Direct adaptive fuzzy controller by changing the output membership functions for nonlinear motion applications

In this paper an adaptive control speed for an induction motor drive is presented. The proposed adaptive scheme uses a Mamdani fuzzy logic controller (MFLC). The parameters, of the membership output function characterizing the linguistic terms in the fuzzy if-then rules change according the adaptation. The MFLC approximates and adaptively cancels an unknown plant non-linearity. The adaptive law is developed for the purpose of tracking a reference speed in a motion system. Based on the Lyapunov theory, the stability of the whole system and the convergence of the tracking error are also discussed. The tracking error is guaranteed to be uniformly stable and ultimately bounded with the aid of an additional supervisory term. Computer simulations show that the effect on the error of both the fuzzy approximation and the external disturbances can be attenuated by the proposed controller. Moreover, experimental results are presented to verify the effectiveness of the method.