Recently, the shape of the Nyquist plot has been proved invariant under frequency transformation in continuous-time linear systems. This letter deals with the discrete-time case where the frequency transformation is performed using an inner frequency transformation of the type z-1→ F(z). Dual results with respect to the continuous case are obtained, showing that the closed-loop stability for the class of transformed systems can be inferred from the order of the transformation and the Nyquist plot of the not transformed system, after calculating the number of unstable poles. Both single-input-single-output (SISO) and multi-input-multi-output (MIMO) systems are considered.
Nyquist Plots Under Frequency Transformations: The Discrete-Time Case
Bucolo M.;Buscarino A.;Fortuna L.;Frasca M.
2022-01-01
Abstract
Recently, the shape of the Nyquist plot has been proved invariant under frequency transformation in continuous-time linear systems. This letter deals with the discrete-time case where the frequency transformation is performed using an inner frequency transformation of the type z-1→ F(z). Dual results with respect to the continuous case are obtained, showing that the closed-loop stability for the class of transformed systems can be inferred from the order of the transformation and the Nyquist plot of the not transformed system, after calculating the number of unstable poles. Both single-input-single-output (SISO) and multi-input-multi-output (MIMO) systems are considered.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
