Centralized PI/PID controllers for nonsquare systems with RHP zeros

Abstract

Two centralized controller-tuning methods, Davison's method [Multivariable tuning regulators: The feed forward and robust control of general servo mechanism problem, IEEE Trans. Auto. Control, 21, 35-21 (1976)] and Tanttu and Lieslehto method [A comparative study of some multivariable PI controller tuning methods, in Intelligent tuning and adaptive control, Pergamon Press, pp 357-362 (1991)], are extended to nonsquare systems with right half-plane zeros. These methods have been applied to two examples with right half-plane zeros in the individual scalar elements-coupled pilot plant distillation columns (2 outputs and 3 inputs) and a crude distillation process (4 outputs and 5 inputs). Simulation studies have been carried out for these examples for both servo and regulatory problems. For the coupled pilot plant distillation column example, the proposed methods are compared with the robust decentralized controller design method proposed by Loh and Chiu [Robust decentralized control of nonsquare systems, Chem. Engng Commun., 158, 157-180 (1997)]. The performance of square and nonsquare controllers is compared for the crude distillation process example.