Observer-Based Solution to the Strictly Positive Real Problem

J. Collado, R. Lozano, Rolf Johansson

Research output: Chapter in Book/Report/Conference proceedingBook chapterResearch


We study the extension of the class of linear time invariant plants that may be transformed into SPR systems introducing an observer. It is shown that for open loop stable systems a cascaded observer achieves the result. For open loop unstable systems an observer-based feedback is required to succeed. In general any stabilizable and observable system may be transformed into an SPR system using cascade or cascade and feedback controllers. This overcomes the old conditions of minimum phase and relative degree one. The result is illustrated with some examples.
Original languageEnglish
Title of host publicationNonlinear and Adaptive Control, Tools and Algorithms for the User
EditorsAlessandro Astolfi
PublisherImperial College Press
ISBN (Print)1-86094-617-8
Publication statusPublished - 2005

Subject classification (UKÄ)

  • Control Engineering


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