Optimal target grasping of a flexible space manipulator for a class of objectives

Space graspers are complex systems, composed by robotic arms placed on an orbiting platform. In order to fulfil the manoeuvres’ requirements, it is necessary to properly model all the forces acting on the space robot. A fully nonlinear model is used to describe the dynamics, based on a multibody approach. The model includes the orbital motion, the gravity gradient, the aerodynamic effects, as well as the flexibility of the links. The present paper aims to design, thanks to nonlinear optimization algorithms, a class of manoeuvres that, given the same target to be grasped, are characterized by different mission objectives. The grasping mission can be performed with the objective to minimize the power consumption. Collision avoidance constraints can be also added when the target is equipped with solar panels or other appendices. In some cases, large elastic displacements should be expected, possibly leading to an inaccurate positioning of the end-effector. Therefore, different design strategies can require that the manoeuvre is accomplished with minimum vibrations’ amplitude at the end-effector. Performance of the different strategies is analyzed in terms of control effort, trajectory errors, and flexible response of the manipulator.     

Discovering the basic strategic orientation of big space agencies

The aim of this paper is to identify the basic strategic orientations of some of the world's main space agencies. This study focuses on the Brazilian, French, European, Japanese, Indian and Russian agencies. Basic strategic orientations indicate the real space exploration objectives of large countries. This is useful because there are some ambiguous areas in the formal strategic documents published by these agencies. The results highlight the common objectives of the agencies studied, which is to have an important role in international political leadership even considering the specific objectives related to the economic and social contexts of the individual countries.     

Validation of attitude/deformation sensing techniques for space flexible manipulators

This paper proposes an approach that makes use of two different techniques to sense and identify both the rigid attitude motion and the flexible dynamics of a manipulator. With the first technique, an accurate attitude motion determination, based on the use of a global navigation satellite systems (GNSS) signals, is performed. For this purpose, some antennas are placed on the manipulator in order to obtain the observable phase of the GNSS signal. The second technique, based on the use of accelerometer sensors, is used in order to identify the dynamic signature during the motion of the flexible link. Specifically, the modal parameters are estimated using data recorded from accelerometers, conveniently placed on the structure, by means of an output-only based approach. The developed algorithms used for both the attitude estimation and the output-only modal analysis are validated by experimental activities carried out on an in-house testbed representing a two flexible arm manipulator.     

Space technology transfer: Spin-off cases from Japan

Government organizations have to justify high expenditure during periods of financial crisis such as the one we are experiencing today. Space agencies have attempted to increase the returns on their investments in space missions by encouraging the commercial use of advanced technologies. This paper describes two technology transfer (TT) cases promoted by JAXA, in order to identify the organizational models and determinants of TT. The development of a TT process from space to Earth not only benefits the aerospace industry but also the network of national companies. The aim of the paper is to investigate who the actors are and the nature of their role, as well as the determinants of the TT process in the Japanese space sector. The case studies confirm the typical path of transfer as ‘Earth–space–Earth’.     

Determination of kinematic state of an orbiting multibody using GNSS signals

Precise attitude determination of the members of a free-flying multibody system is a not so immediate task, due essentially to the large motion of its appendages coupled with their relevant flexibility effects. In fact, sensors used to this aim in current projects, such as optical encoders usually positioned near the joints of each arm, are almost blind to these effects, and clusters of specific redundant sensors should, therefore, be required in order to reconstruct both elastic deformations and rigid motion.Satellite navigation systems (GNSS) offer a suitable and reliable solution to this problem. To exploit the phase of the signal, instead of the traditional pseudo random code, ensures a very high accuracy of the order of magnitude of centimeter. Such a process requires the solution of an initial ambiguity problem, related to the number of integer wavelength included in the length of the member.The aim of the paper is to investigate the capability of this GNSS based technique to reconstruct the kinematics of a flexible multibody system orbiting around the Earth. This analysis requires a simulation including both the multibody dynamics and the navigation system constellation to define the satellites lines-of-sight at each time step.Concerning multibody equations of motion, a Newtonian formulation is adopted in this work. A special attention is required about the choice of the state variables. As the internal forces are associated to the relative displacements between the bodies, which are small fractions of the distance of the multibody spacecraft from the center of the Earth, the task of obtaining these forces from inertial coordinates could be impossible from a numerical point of view. So, the problem is reformulated in such a way that the equation of motion of the system contains global equations, with no internal forces, and local equations, with internal forces. In the latter, only quantities of the same order of the spacecraft dimensions are present.Accuracies achievable in LEO orbit with current GPS and upcoming Galileo systems are evaluated to show the interest of the proposed technique.     

Spatial Influence of Environmental Axes in a Baseball Field

Abstract

We investigated the influence of environmental axes in a baseball field. In Experiment 1, participants walked either a path in the prototypical orientation (home plate to second base) or one which was rotated 225°. Recall for object locations was best when participants imagined themselves aligned with axes salient from the experienced orientation. In Experiment 2, when learning was through a route text, there was less of an influence of environmental axes. In Experiment 3, when participants walked both paths, memories were good for the atypical orientation, suggesting that task-specific spatial cues can be more influential than a prior conceptual north.     

A systematic review of the Space technology transfer literature: Research synthesis and emerging gaps

In order to justify high expenditure during this period of financial crisis, Space Agencies have attempted to increase the returns on their investments in Space missions by encouraging the commercial use of advanced technologies. The development of a technology transfer process from Space to Earth not only benefits the Aerospace industry but also the network of national companies. Technology transfer has been shown to stimulate innovation in business and commerce, support economic growth and provide a return on public investment in research and development (R&D). The aim of this paper is to systematically review the Space technology transfer literature and to suggest directions for future research. The range of research and studies in the literature on this topic requires a systematic review to summarize the results in an unbiased and balanced manner and to interpret these in a way that highlights the research gaps. This article presents an overview of the dominant thinking (explicit in selected articles from 1995 to present), indicating the problems of analysis, research gaps and a future research program.