Stabilization of direct adaptive fuzzy control systems considering minimum approximation error

A method to stabilize a fuzzy logic controller (FLC) is presented in which the sliding mode control (SMC) method and the adaptive control (ADC) scheme are properly incorporated to overcome the unstable characteristics of the conventional FLC. The SMC scheme is adopted to compensate for minimum approximation error (MAE) due to limited approximation capability of FLC which can make the FLC system unstable. The ADC scheme is used to tune the center values of membership functions in a direction of keeping stability. The suggested method can be considered as FLC or SMC, depending on a switching condition and each advantage is shown in terms of FLC or SMC. Finally, simulations are given to illustrate effectiveness of the results.