Kinematic Discussion and Development of a Multi-Legged Planetary Exploration Rover with an Isotropic Leg Arrangement

This study deals with a multi-legged planetary rover with a spherically isotropic leg arrangement. The legged rover is a reliable rover system for exploration on rough terrains, because it can continue walking even after overturning. Moreover, the legged rover can also show a rotational motion by utilizing its isotropic shape. This paper discusses the walking performance of two types of rover shapes: one has a six-leg arrangement based on a regular octahedron and the other has an eight-leg arrangement based on a regular hexahedron. The design procedure of the proposed rover is explained, and a test-bed system, which is developed to demonstrate the fundamental motions, is also presented.     

On actively closing loops in grid-based FastSLAM

Acquiring models of the environment belongs to the fundamental tasks of mobile robots. In the past, several researchers have focused on the problem of simultaneous localization and mapping (SLAM). Classical SLAM approaches are passive in the sense that they only process the perceived sensor data and do not influence the motion of the mobile robot. In this paper, we present a novel integrated approach that combines autonomous exploration with simultaneous localization and mapping. Our method uses a grid-based version of the FastSLAM algorithm and considers at each point in time actions to actively close loops during exploration. By re-entering already visited areas, the robot reduces its localization error and in this way learns more accurate maps. Experimental results presented in this paper illustrate the advantage of our method over previous approaches that lack the ability to actively close loops.     

Collision dynamics of a visual target marker for small-body exploration

MUSES-C mission is the world first sample and return attempt to or from a near-Earth asteroid. In deep space, it is hard to navigate, guide and control a spacecraft on a real-time basis remotely from the earth, mainly due to the communication delay. Thus, autonomy and robotics technologies are required for final approach and landing to an unknown body. In the final descent phase, cancellation of the horizontal speed relative to the surface of the landing site is essential. During the touchdown and sampling phase, the spacecraft will be navigated relative to the asteroid surface using an optical target marker (TM) placed on the asteroid surface. By using the TM as a reference point, navigation during the landing phase will be much more reliable and precise. Thus, it is important to design a TM with as small a coefficient of restitution as possible to reduce the settling time. To develop a small coefficient of restitution of less than 0.1 in vertical direction, the authors propose a novel TM, which is constructed out of a shell with beads stored internally. To better predict the performance of such a TM, analytical and numerical investigations are performed. The validity and the effectiveness of the proposed method are confirmed and evaluated by numerical simulations and flight results.     

Thinning-Based Topological Exploration Using Position Possibility of Topological Nodes

A grid map can be efficiently used in navigation, but this type of map requires a large amount of memory in proportion to the size of the environment. As an alternative, a topological map can be used to represent the environment in terms of discrete nodes with edges connecting them. It is usually constructed by Voronoi-like graphs, but in this paper the topological map is built based on the local grid map by using a thinning algorithm. This new approach can easily extract the topological information in real-time and be robustly applicable to the real environment, and this map can be autonomously built by exploration. The position possibility is defined to evaluate the quantitative reliability of the topological map and then a new exploration scheme based on the position possibility is proposed. From the position possibility information, the robot can determine whether or not it needs to visit a specific end node, which node will be the next target and how much of the environment has yet been explored. Various experiments showed that the proposed map-building and exploration methods can accurately build a local topological map in real-time and can guide a robot safely even in a dynamic environment.     

Development of a high-performance haptic telemanipulation system with dissimilar kinematics

This work addresses selected practical issues regarding the development of a telerobotic system for 6-d.o.f. tasks. The system consists of a hyper-redundant 10-d.o.f. haptic input device ViSHaRD10, a redundant 7-d.o.f. manipulator and a stereo vision system. The redundancy of the haptic input device is exploited to assure large convex workspaces and singularity-free operation. The anthropomorphic construction of the telemanipulator enables intuitive manipulation and increases the user-friendliness of the overall system. As a practical benchmark, an assembly experiment in 6 d.o.f. for the case of a negligible time delay was performed. Issues regarding inverse kinematics, spatial interaction control, transparency and intuitiveness of teleoperation are discussed.