Graphical Stability Analysis of a Control System Having 2-Input and 2-Output Fuzzy Controller

This work deals with the absolute stability of a control system having a 2-input and 2-output fuzzy controller designed by indirect fuzzy reasoning. The absolute stability of the control system is analyzed treating the fuzzy controller as a nonlinear element using Yakubovich's method. The obtained conditions are described by a formulation similar to the usual Popov's condition and a constraining relation between the gains of two types of controller. An example is shown to confirm the analytical result obtained by a graphical method.