Platform Portable Anthropomorphic Grasping with the Bielefeld 20-DOF Shadow and 9-DOF TUM Hand

Röthling F, Haschke R, Steil JJ, Ritter H. Platform Portable Anthropomorphic Grasping with the Bielefeld 20-DOF Shadow and 9-DOF TUM Hand. In: Proc. Int. Conf. on Intelligent Robots and Systems (IROS). IEEE; 2007: 2951-2956

Graphite immobilisation in glass composite materials

Irradiated graphite is a problematic nuclear waste stream and currently raises significant concern worldwide in identifying its long-term disposal route. This thesis describes the use of glass materials for the immobilisation of irradiated graphite prepared by microwave, conventional and sparks plasma sintering methods. Several potential glass compositions namely iron phosphate, aluminoborosilicate, calcium aluminosilicate, alkali borosilicate and obsidian were considered for the immobilisation of various loadings of graphite simulating irradiated graphite. The properties of the samples produced using different processing methods are compared selectively. An investigation of microwave processing using an iron phosphate glass composition revealed that full reaction of the raw materials and formation of a glass melt occurs with consequent removal of porosity at 8 minutes microwave processing. When graphite is present, iron phosphate crystalline phases are formed with much higher levels of residual porosity of up to 43 % than in the samples prepared using conventional sintering under argon. It is found that graphite reacts with the microwave field when in powder form but this reaction is minimised when the graphite is incorporated into a pellet, and that the graphite also impedes sintering of the glass. Mössbauer spectroscopy indicates that reduction of iron occurs with concomitant graphite oxidation. The production of graphite-glass samples using various powdered glass compositions by conventional sintering method still resulted in high porosity with an average of 6-17 % for graphite loadings of 20-25 wt%. Due to the use of pre-made glasses and controlled sintering parameters, the loss of graphite from the total mass is reduced compared to the microwaved samples; the average mass loss is < 0.8 %. The complication of iron oxidation and reduction is present in all the iron containing base glasses considered and this increases the total porosity of the graphite-glass samples. It is concluded that the presence of iron in the raw materials or base glasses as an encapsulation media for the immobilisation of the irradiated graphite waste is not advisable. The production of glass and graphite-glass samples based calcium aluminosilicate composition by spark plasma sintering method is found highly suitable for the immobilisation of irradiated graphite wastes. The advantages of the method includes short processing time i.e. < 40 minutes, improved sintering transport mechanisms, limited graphite oxidation, low porosity (1-4 %) and acceptable tensile strength (2-7 MPa). The most promising samples prepared using spark plasma sintering method were loaded with 30-50 wt% graphite

Bio-Inspired Motion Strategies for a Bimanual Manipulation Task

Steffen JF, Elbrechter C, Haschke R, Ritter H. Bio-Inspired Motion Strategies for a Bimanual Manipulation Task. In: International Conference on Humanoid Robots (Humanoids). 2010

Dexterous Hexrotor UAV Platform

Mobile manipulation is a hot area of study in robotics as it unites the two classes of robots: locomotors and manipulators. An emerging niche in the field of mobile manipulation is aerial mobile manipulation. Although there has been a fair amount of study of free-flying satellites with graspers, the more recent trend has been to outfit UAVs with graspers to assist various manipulation tasks. While this recent work has yielded impressive results, it is hampered by a lack of appropriate testbeds for aerial mobile manipulation, similar to the state of ground-based mobile manipulation a decade ago. Typical helicopters or quadrotors cannot instantaneously resist or apply an arbitrary force in the plane perpendicular to the rotor axis, which makes them inadequate for complex mobile manipulation tasks. Based on the concept of force closure (a term from the dexterous manipulation community), this thesis introduces the new type of dexterous, 6-DoF UAV which provides the unique capability of being able to resist any applied wrench, or generalized force-torque. In this thesis, we describe the importance of force closure for mobile manipulation, explain why it is lacking in current UAV platforms, and describe how our hexrotor provides this important capability as well as exhibiting holonomic behavior

Planning dextrous robot hand grasps from range data, using preshapes and digit trajectories

Dextrous robot hands have many degrees of freedom. This enables the manipulation of objects between the digits of the dextrous hand but makes grasp planning substantially more complex than for parallel jaw grippers. Much of the work that addresses grasp planning for dextrous hands concentrates on the selection of contact sites to optimise stability criteria and ignores the kinematics of the hand. In more complete systems, the paradigm of preshaping has emerged as dominant. However, the criteria for the formation and placement of the preshapes have not been adequately examined, and the usefulness of the systems is therefore limited to grasping simple objects for which preshapes can be formed using coarse heuristics.In this thesis a grasp metric based on stability and kinematic feasibility is introduced. The preshaping paradigm is extended to include consideration of the trajectories that the digits take during closure from preshape to final grasp. The resulting grasp family is dependent upon task requirements and is designed for a set of "ideal" object-hand configurations. The grasp family couples the degrees of freedom of the dextrous hand in an anthropomorphic manner; the resulting reduction in freedom makes the grasp planning less complex. Grasp families are fitted to real objects by optimisation of the grasp metric; this corresponds to fitting the real object-hand configuration as close to the ideal as possible. First, the preshape aperture, which defines the positions of the fingertips in the preshape, is found by optimisation of an approximation to the grasp metric (which makes simplifying assumptions about the digit trajectories and hand kinematics). Second, the full preshape kinematics and digit closure trajectories are calculated to optimise the full grasp metric.Grasps are planned on object models built from laser striper range data from two viewpoints. A surface description of the object is used to prune the space of possible contact sites and to allow the accurate estimation of normals, which is required by the grasp metric to estimate the amount of friction required. A voxel description, built by ray-casting, is used to check for collisions between the object and the robot hand using an approximation to the Euclidean distance transform.Results are shown in simulation for a 3-digit hand model, designed to be like a simplified human hand in terms of its size and functionality. There are clear extensions of the method to any dextrous hand with a single thumb opposing multiple fingers and several different hand models that could be used are described. Grasps are planned on a wide variety of curved and polyhedral object

Dexterous manipulation of unknown objects using virtual contact points

The manipulation of unknown objects is a problem of special interest in robotics since it is not always possible to have exact models of the objects with which the robot interacts. This paper presents a simple strategy to manipulate unknown objects using a robotic hand equipped with tactile sensors. The hand configurations that allow the rotation of an unknown object are computed using only tactile and kinematic information, obtained during the manipulation process and reasoning about the desired and real positions of the fingertips during the manipulation. This is done taking into account that the desired positions of the fingertips are not physically reachable since they are located in the interior of the manipulated object and therefore they are virtual positions with associated virtual contact points. The proposed approach was satisfactorily validated using three fingers of an anthropomorphic robotic hand (Allegro Hand), with the original fingertips replaced by tactile sensors (WTS-FT). In the experimental validation, several everyday objects with different shapes were successfully manipulated, rotating them without the need of knowing their shape or any other physical property.Peer ReviewedPostprint (author's final draft

Bringing a Humanoid Robot Closer to Human Versatility : Hard Realtime Software Architecture and Deep Learning Based Tactile Sensing

For centuries, it has been a vision of man to create humanoid robots, i.e., machines that not only resemble the shape of the human body, but have similar capabilities, especially in dextrously manipulating their environment. But only in recent years it has been possible to build actual humanoid robots with many degrees of freedom (DOF) and equipped with torque controlled joints, which are a prerequisite for sensitively acting in the world. In this thesis, we extend DLR's advanced mobile torque controlled humanoid robot Agile Justin into two important directions to get closer to human versatility. First, we enable Agile Justin, which was originally built as a research platform for dextrous mobile manipulation, to also be able to execute complex dynamic manipulation tasks. We demonstrate this with the challenging task of catching up to two simultaneously thrown balls with its hands. Second, we equip Agile Justin with highly developed and deep learning based tactile sensing capabilities that are critical for dextrous fine manipulation. We demonstrate its tactile capabilities with the delicate task of identifying an objects material simply by gently sweeping with a fingertip over its surface. Key for the realization of complex dynamic manipulation tasks is a software framework that allows for a component based system architecture to cope with the complexity and parallel and distributed computational demands of deep sensor-perception-planning-action loops -- but under tight timing constraints. This thesis presents the communication layer of our aRDx (agile robot development -- next generation) software framework that provides hard realtime determinism and optimal transport of data packets with zero-copy for intra- and inter-process and copy-once for distributed communication. In the implementation of the challenging ball catching application on Agile Justin, we take full advantage of aRDx's performance and advanced features like channel synchronization. Besides developing the challenging visual ball tracking using only onboard sensing while everything is moving and the automatic and self-contained calibration procedure to provide the necessary precision, the major contribution is the unified generation of the reaching motion for the arms. The catch point selection, motion planning and the joint interpolation steps are subsumed in one nonlinear constrained optimization problem which is solved in realtime and allows for the realization of different catch behaviors. For the highly sensitive task of tactile material classification with a flexible pressure-sensitive skin on Agile Justin's fingertip, we present our deep convolutional network architecture TactNet-II. The input is the raw 16000 dimensional complex and noisy spatio-temporal tactile signal generated when sweeping over an object's surface. For comparison, we perform a thorough human performance experiment with 15 subjects which shows that Agile Justin reaches superhuman performance in the high-level material classification task (What material id?), as well as in the low-level material differentiation task (Are two materials the same?). To increase the sample efficiency of TactNet-II, we adapt state of the art deep end-to-end transfer learning to tactile material classification leading to an up to 15 fold reduction in the number of training samples needed. The presented methods led to six publication awards and award finalists and international media coverage but also worked robustly at many trade fairs and lab demos

A shuttle and space station manipulator system for assembly, docking, maintenance, cargo handling and spacecraft retrieval (preliminary design). Volume 2: Concept development and selection

The overall program background, the various system concepts considered, and the rationale for the selected design are described. The concepts for each subsystem are also described and compared. Details are given for the requirements, boom configuration and dynamics, actuators, man/machine interface and control, visual system, control system, environmental control and life support, data processing, and materials