Przeglądaj wg Autor "Orlowski, Przemyslaw"

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  • Miniatura
    PozycjaOpen Access
    Comparison of frequency domain methods for discrete-time, linear time-varying system with invariant eigenvalues
    (International Society for Advanced Research, 2007-10) Orlowski, Przemyslaw; Institute of Control Engineering Szczecin University of Technology
    The main aim of this paper is to compare and evaluate frequency methods applicable for discrete-time (DT) linear time-varying (LTV) systems, in particular: two-dimensional (time, frequency) transfer function (2D-TF), timeaveraged 2D-TF and approximated Bode diagrams calculated using SVD-DFT approach and power spectral density (PSD) properties. The main evaluation criteria is possible applicability to feedback system stability analysis. The paper begins from short theoretical background of frequency methods applicable for LTV systems. Further properties of these methods are compared and discussed on the basis of particular case of parameter controlled switching DT LTV system.
  • Miniatura
    PozycjaOpen Access
    An extension of Nyquist feedback stability for linear time-varying, discrete-time systems
    (International Journal of Factory Automation, Robotics and Soft Computing, 2007) Orlowski, Przemyslaw; Institute of Control Engineering, Szczecin University of Technology
    The paper concerns on extending the classical Nyquist theorem to stability analysis of linear time-varying (LTV) discrete-time (DT) feedback control systems. Frequency methods, are well- known tool for analysis and synthesis for linear time-invariant systems. Unfortunately, the methods cannot be applied for LTV systems. The main objective is to show that Bode plots approximated using SVD-DFT are adequate methods for evaluating stability margins as well as external stability for LTV systems. We assume discrete-time state space models with time dependent system matrices defined on a finite time horizon. To solve the problem we employ discrete Fourier transform and singular value decomposition of a system matrix operator as well as properties of power spectral density.
  • Miniatura
    PozycjaOpen Access
    Periodic Linear Time-Varying System Norm Estimation Using Running Finite Time Horizon Transfer Operators
    (Department of Engineering, University of Ferrara, Ferrara, Italy, 2010-11) Orlowski, Przemyslaw; West Pomeranian University of Technology, Szczecin, Department of Control and Measurements
    A novel method for norm estimation for dynamical linear time-varying systems is developed. The method involves operators description of the system model i.e. transfer operator. The transfer operator defined for finite time horizon can be described by finite dimensional matrix whereas for infinite time horizon the operator is infinite dimensional. The norm estimate for infinite time horizon is based on analysis of a running series of the finite time horizon norm properties.
  • Miniatura
    PozycjaOpen Access
    Properties of the frequency SVD-DFT for discrete LTV systems based on first order examples
    (2006) Orlowski, Przemyslaw; Technical University of Szczecin
    The paper develops frequency analysis tools for linear time-varying (LTV), discrete-time systems. The main method is based on the properties of the Singular Value De-composition (SVD), Discrete Fourier Transform (DFT) and Power Spectral Density (PSD). The analysis is carried out for a system with first order dynamics. The general objective of this paper is to examine how system frequency diagrams are depend on the variability of particular parameters. Especially, it is examined how the variability of three matrices of the state space model (scalars, in the 1st order case) influence the approximated Bode diagrams. A few cases of the variability of each matrix, in particular with different frequencies and phase shifting, are considered. Moreover, the analysis is carried out for different cases of the system parameters. The results of analysis for each case are shown in four diagrams: amplitude, phase, impulse and step responses. On the basis of these examples the most important features in each example are characterized.