Robot trajectory planning using OLP and structured light 3D machine vision

This paper proposes a new methodology for robotic offline programming (OLP) addressing the issue of automatic program generation directly from 3D CAD models and verification through online 3D reconstruction. Limitations of current OLP include manufacturing tolerances between CAD and workpieces and inaccuracies in workpiece placement and modelled work cell. These issues are addressed and demonstrated through surface scanning, registration, and global and local error estimation. The method allows the robot to adjust the welding path designed from the CAD model to the actual workpiece. Alternatively, for non-repetitive tasks and where a CAD model is not available, it is possible to interactively define the path online over the scanned surface

An intelligent real time 3D vision system for robotic welding tasks

MARWIN is a top-level robot control system that has been designed for automatic robot welding tasks. It extracts welding parameters and calculates robot trajectories directly from CAD models which are then verified by real-time 3D scanning and registration. MARWIN's 3D computer vision provides a user-centred robot environment in which a task is specified by the user by simply confirming and/or adjusting suggested parameters and welding sequences. The focus of this paper is on describing a mathematical formulation for fast 3D reconstruction using structured light together with the mechanical design and testing of the 3D vision system and show how such technologies can be exploited in robot welding tasks

Extinction controlled adaptive phase-mask coronagraph

Context. Phase-mask coronagraphy is advantageous in terms of inner working angle and discovery space. It is however still plagued by drawbacks such as sensitivity to tip-tilt errors and chromatism. A nulling stellar coronagraph based on the adaptive phase-mask concept using polarization interferometry is presented in this paper. Aims. Our concept aims at dynamically and achromatically optimizing the nulling efficiency of the coronagraph, making it more immune to fast low-order aberrations (tip-tilt errors, focus, ...). Methods. We performed numerical simulations to demonstrate the value of the proposed method. The active control system will correct for the detrimental effects of image instabilities on the destructive interference. The mask adaptability both in size, phase and amplitude also compensates for manufacturing errors of the mask itself, and potentially for chromatic effects. Liquid-crystal properties are used to provide variable transmission of an annulus around the phase mask, but also to achieve the achromatic {\pi} phase shift in the core of the PSF by rotating the polarization by 180 degrees. Results. We developed a new concept and showed its practical advantages using numerical simulations. This new adaptive implementation of the phase-mask coronagraph could advantageously be used on current and next-generation adaptive optics systems, enabling small inner working angles without compromising contrast.Comment: 7 pages, 6 figure

Current Trends in Research on Behavioral Development in the Federal Republic of Germany

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The state and perspective of developmental psychology in the Federal Republic of Germany is analyzed with respect to (a) professional education, (b) resources for research, (c) actual fields of research, and (d) media of professional communication. Current trends of research were investigated by a combination of multi-category content analyses of national (and international) journal publications, and survey data with respect to research interests and planned studies of German developmentalists. Included among the main trends are: (a) an increasing emphasis on longitudinal studies, sometimes combined with short-term interventions; (b) a growing interest in studies representative of natural conditions; (c) although still relatively rare, some of the studies employ a developmental perspective not only for persons but also for relations between persons and changes in environmental factors; (d) areas of heaviest concentration are cognitive development, social as well as personality development, with a trend towards more molar concepts of action-regulating systems instead of small-range models; (e) a growing number of studies on youth and adolescence; (f) new efforts towards a systematic elaboration of the application perspectives of developmental psychology. Professional education as well as research in developmental psychology was highly influenced by a 6-year program from the Volkswagen foundation. As a result, one could observe an increase in quantity as well as an improvement in quality both of teaching and research. Two further steps are now being planned: (a) a post-graduate program, the first one in German psychology, will start in 1983; (b) further efforts to broaden symmetric international communication and cooperation will be undertaken

Leading in common: principal perspectives on CCSS implementation

The purpose of this dissertation is to explore the experiences of principals leading implementation of Common Core State Standards (CCSS) in North Carolina. In a dynamic time in school leadership in which initiatives are introduced at a rapid pace, it is critical to support school leaders in navigating the change process. Implementation of CCSS in North Carolina, as well as in a number of states throughout the nation, provides an opportunity to explore the leadership of a change initiative aimed at instructional improvement, with the potential to inform the work of principals moving forward. Their successes and challenges are considered through the lens of a conceptual framework developed based on relevant change research and divided into quadrants including Setting the Stage for Change, Aligning Resources in Support of Change, Monitoring and Evaluating, and Refocusing and Sustaining. In an effort to gain greater understanding of the challenges of leading change, specifically CCSS implementation, twelve principals were interviewed using a semi-structured protocol, and their experiences were considered in light of an evolving conceptual framework. This framework, accompanied by the voices of principals as they describe the challenges and successes of leading CCSS implementation, are provided in an attempt to better inform school leaders as they move forward with implementation of change initiatives aimed at instructional improvement

Extinction controlled Adaptive Mask Coronagraph Lyot and Phase Mask dual concept for wide extinction area

A dual coronagraph based on the Adaptive Mask concept is presented in this paper. A Lyot coronagraph with a variable diameter occulting disk and a nulling stellar coronagraph based on the Adaptive Phase Mask concept using polarization interferometry are presented in this work. Observations on sky and numerical simulations show the usefulness of the proposed method to optimize the nulling efficiency of the coronagraphs. In the case of the phase mask, the active control system will correct for the detrimental effects of image instabilities on the destructive interference (low-order aberrations such as tip-tilt and focus). The phase mask adaptability both in size, phase and amplitude also compensate for manufacturing errors of the mask itself, and potentially for chromatic effects. Liquid-crystal properties are used to provide variable transmission of an annulus around the phase mask, but also to achieve the achromatic π phase shift in the core of the PSF by rotating the polarization by 180°.A compressed mercury (Hg) drop is used as an occulting disk for the Lyot mask, its size control offers an adaptation to the seeing conditions and provides an optimization of the Tip-tilt correction

Caractérisation par PIV de la couche limite d'un jet chaud impactant une paroi plane.

International audienceLes matériaux composites tendent à être largement utilisés dans le secteur de l’aéronautique et doivent répondre à des exigences strictes en termes de sécurité incendie. En effet, en situation d’incendie, ces matériaux constitués de matrice polymère et de fibres de carbone peuvent se dégrader sous l’effet d’une flamme. Le travail présenté a pour objectif d’étudier les transferts de chaleur entre une flamme et un matériau composite. Les phénomènes de convection jouent un rôle clef et nécessitent une description fine des champs de vitesse. La Vélocimétrie par Image de Particules (PIV) a donc été utilisée pour mesurer les champs de vitesses en proche paroi. Cependant, la nature de l’écoulement engendre des difficultés pour la mesure de vitesse par PIV. En particulier, la paroi en composite génère une forte réflexion et se déforme sous l’effet de la dégradation thermique. Ainsi les mesures de vitesses ont été effectuées dans plusieurs configurations : avec paroi en acier (inerte) et avec paroi en composite (réactive). Les mesures effectuées montrent que les profils de vitesses sont les même dans les deux cas, indiquant que la perturbation de l’écoulement par la paroi réactive est donc négligeable. Dans les deux configurations, les champs de vitesses obtenus vérifient la théorie pour les jets impactants avec une croissance linéaire des composantes parallèle et perpendiculaire de vitesse dans leurs directions respectives. Comme le prévoie la théorie, une couche limite visqueuse d’épaisseur constante se forme le long de la paroi. En revanche, un écart à la solution analytique est observé pour le rapport entre les composantes parallèle et perpendiculaire de la vitesse. La température élevée du jet et le taux de turbulence de l’ordre de 20% pourraient expliquer cette différence

Towards a Better Understanding of OPD Limitations for Higher Sensitivity and Contrast at the VLTI

Precise control of the optical path differences (OPD) in the Very Large Telescope Interferometer (VLTI) was critical for the characterization of the black hole at the center of our Galaxy - leading to the 2020 Nobel prize in physics. There is now significant effort to push these OPD limits even further, in-particular achieving 100nm OPD RMS on the 8m unit telescopes (UT's) to allow higher contrast and sensitivity at the VLTI. This work calculated the theoretical atmospheric OPD limit of the VLTI as 5nm and 15nm RMS, with current levels around 200nm and 100nm RMS for the UT and 1.8m auxillary telescopes (AT's) respectively, when using bright targets in good atmospheric conditions. We find experimental evidence for the $f^{-17/3}$ power law theoretically predicted from the effect of telescope filtering in the case of the ATs which is not currently observed for the UT's. Fitting a series of vibrating mirrors modelled as dampened harmonic oscillators, we were able to model the UT OPD PSD of the gravity fringe tracker to $<1nm/\sqrt{Hz}$ RMSE up to 100Hz, which could adequately explain a hidden $f^{-17/3}$ power law on the UTs. Vibration frequencies in the range of 60-90Hz and also 40-50Hz were found to generally dominate the closed loop OPD residuals of Gravity. Cross correlating accelerometer with Gravity data, it was found that strong contributions in the 40-50Hz range are coming from the M1-M3 mirrors, while a significant portion of power from the 60-100Hz contributions are likely coming from between the M4-M10. From the vibrating mirror model it was shown that achieving sub 100nm OPD RMS for particular baselines (that have OPD$\sim$200nm RMS) required removing nearly all vibration sources below 100Hz

First results from fringe tracking with the PRIMA fringe sensor unit

The fringe sensor unit (FSU) is the central element of the phase referenced imaging and micro-arcsecond astrometry (PRIMA) dual-feed facility for the Very Large Telescope interferometer (VLTI). It has been installed at the Paranal observatory in August 2008 and is undergoing commissioning and preparation for science operation. Commissioning observations began shortly after installation and first results include the demonstration of spatially encoded fringe sensing and the increase in VLTI limiting magnitude for fringe tracking. However, difficulties have been encountered because the FSU does not incorporate real-time photometric correction and its fringe encoding depends on polarisation. These factors affect the control signals, especially their linearity, and can disturb the tracking control loop. To account for this, additional calibration and characterisation efforts are required. We outline the instrument concept and give an overview of the commissioning results obtained so far. We describe the effects of photometric variations and beam-train polarisation on the instrument operation and propose possible solutions. Finally, we update on the current status in view of the start of astrometric science operation with PRIMA.Comment: 12 pages, 11 figures, SPIE 2010 conference proceeding

Preferências estabelecidas e personalidade: uma abordagem comportamental

TCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.Este estudo tem o objetivo de contribuir para o entendimento da dissonância cognitiva que surge quando preferências estabelecidas com relação a produtos são alteradas à medida em que os consumidores se deparam com informação mais completa do que a existente na escolha inicial. Buscou-se verificar a probabilidade de abandono da escolha preliminar na amostra de consumidores analisada. A contribuição se refere à mediação da habilidade cognitiva e da personalidade nessas decisões. No experimento, os participantes com fraca preferência na escolha inicial – e baixa habilidade cognitiva, além de baixos escores em traços de honestidade-humildade, extroversão e conscienciosidade – tendem a abandonar a escolha inicial. Já os participantes com escores mais altos em todas essas características tendem a não abandonar a sua escolha preliminar