Advertisement

Identification of Chemical Processes for Control Purposes by Relay Techniques

  • C. Scali
Conference paper

Abstract

A new identification technique (ATV+) for completely unknown processes is presented: it allows to build a parametric model from few experimental tests and to design a PID or Model Based Controller. It is also extended to open loop unstable processes and to multivariable processes. The method is compared with the original technique (ATV) and with simpler identification techniques in terms of ease of application, duration of tests and achievable performance.

Simulation results for the case of SISO processes, show that identification obtained by ATV+ technique allows superior performance, both for PID and for Model Based Controllers, thus compensating the longer identification times. In the MIMO case, ATV+ technique leads successfully to the design of decentralized controllers, but the improved knowledge of the system is not compensated by superiority in achievable performance.

Keywords

Stable Oscillation Achievable Performance Automatic Tuning Unknown Process Closed Loop Response 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Cohen G.H., Coon A. (1952) Theoretical Considerations of Retarded Control. Trans. ASME, 75, 827–834Google Scholar
  2. 2.
    Yu C.C. (1998) Autotuning of PID controllers. Springer Verlag London, pp. 7–10Google Scholar
  3. 3.
    Luyben W.L. (1987) Derivation of Transfer Functions for Highly Nonlinear Distillation Columns. Ind. Eng. Chem. Res., 26, 2490–2495CrossRefGoogle Scholar
  4. 4.
    Åström K.J., Hägglund T. (1984) Automatic Tuning of Simple Regulators with Specification on Phase and Amplitude Margins. Automatica, 20, 645–651CrossRefGoogle Scholar
  5. 5.
    Cook P. (1985) Non-Linear Dynamical Systems, Prentice Hall: Englewood Cliffs, N.J. (USA), 52–64Google Scholar
  6. 6.
    Ziegler J.G., Nichols N.B. (1942) Optimum Settings for Automatic Controllers. Trans ASME, 65, 433–444Google Scholar
  7. 7.
    Loh A.P., Hang C.C., Quek C.K- Vasnani V.U. (1993) Autotuning of Multiloop Proportional-Integral Controllers using Relay Feedback. Ind. Eng. Chem. Res. 32, 1102–1107CrossRefGoogle Scholar
  8. 8.
    Shen S.H., Yu C.C. (1994) Use of Relay Feedback Test for Automatic Tuning of Multivariate Systems. Process Systems Eng. 40, 627–646Google Scholar
  9. 9.
    Friman M., Waller K.V. (1994) Autotuning of Multiloop Control Systems. Ind. Eng. Chem. Res., 33, 1708–1717.CrossRefGoogle Scholar
  10. 10.
    Palmor Z.J., Halevi Y., Krasney N. (1995) Automatic Tuning of Decentralized PID Controllers for TITO Processes. Automatica, 31, 1001–1010CrossRefGoogle Scholar
  11. 11.
    Halevi Y., Palmor Z.J., Efrati T. (1997) Automatic Tuning of Decentralized PID Controllers for MIMO Processes. Journal of Process Control, 7, 119–128CrossRefGoogle Scholar
  12. 12.
    Li W., Eskinat E., Luyben, W.L. (1991) An Improved Autotune Identification Method. Ind. Eng. Chem. Res, 30, 1530–1541CrossRefGoogle Scholar
  13. 13.
    Friman M., Waller K.V. (1995) Closed-Loop Identification by Use of Single-Valued Nonlinearities. Ind. Eng. Chem. Res., 34, 3052–3058CrossRefGoogle Scholar
  14. 14.
    Hang C.C., Astrom K.J., Ho W.K. (1991) Refinements of the Ziegler Nichols Tuning Formula. IEEE Proc., Part D, 138, 111–118Google Scholar
  15. 15.
    Friman M., Waller K.V. (1997) A Two-channel Relay for Autotuning. Ind. Eng. Chem. Res., 37, 2662–2671CrossRefGoogle Scholar
  16. 16.
    Semino D., Scali C. (1998) Improved Identification and Autotuning of PI Controllers for MIMO Processes by Relay Techniques. J. Proc. Contr., 8, 219–227CrossRefGoogle Scholar
  17. 17.
    Scali C., Marchetti G., Semino D. (1999) Identification and Autotuning of Completely Unknown Processes. Ind. Eng. Chem. Res., 38, 1987–1997CrossRefGoogle Scholar
  18. 18.
    Marchetti G., Semino D., Scali C. (2000) Accuracy of Autotune Identification Methods and Achievable Performance. IFAC-SYSID: Int. Conf. on System Identification, pap. FrPm 4 /5Google Scholar
  19. 19.
    Marchetti G., Scali C. (1999) A comparison of Relay Techniques for Identification and Autotuning of Chemical Processes. Computers and Chemical Engineering, 20, S305–S308CrossRefGoogle Scholar
  20. 20.
    Marchetti G., Scali C. (2000) Use of Modified Relay Techniques for the Design of Model Based Controllers for Chemical Process Control Purposes. Ind. Eng. Chem. Res. 39 (9), 3325–3334CrossRefGoogle Scholar
  21. 21.
    Parabita P., Marchetti G., Scali C. (2000) Sequential Identification and Autotuning by Relay Techniques of Decentralised Controllers for MIMO Processes. IFAC-ADCHEM 2000: Int. Symp. on Advanced Control of Chemical Processes, 91–96Google Scholar
  22. 22.
    Marchetti G., Parabita P., Scali C. (2000) Sequential versus Simultaneous Relay Techniques for Autotuning of Multivariate Processes, PCI-2000 Int. Conf. on Process Control and Instrumentation; Glasgow (UK), 268–273Google Scholar
  23. 23.
    Marchetti G., Scali C., Lewin D.R. (2001) Identification and Control of Open- Loop Unstable Processes by Relay Methods. Automatica, (in press)Google Scholar
  24. 24.
    Marchetti G., Scali C. (2001) Different Approaches for Relay-Based Identification and Control of Unstable Processes, European Control Conference ECC’01, (accepted)Google Scholar
  25. 25.
    Morari M., Zafiriou E. (1989) Robust Process Control. Prentice Hall: Engle- wood Cliffs, N.J. (USA), 114–124Google Scholar
  26. 26.
    Lee J., Cho W., Edgar T.F. (1990) An Improved Technique for PID Controller Tuning from Closed Loop Tests. AIChE Jnl. 36, 1891–1895CrossRefGoogle Scholar
  27. 27.
    Rotstein G.E., Lewin D.R. (1991) Simple PI and PID Tuning for Open-Loop Unstable Systems. Ind. Eng. Chem. Res, 30, 1864–1869CrossRefGoogle Scholar
  28. 28.
    Shen S.H., Wu J.S., Yu C.C. (1996) Use of Biased-relay Feedback for System Identification. AIChE Jnl., 42, 1174–1180CrossRefGoogle Scholar
  29. 29.
    Luyben W.L. (1986) Simple Method for Tuning SISO Controllers in Multivariate Systems. Ind. Eng. Chem. Process Des. Dev., 25, 654–660CrossRefGoogle Scholar
  30. 30.
    Marchetti G., Tognini F., Scali C. (2000) Closed Loop Identification and Control of Multivariate Chemical Processes: a Case Study. DINIP 2000: Dinamica e Controllo NonLineare nell’Ingegneria di ProcessoGoogle Scholar

Copyright information

© Springer-Verlag Italia, Milan 2002

Authors and Affiliations

  • C. Scali
    • 1
    • 2
  1. 1.Laboratorio di Controllo dei Processi Chimici(CPCLab)Università di PisaPisaItaly
  2. 2.Dipartimento di Ingegneria Chimica(DICCISM)Università di PisaPisaItaly

Personalised recommendations