Grey box identification in closed-loop

Henrik Niemann, Robert Miklos, Niels Kjølstad Poulsen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


The focus in this paper is identification of parameters in closed-loop systems. The system identification approach is based on a reformulation of feedback controllers in terms of its coprime factors. Based on this controller architecture, an auxiliary input is injected into the controller for the identification. The result of this setup is that the closed-loop identification problem is transformed into a standard open-loop identification problem. The models with unknown parameters are given in the form of a linear fractional transformation (LFT) where the direct term gives the nominal system and the other part gives the nonlinear maps of the variation of the unknown parameters into the system. Further, the coprime factors of this system can again be described as LFT of the nominal coprime factors and the parameter variations, i.e. an open-loop LFT identification problem.

Original languageEnglish
Title of host publicationProceedings of 2019 American Control Conference
Publication date1 Jul 2019
Article number8814460
ISBN (Electronic)9781538679265
Publication statusPublished - 1 Jul 2019
Event2019 American Control Conference - Philadelphia, United States
Duration: 10 Jul 201912 Jul 2019


Conference2019 American Control Conference
Country/TerritoryUnited States
SponsorBoeing, GE Global Research, General Motors Co., Mitsubishi Electric Research Laboratory, United Technologies Research Center
SeriesProceedings of the American Control Conference


  • Closed-loop system identification
  • Coprime factorization
  • Feedback controllers
  • Grey box models


Dive into the research topics of 'Grey box identification in closed-loop'. Together they form a unique fingerprint.

Cite this