Positive systems

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Positive systems[1][2] constitute a class of systems that has the important property that its state variables are never negative, given a positive initial state. These systems appear frequently in practical applications,[3][4] as these variables represent physical quantities, with positive sign (levels, heights, concentrations, etc.).

The fact that a system is positive has important implications in the control system design,[5] as the system. It is also important to take this positivity into account for state observer design, as standard observers (for example Luenberger observers) might give illogical negative values.[6]

See also[edit]

Positive feedback


  1. ^ T. Kaczorek. Positive 1D and 2D Systems. Springer- Verlag, 2002
  2. ^ L. Farina and S. Rinaldi, Positive Linear Systems; Theory and Applications, J. Wiley, New York, 2000
  3. ^ http://eprints.nuim.ie/1764/1/HamiltonPositiveSystems.pdf
  4. ^ http://www.iaeng.org/publication/WCE2010/WCE2010_pp656-661.pdf
  5. ^ http://www.nt.ntnu.no/users/skoge/prost/proceedings/ifac2008/data/papers/3024.pdf
  6. ^ http://advantech.gr/med07/papers/T19-027-598.pdf