Abstract
This paper presents a novel model-free (data-based) design method for PI/PID controllers that is based on the direct synthesis approach and specification of the desired closed-loop transfer function for disturbances. The proposed design method directly exploits a set of closed-loop process data without requiring the use of a process model; therefore, it can be applied online to improve the performance of existing underperforming controllers. The tuning formulas for PI/PID controllers are analytically derived and are generally applicable to stable and integrating processes. Furthermore, the tuning formulas contain a single adjustable parameter that enables a designer to address the tradeoff between performance and robustness. Although the controllers are designed for disturbance rejection, the set-point response can be improved independently by using set-point weighting in the PID controllers. Simulation examples covering a wide variety of process dynamics showed that the proposed design method is superior to the model-based direct synthesis design and other existing tuning methods. Furthermore, the proposed method was applied to the nonlinear model equations of a CSTR to show its effectiveness in practical applications.
Published Version
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