Uyanik, I.Saranli, U.Ankaralı, M.Cowan, N. J.Morgül, Ömer2019-02-212019-02-2120190018-9286http://hdl.handle.net/11693/50242This note proposes a new methodology for subspace-based state-space identification for linear time-periodic (LTP) systems. Since LTP systems can be lifted to equivalent linear time-invariant (LTI) systems, we first lift input-output data from the unknown LTP system as if it was collected from an equivalent LTI system. Then, we use frequency-domain subspace identification methods to find an LTI system estimate. Subsequently, we propose a novel method to obtain a time-periodic realization for the estimated lifted LTI system by exploiting the specific parametric structure of Fourier series coefficients of the frequency-domain lifting method. Our method can be used to both obtain state-space estimates for unknown LTP systems as well as to obtain Floquet transforms for known LTP systems. IEEEEnglishlinear time-periodic systemsSubspace methodsSystem identificationTimevarying systemsArticle10.1109/TAC.2018.2867360