Stability analysis of type-2 fuzzy logic controllers

The application of the direct Lyapunov method to the stability analysis of systemscontrolled by type-2 fuzzy logic controllers (FLC) is presented. The method is anextension of a method proposed for type-1 fuzzy systems. It is usually applied tosystems described by state equations and controlled by fuzzy controllers using statevariables as inputs but has been extended to controllers that have the error and theintegral of error of the controlled variable as inputs.The proposed method allows to modify the controller rule base so that the controlledsystem is stable in the operating range defined by the manipulative variable constraints.The method is applied to the stability analysis of a bioreactor and of a CSTR controlledby type-2 FLCs.