Frequency-Domain Subspace Identification of Linear Time-Periodic (LTP) Systems

Ismail Uyanik, Uluc Saranli, Mustafa Mert Ankarali, Noah J. Cowan, Omer Morgul

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


This paper proposes a new methodology for subs-pace-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 an unknown LTP system as if they were collected from an equivalent LTI system. Then, we use frequency-domain subspace identification methods to find the 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 obtain state-space estimates for unknown LTP systems as well as to obtain Floquet transforms for known LTP systems.

Original languageEnglish (US)
Article number8447499
Pages (from-to)2529-2536
Number of pages8
JournalIEEE Transactions on Automatic Control
Issue number6
StatePublished - Jun 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Computer Science Applications
  • Electrical and Electronic Engineering


  • Linear time-periodic (LTP) systems
  • subspace methods
  • system identification
  • time-varying systems


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