Stability regions in the parameter space: D-decomposition revisited

  • Authors:
  • Elena N. Gryazina;Boris T. Polyak

  • Affiliations:
  • Institute of Control Sciences, Russian Academy of Sciences, 65 Profsoyuznaya st., Moscow 117997, Russia;Institute of Control Sciences, Russian Academy of Sciences, 65 Profsoyuznaya st., Moscow 117997, Russia

  • Venue:
  • Automatica (Journal of IFAC)
  • Year:
  • 2006

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Abstract

The challenging problem in linear control theory is to describe the total set of parameters (controller coefficients or plant characteristics) which provide stability of a system. For the case of one complex or two real parameters and SISO system (with a characteristic polynomial depending linearly on these parameters) the problem can be solved graphically by use of the so-called D-decomposition. Our goal is to extend the technique and to link it with general M-@D framework. In this way we investigate the geometry of D-decomposition for polynomials and estimate the number of root invariant regions. Several examples verify that these estimates are tight. We also extend D-decomposition for the matrix case, i.e. for MIMO systems. For instance, we partition real axis or complex plane of the parameter k into regions with invariant number of stable eigenvalues of the matrix A+kB. Similar technique can be applied to double-input double-output systems with two parameters.