Intuitive robust stability metric for PID control of self-regulating processes. Arbogast, J. E., Beauregard, B. M., & Cooper, D. J. ISA Trans., 47(4):420–428, 2008.
Intuitive robust stability metric for PID control of self-regulating processes [link]Paper  doi  abstract   bibtex   
Published methods establish how plant-model mismatch in the process gain and dead time impacts closed-loop stability. However, these methods assume no plant-model mismatch in the process time constant. The work presented here proposes the robust stability factor metric, RSF, to examine the effect of plant-model mismatch in the process gain, dead time, and time constant. The RSF is presented in two forms: an equation form and a visual form displayed on robustness plots derived from the Bode and Nyquist stability criteria. This understanding of robust stability is reinforced through visual examples of how closed-loop performance changes with various levels of plant-model mismatch. One example shows how plant-model mismatch in the time constant can impact closed-loop stability as much as plant-model mismatch in the gain and/or dead time. Theoretical discussion shows that the impact is greater for small dead time to time constant ratios. As the closed-loop time constant used in Internal Model Control (IMC) tuning decreases, the impact becomes significant for a larger range of dead time to time constant ratios. To complete the presentation, the RSF is used to compare the robust stability of IMC-PI tuning to other PI, PID, and PID with Filter tuning correlations.
@Article{SCC.Arbogast.Beauregard.ea2008,
  author    = {Arbogast, Jeffrey E. and Beauregard, Brett M. and Cooper, Douglas J.},
  title     = {Intuitive robust stability metric for {PID} control of self-regulating processes},
  journal   = {ISA Trans.},
  year      = {2008},
  volume    = {47},
  number    = {4},
  pages     = {420--428},
  issn      = {0019-0578},
  abstract  = {Published methods establish how plant-model mismatch in the process gain and dead time impacts closed-loop stability. However, these methods assume no plant-model mismatch in the process time constant. The work presented here proposes the robust stability factor metric, RSF, to examine the effect of plant-model mismatch in the process gain, dead time, and time constant. The RSF is presented in two forms: an equation form and a visual form displayed on robustness plots derived from the Bode and Nyquist stability criteria. This understanding of robust stability is reinforced through visual examples of how closed-loop performance changes with various levels of plant-model mismatch. One example shows how plant-model mismatch in the time constant can impact closed-loop stability as much as plant-model mismatch in the gain and/or dead time. Theoretical discussion shows that the impact is greater for small dead time to time constant ratios. As the closed-loop time constant used in Internal Model Control (IMC) tuning decreases, the impact becomes significant for a larger range of dead time to time constant ratios. To complete the presentation, the RSF is used to compare the robust stability of IMC-PI tuning to other PI, {PID}, and {PID} with Filter tuning correlations.},
  doi       = {10.1016/j.isatra.2008.06.001},
  owner     = {Rushikesh},
  timestamp = {2010.05.07},
  url       = {http://www.sciencedirect.com/science/article/B6V3P-4SYKM0F-1/2/8ef9989b504a95f5eb60c0d321ffd1e2},
}

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