New formulations for quantitative feedback theory

R. E. Nordgren, O. D I Nwokah, M. A. Franchek

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


New formulations are presented for quantitative feedback theory that do not require the direct manipulation of templates in the classical sense. This enables the explicit incorporation of high‐frequency unstructured uncertainty into the problem statement, and allows for constructive existence conditions for the solvability of the QFT problem. Necessary and sufficient conditions for robust stability and robust performance are presented for plants with both parametric and high‐frequency unstructured uncertainty, that parallel their corresponding H counterparts. This work extends the recent contribution of Jayasuriya and Zhao to plants with more general non‐minimum phase characteristics such as RHP poles and zeros and time delays.

Original languageEnglish (US)
Pages (from-to)47-64
Number of pages18
JournalInternational Journal of Robust and Nonlinear Control
Issue number1
StatePublished - 1994


  • Loop shaping H
  • Mixed uncertainty
  • Quantitative feedback theory
  • Robust performance
  • Variable non‐minimum phase

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Chemical Engineering(all)
  • Biomedical Engineering
  • Aerospace Engineering
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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