Application of fuzzy logic controllers in single-loop tuning of multivariable sytem design

The Rosenbrock-Nyquist Array design method is a very valuable design technique for a wide range of practical multivariable feedback control systems. The system designed using this design approach has many nice properties, such as the integrity property. In this design approach, the dominance condition plays an important role. However, the dominance condition achieved using a pre-compensator may be altered and instability or unacceptable performance may occur when facing model uncertainties. In this paper, a fuzzy-PID controller structure is proposed. Using this controller structure, one can design the fuzzy controller more easily and the resulting system performance can also be improved. A hybrid design scheme of using a fuzzy controller as well as the Rosenbrock design methodology is also presented for the multivariable control system design. A numerical example is used to illustrate the robustness enhancement and the effectiveness of the proposed hybrid design scheme.