Abstract
Recently, sliding Mode control (SMC) has been widely used in speed control of electric drive systems. It provides attractive features such as fast dynamic response, insensitivity to variations in plant parameters and external disturbance. However, chattering is one problem, which limits the use of the SMC to control DC motor drives in industry. This paper presents a fuzzy variable structure controller for the DC motor drives. The fuzzy controller is used to adjust the switching gain constant in the sliding mode controller to guarantee the system stability and practically to eliminate the chattering problem. The proposed algorithm thyristors-bridge. The performance of the proposed system is compared with that of traditional variable structure and sliding mode with boundary layers method.