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A candidate to replace PID control: SISO‐constrained LQ control
Author(s) -
Pannocchia Gabriele,
Laachi Nabil,
Rawlings James B.
Publication year - 2005
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.10373
Subject(s) - setpoint , pid controller , control theory (sociology) , estimator , offset (computer science) , controller (irrigation) , control engineering , computer science , engineering , mathematics , control (management) , temperature control , agronomy , statistics , artificial intelligence , biology , programming language
Abstract It is commonly believed that for single‐input/single‐output (SISO) systems, well‐tuned proportional, integral, derivative (PID) controllers work as well as model‐based controllers and that PID controllers are more robust to model errors. In this paper we present a novel offset‐free constrained linear quadratic (LQ) controller for SISO systems, which is implemented in an efficient way so that the total controller execution time is similar to that of a PID. The proposed controller has three modules: a state and disturbance estimator, a target calculation, and a constrained dynamic optimization. It is shown that the proposed controller outperforms PID both in setpoint changes and disturbance rejection, it is robust to model errors, it is insensitive to measurement noise, and it handles constraints better than common anti‐windup PID. Tuning the proposed controller is simple. In principle there are three tuning parameters to choose, but in all examples presented only one was actually varied, obtaining a clear and intuitive effect on the closed‐loop performance. © 2005 American Institute of Chemical Engineers AIChE J, 2005