Orlowski, Przemyslaw2023-05-302023-05-302007Orłowski P. (2007). An extension of Nyquist feedback stability for linear time-varying, discrete-time systems. International Journal of Factory Automation, Robotics and Soft Computing, iss. 2, pp. 51-56. https://hdl.handle.net/20.500.12539/17651828-6984https://hdl.handle.net/20.500.12539/1765The 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.enUznanie autorstwa-Użycie niekomercyjne-Bez utworów zależnych 3.0 Polskadiscrete-time systemstime-varying systemsnon-stationary systemsstabilityfinite time horizonfrequency analysisDyscyplina::Nauki inżynieryjno-techniczneArticle