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Wyszukujesz frazę "Martins, N." wg kryterium: Autor

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    Tytuł:
    Design of an adaptive fuzzy variable structure compensator for the nonholonomic mobile robot in trajectory tracking task
    Autorzy:
    Begnini, M.
    Bertol, W.
    Martins, N. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/971054.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    nonholonomic mobile robot
    trajectory tracking
    variable structure control
    uncertainties and disturbances
    fuzzy compensator
    Lyapunov theory
    Opis:
    A robust adaptive kinematic control strategy, based on the methodology of variable structure control is considered in this paper. Because the dynamics of mobile robots is subject to uncertainties and disturbances, a fuzzy compensator is adopted to estimate them. In order to minimize the tracking errors and to attenuate the chattering phenomenon, an adaptation law for the fuzzy compensator is obtained by Lyapunov stability theory so as to asymptotically stabilize the control system as well as guarantee the convergence of the tracking errors. In terms of comparison with the boundary layer variable structure controller, simulations and experiments verify the feasibility and effectiveness of the proposed kinematic control strategy for the nonholonomic mobile robots under the incidence of uncertainties and disturbances.
    Źródło:
    Control and Cybernetics; 2018, 47, 3; 239-275
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Corrosion Behavior of FeAl and Fe3Al Based Fe-Al-C Alloys in Sulfuric Acid
    Autorzy:
    Silva, A. P.
    Brito, P. P.
    Martins, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/2134209.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    iron aluminides
    microstructure
    mechanical properties
    corrosion resistance
    Opis:
    Iron aluminides are iron-aluminum alloys that have excellent resistance to oxidation at high temperatures with low density, high resistance/weight ratio and a low manufacturing cost. Due to its characteristics, these alloys are presented as an option to replace stainless steels in certain applications. This works intends report the casting process and subsequent analyses involving microstructure, mechanical properties, and corrosion resistance of two Fe-Al-C alloys (Fe-11wt%Al and Fe-25wt%Al, containing 0.31-0.37%C), which were prepared in an induction furnace and poured in a permanent mold. Samples of these alloys were characterized and presented elevated hardness values of 37 HRC (alloy Fe-11wt%Al) and 49.6HRC (alloy Fe-25wt%Al) and microstructure with aluminides type Fe3Al and FeAl and also carbides type K. The Fe-11wt%Al alloy exhibited superior resistance to uniform corrosion, although both Fe-Al-C alloys exhibited significantly higher corrosion rates compared to a binary iron aluminide in 0.5M H2SO4 containing naturally dissolved oxygen.
    Źródło:
    Archives of Foundry Engineering; 2022, 22, 2; 77--82
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Stiffness control of robot manipulators in the operational space using fuzzy mapping of dynamic functions
    Autorzy:
    Bertol, D. W.
    Barasuol, V.
    Martins, N. A.
    De Pieri, E. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/971046.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    stiffness control
    fuzzy mapping
    robot manipulators
    operational space
    trajectory tracking
    Opis:
    In this paper a stiffness control strategy based on the fuzzy mapped nonlinear terms of the robot manipulator dynamic model is proposed. The proposed stiffness controller is evaluated on a research robot manipulator performing a task in the operational space. Tests attempted to achieve fast motion with reasonable accuracy associated with lower computational load compared to the non-fuzzy approach. The stability analysis is presented to conclude about the mapping error influence and to obtain precondition criteria for the gains adjustment to face the trajectory tracking problem. Simulation results that supported the implementation are presented, followed by experiments and results obtained. These tests are conducted on a robot manipulator with SCARA configuration to illustrate the feasibility of this strategy.
    Źródło:
    Control and Cybernetics; 2013, 42, 3; 639-661
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Trajectory tracking of a wheeled mobile robot with uncertainties and disturbances: proposed adaptive neural control
    Autorzy:
    Martins, N. A.
    Alencar, M.
    Lombardi, W. C.
    Bertol, D. W.
    Pieri, E. R.
    Filho, H. F.
    Powiązania:
    https://bibliotekanauki.pl/articles/971045.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    wheeled mobile robot
    trajectory tracking
    kinematic control
    variable structure control
    dynamic control
    sliding mode theory
    neural networks
    Lyapunov theory
    Opis:
    This paper analyses a trajectory tracking control problem for a wheeled mobile robot, Rusing integration of a kinematic neural controller (KNC) and a torque neural controller (TNC), in which both the kinematic and dynamic models contain uncertainties and disturbances. The proposed adaptive neural controller (PANC) is composed of the KNC and the TNC and is designed with use of a modeling technique of Gaussian radial basis function neural networks (RBFNNs). The KNC is a variable structure controller, based on the sliding mode theory and is applied to compensate for the disturbances of the wheeled mobile robot kinematics. The TNC is an inertia-based controller composed of a dynamic neural controller (DNC) and a robust neural compensator (RNC) applied to compensate for the wheeled mobile robot dynamics, bounded unknown disturbances, and neural network modeling errors. To minimize the problems found in practical implementations of the classical variable structure controllers (VSC) and sliding mode controllers (SMC), and to eliminate the chattering phenomenon, the nonlinear and continuous KNC and RNC of the TNC are applied in lieu of the discontinuous components of the control signals that are present in classical forms. Additionally, the PANC neither requires the knowledge of the wheeled mobile robot kinematics and dynamics nor the timeconsuming training process. Stability analysis, convergence of the tracking errors to zero, and the learning algorithms for the weights are guaranteed based on the Lyapunov method. Simulation results are provided to demonstrate the effectiveness of the proposed approach.
    Źródło:
    Control and Cybernetics; 2015, 44, 1; 47-98
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Implementation and performance of a new multiple objective dynamic routing method for multiexchange networks
    Autorzy:
    Martins, L.
    Craveirinha, J.
    Climaco, J.N.
    Gomez, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/307696.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    dynamic routing
    multiple objective routing
    multiexchange telecommunication network performance
    Opis:
    The paper describes new developments of a multiple objective dynamic routing method (MODR) for circuit-switched networks previously presented, based on the periodic calculation of alternative paths for every node pair by a specialised bi-objective shortest path algorithm (MMRA). A model is presented that enables the numerical calculation of two global network performance parameters, when using MMRA. This model puts in evidence an instability problem in the synchronous path computation model which may lead to solutions with poor global network performance, measured in terms of network mean blocking probability and maximum node-to-node blocking probability. The essential requirements of a heuristic procedure enabling to overcome this problem and select "good" routing solutions in every path updating period, are also discussed.
    Źródło:
    Journal of Telecommunications and Information Technology; 2003, 3; 60-66
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the performance analysis of a heuristic approach dedicated to a multiobjective dynamic routing model
    Autorzy:
    Craveirinha, J.
    Martins, L.
    Climaco, J. N.
    Jorge, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/309018.pdf
    Data publikacji:
    2005
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    multiple criteria analysis
    routing
    heuristics
    telecommunications
    Opis:
    In previous works the features and a complete formulation for circuit-switched networks of a multiple objective dynamic routing method (MODR) of periodic state dependent routing type were presented. The aim of the model is to resolve a very complex network bi-objective dynamic routing problem, by recurring to a heuristic for synchronous path selection enabling to obtain a good compromise solution in terms of two network performance measures. In this paper we present a study on the performance of variants of the MODR heuristic of synchronous path selection by using relaxations of the values previously calculated for the two network objective functions. This study permitted the development of an improved version of the initial heuristic. Also a comparison of the analytical values of the network objective functions obtained with selected variants of the initial heuristic with the corresponding results from a known reference method, the real time network routing (RTNR) method, given by a discrete-event simulator for single-service networks, is presented.
    Źródło:
    Journal of Telecommunications and Information Technology; 2005, 3; 14-23
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new multiple objective dynamic routing method using implied costs
    Autorzy:
    Craveirinha, J.
    Martins, L.
    Antunes, C.H.
    Climaco, J.N.
    Powiązania:
    https://bibliotekanauki.pl/articles/307698.pdf
    Data publikacji:
    2003
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    dynamic routing
    multicriteria decision support systems
    traffic management
    Opis:
    There are advantages in considering the routing problem in integrated communication networks as a multiobjective shortest path problem, having in mind to grasp eventual conflicts and trade-offs among distinct objectives and quality of services (QoS) constraints. On the other hand the utilisation of dynamic routing methods in various types of networks is well known to have significant impact on network performance and cost, namely in overload and failure conditions. This paper presents the detailed formulation of a proposal of a multiple objective dynamic routing method (MODR) of periodic state dependent routing type, enabling to represent distinct QoS related metrics and requirements in a consistent manner. The MODR method present formulation is based on a multiple objective shortest path model with constraints and is prepared to use implied costs as one of the metrics. Alternative paths tor each traffic flow are changed as a function of periodic updates of certain QoS related parameters estimated from real time measurements on the routes and trunks of the network. Such paths are computed by a specialised and efficient variant of a bi-objective shortest path constrained algorithm, developed for the MODR, enabling to incorporate flexible requirements on the QoS metrics. The architecture of the routing system is discussed together with the features of its main modules. An illustrative example of application of the MODR path calculation module to a circuit-switched type network using blocking probability and implied cost as metrics, is also presented, considering different overload conditions.
    Źródło:
    Journal of Telecommunications and Information Technology; 2003, 3; 50-59
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Traffic splitting in MPLS networks - a hierarchical multicriteria approach
    Autorzy:
    Craveirinha, J. M. F.
    Cli'maco, J. C. N.
    Pascoal, M. M. B.
    Martins, L. M. R. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/308582.pdf
    Data publikacji:
    2007
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    multicriterial optimization
    multicriteria shortest paths
    routing telecommunication networks
    Internet/MPLS
    Opis:
    In this paper we address a new hierarchical multicriteria routing model associated with a two-path traffic splitting routing method in MPLS networks whereby the bandwidth required by a given node-to-node traffic flow is divided by two disjoint paths. The model has two levels of objective functions and several constraints. An algorithmic approach is presented for calculating non-dominated solutions and selecting good compromise solutions to this problem. Also a number of computational experiments are presented.
    Źródło:
    Journal of Telecommunications and Information Technology; 2007, 4; 3-10
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Gamma-ray computed tomography SCANNERS for applications in multiphase system COLUMNs
    Autorzy:
    Calvo, W. A. P.
    Hamada, M. M.
    Sprenger, F. E.
    Vasquez, P. A. S.
    Rela, P. R.
    Martins, J. F. T.
    de Matos Pereira, J. C. S.
    Omi, N.
    de Mesquita, C. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/148082.pdf
    Data publikacji:
    2009
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    industrial computed tomography
    multiphase flow systems
    non-destructive testing
    gas absorption column
    industrial process optimization
    packed distillation columns
    scanning systems
    Opis:
    Gamma-ray tomography experiments have been carried out to detect spatial patterns in the porosity, in a 0.27 m diameter packed steel column using a first generation computed tomography (CT) system. The CT scanner consists of a NaI(Tl) detector 5.08 cm in diameter, and an encapsulated 137Cs (3.7 GBq) radioactive source, located opposite to the center of the detector. The detector and the source, mounted on a fixed support and the column, can rotated and dislocate by two stepping motors controlled through a microprocessor. Different sizes of stainless steel Raschig rings (12.6, 37.9 and 76 mm) have been examined. The primary objective of this work is to detect spatial patterns and statistical information on porosity variation in packed distillation columns. Horizontal scans, at different vertical positions of the packed bed were made for each size of Raschig rings. Radial porosity variation within the packed bed has been determined. This study has demonstrated that the porosity and its spatial distribution in a metallic packed column can be measured with adequate spatial resolution using the gamma-ray tomography technique. After validation of this first generation CT, the turntable design to rotate and dislocate the 60Co or 137Cs sealed gamma-ray sources and multidetector array for the third generation industrial computed tomography was also developed.
    Źródło:
    Nukleonika; 2009, 54, 2; 129-133
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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