4,248 research outputs found
Development of a smart capture system for On--Orbit--Servicing with space robots
No full textNegli ultimi anni sono stati fatti molti sforzi per sviluppare nuovi settori e nuove tecnologie per migliorare l'affidabilità dei satelliti commerciali. Questo porterà a un nuovo processo di progettazione per i satelliti. In particolare, i satelliti potranno accettare operazioni da altri veicoli spaziali. Sotto il termine ``operazione'' ci sono tutte le missioni che mirano a migliorare o prolungare la vita operativa di un satellite in orbita. Tali missioni includono il rifornimento di carburante, il refurbishment e altre operazioni di risoluzione dei problemi (ad esempio, pannelli solari sbloccati, riparazione del dispiegamento non nominale delle antenne e così via). Tutte queste missioni sono incluse nelle On--Orbit--Servicing (OOS) missions. In queste missioni sono coinvolti un satellite chaser (un robot spaziale, un satellite con uno o più bracci robotici, o un satellite con un sistema di aggancio che fornisce il servizio) e il satellite target (quello che riceve i servizi).
Una tipica missione OOS inizia con la fase in cui il chaser esegue una serie di trasferimenti orbitali per avvicinarsi al satellite target e sincronizzarsi con esso. Successivamente, il robot spaziale può utilizzare il suo braccio robotico per catturare il satellite target e stabilire una connessione rigida tra i due veicoli. Dopo la cattura, il chaser può eseguire i servizi poiché i due satelliti sono rigidamente collegati e si muovono come un corpo unico.
La fase di cattura è una delle più critiche e una delle più importanti per il successo in una missione OOS. Per questo motivo, molti sforzi vengono dedicati allo studio di questa fase poiché coinvolge diversi aspetti: dalla dinamica orbitale allo sviluppo del sistema di cattura. Quest'ultimo è il fulcro di questo lavoro che presenta lo sviluppo di un meccanismo di cattura.
Lo strumento di cattura proposto è stato progettato nell'ipotesi che dovrebbe essere indipendente dal resto del robot spaziale su cui è montato. In pratica, lo strumento di cattura è dotato di una serie di sensori, attuatori e un microcontrollore che lo rendono indipendente dal computer del chaser. In particolare, (1) i sensori stimano la posa dell'interfaccia target, (2) il computer esegue gli algoritmi richiesti per il controllo e la gestione del tool e (3) gli attuatori catturano il satellite target. In questo modo, lo stesso strumento di cattura può essere montato veicoli con diverse architetture. Infatti, il tool calcola i comandi richiesti per catturare il target e li invia al computer del chaser, cosi che il chaser diventa solo il ``sistema di posizionamento'' per lo strumento di cattura. Inoltre, le esigenze computazionali richieste dal computer del robot spaziale diminuiscono.
Lo strumento di cattura si chiama SMArt Capture Kit (SMACK) per sottolineare (1) il fatto che stima la posa del target ed esegue gli algoritmi richiesti in modo autonomo, e (2) la sua capacità di stabilire una connessione rigida tra il chaser e il target.
Questo lavoro illustra e commenta lo sviluppo di SMACK. Lo sviluppo include il design meccanico; i sensori utilizzati; l'algoritmo di navigation che fonde le misure per stimare la posa del target; l'algoritmo di guidance che calcola la traiettoria di approccio; e i test eseguiti per validare l'intero sistema. Inoltre il lavoro presenta anche lo sviluppo della facility usata per testare interfacce di docking e di cattura, tra le quali SMACK.
Nell'ultimo periodo, SMACK è stato adattato per soddisfare i requisiti di un sistema di aggancio (DOCKS) per una missione CubeSat dell'Agenzia Spaziale Europea. DOCKS utilizza lo stesso paradigma di SMACK di avere un sistema autonomo. Vengono illustrati e discussi anche il design, la produzione e i test di DOCKS.In the last decades several efforts have been dedicated to development of new sectors and new technologies in order to improve the reliability of the commercial satellites. This will lead to a new design process for satellites. In particular, the satellites should be able to accept operations by other space vehicles. Under the term ``operation'' there are all the missions that aim to improve the operational capacities or extend the life of an orbiting satellite. Such missions include refuelling, refurbishment and other issue fixing operations (e.g., unstuck solar arrays, remediation of off--nominal deployment of the antennas and so on). All these missions are included in the On--Orbit--Servicing (OOS). The players of these missions are a chaser satellite (a space robot, a satellite with one or more robotic arms, or a satellite equipped with a capture mechanism that provides the service) and the target satellite (the one that receives the services).
A typical OOS mission starts with the chaser that executes a series of orbital transfers in order to approach the target satellite and synchronized with it. After this, the space robot can employ its robotic arm to capture the target satellite and establish a rigid connection between the two players. After the capture, the chaser satellite can execute the services since the two satellites are rigidly connected and they move as one single body.
The capture phase is one of the most critical, and one of the most important to succeed in an OOS mission. For this reason, many efforts are given to the study of this phase since it involves several aspects: from the orbital dynamics to the development of the capture system. This work focuses on the latter by proposing a capture tool to be employed to capture a target satellite.
The proposed capture tool has been designed under the hypothesis that it should be independent from the rest of the space robot on which it is mounted. In practice, the capture tool is equipped with a set of sensors, actuators, and a micro--controller that make it independent from the chaser satellite. In particular, (1) the sensors are employed to estimate the pose of the target, (2) the computer executes the required algorithms to manage and control the tool, and (3) the actuators catches the target satellite. In this new fashion, the capture tool can be mounted on chaser vehicles with different architecture. In fact, the tool computes the required commands and gives it to the computer of the satellite, such that the chaser vehicle becomes the just the ``positioning system'' for the capture tool. Furthermore, the computational needs required by the computer of the space robot is lower.
The capture tool is called SMArt Capture Kit (SMACK) to underline (1) the fact that it estimates the pose of the target and executes the required algorithms autonomously, and (2) its ability to establish a rigid connection between the chaser and the target satellites.
This work will illustrate and discuss the development of SMACK. The development includes the mechanical design; the employed sensors; the navigation algorithm that fuses measurements to estimate the pose of the target; the guidance algorithm that produces the approach trajectory; and the tests performed in order to validate the autonomous capture tool. In addition, the work also presents the development of the facility employed to tests various docking and capture systems, among them there is SMACK.
During the last period, SMACK has been re--designed in order to fit the requirements of a docking system (DOCKS) for a CubeSat mission of the European Space Agency. DOCKS employs the same paradigm of SMACK , as it is an autonomous system. The design, manufacturing and tests of DOCKS are illustrated and discussed as well
Development and test of a robotic arm for experiments on close proximity operations
No full textFuture spacecraft will be provided with special features to enable On-Orbit-Servicing missions. Such features include capture interfaces, proximity sensors, and algorithms for autonomous RVD (Rendezvous and Docking). The reliability standards of the space industry require all these technologies to be tested in relevant environment; to this purpose, several ground testing facilities have been built during the last years. They reproduce many aspects of the free-falling motion of a spacecraft often exploiting two technologies: robotic systems and low friction tables. The first use a virtual environment to compute the effects of the external forces and reproduce the motion of a spacecraft with a robotic arm; the second unbind vehicle mock-ups from friction effects, allowing them to experience a free motion at least in three degrees of freedom. Merging together these two types of facilities gives the possibility to further extend their capabilities. This work presents a series of tests conducted on a custom robotic arm, intended to be integrated with a low friction table. The tests focus on two main aspects: (i) the accuracy of the positioning capability and (ii) the dynamic behaviour of the robotic arm. Both aspects are directly connected with the final purpose of operating in conjunction with a vehicle floating on a low friction table. The paper also presents some improvements of the robotic arm suggested by the results of the tests to fit the requirements on the positioning accuracy. These are represented by three main achievements: (i) the accuracy is comparable with the principal navigation sensor; (ii) the vibrations are below the error of the navigation sensor, and (iii) the ability of the robotic arm in performing a capture task
Smart capture tool for space robots
No full textOn–Orbit–Servicing missions aim to improve the operative life of orbiting satellites. Among the studied technologies, the most promising are satellites equipped with one or more robotic arms (space robots). One robotic arm might be employed to establish a rigid connection with the target satellite, while the other performs the servicing operations. Nowadays, the control of the capture tool is managed by the computer of the space robot. However, it is possible to distribute the control tasks between the capture tool and the space robot.
For this purpose, this paper presents the development of the SMArt Capture Kit (SMACK). SMACK is a standalone capture system equipped with sensors, actuators, and an integrated computer. In this fashion, the capture tool executes the guidance and navigation algorithms, and the control of the actuators; so that the space robot acts as the “positioning” system for the capture tool.
The paper provides a description of all the subsystems of SMACK and their experimental validation. The tests of SMACK at the system level, confirm its capabilities to autonomously perform the capture the target interface
Adrian Caesar speaking at Alex Miller author: A Celebration, held at the National Library, Canberra, 30 October 2011 /
No full textTitle from information supplied by photographer.; Part of the collection: Alex Miller author: A Celebration, held at the National Library of Australia theatre, 30 October 2011.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
[Letter from Alex Bradford to Lieutenant and Mrs. Ray Starner - November 4, 1940]
No full textLetter from Alex Bradford to Lieutenant and Mrs. Ray Starner describing the the current state of affairs that the author was experiencing, including: the London blitz, the moral of the troops on the ground, and the collective company of men opposing the Nazi regime
Alex Haley, author
No full textExamines the life and achievements of Alex Haley, celebrated author of "Roots" and other writings, discussing his life and literary career, as well as his obsession with researching his family's history
Ground Facility for Validation of Proximity Operations: a Hardware–In–the–Loop Experiment
No full textDevelopment of a smart docking system for small satellites
No full textDOCKS is a smart docking system for space vehicles developed by the Department of Industrial Engineering, University of Padova, within the framework of the Space Rider Observer Cube (SROC) mission. The design and development of SROC is being conducted by a consortium of Italian entities under contract with the European Space Agency (ESA). The SROC mission is designed to be a payload on the ESA Space Rider (SR) spaceship. The main objective of the mission is to demonstrate the critical capabilities and technologies required to execute a rendezvous and docking mission in a safety-sensitive context. The space system is composed by a nanosatellite (approximately 12U CubeSat) and a deployment/retrieval mechanism mounted inside the payload bay of SR. During the mission, SROC will be released by SR, will perform inspection manoeuvres on SR and, at the end of the mission, will dock back inside the bay of SR, before reentering Earth with the mothership. The docking functionality is provided by DOCKS. DOCKS is suitable for use onboard micro- and nanosatellites and merges a classical probe drogue configuration with a gripper-like design, to manage the connection between the parts. The system is equipped with a suite of sensors to estimate the relative pose of the target and with a dedicated computer, making it a smart standalone system. A laboratory prototype has been assembled and functionally tested, aiming at the validation of the capability to passively manage misalignments during the docking manoeuvre
Description by author Alex Irvine of his recent participation in the San Diego C
No full textDescription by author Alex Irvine of his recent participation in the San Diego Comic-Con, one of the largest conferences of comic/media/book producers and consumers. Irvine was there to promote his new fiction book, One King, One Soldier, published by Del Rey
Recovery through contradiction?
No full textWith this new drug strategy, the circle has turned. It was a Conservative government
that introduced the first drug strategy, Tackling Drugs Together, in 1995. This aimed
to reduce drug related crime, protect young people and reduce health harms by
discouraging drug use. It was criticised at the time for having unrealistic, intangible
aims and for not providing the necessary funding. New Labour’s strategies introduced
increasingly specific targets and massively expanded the funding of treatment. This
new Coalition strategy has no targets and provides no new funding
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