Identification of Chemical Processes for Control Purposes by Relay Techniques
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.
KeywordsStable Oscillation Achievable Performance Automatic Tuning Unknown Process Closed Loop Response
Unable to display preview. Download preview PDF.
- 1.Cohen G.H., Coon A. (1952) Theoretical Considerations of Retarded Control. Trans. ASME, 75, 827–834Google Scholar
- 2.Yu C.C. (1998) Autotuning of PID controllers. Springer Verlag London, pp. 7–10Google Scholar
- 5.Cook P. (1985) Non-Linear Dynamical Systems, Prentice Hall: Englewood Cliffs, N.J. (USA), 52–64Google Scholar
- 6.Ziegler J.G., Nichols N.B. (1942) Optimum Settings for Automatic Controllers. Trans ASME, 65, 433–444Google Scholar
- 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
- 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
- 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
- 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.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.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.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.Morari M., Zafiriou E. (1989) Robust Process Control. Prentice Hall: Engle- wood Cliffs, N.J. (USA), 114–124Google Scholar
- 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