1,721,258 research outputs found
Soft and energy-efficient robotic capture of tumbling spacecrafts
Full text linkThe autonomous capture of non-cooperative objects with unknown dynamic parameters is a priority task for near future space activities. This key technology can be used in several space robotic missions such as in refuelling, repairing, servicing satellites, or for the removal of space debris. In the capturing operation, an accurate robot trajectory control should be used in order to minimize the impact force at the time of capture, and the robotic system should dampen the spin motion of the target in the post-capture phase. Indeed, the impact force could damage either the manipulator or the target, cause an undesired spacecraft attitude destabilization, or cause the target to be pushed away. Therefore, the robot trajectory has to be computed in such a way that the relative velocity between the robot end-effector and the target at the time of capture is very small. Moreover, the spacecraft attitude deviation should be minimized during and after the capture in order to maintain the communication link with the ground station. In this operative scenario there are several unsolved issues, mainly concerning the accurate identification of the dynamic parameters of the target, and the design and implementation of effective systems for impact reduction and motion damping of the target satellite in the post-capture scenario. In this paper, a novel control method which carries out the motion damping of the spinning target in the post-capture phase in an energy-efficient way is presented, thus enhancing the system useful life. The control method is also able to identify the main inertial parameters of the target satellite during the post-capture motion. Moreover, a new mechatronic system to dampen and reduce the effects of the impact between the robotic arm and the target satellite is developed, using compliant joints and backlash which can be activated/deactivated during the impact. Both the aforementioned systems are tested and demonstrated by means of dynamic simulations for evaluating their performance. Several test cases with different spin of the target are considered in order to simulate real space robotic operations scenarios. Finally, a real prototype has been developed and tested in laboratory in a simulated microgravity test facility in order to experimentally validate the proposed concepts
Energy-efficient motion of a space manipulator
No full textIn space robotics missions, either in the scenario of space servicing or debris capture, both the minimization of the energy required for the manipulator manoeuvre and the minimization of the reactions transferred to the base spacecraft are of crucial importance. Indeed, both of them are related to the possibility of having a longer system operative life in space: for the energy minimization this is straightforward, and for the reaction minimization this is due to the fact that the Attitude Control System is going to spend less fuel for attitude recovery and correct pointing of antennas after the manipulator manoeuvre if the reactions transferred to the base spacecraft have been minimized. In this paper, a minimum kinetic energy inverse kinematics solution for redundant manipulators has been introduced and validated by simulation. Its performance has been compared to the classical inverse kinematics solution which minimizes joint velocities and to the one that minimizes the reaction torque transferred to the base spacecraft for a 3-degrees-of-freeedom planar manipulator. Two different end-effector trajectories have been used for validation and then for the comparison of the different inverse kinematics solutions in terms of: total energy required for performing the task, maximum required power, maximum kinetic energy, maximum reaction torque, and maximum joint angles, velocities, and accelerations. Finally, the new concept of iso-energy curve has been introduced, and a set of them has been drawn over the robot workspaces, which have been computed using the kinetic energy minimization solution and the reaction torque minimization solution, considering or not the robot joint limits. This method shows that preferential minimum energy directions exist for the robot end-effector motion, and these are approximately the same for the different inverse kinematics solutions considered
HOTDOCK and the MOSAR Walking Manipulator, Technologies for Modular Spacecraft Assembly and Reconfiguration
No full textThe concept of modular and reconfigurable spacecraft is a possible gamechanger solution to answer the future challenges of the space industry and exploration, that includes, space sustainability, economical profitability, system reliability and large structure on-orbit assemblies. This paper introduces the EC H2020 MOSAR project, aiming at refining and demonstrating the concept of modular spacecraft. More specifically, the chapter will focus on the design, validation and future perspectives of the two robotic system developments, which are the standard interconnect (SI) HOTDOCK and the MOSAR Walking Manipulator (MOSAR-WM). The exploitation of standard interconnects, providing mechanical /data/power/thermal transfers between connected entities, as well as more advanced and capable robotic systems, for performing the operations, open new horizon of possibilities for future space missions, ranging from On-Orbit Servicing of existing satellites to large On-Orbit Assembly and reconfiguration of modular spacecraft
Xian zheng du shu jue /
No full textBlockprint.Double leaves, oriental style, in case.Mode of access: Internet
The AgriRover : a mechatronic platform from space robotics for precision farming
No full textThis paper reports an investigation of a novel development by spinning off space robotic technologies into agriculture and dissemination of the findings of AgriRover project, which is the first of its kind in exploiting and applying space robotic technologies in precision farming. To measure energy performance of mobile platform, a new dynamic total cost of transport is proposed and validated. An autonomous navigation system based on a rover control architecture has been developed to enable the AgriRover to traverse safely in unstructured farming environments. A novel and agriculture- specific object recognition algorithm has been investigated and implemented to enable higher degree of intelligence based on more smart data processing capability. A novel soil sample collecting mechanism has been designed and prototyped for onboard and in-situ soil quality measurement. The design of the whole system has benefited from the use of a mechatronic design process known as the Tiv model through which a planetary rover is reinvented into the AgriRover for agricultural applications. The AgriRover system has gone through three field trials in the UK and China and some of these results are reported
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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