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Search Results: 1 - 10 of 119079 matches for " T.;Motta "
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An investigation of singularities in robot kinematic chains aiming at building robot calibration models for off-line programming
Motta, J. M. S. T.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2005, DOI: 10.1590/S1678-58782005000200013
Abstract: robot calibration is a term applied to the procedures used in determining actual values that describe the geometric dimensions and mechanical characteristics of a robot or multibody structure. a robot calibration system must consist of appropriate robot modeling techniques, accurate measurement equipment, and reliable model parameter determination methods. for practical improvement of a robot's absolute accuracy, error compensation methods are required that use calibration results. important to robot calibration methods is an accurate kinematic model that has identifiable parameters. this parameterized kinematic model must be complete, continuous and minimal. this work concerns to the implementation of techniques to optimize kinematic models for robot calibration through numerical optimization of the mathematical model. the optimized model is then used to compensate the model errors in an off-line programming system, enhancing significantly the robot kinematic model accuracy. the optimized model can be constructed in an easy and straight operation, through automatic assignment of joint coordinate systems and geometric parameter to the robot links. assignment of coordinate systems by this technique avoids model singularities that usually spoil robot calibration results.
Gest o de qualidade no laboratório clínico
V. T. Motta,J. C. Corrêa,L. R. Motta
Revista Brasileira de Ciências Farmacêuticas , 2004, DOI: 10.1590/s1516-93322004000300024
The evolution of the high-energy cut-off in the X-Ray spectrum of the GX 339-4 across a hard-to-soft transition
S. Motta,T. Belloni,J. Homan
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.15566.x
Abstract: We report on X-ray observations of the black-hole candidate GX 339-4 during its 2006/2007 outburst. The hardness-intensity diagram of all RXTE/PCA data combined shows a q-shaped track similar to that observed in previous outbursts. The evolution through the HID suggests that in the early phase of the outburst the source underwent a sequence of state transitions, from the hard to the soft state, which is supported by our timing analysis. Broadband (4-200 keV) spectra, fitted with an exponentially cutoff powerlaw, show that the hard spectral component steepens during the transition from the hard to the soft state. The high-energy cutoff decreased monotonically from 120 to 60 keV during the brightening of the hard state, but increased again to 100 keV during the softening in the hard intermediate state. In the short-lived soft intermediate state the cutoff energy was ~ 130 keV, but was no longer detected in the soft state. This is one of the first times that the high-energy cut-off has been followed in such detail across several state transitions. We find that in comparison to several other spectral parameters, the cut-off energy changes more rapidly, just like the timing properties. The observed behaviour of the high energy cutoff of GX 339-4 is also similar to that observed with RXTE-INTEGRAL-Swift during the 2005 outburst of GRO J1655-40. These results constitute a valuable reference to be considered when testing theoretical models for the production of the hard component in these systems.
Fast variability as a tracer of accretion regimes in black hole transients
T. Mu?oz-Darias,S. Motta,T. M. Belloni
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17476.x
Abstract: We present the rms-intensity diagram for black hole transients. Using observations taken with the Rossi X-ray timing explorer we study the relation between the root mean square (rms) amplitude of the variability and the net count-rate during the 2002, 2004 and 2007 outbursts of the black hole X-ray binary GX 339-4. We find that the rms-flux relation previously observed during the hard state in X-ray binaries does not hold for the other states, when different relations apply. These relations can be used as a good tracer of the different accretion regimes. We identify the hard, soft and intermediate states in the rms-intensity diagram. Transitions between the different states are seen to produce marked changes in the rms-flux relation. We find that one single component is required to explain the ~ 40 per cent variability observed at low count rates, whereas no or very low variability is associated to the accretion-disc thermal component.
On the outburst evolution of H1743-322: a 2008/2009 comparison
S. Motta,T. Mu?oz-Darias,T. Belloni
Physics , 2010, DOI: 10.1111/j.1365-2966.2010.17246.x
Abstract: We present two observational campaigns performed with the RXTE satellite on the black hole transient H 1743-322. The source was observed in outburst on two separate occasions between October-November 2008 and May-July 2009. We have carried out timing and spectral analysis of the data set, obtaining a complete state classification of all the observations. We find that all the observations are well described by using a spectral model consisting of a disk-blackbody, a powerlaw + reflection + absorption and a gaussian emission component. During the 2009 outburst the system followed the canonical evolution through all the states seen in black hole transients. In the 2008 outburst only the hard states were reached. The early evolution of the spectral parameters is consistent between the two epochs, and it does not provide clues about the subsequent behavior of the source. The variation of the flux associated to the two main spectral components (i.e. disk and powerlaw) allows us to set a lower limit to the orbital inclination of the system of >= 43{\deg}.
X-ray spectral and timing investigations of XTE J1752-223
H. Stiele,T. Munoz-Darias,S. Motta,T. Belloni
Physics , 2011,
Abstract: We report on X-ray monitoring observations of the transient black hole candidate (BHC) XTE J1752-223 with the Rossi X-ray Timing Explorer (RXTE). The source was discovered on 2009 October 23 and during its low/hard state, which lasted for at least 25 days, all timing and spectral properties were similar to those of Cyg X-1 during its canonical hard state. The combined PCA/HEXTE spectra were well fitted by an absorbed broken powerlaw with a high energy cutoff. When RXTE observations were resumed, after an observational gap due to solar constraint, the source was in the hard intermediate state. The evolution through the hardness intensity diagram and the timing properties observed in the power density spectrum suggest that the source crossed all the canonical BHCs states. We discuss the different states and present the results of our spectral and timing investigations.
Theoretical and practical aspects of robot calibration with experimental verification
Ginani, Luciano Selva;Motta, José Maurício S. T.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2011, DOI: 10.1590/S1678-58782011000100003
Abstract: one of the greatest challenges in today's industrial robotics is the development of off-line programming systems that allow drastic reduction in robots' reprogramming time, improving productivity. the article purpose is to pave the way to the construction of generic calibration systems easily adapted to any type of robot, regardless their application, such as modular robots and robot controllers specifically designed for non-standard applications. a computer system was built for developing and implementing a calibration system that involves the joint work of computer and measurement systems. each step of this system's development is presented together with its theoretical basis. with the development of a remote maneuvering system based on abb s3 controller experimental tests have been carried out using an irb2000 robot and a measurement arm (itg romer) with 0.087 mm of position measurement accuracy. the robot model used by its controller was identified and the robot was calibrated and evaluated in different workspaces resulting in an average accuracy improvement from 1.5 mm to 0.3 mm.
Experimental validation of a 3-D vision-based measurement system applied to robot calibration
Motta, J. M. S. T.;McMaster, R. S.;
Journal of the Brazilian Society of Mechanical Sciences , 2002, DOI: 10.1590/S0100-73862002000300011
Abstract: one of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. a large number of robot measurement systems are now available commercially. yet, there is a dearth of systems that are portable, accurate and low cost. in this work a measurement system that can fill this gap in local calibration is presented. the measurement system consists of a single ccd camera mounted on the robot tool flange with a wide angle lens, and uses space resection models to measure the end-effector pose relative to a world coordinate system, considering radial distortions. scale factors and image center are obtained with innovative techniques, making use of a multiview approach. the target plate consists of a grid of white dots impressed on a black photographic paper, and mounted on the sides of a 90-degree angle plate. results show that the achieved average accuracy varies from 0.2mm to 0.4mm, at distances from the target from 600mm to 1000mm respectively, with different camera orientations.
Modeling, optimizing and simulating robot calibration with accuracy improvement
Motta, José Maurício S. T.;Mcmaster, R. S.;
Journal of the Brazilian Society of Mechanical Sciences , 1999, DOI: 10.1590/S0100-73861999000300002
Abstract: this work describes techniques for modeling, optimizing and simulating calibration processes of robots using off-line programming. the identification of geometric parameters of the nominal kinematic model is optimized using techniques of numerical optimization of the mathematical model. the simulation of the actual robot and the measurement system is achieved by introducing random errors representing their physical behavior and its statistical repeatability. an evaluation of the corrected nominal kinematic model brings about a clear perception of the influence of distinct variables involved in the process for a suitable planning, and indicates a considerable accuracy improvement when the optimized model is compared to the non-optimized one.
Phytopatological monitoring of Inonotus rickii and GPS-GIS applications, Rome, Italy
Mazza G,Moriondo M,Motta E,Annesi T
Forest@ , 2008, DOI: -
Abstract: Plant disease management may be improved by collecting, storing, manipulating, analysing and displaying epidemiological information using a Geographic Information System (GIS), a useful tool to evaluate plant disease problems in a spatial context. In this study, GIS analysis was applied along with global positioning systems (GPS) to integrate field data-collected with the spatial distribution of the pathogen Inonotus rickii. This pathogen provokes a decay of sapwood/heartwood and cankers, determining a progressive crown dieback and structural weakness of the trees, therefore increasing risk of branch breaks and tree failures. It is widespread in tropical and subtropical countries and it has already been recorded in many areas in Rome on Acer negundo, Albizia julibrissin, Koelreuteria paniculata, Celtis australis and Platanus x acerifolia. A survey was carried out in different boulevards of A. negundo and A. julibrissin with the aim of evaluating disease symptoms such as sparse foliage, dead twigs and branches, wood decay and presence of fungal structures. In this survey, I. rickii was recorded also on Robinia pseudoacacia, which is a new host. The study allowed to obtain thematic maps showing the spatial distribution of all infected trees, as well as the presence of anamorph and/or teleomorph structures of the fungus. Moreover, a map representing the incidence of the pathogen in different boulevards was obtained. The usefulness of GIS analysis in studies aimed to support and refine management strategies for disease control in urban trees is discussed.
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