الفهرس 
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Abstract
The three phase induction motor is one of the most widely used machines in industrial applications, due to its low cost and maintenance requirements, robustness and simple construction. However, the nonlinearity of the induction motor model makes it difficult to control. Field oriented control of induction motor has proven, in the past two decades, to be one of the most effective methods to control the induction motor. This technique has the merit of decoupling the torque (or speed) dynamics and the flux dynamics and thus, the induction motor can be treated in the same manner as a dc machine. However, this method is very sensitive to external load disturbances and motor parameter variations.
Sliding mode control is a well known robust control technique. Therefore, a sliding mode controller was introduced to the field oriented control system in order to avoid the aforementioned drawbacks of the field oriented control system. But in sliding mode control the upper bound of uncertainties must be known in order to properly adjust the controller parameters. Since these uncertainties are practically difficult to obtain, they must be estimated during the system operation.
Fuzzy inference systems have also proven to be an effective method to model non-linear, ill-defined systems and systems with uncertainties by means of expert knowledge. Therefore, the merits of combining the sliding mode controller with a fuzzy controller were studied, and a fuzzy inference mechanism was proposed in order to compensate for the system uncertainties seen by the sliding mode controller. Another problem facing the sliding mode controller is the high chattering phenomenon and the high control effort required in order to satisfy the sliding mode condition for all values of uncertainties. Therefore, an adaptive fuzzy sliding mode controller is proposed. In this controller an adaptation algorithm for the centers of the fuzzy membership functions is applied, in order to obtain an optimal compensation for the uncertainties, so that the control effort is minimized and the chattering phenomenon is reduced.
In this thesis, the performances of sliding mode controller, fuzzy sliding mode controller and the adaptive fuzzy sliding mode controller, operating in a field oriented controlled induction motor, are investigated. Simulation results are shown to verify the effectiveness of the proposed controller.