Conference Paper

Two-Degree-of-Freedom PI/PID tuning approach for smooth control on cascade control systems

Dept. de Autom., Univ. de Costa Rica, San Jose, Costa Rica
DOI: 10.1109/CDC.2008.4738796 Conference: Decision and Control, 2008. CDC 2008. 47th IEEE Conference on
Source: IEEE Xplore

ABSTRACT A design approach for two-degree-of-freedom (2-DOF) PID controllers within a cascade control configuration that guarantees smooth control is presented in this paper. The rationale of operation associated to both, the inner and outer controllers, determines the need of good performance for disturbance attenuation (regulation) as well as set-point following (tracking). Therefore the use of 2-DOF controllers is introduced. However the use of 2-DOF controllers introduces additional parameters that need to be tuned appropriately. Specially for the case of PI/PID controllers there are not known clear auto-tuning guidelines for such situation. The approach undertaken in this paper provides the complete set of tuning parameters for the inner (2-DOF PI) controller and the outer (2-DOF PID) controller. The design equations are formulated in such a way that a non-oscillatory response is specified for both the inner and outer loop. A side advantage of providing the complete set of parameters is that it avoids the need for the usual identification experiment for the tuning of the outer controller.

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    ABSTRACT: This paper proposes a new tuning method for PI controllers in two-degree-of-freedom (2DOF) structure. In design approach, first order plus dead time (FOPDT) model is used. The aim is to have good set-point response and disturbance rejection and also maximum robustness to model uncertainties. The tuning strategy is based on using Butterworth rules and genetic algorithm optimization. Simulation results demonstrate the effectiveness and validity of proposed method in coping with conflicting design objectives for a wide variety of processes including minimum phase and non-minimum phase and also integrating processes.
    Computer-Aided Control System Design (CACSD), 2010 IEEE International Symposium on; 10/2010

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