Figure 7 - uploaded by Evangelos Papadopoulos
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A Dynamic Singularity at point E does not allow the end-effector to move from point A to D. The teleoperator planner suggests path ABCD which avoids singularities.
Source publication
Free-flying space robotic devices, in which manipulators are mounted on a thruster-equipped spacecraft, will assist in the construction, repair and maintenance of satellites and future space stations. Operation in a free-floating mode, in which spacecraft thrusters are turned off, increases a system's life. The teleoperation of free-floating system...
Contexts in source publication
Context 1
... can be seen that unlike fixed-based kinematic singularities (q 2 = 0°, ±180°) infinite more singular pairs (q 1 ,q 2 ) exist. Figure 5 depicts the example system in a typical dynamically singular configuration with (q 1 ,q 2 ) = (-65°, -11.41°). For this system, the PIW is represented by the light gray hollow disk, shown in Figure 7. The dark area hollow disks correspond to the PDW. ...
Context 2
... dark area hollow disks correspond to the PDW. Let the system's end-effector initially be at point A: (x,y) = (2,0), which belongs in the system's PDW, see Figure 7. The initial configuration of the system is (q 1 ,q 2 ) = (-58°, 60.3°) which corresponds to an initial spacecraft orientation q = 21°. ...
Context 3
... path is found as follows: The planner first chooses some random point C in the PIW. The end-effector is moved from the desired point D, to point C: (0.8, 0.5), see path DC in Figure 7. Although a straight line motion is used here, in general a joint space path guarantees the avoidance of singularities. ...
Citations
... Control properties of space robots, as mentioned earlier, and missions planned for them make the control design an interesting and quite challenging problem. Although there already exist algorithms which allow controlling underactuated robots and manipulators [4][5][6], there are still many open problems and room for new research in this area, since controllers are usually dedicated to specified missions and space robots performing them. Thus, some more general mission oriented approaches are welcome. ...
The paper presents a model-based tracking controller design for a freefloating space robot for a mission scenario of intercepting an object. Such missions are of interest due to a growing number of objects needed to be removed from space. The free-floating mode requires spacecraft thrusters to be off and linear and angular momentum are conserved then. Momentum conservation generates holonomic and nonholonomic constraint equations, respectively. The free-floating mode implicates underactuation, so the robot becomes multi-constrained. Many control algorithms are designed for underactuated robots but they are specific mission and robot dependent. Motivations for the presented research come from the growing space exploration, which results in more space debris and requires sophisticated removal services. Service tasks and debris removal need to be performed by specialized robots. The debris interception scenario presented in the paper consists of estimation of target properties, a controller design to track and intercept the debris, and move it to the graveyard orbit. Simulation results of the theoretical control development for the robot intercepting a non-tumbling object are provided.
... Furthermore, some of these domains make the physical co-presence of human operators nearby the robot difficult or inefficient, and thus create the need for some degree of remote tele-operationwhich could vary on a whole range including direct tele-operation and supervisory control [10]. Such application domains of robot tele-operation include hazardous or difficult to access environments, such as radioactive environments ( [11,12]), underwater ( [13,14]), space ( [15,16]), demining ( [17,18]), military, medical operations when a specialist is not locally available ( [19,20]), etc. ...
An important motivation for achieving effective embodied robotic telepresence comes not only from application areas where the robot will be teleoperated all of the time, but also, as we shall argue, in cases where the current state of the art of autonomous AI can cater for a significant percentage of the operating time of the robot, but is not yet good enough to support the application alone. The main motivation for the system presented here comes from such cases where adjustable and sliding autonomy can be applied, and more specifically towards applications of androids in shopping malls, as receptionists, tutor robots etc. In the system presented in this paper, the arms, neck, facial expressions, eyes, lips and voice of the Ibn Sina android robot are controlled on the basis of the body movements and voice of a remote operator, while the operator is experiencing the world through the eyes and ears of the robot, fed to a head-mounted display and headphones. The system is the first android telepresence system using very-low cost operator interface equipment (kinect and webcam) while supporting arm, neck, and expression control. We present a set of generic requirements, followed by an extensive description of our system architecture, video demonstrations of actual operation, a discussion, and multiple interesting extensions.
Dans cette thèse, le problème du contrôle d’attitude de satellites agiles à l’aide de grappes d’actionneurs gyroscopiques (AGs) est considéré et plus particulièrement son application au contrôle de micro/nanosatellites (10-100 kg). Afin d’analyser les configurations de grappe les plus pertinentes pour les nanosatellites, des outils d’analyse topologique sont développés. Après une comparaison des différentes configurations, le choix se porte sur une grappe pyramidale de six actionneurs gyroscopiques. Des analyses plus approfondies de cette grappe (avec et sans cas de panne d’actionneurs gyroscopiques) permettent de déduire des contraintes que la loi de pilotage doit vérifier pour être adaptée à ce système, en particulier pour le passage de singularités.Le cahier des charges initialement défini pour la thèse est alors étoffé et précisé. Pour y répondre, après analyse de la littérature, une nouvelle structure de loi de pilotage ainsi qu’une formulation différente des équations cinématiques sont développées. Cette structure est basée sur l’algorithme du filtre de Kalman étendu. Elle a pour avantages de répondre aux exigences en termes de calcul temps réel au bord des satellites, de flexibilité sur la gestion des contraintes et de facilité d’adaptation en cas de pannes. En outre, une procédure de génération de boucle de commande, englobant la loi de pilotage et un contrôleur robuste du système, est proposée. La généralisation de cette boucle de commande est illustrée sur des bras manipulateurs à base fixe et spatiaux.En parallèle, l’étude du passage des singularités internes intraversables dans les grappes d’actionneurs gyroscopiques mène à une nouvelle stratégie d’évitement de ces singularités. Elle consiste à insérer une connaissance de la topologie du système pour améliorer la précision dans le pilotage. Des simulations sur des modèles de satellites représentatifs illustrent les résultats de la loi de pilotage dans différents cas de panne. La grappe d’actionneurs et la boucle de commande développées seront testées dans le cadre d’une expérimentation en microgravité, et les objectifs de cette expérience sont détaillés dans ce mémoire.
The interdisciplinary journal publishes original and new results on recent developments, discoveries and progresses on Discontinuity, Nonlinearity and Complexity in physical and social sciences. The aim of the journal is to stimulate more research interest for exploration of discontinuity, complexity, nonlinearity and chaos in complex systems. The manuscripts in dynamical systems with nonlinearity and chaos are solicited, which includes mathematical theories and methods, physical principles and laws, and computational techniques. The journal provides a place to researchers for the rapid exchange of ideas and techniques in discontinuity, complexity, nonlinearity and chaos in physical and social sciences.
No length limitations for contributions are set, but only concisely written manuscripts are published. Brief papers are published on the basis of Technical Notes. Discussions of previous published papers are welcome.
