Interception of a free-rotating satellite: an autonomous rendezvous scenario, Journal of Telecommunications and Information Technology, 2007, nr 1

The spacecraft’s lifetime is often limited by reliability and redundancy of its components. Furthermore, serious restrictions on duration of spacecraft operations are posed by finite amount of fuel or cooling agent. It is also clear that once a satellite is launched, it is extremely difficult to replace/modify its hardware on the orbit. Future spacecraft missions, especially huge planetary orbiters, will require servicing support from autonomous unmanned satellites. In this paper we introduce and analyze a new scenario for interception of a free rotating satellite ion a Keplerian orbit. The scenario is divided into several stages to be executed by the servicing satellite: attitude determination of the target object; own motion planning; determination of the optimal target position and orientation before docking; controlled approach, i.e., decreasing of a range between satellites; orbiting of the servicing satellite around the target satellite; docking, i.e., radial degreasing of the intersatellite range till the satellites contact, while keeping constant the relative orienta- tion between them. The control algorithm for the servicing satellite motion during its maneuvers is described. Finally, a few examples of satellite motion simulations according to the proposed scenario are presented

Entity Graph Extraction from Legal Acts -- a Prototype for a Use Case in Policy Design Analysis

This paper presents research on a prototype developed to serve the quantitative study of public policy design. This sub-discipline of political science focuses on identifying actors, relations between them, and tools at their disposal in health, environmental, economic, and other policies. Our system aims to automate the process of gathering legal documents, annotating them with Institutional Grammar, and using hypergraphs to analyse inter-relations between crucial entities. Our system is tested against the UNESCO Convention for the Safeguarding of the Intangible Cultural Heritage from 2003, a legal document regulating essential aspects of international relations securing cultural heritage.Comment: 17 pages, 10 figure

Application of predictive control for manipulator mounted on a satellite

Specific conditions of on-orbit environment are taken into account in the design of all devices intended to be used in space. Despite this fact malfunctions of satellites occur and sometimes lead to shortening of the satellite operational lifetime. It is considered to use unmanned servicing satellite, that could perform repairs of other satellites. Such satellites equipped with a manipulator, could be used to capture and remove from orbit large space debris. The critical part of planned missions is the capture manoeuvre. In this paper a concept of the control system for the manipulator mounted on the satellite is presented. This control system is composed of the trajectory planning module and model predictive controller (the latter is responsible for ensuring precise realization of the planned trajectory). Numerical simulations performed for the simplified planar case with a 2 DoF manipulator show that the results obtained with the predictive control are better than the results obtained with adaptive control method

MUPUS insertion device for the Rosetta mission, Journal of Telecommunications and Information Technology, 2007, nr 1

An original mechanical device designed to insert a penetrator into a cometary nucleus in an almost gravityfree environment is described. The device comprises a hammer and a power supply system that stores electrical energy in a capacitor. The accumulated energy is discharged through a coil forming a part of electromagnetic circuit that accelerates the hammer. The efficiency of converting the electrical energy to kinetic energy of the hammer is not very high (amounts to about 25%), but the system is very reliable. Additionally, the hammer energy can be chosen from four power settings, hence adjustment of the stroke’s strength to nucleus hard- ness is possible. The device passed many mechanical, func- tional, thermal and vibration tests and was improved from one model to another. The final, flight model was integrated with the lander Philae and started its space journey to comet Churyumov-Gerasimenko in March 2004

Development of the optical system for the SST-1M telescope of the cherenkov telescope array observatory

The prototype of a Davies-Cotton small size telescope (SST-1M) has been designed and developed by a consortium of Polish and Swiss institutions and proposed for the Che-renkov Telescope Array (CTA) observatory. The main purpose of the optical system is to focus the Cherenkov light emitted by extensive air showers in the atmosphere onto the focal plane detectors. The main component of the system is a dish consisting of 18 hexagonal mirrors with a total effective collection area of 6.47 m2 (including the shad-owing and estimated mirror reflectivity). Such a solution was chosen taking into ac-count the analysis of the Cherenkov light propagation and based on optical simulations. The proper curvature and stability of the dish is ensured by the mirror alignment system and the isostatic interface to the telescope structure. Here we present the design of the optical subsystem together with the performance measurements of its components.0SCOPUS: cp.pinfo:eu-repo/semantics/publishe

Impedance Control Using Selected Compliant Prismatic Joint in a Free-Floating Space Manipulator

The success of space missions like capture-and-deorbit or capture-and-service relies on the ability of the capturing satellite to establish a stable mechanical connection by its gripping tool with the object being intercepted. Most of the potential objects of capture missions are not equipped with dedicated docking ports; hence, the satellite robot intercepting them will have to provide the mechanical compliance necessary for the safe establishment of contact between the two structures. Articulated robotic arms with controlled mechanical impedance are one set of promising solutions for this challenge. In this study, the authors discuss how the mechanical impedance realized only along a single axis can be useful for facilitating the contact between the manipulator arm’s end effector of a free-floating robot and an uncooperative object in microgravity. By distinguishing a dominant direction in the final approach and contact establishment maneuver, the need for impedance control of six degrees of freedom may be relaxed, and a single prismatic joint with controlled impedance can be used at the end effector. Such architecture is simulated and compared with the full model-based six-degree-of-freedom Cartesian impedance control of a free-floating manipulator. Authors then discuss the limitations and possibilities of such architecture in a potential practical setting

Zastosowanie sterowania impedancyjnego robotem kosmicznym typu free-floating w kontekście usuwania śmieci kosmicznych

A broad and significant class of space debris can be mitigated by means of a satellite, capable of capturing a large non-cooperating object by using a robotized arm with a gripper. The capture operation typically comprises of an approach, a close-on manoeuvre, establishing contact between the robotic grappler arm and a suitable feature on the target satellite, and finally it is concluded when a positive mechanical connection is achieved by the gripper closed on that feature. The phase of establishing contact poses a critical challenge in this scenario, since the target typically will be tumbling with respect to the chaser satellite causing high forces on the gripper and the robotic arm. A family of control methods known collectively as impedance control is typically employed in terrestrial robots for tasks involving an interaction with an environment, especially the dynamic contact. In this work, we present the model-based impedance control applied to a robotic manipulator on a free floating base. The derivation of impedance control law for a robotic manipulator on a free floating satellite, involving Generalized Jacobian Matrix (GJM), is presented, followed by simulation results comparing the loads in the manipulator joints against a classical GJM-based Cartesian controller. The simulation results show that the impedance controlled free floating robotic manipulator completes the task of trajectory following amid contact with unknown target with lower torques in the robot joints.Wiele obiektów orbitujących Ziemię stanowią wyeksploatowane lub nieczynne satelity i inne urządzenia kosmiczne oraz ich fragmenty. Poruszając się w sposób niekontrolowany po orbitach aktywnie wykorzystywanych stanowią zagrożenie dla czynnych satelitów, stacji kosmicznej, astronautów jak i również rakiet wynoszących w przestrzeń kosmiczną nowe satelity. Obiekty te uznawane są za śmieci kosmiczne. Zdolność chwycenia i manipulowania niewspółpracującym obiektem na orbicie Ziemi przez robota satelitarnego pozwoliła by na zmniejszenie liczby śmieci kosmicznych i zagrożeń z nimi związanych w dwojaki sposób: po pierwsze umożliwiła by chwycenie i usunięcie śmieci kosmicznych znacznej wielkości z orbity, po drugie dała by możliwość serwisowania i tym samym przedłużenia okresu eksploatacyjnego satelitów będących blisko końca swojej nominalnej misji, zapobiegając by stały się one śmieciami kosmicznymi. Oba te zastosowania wymagają fizycznego wejścia w kontakt pojazdu kosmicznego chwytającego oraz obiektu chwytanego. W naziemnych zastosowaniach robotów, w których dochodzi do kontaktu manipulatora robota z otoczeniem, powszechnie stosowane są metody sterowania impedancyjnego. W niniejszym tekście autorzy proponują wykorzystanie sterowania impedancyjnego w oparciu o model (model-based impedance control) do realizacji manewru wejścia w kontakt końcówki manipulatora robota satelitarnego z niewspółpracującym obiektem w stanie nieważkości. W pracy przedstawiono wyprowadzenie prawa sterowania impedancyjnego manipulatorem o swobodnej bazie w oparciu o model, z wykorzystaniem jakobianu uogólnionego (Generalized Jacobian Matrix, GJM), oraz rezultaty symulacji manewru wejścia końcówki roboczej manipulatora kosmicznego w kontakt z nieważkim obiektem. Wyniki symulacji pokazują, że zaproponowane prawo sterowania pozwala realizować zadanie śledzenia trajektorii zachowując momenty i obciążenia w przegubach robota na niskim poziomie

Control System for Free-Floating Space Manipulator Based on Nonlinear Model Predictive Control (NMPC)

Manipulator mounted on an unmanned satellite could be used for performing orbital capture maneuver in order to repair satellites or remove space debris from orbit. Use of manipulators for such purposes presents unique challenges, as high level of autonomy is required and the motion of the manipulator influences the position and orientation of the manipulator-equipped satellite. This paper presents a new control system that consists of two modules: trajectory planning module (based on trajectory optimization algorithm) and Model Predictive Controller. Both mod

Nonlinear model predictive control (NMPC) for free-floating space manipulator

Manipulators are widely used in orbital operations, for example, Mobile Servicing System on the International Space Station and Shuttle Remote Manipulator System are used for several years. Such manipulators are operated by astronauts and mounted on large platforms, thus influence of manipulator motion on the state of the platform is not significant. Application of manipulators for capture maneuvers in unmanned On-Orbit Servicing or Active Debris Removal missions requires reliable control algorithms that take into account the free-floating nature of the manipulator-equipped spacecraft. In this paper the possibility of using Nonlinear Model Predictive Control (NMPC) for controlling such manipulators is presented. Numerical simulations for a simplified planar case show effectiveness of the proposed controller

Concept of a 3D-Printed Voronoi Egg-Shaped Habitat for Permanent Lunar Outpost

The article presents a concept of a lunar base that would take advantage of the natural shape of an egg. Several versions of egg-shaped habitat structures characterized by different sizes are presented. Possible locations of habitats both on lunar surface and in craters were discussed. Advantages and disadvantages of particular locations were also pointed out. The proposed in the paper concept of an egg-shaped structure is characterised by a spatial character based on Voronoi diagram and would be implemented using a 3D-printed method. The presented 3D-printed structure was designed to be light and suitable to be covered by lunar soil. As a necessity in the developed concept, in situ resources utilization was addressed in order to generate products using local sources to reduce the number of materials that would be required to be transported from Earth. At the end of the paper, future areas of research and tests are highlighted