N2SID: Nuclear norm subspace identification of innovation models

Michel Verhaegen, A Hansson

Research output: Contribution to journalArticleScientificpeer-review

37 Citations (Scopus)
30 Downloads (Pure)


The identification of multivariable state space models in innovation form is solved in a subspace identification framework using convex nuclear norm optimization. The convex optimization approach allows to include constraints on the unknown matrices in the data-equation characterizing subspace identification methods, such as the lower triangular block-Toeplitz of weighting matrices constructed from the Markov parameters of the unknown observer. The classical use of instrumental variables to remove the influence of the innovation term on the data equation in subspace identification is avoided. The avoidance of the instrumental variable projection step has the potential to improve the accuracy of the estimated model predictions, especially for short data length sequences
Original languageEnglish
Pages (from-to)57-63
Publication statusPublished - 2016

Bibliographical note

Accepted Author Manuscript


  • Subspace system identification
  • Optimization
  • Structural constraints
  • Innovation state space models


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