Decentralized Control with Process Frequency Response Identification

J. Macháček (Czech Republic)


Multivariable system, decentralized control, relay autotuning, identification, PID controller.


Design of decentralized controllers is based on knowledge of process model. When model of the process is not a priori known, basic information about system can be obtained by relay autotuner. Controllers tuning is realized in a few iterations with repeated relay test, e.g. by sequential method. This approach may be improved, when an approximation system model is derived. This paper deals with process frequency response identification from relay test by FFT and with calculation controllers parameters directly from these responses. This approach eliminates errors arising from building of a parametric model in form of transfer function with unknown structure. Time of experimental work on real process is saved, as great part of experiment is simulated on computer. The procedure is demonstrated on simulation example for a system with two inputs and two outputs. Only two experiments are required for controllers tuning.

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