On-line relay test for automatic tuning of PI controllers for stable processes

Abstract

The applicability of the basic relay tuning method is extended by a robust on-line method to tune proportional–integral controllers without breaking the closed-loop control. A relay is connected in parallel to the controller to induce self-oscillation and then simple measurements are made only on the half period of limit cycle output to obtain a first-order plus dead time model of the process dynamics. A non-iterative optimum tuning formulae is developed in order to reduce the control signal variations. The simulation and experimental studies are presented to validate the design method.

Keywords

Control efforts identification on-line tuning relay feedback test

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