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    Wyświetlanie 1-13 z 13
    Tytuł:
    Professor Andrzej Szczepan Białynicki-Birula (1935–2021)
    Profesor Andrzej Szczepan Białynicki-Birula (1935–2021)
    Autorzy:
    Jackowski, Stefan
    Powiązania:
    https://bibliotekanauki.pl/articles/2121379.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Andrzej Białynicki-Birula
    algebraic geometry
    algebraic topology
    University of Warsaw
    Opis:
    Andrzej Białynicki-Birula, Professor at the University of Warsaw died on April 19, 2021 at the age of 85. He was an outstanding mathematician, who made impor- tant contributions to algebra and algebraic geometry. He published many im- portant articles in most prestigious journals such that Annals of Mathematics, Inventiones mathematicae, Topology, American Journal of Mathematics. Profes- sor Białynicki graduated from the University of Warsaw and obtained Ph.D. from the University of California at Berkeley in 1960. After his return to Poland he initiated and played a major role in modernization of research and university curricula in a broad spectrum of mathematical disciplines related to algebra. He has published several textbooks on linear algebra, algebra, algebraic geometry and cryptography, which are currently used at the University of Warsaw and ma- ny other Polish universities. Professor Białynicki-Birula served as the dean of the Faculty of Mathematics, Informatics and Mechanics (1977–1981) and as the vice-rector of the University of Warsaw (1985–1987). He was an ordinary mem- ber of the Polish Academy of Sciences, and a member of the Academia Europea. In recognition of his achievements Professor Białynicki-Birula received several prizes and distinctions, among them the Officers Cross of the Order Polonia Res- tituta. Professor Białynicki-Birula was also an art collector, particularly interested in a gothic sculpture, on which he was an expert. In his summerhouse near Belo- russian border he was renovating and collecting ethnographic objects related to everyday life and work of peasants. He left a wife, Magdalena Borsuk-Białynicka, a professor of palaeontology, two daughters, a son and 11 grandchildren.
    Źródło:
    Nauka; 2021, 4; 187-199
    1231-8515
    Pojawia się w:
    Nauka
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Algebraic Riccati equation based Q and R matrices selection algorithm for optimal LQR applied to tracking control of 3rd order magnetic levitation system
    Autorzy:
    Kumar E, V.
    Jerome, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/140600.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    algebraic Riccatti equation
    linear quadratic regulator
    magnetic levitation
    system
    weighting matrices
    command following
    cost function
    Opis:
    This paper presents an analytical approach for solving the weighting matrices selection problem of a linear quadratic regulator (LQR) for the trajectory tracking application of a magnetic levitation system. One of the challenging problems in the design of LQR for tracking applications is the choice of Q and R matrices. Conventionally, the weights of a LQR controller are chosen based on a trial and error approach to determine the optimum state feedback controller gains. However, it is often time consuming and tedious to tune the controller gains via a trial and error method. To address this problem, by utilizing the relation between the algebraic Riccati equation (ARE) and the Lagrangian optimization principle, an analytical methodology for selecting the elements of Q and R matrices has been formulated. The novelty of the methodology is the emphasis on the synthesis of time domain design specifications for the formulation of the cost function of LQR, which directly translates the system requirement into a cost function so that the optimal performance can be obtained via a systematic approach. The efficacy of the proposed methodology is tested on the benchmark Quanser magnetic levitation system and a detailed simulation and experimental results are presented. Experimental results prove that the proposed methodology not only provides a systematic way of selecting the weighting matrices but also significantly improves the tracking performance of the system.
    Źródło:
    Archives of Electrical Engineering; 2016, 65, 1; 151-168
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Impact of control representations on efficiency of local nonholonomic motion planning
    Autorzy:
    Duleba, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/202269.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    motion planning
    nonholonomic systems
    Lie-algebraic methods
    controllability
    optimization
    Opis:
    In this paper various control representations selected from a family of harmonic controls were examined for the task of locally optimal motion planning of nonholonomic systems. To avoid dependence of results either on a particular system or a current point in a state space, considerations were carried out in a sub-space of a formal Lie algebra associated with a family of controlled systems. Analytical and simulation results are presented for two inputs and three dimensional state space and some hints for higher dimensional state spaces were given. Results of the paper are important for designers of motion planning algorithms not only to preserve controllability of the systems but also to optimize their motion.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2011, 59, 2; 213-218
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    State estimate based control design using the unified algebraic approach
    Autorzy:
    Filasova, A.
    Krokavec, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/229891.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    state feedback
    linear estimation
    linear matrix inequalities
    constrains
    Opis:
    The LMI based method for the control with the state estimate, subject to the input variable constraints in the state feedback control of the linear MIMO systems, is presented in the paper. For this problem are obtained the state feedback as well as the estimator gain matrices that capture the required stability by solving the linear matrix inequalities formulated in the sense of the unified algebraic approach. The method is particularly effective when the input variable constraints and the system output are of interest.
    Źródło:
    Archives of Control Sciences; 2010, 20, 1; 5-18
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Single-Frame Attitude Determination Methods for Nanosatellites
    Autorzy:
    Cilden Guler, D.
    Conguroglu, E. S.
    Hajiyev, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/221643.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    attitude determination
    single-frame methods
    algebraic method
    covariance analysis
    vector observation
    Opis:
    Single-frame methods of determining the attitude of a nanosatellite are compared in this study. The methods selected for comparison are: Single Value Decomposition (SVD), q method, Quaternion ESTimator (QUEST), Fast Optimal Attitude Matrix (FOAM) − all solving optimally the Wahba’s problem, and the algebraic method using only two vector measurements. For proper comparison, two sensors are chosen for the vector observations on-board: magnetometer and Sun sensors. Covariance results obtained as a result of using those methods have a critical importance for a non-traditional attitude estimation approach; therefore, the variance calculations are also presented. The examined methods are compared with respect to their root mean square (RMS) error and variance results. Also, some recommendations are given.
    Źródło:
    Metrology and Measurement Systems; 2017, 24, 2; 313-324
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Performance analysis of regularization algorithms used for image reconstruction in computed tomography
    Autorzy:
    Wysoczański, D.
    Mroczka, J.
    Polak, A. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/201356.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    computed tomography
    image reconstruction
    algebraic approach
    regularization methods
    Opis:
    Computed tomography is one of the most significant diagnostic techniques in medicine. This work is focused on hard-field imaging, where signals take a form of straight rays and the reconstructed image can be presented as a matrix with unknown pixels. Algebraic methods for direct computation of the image have not been used in practice because of the scale of the problem and numerical errors appearing in the solution. The aim of this work was to analyse the performance of direct algebraic algorithms for tomographic image reconstruction including regularisation mechanism such as: generalised regularisation, Tikhonov regularisation, Twomey regularisation and ridge regression (RR), as well as comparing the results with the filtered backprojection (FBP) as the reference method. The performed analyses demonstrated that the regularised algebraic methods are more accurate than the commonly used FBP, and RR appeared the most precise among them. Additionally it was shown that the invariant system matrix (inverted during calculations) can be easily determined by solving the forward problem. Finally, potential directions of further research have been pointed out.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2013, 61, 2; 467-474
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Algebraic multigrid preconditioning for iterative eigensolvers
    Algebraiczne wielosiatkowe uwarunkowanie iteracyjnych procedur dla zagadnień własnych
    Autorzy:
    Krüger, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/224225.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    dynamika pojazdów
    teoria konstrukcji
    zagadnienia brzegowe
    vehicle dynamics
    design theory
    boundry-value problems
    Opis:
    The paper presents a comparative study of iterative solvers for eigen- problems, which arise e.g. in solid mechanics or structural analysis. We consider problems obtained by discretization of elliptic and self-adjoint partial differential operators. Typically, only a few of the smallest eigen- values of these problems are to be computed. We discuss various gradient based preconditioned eigensolvers which make use of algebraic multigrid preconditioning. We present algorithms together with numerical results. Performance characteristics are derived by a comparison with the solution of test problems. We show that known advantages of algebraic multigrid preconditioning (e.g. for boundary-value problems with large jumps in the coefficients) transfer to the eigensolvers considered here.
    Algebraiczne wielosiatkowe uwarunkowanie iteracyjnych procedur dla zagadnień własnych. Praca przedstawia przegląd metod iteracyjnych dla zagadnień własnych, z jakimi mamy do czynienie w zadaniach analizy dynamiki pojazdów, lub w teorii konstrukcji. Badano zagadnienia własne dla macierzy otrzymywanych dla przypadków dyskretyzacji eliptycznych samosprzężonych operatorów różniczkowych. Częstokroć tylko kilka najmniejszych wartości własnych takich macierzy jest potrzebnych. W praktyce analizujemy rozmaite metody i uwarunkowania oparte na podejściu gradientowym, które wykorzystują algebraiczne techniki wielosiatkowe. W pracy przedstawione są zarówno algorytmy, jak i wyniki numeryczne otrzymane z testów porównujących różne metody. Wykazano, że znane zalety algebraicznego uwarunkowania wielosiatkowego (np. w przypadku zagadnień brzegowych z dużymi skokami współczynników) przenoszą się do zagadnień własnych rozpatrywanych w tej pracy.
    Źródło:
    Archives of Transport; 2010, 22, 1; 97-108
    0866-9546
    2300-8830
    Pojawia się w:
    Archives of Transport
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical error bound of optimal control for homogeneous linear systems
    Autorzy:
    Daraghmeh, Adnan
    Qatanani, Naji
    Powiązania:
    https://bibliotekanauki.pl/articles/229410.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    time-invariant systems
    quadratic cost function
    linear quadratic regulator
    algebraic Riccati equation
    Hamiltonian function
    L2 norm
    Opis:
    In this article we focus on the balanced truncation linear quadratic regulator (LQR) with constrained states and inputs. For closed-loop, we want to use the LQR to find an optimal control that minimizes the objective function which called "the quadratic cost function” with respect to the constraints on the states and the control input. In order to do that we have used formal asymptotes for the Pontryagin maximum principle (PMP) and we introduce an approach using the so called The Hamiltonian Function and the underlying algebraic Riccati equation. The theoretical results are validated numerically to show that the model order reduction based on open-loop balancing can also give good closed-loop performance.
    Źródło:
    Archives of Control Sciences; 2019, 29, 2; 323-337
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new algebraic LQR weight selection algorithm for tracking control of 2 DoF torsion system
    Autorzy:
    Elumalai, V. K.
    Subramanian, R. G.
    Powiązania:
    https://bibliotekanauki.pl/articles/140978.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ARE
    high gain observer
    LQR
    Q and R matrices
    2 DoF torsion system
    trajectory tacking
    Opis:
    This paper proposes a novel linear quadratic regulator (LQR) weight selection algorithm by synthesizing the algebraic Riccati equation (ARE) with the Lagrange multiplier method for command following applications of a 2 degree of freedom (DoF) torsion system. The optimal performance of LQR greatly depends on the elements of weighting matrices Q and R. However, normally these weighting matrices are chosen by a trial and error approach which is not only time consuming but cumbersome. Hence, to address this issue, blending the design criteria in time domain with the ARE, we put forward an algebraic weight selection algorithm, which makes the LQR design both simple and modular. Moreover, to estimate the velocity of a servo angle, a high gain observer (HGO) is designed and integrated with the LQR control scheme. The efficacy of the proposed control scheme is tested on a benchmark 2 DoF torsion system for a trajectory tracking application. Both the steady state and dynamic characteristics of the proposed controller are assessed. The experimental results accentuate that the proposed HGO based LQR scheme can guarantee the system to attain the design requirements with minimal vibrations and tracking errors.
    Źródło:
    Archives of Electrical Engineering; 2017, 66, 1; 55-75
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Distributed controllability of one-dimensional heat equation in unbounded domains: The Greens function approach
    Autorzy:
    Khurshudyan, Asatur Zh.
    Powiązania:
    https://bibliotekanauki.pl/articles/229527.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    lack of controllability
    exact controllability
    approximate controllability
    nullcontrollability
    Green’s function
    heuristic method
    infinite system of algebraic equations
    regularity
    fully regularity
    Opis:
    We derive exact and approximate controllability conditions for the linear one-dimensional heat equation in an infinite and a semi-infinite domains. The control is carried out by means of the time-dependent intensity of a point heat source localized at an internal (finite) point of the domain. By the Green’s function approach and the method of heuristic determination of resolving controls, exact controllability analysis is reduced to an infinite system of linear algebraic equations, the regularity of which is sufficient for the existence of exactly resolvable controls. In the case of a semi-infinite domain, as the source approaches the boundary, a lack of L2-null-controllability occurs, which is observed earlier by Micu and Zuazua. On the other hand, in the case of infinite domain, sufficient conditions for the regularity of the reduced infinite system of equations are derived in terms of control time, initial and terminal temperatures. A sufficient condition on the control time, heat source concentration point and initial and terminal temperatures is derived for the existence of approximately resolving controls. In the particular case of a semi-infinite domain when the heat source approaches the boundary, a sufficient condition on the control time and initial temperature providing approximate controllability with required precision is derived.
    Źródło:
    Archives of Control Sciences; 2019, 29, 1; 57-71
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Novel solutions on model-based and model-free robotic-assisted ankle rehabilitation
    Autorzy:
    Arceo, Juan Carlos
    Alvarez, Jorge
    Armenta, Carlos
    Lauber, Jimmy
    Cremoux, Sylvian
    Simoneau-Buessinger, Emilie
    Bernal, Miguel
    Powiązania:
    https://bibliotekanauki.pl/articles/1409032.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    active disturbance rejection
    computed torque control
    differential algebraic equations
    parallel rehabilitation robot
    real-time implementation
    system identification
    Opis:
    In this report, ankle rehabilitation routines currently approved by physicians are implemented via novel control algorithms on a recently appeared robotic device known as the motoBOTTE. The physician specifications for gait cycles are translated into robotic trajectories whose tracking is performed twofold depending on the availability of a model: (1) if obtained via the Euler-Lagrange approach along with identification of unknown plant parameters, a new computed-torque control law is proposed; it takes into account the parallel-robot characteristics; (2) if not available, a variation of the active disturbance rejection control technique whose parameters need to be tuned, is employed. A detailed discussion on the advantages and disadvantages of the model-based and model-free results, from the continuous-time simulation to the discrete-time implementation, is included.
    Źródło:
    Archives of Control Sciences; 2021, 31, 1; 5-27
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Construction of Generalized Rademacher Functions in Terms of Ternary Logic : Solving the Problem of Visibility of Using Galois Fields for Digital Signal Processing
    Autorzy:
    Vitulyova, Elizaveta S.
    Matrassulova, Dinara K.
    Suleimenov, Ibragim E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2055235.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    digital signal processing
    non-binary Galois fields
    fourier transform
    rademacher functions
    walsh function
    multivalued logic
    visibility problem
    algebraic extensions
    ternary representation of number
    Opis:
    Generalized Rademacher functions, constructed as a sequence of elements of Galois fields are intended to find the spectral representation of signals with levels. These functions form a complete basis on the interval corresponding to -1 discrete time intervals and for passing into the classical Rademacher functions. The advantage of such spectra obtained using Galois Fields Fourier Transform is that the range of variation of the spectrum amplitudes remains the same as the range of variation of the original signal, which is modeled on discrete time functions taking values in the Galois field.
    Źródło:
    International Journal of Electronics and Telecommunications; 2022, 68, 2; 237--244
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On an episode in academic contacts of Jacek Hawranek and Jan Zygmunt with Professor Bogusław Wolniewicz
    O pewnym epizodzie w kontaktach naukowych Jacka Hawranka i Jana Zygmunta z Profesorem Bogusławem Wolniewiczem
    Autorzy:
    Zygmunt, Jan
    Powiązania:
    https://bibliotekanauki.pl/articles/2097360.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    semilattice
    formal ontology of situations
    algebraic logic
    history of Polish logic
    Bogusław Wolniewicz
    półkrata
    formalna ontologia sytuacji
    logika algebraiczna
    historia logiki polskiej
    Opis:
    W eseju przedstawione zostały wybrane kontakty naukowe Jacka Hawranka i Jana Zygmunta z Profesorem Bogusławem Wolniewiczem w okresie od końca lat osiemdziesiątych XX w. do początku XXI w. Kontakty dotyczyły algebraicznych aspektów ontologii sytuacji, a od pewnego momentu – jednego tylko pytania sformułowanego w nocie A question about join-semilattices (Wolniewicz 1990). Esej streszcza dyskusję naukową między B. Wolniewiczem a J. Hawrankiem i J. Zygmuntem, w rezultacie której powstał artykuł Wokół pewnego zagadnienia z dziedziny półkrat górnych z jednością (Hawranek, Zygmunt 1993), zawierający próbę odpowiedzi na pytanie Wolniewicza. Artykuł Hawranka i Zygmunta jest niżej przedrukowany, a niniejszy esej jest też pomyślany jako wstęp historyczno-analityczny do jego lektury. Historia kontaktów: Wolniewicz – Hawranek & Zygmunt została ukazana za pomocą zachowanej korespondencji, która jest dość obficie cytowana. W listach Profesor Wolniewicz jawi się jako badacz-pasjonat, otwarty na dyskusję, gotowy do dzielenia się z innymi swoimi trudnościami i sukcesami badawczymi.
    Źródło:
    Przegląd Filozoficzny. Nowa Seria; 2018, 3; 149-162
    1230-1493
    Pojawia się w:
    Przegląd Filozoficzny. Nowa Seria
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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