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Tuning PI controllers for stable processes with specifications on gain and phase margins

Written by ISA Transactions | Feb 6, 2013 5:00:18 PM

This is from a series of articles from the journal ISA Transactions.  ISA Transactions articles are free to ISA members, or can be purchased from Elsevier Press.

 

Fig. 1. IMC control strategy.

 

Abstract: In industrial practice, controller designs are performed based on an approximate model of the actual process. It is essential to design a control system which will exhibit a robust performance because the physical systems can vary with operating conditions and time. Gain and phase margins are well known parameters for evaluating the robustness of a control system. This paper presents a tuning algorithm to design and tune PI controllers for stable processes with a small dead time while meeting specified gain and phase margins. Simulation examples are given to demonstrate that the proposed design method can result, in a closed-loop system, in better performances than existing design methods which are also based on user-specified gain and phase margins.

 

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