increases the work-load for operators, particularly where the vehicle and the operator are far apart. To reduce the work-load, we aim to realize a sensor-based autonomous controller of flippers to enable a dasiasemi-autonomous operationpsila of tracked vehicles. In this research, two laser range sensors are used for terrain sensing, and gyro sensors are used for the measurement of the robotpsilas attitude. Based on such sensor system, we propose a strategy of simple sensor-based motion of active flippers for tracked vehicles to enable a semi-autonomous operation. In this paper, we introduce a strategy of motion of active flippers. Finally, we report several experimental results to verify the validity of our approach.

In this paper, the authors present a novel criterion for path planning based on the visibility index caused by obstacles detected through laser range sensors when exploring lunar craters. The proposed path planning algorithm calculates an index based on terrain roughness, path length and occlusion, and determines the areas where obstacles may limit the visibility of the area where the rover must go next. The derivation of the visibility index is explained in detail and the algorithm steps are described throughly. Simulations were carried out in order to test the proposed algorithm and a results are presented.

Tracked vehicles have the advantage of stable locomotion on uneven terrain, and, as a result, such mechanisms are used for locomotion on outdoor robots, including those used for search and rescue. However, such mechanisms always slip when a tracked vehicle follows a curve, and the slippage generates large accumulated positioning errors in the vehicle compared with conventional wheeled mobile robots. To improve the accuracy of the odometry and enable a path-following control, the estimation of the track slippage is essential. In this paper, we propose an improved method of odometry for tracked vehicles to follow a straight line or a curve. In this method, the vehicle estimates the slip ratios using two encoders (attached to the actuators) and a gyro-sensor. Based on the improved odometry, the path-following control of tracked vehicles is significantly improved. The validity of the method was confirmed with experiments involving our tracked vehicle on several types of surfaces.