Modeling, Identification and Control (Apr 2013)

Relaxed Ziegler-Nichols Closed Loop Tuning of PI Controllers

  • Finn Haugen,
  • Bernt Lie

DOI
https://doi.org/10.4173/mic.2013.2.4
Journal volume & issue
Vol. 34, no. 2
pp. 83 – 97

Abstract

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A modification of the PI setting of the Ziegler-Nichols closed loop tuningmethod is proposed. The modification is based on a combination of the Skogestad SIMCtuning formulas for ''integrator plus time-delay'' processes with the Ziegler-Nichols tuning formulas assuming that the process is modeled as an ''integrator plus time-delay'' process. The resulting PI settings provide improved stability margins compared with those obtained with the original Ziegler-Nichols PI settings. Compared with the well-known Tyreus-Luyben PI settings, the proposed PI settings give improved disturbance compensation. For processes with zero or a negligible time-delay, but with some lags in the form of time-constants, tuning based on ultimate gain and ultimate period may give poor results. Successful PI settings for such processes are proposed.

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