Station spatiale

Résumé

vignette|Extérieur de la Station spatiale internationale en novembre 2009. Une station spatiale est une installation en orbite ou déposée sur un astre, habitée par un équipage humain pendant une période prolongée, ne disposant pas de moyens de propulsion autonomes ou ne disposant que de moyens de propulsion réduits. Jusqu'à présent, seules des stations spatiales destinées à être en orbite terrestre basse ont été construites. Elles sont désignées comme « stations orbitales ». Les stations spatiales sont conçues pour rester en orbite de quelques semaines à plusieurs années. Les seules stations actuellement en activité sont la Station spatiale internationale et la Station spatiale chinoise en voie d'achèvement. Les stations précédentes étaient celles des programmes soviétiques Almaz, Saliout et Mir, la station spatiale américaine Skylab ainsi que les stations chinoises Tiangong 1 et Tiangong 2. À l'avenir, plusieurs stations devraient voir le jour telle la Lunar Orbital Platform-Gatewa

Source officielle

https://fr.wikipedia.org/wiki/Station_spatiale

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Feasibility Study and Preliminary Design of Lunar Reconnaissance Drone

Jean-Paul Richard Kneib, Thomas Pfeiffer, David Rodriguez Martinez, Erik Uythoven

With orbiting stations and ground bases planned to be built, we are yet to master the ability to explore long term and long range over areas of the Moon often characterised by an extreme topography, dauntingly low temperatures, and wedged with what are known as Permanently Shadowed Regions (PSRs). This represents significant challenges for traditional ground exploration approaches, often relying on individual, limited-range, slow, wheeled rovers. Precise knowledge about the terrain for an optimised route planning is crucial and often relies on limited-resolution satellite data from lunar orbiters, data that are even more limited in PSRs. The need for a long-range yet simple and lightweight scouting method is becoming more and more apparent. The goal of this project is to study the feasibility of a compact, lightweight, and versatile lunar reconnaissance drone that can be quickly deployed and refuelled from a ground vehicle or a rover. The drone will be capable of producing high-resolution maps (~10cm/px) that can be used to optimise mission planning and assist robotic assets on the ground. This innovative mission design was developed using established Systems Engineering tools and approaches. It highlights the main challenges of such a system and sets the baseline for future developments.

2022

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A global approach to the problem of model-based control of fast parallel robots is proposed in this work. Fundamental differences between the well-known serial arms and parallel manipulators are first explained. A formalism inspired from Denavit-Hartenberg's makes it possible to parametrize any parallel manipulator by handling it as two tree robots connected through six standard links. Then, it is shown that kinematics and dynamics modeling is greatly simplified when the robot's state is represented both by the variables associated to the actuated joints and the variables specifying the end-effector's position in operational space. The inverse dynamics model of any parallel manipulator can then be put under a standard form called "in the two spaces". A Newton-Euler based algorithm is proposed for the real-time computation of the model in the two spaces its complexity is shown not to be much larger than for serial arms. Through Lagrangian mechanics, the model in the two spaces allows analysis of the robot's dynamics properties, such as passivity. These properties are shown to be equivalent to those of serial arms, except that parallel robots offer good performances only in a restricted workspace in which their Jacobian matrix remains bounded. Various control strategies for the trajectory tracking problem for fast robots are then examined. The advantages of model-based approaches combined with robust feedback laws in operational space are described. It is shown that a control loop in operational space requires less computations than in joint space for a parallel robot. Moreover, such a scheme can be very efficiently be implemented on a multiprocessor control unit that exploits the intrinsically parallel and pipeline structure of the required algorithms. Finally, the proposed approach is applied to the Delta parallel manipulator. A systematic approach leads to the kinematics and dynamics models of this robot, which are expressed under a very compact form. The analysis of the Delta's Jacobian matrix as well as some simulation results reveal the advantages and weak points of this manipulator. The implementation of a model-based control law for the Delta on a control unit with four Transputers is described. Some results obtained on a Delta with a crank belt reduction are presented and discussed.

EPFL1994

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This dissertation presents the results concerning the development of an innovative high spectral resolution waveguide spectrometer, from the concept to the prototype demonstration and the test results. The main innovative aspects of this instrument are the enhanced throughput and the large spectral bandwidth in a static design without mechanism. These innovations are based on the customized pattern of nano-samplers fabricated on the surface of a planar waveguide, which allow enhancing the throughput and to increase the measurement points of the interferogram necessary for increasing the spectral bandwidth in a static way. On the other hand, the propagation in the unconfined direction of the planar waveguide is controlled using an adapted front-end optics to maintain the superposition of forwarding and reflected beams to form the interferogram under the nano-samplers. Polymeric- and silicon oxynitride-based planar waveguides were manufactured, evaluated and tested for studying mode profile in planar waveguides. The nano-samplers are gold nanodisks of few tens of nanometers in diameter and thickness, optimized for sampling the visible light coupled in the waveguide module of the spectrometer. A waveguide spectrometer prototype is made in silicon oxynitride/silicon dioxide technology and characterized in visible range at 633 and 685 nm using stable monochromatic laser sources. This waveguide spectrometer shows a nominal bandwidth of 256 nm thanks to a custom pattern of nanodisks providing 0.25 ÎŒm sampling interval at central wavelength of 633 nm. The targeted prototype in the near future is a highly integrated spectrometer, with an approximate footprint of a few cubic millimeters, excluding the volume required by the front-end optics and the detector electronics. This new type of instrument can be adapted for various spectral ranges where the material for the waveguide, the nano-samplers and the detectors are available and compatible (from ultraviolet to mid-infrared). This instrument has the potential to be used for numbers of space applications, for instance for the applications where the sample is in a close proximity to the spectrometer (e.g. mineralogy from a rover or active gas detection in a capsule or space station), or in remote sensing applications (e.g. atmospheric observations from a satellite). In addition, the principle idea is to group several of such spectrometers to allow hyperspectral imaging: a 1D array of spectrometers to form an acquisition line to image with lateral scanning, heading towards a full cube of spectrometers in a 2D image acquisition scheme to probe directly a complete scene (the concept of "FPAS" - focal plane array spectrometer). This technology is also adaptable for vast commercial applications in tele-surveillance, optical metrology, genomics and medical domain. At the system level, the full instrument optimization is taken into account in this dissertation, including front-end optics and the detector. Different subsystems are evaluated, developed and tested in order to integrate and demonstrate a complete prototype.

EPFL2016

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EPFL2016

EPFL1994